Fundamentals of biomedical engineering

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This book is designed to explain the fundamentals of biomedical engineering in the areas of biomechanics, biofluid flow, biomaterials, bioinstrumentations and in use of computing in biomedical engineering. Though this book is chiefly based on the syllabus of Uttar Pradesh Technical University, but an effort has been made to cover the syllabus of several other universities as well as based on my experience of teaching.

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Copyright © 2007, New Age International (P) Ltd., PublishersPublished by New Age International (P) Ltd., Publishers

All rights reserved.No part of this ebook may be reproduced in any form, by photostat, microfilm,xerography, or any other means, or incorporated into any information retrievalsystem, electronic or mechanical, without the written permission of the publisher.All inquiries should be emailed to [email protected]

PUBLISHING FOR ONE WORLD

NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS4835/24, Ansari Road, Daryaganj, New Delhi - 110002Visit us at www.newagepublishers.com

ISBN (13) : 978-81-224-2549-9

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‘Bio’ denotes all things which are connected with life. Firstly man has learnt the use of herbsfor treatment and the knowledge of botany becomes essential for the practitioner of medicine.Gradually man has learnt to apply laws of physics and chemistry to living things which has led to theevolution of sciences of biophysics and biochemistry. In recent years, there has been rapid progressin the field of the health care. The need to effectively utilize high technology equipment and systemsin the health care necessitates the expertise of clinical engineers, hospital physicians and computerscientists. Hardly any patient today would pass through a hospital or even a family physician’schamber without the use of this technology.

The knowledge of basic engineering and the need of biomedical engineers in health care isincreasingly accepted. The biomedical engineering is the inter marriage of engineering and medicine.The biomedical engineering as a subject has been introduced in the engineering courses to equip theengineering graduates to work in the health care industry. It is, therefore, essential for engineeringstudents of almost all disciplines to have a sound knowledge of biomedical engineering. This book isdesigned to explain the fundamentals of biomedical engineering in the areas of biomechanics, biofluidflow, biomaterials, bioinstrumentations and in use of computing in biomedical engineering. Thoughthis book is chiefly based on the syllabus of Uttar Pradesh Technical University, but an effort hasbeen made to cover the syllabus of several other universities as well as based on my experience ofteaching.

I have endeavoured to present a systematic explanation of the basic concepts of the biomedicalengineering by firstly introducing the topics of anatomical terms and planes, terms related to movementsmedical terminology, histology and physiological systems of the body. A large number of objectivetype questions are included to enhance the understanding of the principles of theory.

I express my gratitude to Dr. Jasdev Singh Sawhney, FRCR and Dr. Pooja Sachdev SawhneyMRCP for their valuable suggestions which have helped me immensly in conceptualizing and writingthis book. I am also thankful to my doctoral guide, Dr. S. Prasad, NIET Greater Noida for moralsupport. I am also thankful to Dr. Sujay K.Guha, SMS, IIT kharagpur who has been my inspirationin the field of biomedical engineering.

I am also thankful to Dr. V.K. Goswami and the faculty of GNIT, Greater Noida specially Mr.Devraj Tiwari of Mechanical, Prof O.P. Sharma and Mr. Manish of Information Technology, Mrs.Minakshi Awasthi of Physics and Mr. S.D. Nautyal of library for their contributions.

Above all, I wish to record my sincere thanks to my wife, Jasbeer Kaur for her patienceshown throughout the preparation of this book. I am also thankful to the staff of New Age Publishers

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who have associated with the completion of this book. Last but not least, I want to thank Mr. K.K.Aggarwal, chairman and Dr. A.M. Chandra, Director of Lord Krishna College of Engineering,Ghaziabad where I joined recently for their constant encouragement.

I would appreciate receiving constructive suggestions and objective criticism from studentsand teachers alike with a view to further enhancing the usefulness of the book by e-mailing [email protected]

G.S. SAWHNEY

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Preface v

1. Introduction 1

2. Concepts of Physics, Mechanics and Fluid Mechanics 23

3. Biomedical Engineering 33

4. Biomechanics of Bone 38

5. Biomechanics of Soft Tissues 48

6. Skeletal Joints 52

7. Mechanics of the Spinal Column 57

8. Mechanics of Upper Limbs 62

9. Mechanics of Lower Limbs 74

10. The Cardiovascular System and Blood Flow 89

11. The Respiratory System 111

12. Kidney and Blood Flow 122

13. Prosthesis and Therapeutic Devices 127

14. Orthosis 141

15. Metallic Biomaterials 146

16. Polymeric Biomaterials 151

17. Bioceramics 158

18. Composite Biomaterials 162

19. Biogradable Polymeric Biomaterials 165

20. Orthopedic Prostheses Fixation 167

21. Physiological Signals and Transducers 169

22. Signal Processing 181

23. Digital Image Acquisition and Processing 186

24. Radiography 194

25. Computed Tomography 204

26. Magnetic Resonance Imaging 213

27. Ultrasound Imaging 219

28. Radioisotopes and Radiotherapy 226

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29. Nuclear Medicine 232

30. Health Care Information and Communication 235

31. Biotelemetry 239

32. Application of Computer in Medicine 244

33. Telemedicine 249

34. Database Design Topologies and Network Security 255

Bibliography 260Index 262

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If only tool in your bag is a hammer then every problem in the world appearsto be a nail.

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1. The body is made up of the head, trunk andlimbs. The trunk consists of the neck, thorax(chest) and abdomen (belly). The lower partof the abdomen is the pelvis. This word is

also used for the bones of the pelvis. Thelowest part of the pelvis or in other wordsthe lowest part of the trunk is the perineum.The central axis of the trunk is the vertebralcolumn, and the upper part of it (cervicalpart) supports the head.

Head

Neck

Thorax

Abdomen

Thigh

Leg

Foot

Planter surface

Arm

Fore Arm

Ulnar side PelvisPerineumHand

Dorsal surface

Palmar surface

Dorsal surface

Radial side

ANATOMICAL TERMS AND PLANES

Anatomical Terms

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2. The main parts of the upper limb are thearm, forearm and hand. Arm in strictanatomical term means the upper arm (thepart between the shoulder and elbow)however, this word is commonly used forthe whole of the upper limb.

3. The main parts of the lower limb are thethigh, leg and foot. Here also leg in strictanatomical form means the lower leg (thepart between the knee and foot) but theword is commonly used for whole of thelower limb.

4. In order to describe the positions ofstructure in human anatomy, the body isassumed to be standing upright with the feettogether and the head and eyes looking tothe front with the arms straight by the sideand the palms of the hands facing forwards.This is the anatomical position andstructures are always described relative toone another using this as the standardposition. This is also applicable even whenthe body is lying on the back to bed or whenlying on a dissecting table.

5. The ‘Median plane’ is an imaginary verticallongitudinal line through the middle of thebody from front to back, dividing the bodyinto right and left halves. The ‘sagittal plane’is any plane that is parallel to the medianplane. The adjective ‘medial’ means nearerto the median plane, and ‘lateral’ meansfarther from it. Thus we can say inanatomical position, the little finger is onthe medial side of the hand and the thumbis on the lateral side, similarly the great toeis on the medial side of the foot and the littletoe on the lateral side. If we consider forearmwhich has two bones with radius bone onthe lateral side and ulna bone on the medialside, then the adjective ‘radial’ and ‘ulnar’can be used instead of lateral & medial.Similarly in the lower leg where there aretwo bones, the fibula on the lateral side andthe tibia on the medial side, the alternativeadjectives ‘fibular’ and ‘tibial’ can be used.

6. ‘Coronal planes’ are imaginary planes at rightangles to the median plane. Horizontal ortransverse planes are at right angles to boththe median and coronal planes.

Coronal p lane

M ed ian plane

Horizon ta l o r

T ransverse p lane

Planes

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7. The terms ‘anterior’ and ‘posterior’ are usedto indicate the front or back of the bodyrespectively. Therefore we have anterior andposterior view of the body or any part ofbody or organ. It is also used to describethe relationship of two parts. One is said tobe anterior or posterior to the other if it iscloser to anterior or posterior to the bodysurface. Hence on the face, the nose isanterior to the ears and the ears are posteriorto the nose. Sometimes ‘ventral’ is usedinstead of posterior.

8. In describing the hand, the term ‘palmar’and ‘dorsal’ surfaces are used instead ofanterior and posterior. Similarly in describingthe foot, the ‘plantar’ and ‘dorsal’ surfaces,are used instead of lower and upper surfaces.

9. The terms ‘proximal’ and ‘distal’ describethe relative distances from the roots of thelimbs. The arm is proximal to the forearmand the hand is distal to the forearm.

10. The terms ‘superior’ and ‘inferior’ meansnearer the upper or lower end of the bodyrespectively. Hence the nose is superior tothe mouth and, inferior to the forehead.‘Superficial’ means near the skin surfaceand ‘deep’ means farther away from thesurface. The terms ‘internal’ and ‘external’are used to describe the relative distance ofa structure from the centre of an organ orcavity. ‘Ipsilateral’ and ‘contra-lateral’ areused for parts on the same side or not ofthe body. Hence, left hand and left foot are

ipsilateral while the left biceps branchiimuscle and the right rectusfemoris muscle,are contralateral. The ‘supine’ position ofthe body is lying on the back and the ‘prone’position is lying face downward.

1. Wherever two or more bones meet, it isknown as a joint. The degree of mobilityvaries from joint to joint. Some joints haveno movement (as in bones of skull), somehave only slight movement (as in vertebrae)and some are freely morable. Thesemovements are made in any of three planesas explained above. Different terms are usedto describe the movements as explainedbelow.

2. ‘Flexion’ is a movement that takes place ina sagittal plane. It is infact folding of thebones so as they may come nearer. Forexample, flexion of the elbow joint bring theanterior surface of the forearm to the anteriorof the arm. It is usually an anteriormovement but it can be posterior movementalso as in the case of the knee joint.‘Extension’ means unfolding or straighteningthe joint. The movement usually takes placein a posterior direction. However, flexionand extension of trunk takes place in thecoronal plane (lateral).

TERMS RELATED TO MOVEMENTS

Extension Flex ion

Flex ion

Extension

Flex ion

ExtensionShou lder jo in t E lbow join t Knee joint

Flexation and Extension

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3. ‘Abduction’ of a limb is the movement awayfrom the midline of the body in the coronalplane. ‘Adduction’ of a limb is the movementtowards the body in the coronal plane. In

the fingers and toes abduction signifies thespreading of these parts and adductionindicates the drawing together of these parts.

4. ‘Rotation’ is a term applied to the movementof a part of the body around its long axis. Itcan be.

(a) ‘Medial rotation’, which is themovement that takes place in the

Abduction

Adduction

Shoulder Hip Joint Fingers

Abduction

Adduction

Adduction

Abduction

Abduction and Adduction

anterior surface of the part when facingmedially.

(b) ‘Lateral rotation’ is the movement thattakes in the anterior surface of the partfacing laterally.

Medical Rotation of Shoulder Rotation of Shoulder

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(c) ‘Pronation of the forearm’ is medialrotation of the forearm in such a mannerthat the palm faces posteriorly.

(d) ‘Supination of the forearm’, is a lateralrotation of forearm from the pronatedposition so that palm of the hand comesto face anteriorly.

Pronation of Forearm Supination of Forearm

5. ‘Circumduction’, is the combination of fourmovements which is in sequence of themovements of flexion, extension, abductionand adduction.

6. Inversion is the movement of the foot sothat the sole faces in a medial direction whileeversion is the opposite movement of thefoot so that the sole faces in a lateraldirection.

Circumduction of ShoulderJoint

Inversion of Foot Eversion of Foot

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MEDICAL TERMINOLOGY

1. Engineers and technicians working inmedical field have to learn enoughphysiology, anatomy and medicalterminology to be able to discuss problemsintelligently with members of medicalprofession. They face great difficulty in

learning medical terminology. However witha few simple rules, medical terminology, canbe understood more easily. Most medicalwords have been derived from latin andGreek. Most words consist of a root or basewhich is modified by a prefix or suffix orboth. The root is often abbreviated whenthe prefix or suffix is added.

PREFIXES

Prefix Stands for Prefix Stands for

a without or not mat bad

ab away from medio Middlead toward meta beyond

an absence of micro smallante before ortho straight, correct

antero in front para besideoxy containing oxygen

anti against patho disease

bi two peri outsidedia through poly many

dys painful pseudo falseendo within retro backward

epi upon sub beneatheu good supra above

ex away from tachy fastexo outside trans across

hyper overhypo under or less tri threeinfra below ultra beyond

intra within uni single, one

SUFFIXES

Suffix Stands for Suffix Stands for

algia pain emia bloodcenteses puncture iasis a processclasia remedy itis inflammationectasis dilation oma swelling, tumorectomy cut sclerosis hardeningedema swelling

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Roots Stands for Roots Stands for

adon gland gaster stomach

arteria artery haemo/hemo bloodarthros joint hepar liver

branchion arm hydro waterbranchus windpipe larynx throatcardium heart nephros kidney

cephalos brain neuron neuroncolon intestine odynia pain

costa rib os/osteon boneCranium head ren kidney

derma skin spondylos vertebraepithelium intestine stoma mouth

ostium orifice, mouth thorax chestpharynx throat trachea windpipe

phlebos vein vene veinpleura chest vesica bladderpsyche mind

pulmones lungspyelos pelvis

2. Examples of synthesis of words

(a) peri + cardium = pericardium

= outside the heart

(b) an + emia = anemia

= absence of blood

(c) hypo + oxygen = hypoxia

= lack of oxygen

(d) hyper + ventilation = hyperventilation

= over breathing

(e) tachy + cardia = tachycardia

= rapid heart action

(f) intra + venous = Intravenous

= within vein

ROOTS

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(g) Intra + vascular = intravascular

= within blood vessel

(h) arthros + itis = arthritis

= inflamation of joint

(k) hyper + tension = hypertension

= high arterial blood pressure

(l) patho + phobia = pathophobia

= fear of disease

(m) sclero + dermatitis = sclerodermatitis

= hardening of skin

(n) gastroenteritis = gastro + intestine + ities

= inflammation of the mucous membranes of both stomach andintestine

(o) Arteries = Aeir (air) + tercm (to keep).It is a greek word. After death thearteries (blood vessels to take blood toorgans) are usually empty of bloodwhereas the veins (blood vessels totake blood to heart) are full of clottedblood. The ancient concluded from this,that the arteries carried air. Hence thename given to these vessels as arteries.

(p) Robotic = Robota (Slave) + ic (Like).In 1921, Czech dramatist, KARELCAPEK published ROSSUM’sUNIVERSAL ROBOTS. Based on this,the word “robot” has been coined forsomething working as slave. A Robotis any mechanical device operatedautomatically to perform in seeminglyhuman way. Current research effortsfocus on creating a smart robot thatcan hear, touch, taste & consequentlymake decision. Robots do not have to

look like humans and it is functions,not form which matters. Robots havecapability to interact with humans viasynthesised speech. They have visionsensors to identify obstructions, roadblocks and detect motion in theenvironment. They can navigate andmake documentation. They can beprogrammed to make decisions.Robotic intensive care cart is beingused in intensive care unit. Robots canbe used as device to provide technicalaids to the handicapped.

1. In this book many medical words have beenused which are unfamiliar to the readers.The glossary of medical words which willbe used in this book is presented inalphabetical order.

MEDICAL GLOSSARY

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Bifurcation – Branching as in blood vessel.

Bioelectricity – Electrical phenomenon thatappear in living tissue.

Brachial – Relating to the arm or acomparable process.

Bradycardia – A slow heart rate.

Bronchus – Bronchial tubes, (air passage)i.e., two branches of tracheagoing into the right and theleft lungs.

Bundle of His – A small band of cardiacmuscle fibers transmitting thewave of depolarization fromthe atria to the ventriclesduring cardiac contraction.

Capillaries – Smallest vessels of the bloodvascular system connectingarterioles with venulesand forming or networkthroughout.

Cardiac – Pertaining to the heart

Cardiology – The study of the heart aboutits action and diseases

Cardiovascular – Relating to the heart and bloodvessels.

Catheter – A tubular device inserted inany passage of body to keepit open or to inject orwithdraw fluid.

Cell – A smallest living mattercapable of functioning as anindependent unit.

Cerebellum – A part of brain to coordinatemuscle and to maintainequilibrium.

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Anatomy – A study of the structure ofthe body and the relationshipof its constituent parts toeach other.

Alveoli – Air sacs in the lungs formedat the terminals of abronchiole. It is the thinmembrance of the alveoli thatallows oxygen to enter theblood stream.

Aorta – The great trunk artery thatcarries blood from heart to bedistributed by branch arteriesthroughout the body.

Aortic valve – Outlet valve from leftventricle to the aorta.

Arrhythmia – An alteration in rhythm of theheart beat either in time orforce.

Arteriole – One of the small terminalbranch of an artery that endsin capillaries.

Artery – A vessel through which theblood is pumped away fromthe heart.

Atrio ventricular – Located between an atriumand ventricle of the heart.

Atrium – A main chamber of the heartinto which blood returns fromcirculation

Auscultation – The act of listening forsounds in the body.

Axon – A never cell process whichconducts impulse away fromthe cell body of a neuron.

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Collagen – Literally meaning is glueproducing. The major portionof the white fibers ofconnective tissue and bone.

ComputerisedAxial tomography (CAT) : A technique combining

X-ray and computer technol-ogy for visualisation ofinternal organs and bodystructure.

Coronary arteryand sinus – vessels carrying blood to &

from the walls of the heartitself.

Cortex – Outer part of an organ orbody structure.

Cranium – The part of the head thatencloses the brain.

Defibrillation – The correction of rapidirregular contraction of theheart

Diastole – Dilation of the cavities of theheart as they fill with the bood.

Diastolic – Pertaining to the diastole.Diastolic blood pressure islower.

Dicrotic – Second expansion of arterythat occurs during the diastoleof the heart (a dicrotic notchin the blood pressure wave)

Electro cardiogram

(ECG) – A record of the electricalactivity of the heart.

Embryo – An organism in early stagesfrom conception.

Enzyme – A protein secreted by cellsthat acts as a catalyst toinduce chemical changes inother substances and itselfremains unchangedby the process.

Epilepsy – A disorder marked bydisturbed electrical rhythmsof the nervous system.

Fluoroscopy – Process to observe internalstructure by X-ray.

Hemorheology – The science of rheology of theblood, the relation of pressure,flow volume and resistance toblood vessels.

Heparin – An acid in tissue which makethe blood incoaguable.

Hormone – A chemical substance formedin one organ and carried inblood to another organ.Depending on the specialityof their effects, hormonescan alter the functional activityand sometimes structure ofone or more organs.

Hypoxia – Lack of oxygen.

Inferior venacava – Main vein feeding back to the

heart from systemiccirculation below the heart.

In-vivo – In living body chemicalprocess occuring within cell.

Ischemic – A localized anaemia due to anobstructed circulation.

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Isometric – Having same length. A muscleacts isometrically when itapplies force withoutchanging its length.

Isotonic – having same tone. A muscleacts isotonically when itchanges length withoutchanging much the force itexerts.

Korotkoff sounds – Sounds produced by suddenpulsation of blood beingforced through a partiallyoccupied artery and heardduring ausculatory bloodpressure determination.

Latency – Time delay between stimulusand responses

Liver – the largest gland of the bodylying beneath the diaphragm.It is irregular in shape andweight from 3 to 3 ½ poundsor about 1/40 the weight ofthe body. It secretes the bileand it is also of greatimportance in bothcarbohydrate & proteinmetabolism.

Lung – The organ of respiration inwhich aeration of the bloodtakes place.

Membrane – A thin layer of tissue thatcovers a surface or divides aspace or organ

Metabolism – The sum of all the physicaland chemical processes bywhich the living organisedsubstance is produced andmaintained.

Mitral valve – Valve between the left atriumand ventricle of the heart.

Motor – A muscle, nerve or centre thateffects or producesmovement.

Myelin – A fat like substance forminga sheath around certain nervefibers

Myocardium – The walls of the chamber ofthe heart which contain themusculature which actsduring the pumping of blood.

Myograph – An apparatus for recordingthe effects of the muscularcontraction

Necrosis – Death of tissue

Nerve – A cord like structure thatconveys impulse from onepart of the body to another.

Neuron – A nerve cell.

Orthosis – Making straight, thecorrection of maladjustment.

Oxyhaemoglobin – A compound of oxygen andhaemoglobin which is formedin lungs whereby oxygen iscarried through the arteries tothe body tissue.

Pathology – The science and study ofdisease, its causes and cure.

Perfuse – To pour over or through.

Permeate – To pass through the poresPneumograph – The recording of the thoractic

movement or volume changeduring respiration.

Prosthesis – Artificial substitution of amissing or diseased part thelike lower limb.

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Protein – Part of cell and each cell is three-fourth protein.

Pulmonary – Associated with lungsPulse pressure– The difference between systolic

and diastolic blood pressure.

Radioisotope – An isotope that is radioactiveproduced artificially from thebasic element by the action ofneutrons, protons, deutrons oralpha particles in cyclotron bychain reaction. These are usedas tracer with stable element(labeled) by injecting in body tostudy the functioning of organs.

Radiology – The chief X-rays methods usedin the examination of the chestwhich are fluoroscopy,radiography, tomography andbronchography.

Semi lunarpulmonary valve – Outlet valve from the right

ventricle into the pulmonaryartery.

Sinoatrial – The pacemaker of the heart,cardiac muscle which isresponsible for initiating eachcycle.

Sphygmomanometer– Instrument for measuring blood

pressure (arterial).Spirometer – Instrument for measure air

which is entering and leaving thelungs.

Spleen – It is a blood forming organ inearly life. It is storage organ forcorpuscles and because of largenumber of macrophages acts asa blood filter.

Stenusis – Narrowing of a duct or canal.Stroke volume – Amount of blood pumped

during each heartbeat.Superior venacava – Main vein feeding back to the

heart from systemiccirculation above the heart.

Systemic – Pertaining to or affecting thebody as a whole.

Systole – The contraction specially ofventricles during which bloodis forced into the aorta andthe pulmonary trunk.

Tachycardia – Rapid heart action.

Tendon – A fibrous cord or band thatconnects a muscle to a bone.It consists of tissue fasciclesof very densely arrangedalmost parallel collagenousfibres.

Thorax – The part of the body betweenneck and abdomen.

Thrombus – Clotting of blood within ablood vessel

Tissue – Similar cells united in theperformance of a partcularfunction.

Trachea – The main trunk of the systemof tubes by which air goes inor comes out of the lungs.

Tricuspid valve – The valve connecting rightatrium to right ventricle.

Ventricle – A chamber in heart whichreceives blood from atriumand forces it into arteries.

Venule – A small vein.

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1. All organs of the body are formed of tissues.A tissue is a collection of similar type of cells,which are associated with some intercellularmatrix (ground substance) governed bysome laws of growth and development.These cells are adopted to perform the samefunction or functions. Tissues are usuallyclassified into four main categories:

(a) Epithelial tissue

(b) Connective tissue

(c) Muscular tissue

(d) Nervous tissue

2. Epithelium : It is a lining or covering tissue.It is a sheet of cells that cover externalsurface or lines of internal surface of thebody. It can be simple, pseudostratified orstratified epithelium.

3. Connective tissue: It has few cells and alarge amount of non living ground substanceor matrix. It can be:

(a) Connective tissue proper

(b) Skeletal tissue

(c) Fluid connective tissue

4. Connective tissues proper as name suggests,connect and anchor parts and give supportto the body and its organs. For this reason,connective tissue is also known assupporting tissue. Connective tissue andskeletal tissue (cartilage and bone) have toperform mechanical functions.

5. The skeletal tissue includes the cartilages andthe bones which form the structure of thebody skeleton. The bones and cartilages haveconsiderable rigidity. This is a feature whichenables them to act as levers which is ofgreat importance in the movement of limbs.The bones and the cartilages also providesurfaces for the attachment of muscleswhich provide force for the movement.Skeleton also protects the internal organsbesides giving shape to the body. Cartilages

are four types. Hyaline cartilage is boundedby fibrous membrane which is supplied byblood vessels and through it nutritivesubstances diffuse into the cartilage.Cartilage grows by the addition of new layerson the outside. Hyaline cartilage occurs atthe ends of the long bones. It has greatresistance wear and covers the articularsurfaces of nearly all synovial joints. Yellowelastic cartilage has great elasticity due tothe presence of large number of yellowelastic fibers. It is found at the end of thenose and in the pinna of the ear. Calcifiedcartilage has its matrix impregnated withcalcium salts. It is found in the pelvis andat the head of the humerus and femur bones.White fibrous cartilage has a large numberof white fibers. It is found in the discs ofvertebral hyaline cartilage and fibrocartilagefound to calcify or even ossify in later life.Bone is a connective tissue in which thematrix is inpregnated with various saltswhich contribute to about two third of itsweight. Bone is developed by two methods(1) membranous (2) endochondral. In firstmethod the bone is developed directly froma connective tissue membrane. For example,the bones of the vault of the skull aredeveloped rapidly by the membranousmethod in the embryo. In the second, acartilagious model is laid down which isreplaced by bone. The long bones of thelimbs are developed by endochondralossification. Bones have fine canals whichjoin with blood vessels and bone marrow.At birth, the marrow of all the bones of thebody is red and hematopoietic (formingblood cells). The blood forming activitygradually lessens with age and red marrowis replaced by yellow marrow.

6. Fluid connective tissue: Blood is liquidconnective tissue. It is red coloured fluid. Itconsists of liquid portion which is calledplasma and of three different kinds of cellswhich are red blood corpuscles(erythrocytes), white blood corpuscles

HISTOLOGY

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(leucocytes) and platelets (thrombocytes).Plasma is the liquid portion of the blood ofwhich it forms about two-third and containsabout 80% of water. It is almost colourlessclear fluid and contains an everchangingvariety of substances in solution andsuspension. Among the various substancespresent in the plasma are gases, absorbedfood material, inorganic salts, vitamins,metabolic waste products, hormones, antitoxin and a soluble blood protein calledfibrinogen. The cytoplasm of red corpusclescontains a pigment, the haemoglobin whichmakes these cells appear red. In bulk thesecells give blood its red colour. Thehaemoglobin combines readily withoxygen to form an unstable compound,oxyhaemoglobin. In the tissues it breaks upreleasing the oxygen. Here it combines withcarbondioxide to form an unstablecompound, carboxy haemoglobin, whichbreaks up in the lung, releasingcarbondioxide for expiration. Haemoglobin,therefore, transports the gases and as suchplays a vital part in respiration. The redcorpuscles are formed in liver and spleenwhich also destroy the worn out corpuscles.As these are nucleated, they live for a prettylong time. The white blood corpuscles(leucocytes) are small, semitransparent,nucleated and amoeboid cells. These cancrawl out between neighbouring endothelialcells and hence are found in every nook andcorner of the body. At part of body havinginfections, they accumulate in very largenumbers and serve to defend the bodyagainst the disease germs. They are able toeat bacteria and other germs in an amoebalike manner. This process is known asphagocytosis and hence they are known asphagocytes. Some of the WBC are killed bybacterial acids. Thus they may accumulateat the seat of infection as living or deadbacteria, leucocytes and disintegrating cells.All these form a whitish or yellow mass

which is called pus. Leucocytes are alsouseful in transporting waste particles and fatglobules. These are produced in the bonemarrow and lymphatic glands and aredestroyed in the lymph organs.Thrombocytes or platelets contain achemical which plays an important role inthe clotting of blood. The various functionsof blood are :

(a) Transport of gases : RBC combines withoxygen to form oxyhaemoglobin whichbreaks up and release oxygen in tissues.In tissues, RBC combines with carbon-di-oxide to form carboxy haemoglobinwhich breaks up in the lungs to releasecarbondioxide for expiration.

(b) Transport of food material: All theabsorbed food circulated by the bloodtill it is taken up and used by tissue cells.

(c) Transport of substances: Many othersubstances such as enzymes, hormonesand anti toxins are transported by theblood to the places where they arerequired.

(d) Defence against disease: This iseffected in two ways. Firstly the whiteblood corpuscles feed on diseasegerms. Secondly blood possessescertain antioxins which unite chemicallywith toxins and then neutralize them.

(e) Equalization of the body temperature:As the blood circulate throughout thebody, it brings about an equalization ofthe body temperature by transferringheat from one part to another.

(f) Transport of metabolic wastes: Thenitrogenous waste material is carried bythe blood to the liver where it isconverted into urea. The later is nowcarried by the blood to the kidney whereit is removed out along with the urine.

(g) Clotting of blood: Blood has a solublesolution called fibrinogen which isconverted into a mesh work of fine

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threads of insoluble fibrins. In the meshof fibrins, various types of corpusclesget entangled to form a blood clot whichis also known as coagulation. Theconversion of fibrinogen into fibrin isaffected by the action of an enzymecalled thrombin. Free thrombin is notpresent in the blood but it is formed byits precursor (inactive enzymeprothromboplastin) in presence ofcalcium ions. Calcium ions are presentin blood but free thromboplastin isabsent in blood. However it is presentin other solid tissues. Hence when aninjury occurs, thromboplastin isreleased by the injured tissues. Thethromboplastin then acts with calciumupon the prothrombin, changing it tothrombin. The thrombin then acts uponthe fibrinogen and converts it to fibrin.

7. Muscular tissue: It consists of cells in theshape of fibres of different lengths. Inter-cellular elements are almost absent. Themuscular tissues are of three types :

(1) Striped or voluntary

(2) Unstriped or involuntary

(3) Cardiac

The striped muscles are under thecontrol of ‘will’ and they are wide andnontapering. In the striped muscle,fibres are united in parallel bundleswhich is continuous with the connectivetissue sheath surrounding the tendonsthat unite the muscle to the skeleton.Unstriped muscles are made ofelongated, spindle shaped, flattenedfibres which are rarely forked at theends. The number of unstriped musclefibres are united together by a minutequantity of intercelluar substance intoa thin and flat band and a number ofsuch bands are bound together byconnective tissues into a larger bundle.The unstriped muscles are not in thecontrol of ‘will’ and they are found inthe alimentary canal, the lungs and theblood vessels. The cardiac muscles arefound only in the wall of the heart. Thestructure is somewhat inbetweenstriped and unstriped muscles. Thesemuscles contract rhythmically andthese muscles are immune to fatigue.

Nucleus Nucleus

Nucleus

8. Nervous tissue: They consists of

(1) nerve cell

(2) nerve fibre.

Nerve cells are known as neurons.

Each neuron consists of a cell bodyfrom which arises a system ofbranching fibres. The number of fibresis variable. On this basis, neurons areclassified into three types:

Striped Muscle Unstriped Muscle Cardiac Muscle

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(1) neurons with many processes arecalled multipolar.

(2) neurons with two procesess arising atopposite poles are known as bipolar.

(3) neurons having two processes arisingfrom the same pole are known asunipolar. The cytoplasm of each neuroncontain a large and spherical nucleus,large number of dark staining minuteparticles (Nissl Granules) and numerouscytoplasmic strands known asneurofibrillae. Neurofibrillae help in thepassage of the nerve impulse.

PHYSIOLOGICAL SYSTEMS OF THE BODY

1. In our body, we have mechanical, electrical,chemical, thermal, pneumatic, hydraulic andmany other types of system. Each systemcommunicates internally with other systemsof the body and externally it communicates

with surroundings. We have a multi levelcontrol system with its communicationnetwork which organises these internalsystems to perform many complexfunctions. We are able to sustain our livesdue to organised operations of all theseinternal systems and their varioussubsystems. In medical terms, a study ofthe structure of the body and the relationshipof its constituents parts to each other isknown as ‘Anatomy’ while the study offunction of these parts as a system is knownas physiology. The major functionalphysiological systems of the body are:

(a) The cardiovascular system(b) The biochemical system(c) The respiratory system(d) The nervous system(e) The excretory system(f) The locomotor system(g) The digestive system

Communication with Energy and Mass Transfer with Surroundings

Mass (M )2

Solid WasteLiquid WasteExpired airPerspiration

Mass (M )1

Food IntakeLiquid IntakeInspired Air

Energy (E )2

Body movementTactile sensation

Energy (E )1Light visionVibration (hearing)Flow (smell)

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2. The cardiovascular system: Thecardiovascular system is a closed hydraulicsystem. It has heart and blood vessels. Theheart works as a four chamber pump. Theblood vessels are flexible and sometimeselastic tubing of varying sizes. The tubings

Cardiovascular system

Righ t a trium R ight ventric le Pulm onary a rte ry

Left Le ft Pu lm onary Lungsventricle a tr ium ve in

Aorta

change their sizes to control blood pressure,for example arteries and arterioles. Certaintubings act as reservoirs as they can controltheir volume as per the requirements by asystem of valves and variable resistance toflow by constriction and dilation of thecontrol blood tubings. These tubings areveins and they take blood back to heart. Theheart acts as two functionally isolated twostages pumps working in parallel. In firststage of each pump, the blood is taken intothe reservoirs (atriums) from the systemand it is pumped into second stage reservoirs(ventricles). The action of the second stageis so well coordinated that the blood ispumped into the system immediately whenit is received from the first stage. The circuitof the blood is shown in the diagram. Rightside of the heart collects blood from the

hydraulic system through veins and pumpsit to the lungs for oxygenation. The left sideof the heart receives blood from the lungs(oxygenation system), and pumps it intothe main hydraulic system which is formedby the various organs of the body. The heartrate and stroke volume are constantlychanged to control the flow of the blood inthe system to meet the requirements of bodyparts. The blood performs all functions aselaborated in para 25 of this chapter. Theblood flows in laminar manner. Superiorvena cava is a large venous channel whichcollects blood from the upper half of thebody and delivers into the right atrium. Ithas no valve. The inferior vena cava (largerthan superior vena cava) also opens intoright atrium. It returns the blood to the heartfrom the lower half of the body. Since theblood in the inferior vena cava has to flowagainst gravity at times, special one wayvalves are located in it to prevent gravityfrom pulling blood against the direction offlow. The cardiac output flow rate andvolume of the fluid at various places in thebody are important indicators for properfunctioning of the system.

Righ t A trium Left Atrium

Righ t V entricle Left Ventr ic le

To Lungs To A orta

From veins From lungs

Heart Works a Pump

Blood Circuit

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18 FUNDAMENTALS OF BIOMEDICAL ENGINEERING

3. The biochemical system: There are manychemical systems in our body that produceenergy for the functioning of our body. Theenergy is required for growth, bodyfunctions and body repairs. These chemicalsystems are interconnected and these canbe considered as the subsystems of a veryefficient chemical factory. There is a singlepoint intake of fuel (food, water and air) forthis factory which is also source for allchemical reactions which are taking placeinside the body. This chemical factory alsocontains all monitory devices which areessential to carry out necessary control foreach chemical operation. The waste disposalsystem is also a part of this biochemicalsystem.

4. The respiratory system: The respiratorysystem is a pneumatic system which ensuresexchange of gases by a biological processwhich is termed respiration. The bodyrequires oxygen to combine with carbon,hydrogen and other nutrients to produce heatand energy for sustenance of life. The entireprocess of taking inside oxygen fromsurroundings, transporting it to body cells,removing the carbondioxide from the cellsand pushing out the carbondioxide intosurrounding is called respiration. Air entersthe lungs through air passages which includethe nasal cavities, pharynx, larynx, trachea,bronchi and bronchioles. The lungs areelastic bags located in a closed cavity, calledthe thorax. The diaphragm is a special bellshaped muscle located at the bottom of theclosed cavity. When this diaphragmcontracts, thorare is pulled downward,enlarging the closed cavity. The resultantincrease in the volume of the closed cavity,a negative pressure (vacuum) is createdwhich is relieved by air entering the lungsfrom the surroundings. When the diaphragmmoves up and reduces the volume of thethorax, the used air with carbon dioxide ispushed out of the lungs. Oxygen is taken

into the blood from the incoming air in about300 million alveoli present in the lungs. Theoxygen and haemoglobins in blood formoxyhaemoglobins and carbondioxideremoved from the blood is pushed out fromlungs to the surroundings. An automaticcontrol system maintains pneumatic pumpoperation (rate of contraction of diaphragm)at a speed that is adequate to supply oxygenand to remove carbondioxide as required bybody. It is also possible to accelerate ordeacelerate the operation of the pneumaticpump by manual control whenever it isrequired. Automatic control returnswhenever manual control is not applied.

5. The nervous system: The nervous systemconsists of control and communicationnetwork which coordinates the functions ofall parts of the body. The brain is the centralinformation processor and it works as acomputer. It has memory, power tocompute, capability to make decisions andinnumerous input, and output channels forcommunication. These channels formcomplicated networks with manyinterconnections (nodes) which take singnalsfrom a large number of sensory devices(each sensory device detects light, sound,pressure, heat and chemicals) to the brain(computer) for analysis. Some network isagain used to take the output control signalsfrom the brain to the motor units of themuscles to carryout the desired motion orto exert force. The nerves form signal linesto carry signals (informations) generated bythe nerve action potentials (sensory devices)to the brain and same signal lines are usedto carry control signals generated by thebrain for the motor units. In addition to thecontrol of the brain, a large number of simpledecision making devices in the form of spinalreflexes are present in the body to controlindependently some motor devices fromcertain sensory inputs. Example of this is

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INTRODUCTION 19

the Portal system which consist of vein andcapillary network.

6. The excretory system : It consists of allorgans that are responsible for the removalof waste products formed by metabolism inthe organisms. The kidneys are the majorexcretory organs in man. The left kidney islocated at slightly higher level than rightkidney, one on each side of the vertebralcolumn. The kidneys have ‘bean’ shape andthey are also called renes from which it isknown as rent. The renal tubules act as filtersto remove from the blood (1) Excess water(2) Urea and uric acid (3) Excess mineralsalts (4) Yellow pigments from the bile. Themixture of these substances forms urine.When the human kidneys fail to function,the urine accumulates in the blood resultingdeath of the person from toxic poisoning.

7. The locomotor system: The systemprovides locomotion or movement to thebody. Bones and joints play an important rolefor this system. Statics and dynamics of themusculoskeletal system; forces and motionsacting in the skeletal system; forces andmovements within the body; behaviour ofbones, tendons, ligaments and cartilages forstress and strains; and prosthesis design etc.will be covered in details in later chapters.

8. The digestive system: It includes all organsthat help in ingestion, digestion, absorptionand egestion of undigested food. It includesthe alimentary canal and asociated glands likeliver and pancreas etc. The liver is the largestgland in the body. It is located on the rightside, just under the diaphragm. It hasirregular shape and it weighs 3 to 3 ½ pounds(1/40th the weight of the body). It secretesbile juice which plays an important role inmetabolism of both carbohydrate and protein.The nitrogenous waste material is carriedby the blood to the liver where it isconverted into urea. Bile pigments arederived from the breakdown of hemoglobin

from worn out red blood corpuscles. Bilepigments colour undigested food. The otherimportant gland is pancreas which secretedigestive pancreatic juice and discharge itinto intestine. This is done by exocrine partof the pancreas. The endocrine part secreteshormones like insulin. Insulin promotesglucose utilization, protein synthesis and theformation and storage of neutral lipids.Insulin is given to the persons suffering fromdiabetes.

9. Cell, DNA and atoms: Our body possessnumerous cells (almost 10,000 trillion) ofalmost some few hundred varities. Each cellperforms an important role to keep us fit.All activities like standing, walking, talkingand playing are possible through these cells.The cells extract nutrients from food,distribute the energy and remove the wastefrom the body. They also fight againstbecteria and billion of cells die daily in thisprocess.

10. Inside every cells is a nucleus which has 46chromosomes (23 come from father and 23come from mother). Chromosomes carryall instructions necessary for our growth andto maintain us. They contain long strandsof chemical called DNA.

11. In microscopic level, each cell of our bodyis made of atoms. We have in our bodyabout 63% by hydrogen atoms, 25.5%oxygen atoms, 9.5% carbon atoms, 1.5%nitrogen atoms and only 0.5% atoms of otheratoms (Iron, Cobalt, Sodium and Potasiumetc). When we die our atoms will dissembleand move off to form new uses elsewhereas atoms can not be destroyed. Some atomsmay form a part of a flower or other humanbeing or a drop of rain. It is also possiblethat we may be having atoms in our bodywhich once belonged to Budha, Gandhi orNehru.

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12. Cloning: Cloning occurs in nature for simple

organisms (bacteria and viruses) which

reproduce by splitting when their DNA has

replicated itself. Cloning can also be done in

humans and other animals when a single

fertiliged egg divides and separates to form

two or more identical individuals. Gene

cloning is generally done in the laboratory by

means of the polymerisation chain reaction

which enables to reproduce millions of

identical gene in short time. In animal cloning,

the donor's DNA is introduced into egg of

another animal of same species after egg's

DNA has been removed. The egg is then

inserted into surrogate animal's womb and

pregnancy procceds as normal. Another

genetic advancement is the creation of

transgenic animals which can be used for the

production of human compatible organs such

as hearts. Pigs are being used for this purpose.

Egg Donor

Egg Donor

Ce ll w ith DNA only

Ce ll m ultip liesproducing an embryo

Ce ll and egg arefused toge ther

Em bryoim p lanted in to

surrogate anima l

Egg w ithou t DNA

Cloning of Animal

Desired gene of DNA (Hum an)

Iden tification Free ing G ene G ene in jection

Creating Transgenic Animal

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Fill up the gaps

1. The body is made up of the head, ______and limbs. ((a) arms (b) trunks)

2. The vertebral column is _______axis oftrunk. ((a) central (b) middle)

3. The upper limbs by the sides of the trunk is_______ position ((a) erect (b) anatomical)

4. Sagittal plane is parallel to _______ plane.((a) median (b) lateral)

5. Horizontal plane is also known as ________plane. ((a) median (b) transverse)

6. The adjective medial means ______ to medianplane. ((a) nearer (b) farther)

7. The adjective radial and ‘ulnar’ can be usedinstead of ______. ((a) medial and lateral(b) lateral and medial)

8. The terms ‘anterior’ and ‘posterior’ are usedto indicate _______ of the body respectively.((a) back and front (b) front and back)

9. Nose is _______ to the ears. ((a) anterior(b) posterior)

10. The term ‘palmer’ and ‘dorsal’ surfaces ofthe hand. ((a) anterior and posterior (b)posterior and anterior)

11. The arm is ______ to the forearm. ((a) distal(b) proximal)

12. The mouth is _______ to the nose. ((a)superior (b) infevior)

13. If a person is lying, them he is in ________position. ((a) supine (b) prone)

14. Flexion is the _______ of the bones andextension is _______ of the bones. ((a)unfolding, folding (b) folding, unfolding)

15. Flexion and extension of trunk takes placein the ________ plane. ((a) medial (b)lateral)

16. ________ of the limb is the movement awayfrom the midline of the body in the coronal

OBJECTIVE TYPE QUESTIONS

plane while _____ of the limb is themovement towards the body in the coronalplane. ((a) adduction, abduction (b)abduction, adduction)

17. Rotation is a term applied to the movementof a part of the body around its _______axis. ((a) central (b) long)

18. ________ is the movement of the foot sothat the sole faces in medial direction while______ is the opposite movement so thatthe sole faces in a lateral direction. ((a)Eversion, Inversion (b) Inversion, Eversion)

19. Blood is ______ tissue. ((a) Epithelial (b)Connective)

20. ______ tissue has to perform mechanicalfunction. ((a) skeletal (b) fluid connective)

21. All organs of the body are formed of ______.((a) flesh (b) tissue)

22. Tissue is a collection of similar type of_____. ((a) fibres (b) cells)

23. Epithelium is ______ tissue. ((a) covering(b) connecting)

24. Cartilages and bones are _____ tissues. ((a)supporting (b) skeletal)

25. Blood consists of liquid portion (plasma) and______ different kinds of cells. ((a) two(b) three)

26. The haemoglobin is the pigment in ______corpuscles which makes the blood red.((a) erythrocytes (b) leucocytes)

27. Transport of gases (oxygen and carbondioxide) is done by _____ of RBC (Red bloodcorpuscles). ((a) haemoglobin (b) platelets)

28. The haemoglobin combines with oxygen toform oxyhaemoglobin in ______. ((a)lungs(b) tissues)

29. The haemoglobin combines with carbondioxides to form carboxy haemoglobin in_______. ((a) lungs (b) tissues)

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ANSWERS

30. The corpuscles which are able to eat bacteriaand other germs so as to defend the bodyagainst disease are ______.((a) RBC (b)WBC

31. The clotting of blood is done by ____. ((a)thrombocyctes (b) leucocytes)

32. Striped muscle tissues are _____ the controlof ‘will’. ((a) under (b) not under)

33. The muscles of joints are ______ muscles.((a) striped (b) unstriped)

34. The alimentary canal, the lungs and the bloodvessels have _____ muscles. ((a) unstriped(b) striped)

35. The ______ muscle is found only in the wallof heart. ((a) unstriped (b) cardiac)

36. The study of the parts of the body is ____and the function of the parts is _____. ((a) physiology, anatomy (b) anatomy,physiology)

37. The vascular system is a closed _____system. ((a) hydraulic (b) pressure)

38. The heart works as ____ chambers pump.((a) two (b) four)

39. The heart can be considered as _____ stagespumps. ((a) two (b) four)

40. The respiratory system is a ____ system.((a) air (b) pneumatic)

41. The ______ is the central informationprocessor of the nervous system. ((a) motorunits (b) brain)

42. The _____ is the major organ of theexcretory system. ((a) liver (b) kidney)

43. The filtering of the blood for removal ofwastage is done in ____. ((a) liver (b)kidney)

44. The digestive system includes ____ andassociated glands. ((a) stomach (b)alimentary canal)

45. The digestive pancreatic juice and insulin issecreted by _____. ((a) liver (b) pancreas)

46. Red blood cells are formed in the ______.((a) liver (b) bone marrow)

47. The valves are found in only _____ ((a) artery(b) vein)

48. Artery takes the blood _____ and vein takesthe blood _____ the heart. ((a) away,towards (b) towards, away)

49. A portal system is ______. ((a) vein (b) veinand capillary network)

50. An artery has ______ wall than a vein. ((a)thicker (b) thinner)

1. (b) 2. (a) 3. (b) 4. (a) 5. (b) 6. (a) 7. (b) 8. (b)

9. (a) 10. (a) 11. (b) 12. (b) 13. (a) 14. (b) 15. (b) 16. (b)

17. (b) 18. (b) 19. (b) 20. (a) 21. (b) 22. (b) 23. (a) 24. (b)

25. (b) 26. (a) 27. (a) 28. (a) 29. (b) 30. (b) 31. (a) 32. (a)

33. (a) 34. (a) 35. (b) 36. (b) 37. (a) 38. (b) 39. (a) 40. (b)

41. (b) 42. (b) 43. (b) 44. (b) 45. (b) 46. (b) 47. (b) 48. (a)

49. (b) 50. (a)

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Difficult we shall do now, Impossible we shall take afterwards.

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INTRODUCTION

1. Physics is the study of nature and law.Nature governs with laws and to explain thelaws, the science of physics is developed.Physics is concerned with the basic ruleswhich are applicable to all objects whetherinnert or living. Therefore understanding ofphysics helps us to apply these laws in thestudy of bio and medical sciences. No onehas been given authority to frame the lawsof physics. These laws were discoveredwhile observing the events happening innature. A falling apple from a tree gaveNewton an idea of law of gravitation.Mathematics has given us a concept ofinduction and deduction reasoning. When aperson makes observations or experimentsand on their basis, reaches a conclusion,then it is said to be inductive reasoning.Deductive reasoning on other hand, proceedsfrom assumptions rather than observations.It is usually by inductive reasoning thatmathematical results are discovered whilethey are proved by deductive reasoning.

1. Mechanics is a science which deals with thestate of rest or the state of motion of bodyunder the action of forces. The applicationof this science to actual problems is calledapplied mechanics. Statics is the branch ofmechanics which relates to bodies at rest.Dynamics is the other branch of mechanicswhich deals with bodies in motion. Theanalysis of force system on bodies is basedon some of basic laws which arefundamental laws of mechanics. First lawof motion states that a body tends to stay instate of rest or of uniform motion unless anexternal force is applied. Second law ofmotion states that the rate of change ofmomentum of a body is directly proportionalto the applied force and in same directioni.e., force = mass × acceleration.Third lawof motion states that for every action, thereis an equal and opposite reaction.

2. If all the forces in a system lie in single plane,then it is called a coplanar force system. Ifthe line of action of all forces lie along a

MECHANICS

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single line, then it is called a collinear forcesystem. If all forces pass through a singlepoint, it is called a concurrent force system.

3. Moment of a force about a point is themeasure of its rotational effect. It is theproduct of the magnitude of the force andthe perpendicular distance of the point fromthe line of action of the force. The pointfrom where the moment taken is called“moment centre” and the perpendiculardistance of the point from the line of actionof the force is called “moment arm”

4. Forces on a body can be applied forces andnon applied forces. Non applied forces areself weight and reactions. Self weight alwaysact vertically downward and it is equal tothe product of mass and gravitationalacceleration. Reactions are self adjustingforces developed by other bodies or surfaceswhich are equal and opposite to forces(actions) exerted by the body. For smoothcontact, the direction of reaction is normalto the surface of contact.

5. Free body diagram of a body is a diagram inwhich the body under consideration is freedfrom all the contact surfaces with reactionforces and diagram of the body is shownwith applied forces and reaction forces atpoints where body was making contact withother surfaces. Reaction at joints andmuscles forces are worked out by drawingfree body diagrams.

T = T en sio n R = R e ac tio n m g = w eigh t

F re e B o dy

D ia gra m

T

R

m g

6. A body is said to be in equilibrium under asystem of coplanar forces if ΣPx = 0 andΣPy = 0. The resultant of coplanarconcurrent forces not in equilibrium is given

by

R = 2 2( ) ( )px pyΣ + Σand angle of inclination is given by tan–1

y

x

P

P

Σ

Σwhere Σpx and ΣPy are sum of resolved

forces in x and y directions.7. A body is said to be in equilibrium under

coplanar force system if ΣPx = 0,ΣPy = 0 and ΣM = 0. Hence we see that thecondition of equilibrium gives threeequations to find only three unknowns. Asystem of forces is determinate incase it hasthree unknowns only, otherwise it isindeterminate. Lami's theorem of equilibrumcan be applied for three concurrent forces.According to it, the forces are proportionalto sine of the angle between other twoforces.

Hence, 1

23sin

p

α = 2

13sin

p

α = 3

12sin

p

αP 3 P 2

P 1

α13

α23

α12

8. Friction : When a body moves or tends tomove over another body, a force opposingthe motion is developed at contact surface.Friction force = coefficient friction force isalways less than static friction. Friction canbe reduced by lubricating the contactingsurface. Dry surface friction is alwaysgreater than wet surface friction. Frictioncan always be reduced if contact betweenthe surfaces can be avoided by keeping alayer of liquid in between the surfaces.Synovial joints in our body work on sameprinciple.

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–x

+y

a 1a2

y1 y2

o +x

+y

oo

+y

x

–y

x oa1 1x oa2 2

–x o

9. Bending and torsonal stresses: Thebending equation is applicable where shear

force is zero and it is given by M

I=

E

R= y

σ

where M = applied moment, I = moment ofinertia, R = radius and curvature, σ =bending stress, E = Young's modulus and y= layer from centre where bending stress isbeing analysed. Moment of inertia is nothingbut second moment of area or mass.Moment of inertia of a lamina is

(a) Moment of inertia about x – x

=Ix = a1 y21 + a2 y2

2 ..... = Σay2

(b) Moment of inertia about y – y

= Iy = a1x12 + a2x

22 .... = Σax2

(c) Moment of inertia of circular section =

Ixx = Iyy =4

64

(d) Moment of inertia of hollow circularsection

= Ixx = Iyy = 64

π (D4 – d4)

Similarly for pure torsion we can apply

p

T

I =

r

τ =

G

l

θ where T = Torque, Ip = polar

moment of inertia, τ = shear stress r = radius, G =rigidity modulus, l = length and θ = angle of twist.

10. Centre of gravity: The entire mass of abody is assumed to be concentrated at apoint and the force of gravity acts at thispoint which is called the centre of gravity.The centre of gravity of a body is located ata point about which sum of moments ofweights of all its particles is zero. Hence ifthe body is supported at its centre of gravity,the body will remain in rotational equilibriumas the moment of weight of all its particlesabout the point of support will be zero.

y1

y2

ox

y3

x1x2 x3

m 1

m 2

m 3

y

m 1

m 2g

m cg

g CG (Total weigh t=m g + m g + m g)1 2 3

xcg

ycg

Centre of Gravity of Particles

Consider a body with three particles only withmasses as m1 m2 and m3. The moment of threeparticles at point '0' about y – y axis is equal to m1gx1 + m2 g x2 + m3 g x3. Total mass of the body atcentre of gravity (CG) is m1 + m2 + m3 and momentof inertia is equal to (m1 + m2 + m3) g × xcg.

Hence, xcg = 1 1 2 2 3 3

1 2 3

m x m x m x

m m m

+ ++ +

= i i

i

m x

Σ

and ycg = i i

i

m y

Σ. There is another method to find

the centre of gravity by actually balancing the body

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on a knife edge in three planes i.e., median plane,coronal plane and horizontal plane. The point ofbalance will give the line in that plane on which thecentre of gravity of the body is lying.The intersection of these three lines will give theactual centre of gravity of the body from a point inspace. Statistical method can also be used for finding

Horizontal Plane

y

Median Plane

x

z

Coronal plane

the centre of gravity. A man (weight = wm) is lyingsupine on a board (weight = wb) and reaction forceRA and RB are read from the measuring scale. Thelength of board is 'l' and its weight will act at l/2

while weight of the man acts at xcg from point A.The free body diagram of the body is shown in thefigure. Now ΣPy = 0, therefore RA + RB = wm+ wband wm can be found out. Similarly ΣMA = 0,therefore,

2

l × wb + xcg × wm – l × RB = 0, and xcg

can be found out. Similarly ycg and zcg canbe found out.

A B

Board we ight wb

we ighing sca le

W eigh ing sca le

W eigh t o f m an = w m

Aw m

R Aw b

B

R B

xCG

l/2

l11. The centre of gravity of a man depends on

the relative position of his limbs (lower andupper) as compared to the anatomicalposition. Locations of the centre of gravityof upper and lower limbs will changedepending upon their positions which willchange the overall centre of gravity of theman. If knee is flexed backwards, the centreof gravity of leg as well as that of the manwill shift backwards. Smilarly, the centre ofgravity of arm as well as the man shiftsforward if the elbow is flexed. An athleticcan take full advantage by positioning hislimbs so as to shift his centre of gravity ashigh as possible while jumping over the highbar.

Positioning of Limbs toHelp While Jumping

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1. Viscosity : It is defined as the property of afluid which determines its resistance toshearing stresses. It is a measure of internalfluid friction which exerts resistance to flow,It is primarily due to cohesion and molecularmomentum exchange between fluid layerswhich appears as shearing stresses betweenthe moving layers of the fluid when the flowtakes place. An ideal fluid one which has noviscosity. But no fluid is exists which canbe classified as an ideal fluid having zeroviscosity. However fluids with very smallviscosity can be considered as ideal fluids.In the figure, a fluid flow is shown on asolid boundary when two layers are 'dy' apartand moving one over the other with differentvelocities, say 'u' and 'u + du'. The top layercauses a shear stress on the adjacent lowerlayer and this lower layer also cause a shearstress on the layer lower to it and this goeson. According to Newton's law of viscosity,the shear strees (τ) on a fluid element layeris directly proportion to the rate of shear

strain or the rate of change of velocity du

dy

.

dy

y

u

u + du

τ ∝ du

dy

τ =µdu

dy

µ =dynamic viscosity

Solid Boundary

or µ = ( )/du dy

τ =

stress

strainThe viscosity can be defined as shear stress requiredto produce unit rate of shear strain. The unit ofviscosity

= 2

Force × Time

(length)

= 2

Newton Second

(meter)

and one poise = 1/10 Ns/m2. Kinematic viscosity isdefined as the ratio between the dynamic viscosityand density of the fluid.

Hence, v =Viscosity

density =

µρ

and it has unit = 2(metre)

second=

2m

s.

One stoke =10–42m

s. The fluids which

follow Newton's law of viscosity are knownas Newtonian fluid. Hence fluids can beclassified as :

(a) Newtonian fluids : These fluids followNewton's viscosity equation. For suchfluids, µ does not change with rate ofdeformation. Water, kerosene and airare Newtonian fluids.

(b) Non Newtonian fluids : Fluids whichdo not follow the linear relationshipbetween shear stress and rate ofdeformation are termed as nonNewtonian fluids. Solutions,suspensions (slurries), mud flows,polymer solutions and blood areexamples of non Newtonian fluids.These fluids are generally complexmixture and they are studied underrheology (a science of deformation andflow).

(c) Plastic fluid : Non Newtonian fluid inwhich initial yield stress is to be exceededto cause a continuous deformation.

FLUID MECHANICS

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PREFIXES

(d) Ideal fluid : Fluid is incompressible andhas zero viscosity. Stress is zeroregardless of motion of the fluid.

2. Boundary layer: When a real fluid flowspast a solid boundary, the fluid particlesadhere to the boundary and the condition ofno slip occurs. It means that the velocity offluid close to the boundary will be same asthat of the boundary. In case the boundaryis stationary, the fluid velocity at theboundary will be zero. As we move furtheraway from the boundary, the velocity of thefluid will be higher. Due to variation ofvelocity as we move away from theboundary, a velocity gradient (du/dy) willexist. The velocity of the fluid increasesfrom zero velocity on the stationaryboundary to free stream velocity (u) of thefluid in the direction normal to the boundary(y). The theory dealing with boundary layerflow is called boundary layer theory.

Flow Solid B oundary

Boundary Layer

According to this, the flow in theneighbourhood of the solid boundary maybe divided into two regions :

(a) A very thin layer of fluid called theboundary layer is in the immediateneighbourhood of the solid boundarywhere the variation of velocity existsfrom zero at solid boundary to freestream velocity in the direction normalto the boundary. In this region, avelocity gradient = du/dy exists andhence the fluid exerts a shear stress onthe boundary in the direction of flow.τ (shear stress) = µ du/dy where µ =

viscosity.

(b) The velocity of the fluid outside theboundary layer is constant and equal tothe free stream velocity. There is novelocity gradient in this region andhence shear stress is also zero in thisregion.

3. Flow in tube: When a fluid enters a tube/pipe from a large reservoir where thevelocity is uniform and parallel to the axisof the tube (as shown in the figure), thevelocity profile is a flat surface at the entry.Immediately on entry, the fluid velocity invicinity of the surface of the tube is affectedby friction force. However, the velocityprofile far from the surface and near the axisof the tube remains still flat (same as freeflow). As the fluid moves further in the tube,flat portion decreases and some distanceafter, a paraboloidal velocity profile for thefully developed flow is reached. The flowat the inlet and flow beyond point A (regionIII) is called fully developed flow.

I

II

I

III

A

The entry length is defined as the length inwhich 99% of the free flow velocity isattained. The flow in the entry length portionconsists of two parts:

(1) the flow in region I near the tube sur-face is called boundary layer flow.

(2) the flow in the region II is called coreflow (plug flow)

4. Laminar and turbulent flow: The particlesmove in curved unmixing layers or streamsand follow a smooth continuous path in thelaminar flow. The paths of fluid movementare well defined and the fluid particles retain

Boundary Layer

Flow Tube and Entry Length

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their relative positions at successive crosssections of the flow passage in the laminarflow. There is no transverse displacementof fluid particles. Soldiers marching inorderly manner is an analogy to laminar flow.In turbulent flow, the motion of fluidparticles is irregular. The fluid particles movealong erratic and unpredictable paths. Thevelocity of fluid particle fluctuates bothalong the direction of flow and alsoperpendicular to the flow. A crowd ofcommuters on a railway station rushing forboarding a train is an analogy.

The Reynolds numbers is a dimensionlessnumber which is used to predict whetherthe flow is laminar or turbulent in a tube.The Reynold's number = Inertial force/viscous force = ρu2D2/ µuD = ρuD/µ =uDv, where µ = viscosity, v = kinematicviscosity = µ/ρ, ρ = density, u = velocityand D = diameter of tube. If inertia force ismuch higher than viscous force, Reynoldsnumber will be more and less chance forthe flow to be laminar. In a tube, turbulentflow occurs when Reynolds number > 6000.For laminar flow in a tube, following areapplicable:

(a) Strear stress τ = –P

x

∂∂

. 2

r where r =

radius of layer and P

x

∂∂ = Pressure gra-

dient along direction of flow.

(b) Velocity u = – 1

P

x

∂∂ (R2 – r2) where

R = radius of tube, r = radius of layer

(c) Ratio of maximum velocity to averagevelocity = 2

(c) Loss of pressure head = 2

32 µu L

g Dρ

where u = Flow

Area and L = Length of

flow.

5. The tube must have same thickness of the

wall depending upon the pressure of the

fluid. Thickness (t) = p

Pr

σ where P =

pressure, r = radius and pσ = permissible

stress

Radius = r

Th ickness = t

Pressure (p)

6. Equation of continuity and Bernaulli'sequation. The total mass of fluid goinginside the tube through any cross sectionremains same. Therefore the equation ofcontinuity is A1u1 = A2 u2, where A standsfor cross sectional area and u stands forvelocity. As per Bernaulli's equation, the totalhead of the fluid remains constant at everycross section of the tube. The Bernoulli'sequation is

P + 1

2 ρu2 + ρgh = constant where

P = pressure, ρ = density, g = coefficient ofgravity, h = height of cross section from adatum line and u = velocity of the fluid.

7. Applications of Bernaulli's equation. Thespeed of liquid coming out through a hole ina tank at a depth 'h' below the free surfaceis the same as that of a particle falling freelythrough the height 'h' under gravity i.e., u =

2gh . This is known as Torricelli's

theorem. When a person is bleeding, we tryto reduce 'h' so that blood flow can bereduced. Other application is Aspirator pumpwhich works on the principle that thepressure of fluid decreases where ever itsspeed increases. As shown in the figure, theair is pushed through a narrow opening at

Thin Tube

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'A' resulting in drop of pressure. The liquidin the bowl is raised by the pressure dropand liquid is sprayed with the expelled air. Acricket ball having a shining side and rougha side on the left and right as shown in thefigure will deviate towards the shining sideas air passing over the shining side will faceless resistance and gain more speed resultingin lower pressure as compared to the roughside. Similarly, an aerofoil has longerdistance at the top surface as compared tothe bottom surface which makes the airmove at higher speed at the top surface ascompared to the bottom surface resulting inlower pressure at top the surface and higherpressure at the bottom surface whichprovides a lift to the aerofoil. A venturi tubeis used to measure the flow of speed of afluid in a tube. The tube has a constriction(throat) which makes the fluid flow at higherspeed resulting in drop of pressure at throat.The pressure P1 – P2 = ρg (h1 – h2) asshown in the figure. Alsov2

2 – v12 = 2g(h1 – h2) where v1 and v2 are

velocities. Knowing A1and A2 (areas), therate of flow of liquid past a cross-sectioncan be found out.

u

h

u = 2gh

Deviation

Sh in ing Rough

v1 v2

v > v1 2

Cricket ball

A Liqu id spray

bow l

Venturi Tube

Constriction

P 1

v1

h 1

P 2

v2

h 2

h – h1 2

v1

L ift

v > v1 2

v2

8. Pascal's law : If the pressure in a liquid ischanged at particular point, the change istransmitted to the entire liquid without beingdiminished in magnitude. Pascal's law hasseveral applications like hydraulic lift andreaction force at the joints of our body asshown in the figure.

F

A 1

W

A 2

P A = F1 1

P A = W1 2

P = P RESSURE CO NSTANT1

Area A >> A 2 1 W >> F

Torricell's Theorem

Aspirator Pump

Aerofoil

Hydraulic Lift

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Reaction Force at Joint

Reaction R is always vertical due to

uniform flu id p ressure

FB D

Fluid

R

9. Gauge pressure : The standard atmosphericpresure is defined as the pressure producedby a column of mercury of 760 mm high.Hence Patm = ρgh = (13.6 × 103) × 9.8 ×

760

1000 = 1.01 × 105 pascal = 1.01 bar.

Pressure of the vessel can be higher or lowerthan atmospheric pressure. Pressure ismeasured by a manometer. Manometer is aU-tube with one end opens to atmosphereand other is connected to vessel.

P abe

P atm

hgh v

P = P + G auge P r

= P + × h × g W here h = he ight

abs

g

atm

atm HG gρ

P = P – Vacuum Pr = P – × h × g where h = vacuum heigh t

abs

v

atm

atm HG vρ

P abs

P atm

If pressure in vessel (Pabs) is lower thanPatm, mercury is forced into the limbconnected to vessel. Higher thanatmospheric pressure is known as gaugepressure while lower pressure thanatmospheric pressure is called vacuumpressure. The flow in cardiovascular systemis higher than atmospheric pressure and flowat various places is given by gauge pressureonly. The blood pressure of a healthy personis 120/80mm Hg (gauge pressure) duringsystole/diastole.

1. Temperature is an intensive property of asystem (intensive property does not dependupon mass) and indicates relative hotnessor coldness from the reference states.Boiling point and freezing point of waterare acceptable reference states.Thermometer is a temperaturemeasurement system which can show somechange in its characteristics (termed asthermometric property) due to heatinteraction taking place with the body whosetemperature is being measured.Temperature is measured either incentrigrade or fahrenheit for human body.The relation between these two

thermometers is 100

cT=

– 32

180fT

where Tc =

temperature in centrigrade, and Tf =temperature in fahrenheit. Boththeromometers are mercury scalethermometers in which length of mercurycolumn is proportion a to temperature ofthe body. The normal oral (mouth)temperature of a healthy person is about37°C or 98.6°F. The underarm temperatureis one degree lower, whereas the rectaltemperature is one degree higher than thatof oral temperature. The temperaure ofbody is controlled by the body so that itremains constant as 37°C. However duringfever, the temperature of body increasesas temperature control mechanism fails,thus causing additional metabolism becausehigher temperature inside the bodyaccelerates the chemical reactions. Duringfever, shivering takes place as the blooddoes not flow to skin and muscle tissueswhich is essential to keep them warm.When body temperature falls to normaltemperature, increased sweating takesplace as additional heat is eliminated.

TEMPERATURE

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Fill up the gaps1. Static is the branch of mechanics which

relates to bodies in _____. ((a) rest (b)motion)

2. If all the forces in a system lie in single plane,then it is called a ____ force system. ((a)coplanar (b) concurrent)

3. If all the forces in a system pass through apoint it is called a _____ force system. ((a)coplanar (b) concurrent)

4. Lami's theorem can be applied for three_____ force system. ((a) coplanar (b)concurrent)

5. The condition of equilibrium in a coplanarforce system gives ____ equations. ((a)Three (b) two)

6. The fluids which follows T = µ du/dy arecalled _____ fluids. ((a) Ideal (b)Nowtonian)

7. Blood is a _____ fluid. ((a) Newtonian (b)non Newtonian)

OBJECTIVE TYPE QUESTIONS

8. Ideal fluid has _______ viscosity. ((a) unit(b) zero)

9. The ratio of Inertia force and viscous forceis ______ number. ((a) Rayleigh (b)Reynold)

10. Turbulent flow has _____ value of Reynoldnumber. ((a) lower (b) higher)

11. The _____ is used for measuring gauge orvacuum pressure. ((a) manometer (b)pressure meter)

12. The blood pressure is always given in _____.((a) gauge height (b) vacuum height)

13. P + ½ ρu2 + ρgh = constant is known as______ equation. ((a) hydraulic (b) Bernoulli)

14. A1u1 = A1 u2 wher A = area and u = velocityis known as ______equation. ((a) continuity(b) constant)

15.M

I =

E

R = y

σ is called _____equation. ((a)

Bending moment (b) Torsion)

ANSWERS

1. (a) 2. (a) 3. (b) 4. (b) 5. (a)6. (b) 7. (b) 8. (b) 9. (b) 10. (b)

11. (a) 12. (a) 13. (b) 14. (a) 15. (a)

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1. Prefix “bio” denotes something connectedwith life. When basic science of physics andchemistry have been applied to living things,this intermarriage has been named asbiophysics and biochemistry. Hence,marriage of discipline of medicine andengineering is called biomedical engineering.The aim of biomedical engineering is theapplication of the methodology andtechnology of physical sciences andengineering to the problem of the livingsystems with emphasis on diagnosis,treatment and prevention of diseases in man.

2. Access to adequate health care is comparableto the fundamental rights of a human being.The view has led to the development of largeand sophisticated health care systems. Thecomponents of health care include preventivemedicine, diagnosis, therapy andrehabilitation. The critical element in thischain is diagnosis. Once a physician makesa diagnosis and institutes therapy, diagnosticprocedures are used then to monitor therapyand to assess its adequacy to maintain ormodify the therapy. High technology medicalequipments are being introduced in healthcare industry as this industry is growing at

fast rate. High technology equipmentsnormally require more skills. To control thecorrect functioning of these equipments, onehas to understand its basic operatingprinciples and be able to apply someperformance assurance tests for thatpurpose. The physicians utilizing the resultsproduced with these equipments need tounderstand the limitation of the technology.Hence physicians and biomedical engineerscan not work in isolation.

1. Science and technology are evolving rapidly.This creates the potential for applying theseinnovations also to health care products.Improved and cheaper version of old medicalequipment and new equipment have beenemerging as a consequence of this. Advancedmedical equipment mean innovativeproducts which may be technologicallysimple or complicated. Examples of theseinclude :

(a) Artificial organs, such as heart valves,hip joints and implanted pacemakers.More research in medical science toensure reliability and durability.

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Good things come to those who wait, but better things come to those who try.

INTRODUCTION

ADVANCED MEDICAL EQUIPMENT ANDSYSTEMS

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(b) Patient-monitoring equipment which usesophisticated transducers together withmicroelectronics, microprocessor andsoftware for processing the measuredsignals.

(c) Information system for patient datamanagement and for decision supportintegrating various sources of patientdata and incorporating knowledgebased techniques (artificial intelligence,expert system) for the interpretation ofthe compiled data.

(d) Imaging of the anatomy and functionsof the human body. The technology forobtaining and storing the images ischanging from film to digital integra-tion of the various image sources with“picture archiving and communicatingsystem” (PACs) and image processingstations is the present practice.

(e) Automated laboratory equipment for theprocessing of patient samples (blood,urine etc). It has cut down the cost bymaking tests simpler, accurate andfaster. Information systems areextensively used to manage the process,for quality control and for producinglaboratory reports, for archiving or fordisplay to treating physicians.

(f) Technical aids for the handicapped (andfor the elderly) comprising both simpleand complex devices. Development ininformation technology and in robotics,have opened up new possibilities toprovide technical aids to thehandicapped both at home and at work.(More on robotic refer chapter1)

1. The effective utilization of high technologyequipment and systems necessitates thetechnical expertise of clinical engineers,hospital physicists and computer scientists.

The efficient and cost effective utilizationof a new technology also requires carefulplanning in organisation and ways ofoperation. Any new equipment introducedwould require engineers to operate and tomaintain it. Regular service and regularpreventive maintenance combined withperformance assurance procedure is morecost effective. The installation of newequipment can be expensive in terms of bothactual purchasing and installation costs; andadditional technical staff requirements tooperate and maintain.

1. As name suggests, biomedical engineeringis interaction of medicine and engineeringHence biomedical engineering can be definedas application of the knowledge gained by across fertilization of engineering and thebiological sciences so that both will be morefully utilized for the benefit of man.

1. The field of biomedical engineering is everexpanding as new engineering applicationsin medical field are emerging. A tendencyhas been seen to describe the personnelworking in different speciality areas of bioengineering with the name of the area. Atendency has arisen to call the biomedicalengineer as person working in the interfacearea of medicine and engineering whereasthe practitioner working with physician andpatient is called a clinical engineer. Similarlytitles of hospital engineer, medical engineer,bioinstrumentation engineer, biomaterialengineer and rehabilitation engineer are beingused depending upon personnel working indifferent speciality areas of biomedicalengineering. Speciality areas are :(a) B i o i n s t r u m e n t a t i o n : I t i m p l i e s

measurements of biological variableswhich help the physicians in diagnosing

BIOMEDICAL ENGINEERING

SPECIALITY AREA OF BIOMEDICALENGINEERING

REQUIREMENT FOR ADVANCEDMEDICAL EQUIPMENT

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and treatment. For the measurement ofbiological variables, applications ofelectronics and measurement techniquesnecessitate understanding andknowledge to operate the devices. Inorder to handle data, computers areessential part of bioinstrumentation.Large amount of information in medicalimaging system can be processed by acomputer.

(b) Clinical engineering: It is application ofengineering knowledge to health care inhospitals.Clinical engineer withphysician, nurses and other staff form ahealth care team so that health carefacilities (patient monitoring equipment,diagnosing equipment, technical aidsfor the handicapped) can be effectivelyutilised and computer data base can bemaintained.

(c) Biomaterial engineering: Bomaterialsinclude both living tissues and artificialdeveloped materials which are suitablefor implantation. Materials can be metalalloys, ceramics and polymers whichmust be chemically inert, stable andmechanically strong to withstand therepeated forces for a lifetime.

(d) Cellular, tissue and genetics engineering:With advancement in biomedical field, itis possible to tackle the biomedicalproblems at microscopic and nenoscopiclevel. The anatomy biochemistry andmechanics of cellular and subcellularstructure are studied to understanddisease process and to find out suitabletherapy to overcome malfunctioning.

(e) Medical imaging engineering: There aremany techniques to generate the imageof organs inside the body. Various raysand radiations like ultrasound, X-rays andnuclear radiation with physicalphenomenons like magnetism, sound,fluorescence and reactions onphotographic film, can be used togenerate or display internal image of thebody. These images can be digitized so

that data can be handled by the computer.(f) Rehabilitation engineering: Rehabilita-

tion relates to both handicapped andelderly persons. Rehabilitation engineer-ing aims to enhance the capabilities andto improve the quality of life of per-sonnel having physical and cognitiveimpairment. The development of pros-thesis for amputees, provision of properwheel chair to paraplegic which per-mits regular exercise for fitness so thatregular assessment of the functionalcapacity can be made and assistive de-vices for elderly persons are some ofthe contributions of rehabilitationengineering.

(g) Orthopadic biochemistry: It is the fieldin which malfunctioning of bones,muscles and joints is studied so thatartificial joints for replacement can bedesigned.

(b) System physiology: It is the field in whichengineering techniques and tools are usedto gather a comprehensive understandingof the function of living organismsranging from bacteria to human body.Computer is used to model physiologicalsystems for analysis and understanding.

2. Biomedical engineer is a professional whohas expertise both in biological sciences andengineering field so as to effectively andsafely manage medical devices andinstruments, for an overall enhancement ofhealth care. He can use engineeringexpertise to analyse and solve problems inbiology and medicine providing an overallimprovement of health care. Otherdefinitions by various committes are :

(a) A clinical engineer is a professional whobrings to health care facilities a level ofeducation, experience and accomplish-ment which will enable him toresponsibly, effectively and safelymanage and interface with medicaldevices, instruments and systems and

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the use of these for patient care,because of high level of competenceand responsibly. He can directly servethe patient, physician, nurse, and otherhealth care professionals to use of themedical instrumentations.

(b) Biomedical engineer is a person workingin research or development in theinterface area of medicine andengineering whereas the practitionerworking with physician and patient iscalled a clinical engineer.

(c) Biomedical engineer is a professionalwho applies knowledge gained by across fertilization of engineering and thebiological sciences so that both will bemore fully utilized for the benefit of man.

(d) A biomedical equipment technician is anindividual who is knowledgeable aboutthe theory of operation, the underlyingphysiologic principles, and the practical,safe clinical applicaton of biomedicalequipment. His capabilities may includeinstallation, calibration, inspection,preventive maintenance and repair ofgeneral biomedical and related technicalequipment as well as operation orsupervision of equipment control, safetyand maintenance programmes andsystems.

3. With the need of sophisticated health caresystem and advent of advanced medicalequipment, there is a growing demand ofbiomedical engineers. There is a growingdemand for them in these places:

(a) In hospital as clinical engineer

(b) In industry involving manufacturingbiomedical equipment

(c) In research facilities of educationalmedical institutions.

(d) In government regulatory system forproduct testing and safety

(e) In performance testing of a newproduct or existing product in hospital

(f) In establishing safe standards fordevices

(g) In managerial position as technicaladvisor in marketing department

(h) In creating design to understand livingsystem and technology

(j) In coordinating and interfacing functionusing background in engineering as wellas medical field

(k) In university and in teaching institutions.Biomedical engineers can effectivelysupervise laboratories and equipment inresearch institutions

OBJECTIVE TYPE QUESTIONS

Fill up the gaps1. Access to adequate health care is comparable

to the ________ right (a) fundamental (b)human

2. High _________ medical equipment arebeing introduced in health care industry (a)finish (b) technology

3. Proper working of the equipment is indicated

by performance ______ tests (a) assurance(b) quality

4. Marriage of discipline of medicine andengineering is called _________ (a) medicalengineering (b) biomedical engineering

5. Bioinstrumentation measures ______variable (a) physical (b) biological

6. Biomaterial are used for _________(a) implantation (b) instruments

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7. Preventive medicine, diagnosis, therapy andrehabilitation are the components of________ (a) medicine (b) health care

8. High technology equipments normallyrequire more _________ (a) skill (b) men

9. Physicians and biomedical engineers_________ work in isolation (a) can (b)cannot

10. Information system integrate patient data and________ based techniques for the

ANSWERS

interpretation of the compiled data (a)knowledge (b) technical

11. Storage of images is changing from film to_______ (a) digital (b) written

12. Development in _______ has opened up newpossibilities to provide technical aids tohandicapped both at home and at work (a)robotics (b) treatment

13. Total cost of new equipment include bothequipment cost and cost of ________(a)technical staff (b) additional technical staff

1. (a) 2. (b) 3. (a) 4. (b) 5. (b)6. (a) 7. (b) 8. (a) 9. (b) 10. (a)

11. (a) 12. (a) 13. (b)

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To see and understand the big picture, You've got to meet the master painter

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1. Bone is a living tissue capable of altering itsshape and mechanical behaviour by changingits structure to withstand the stresses towhich it is subjected. Bones form the body'shard, strong skeletal framework. Each bonehas a hard, compact exterior surrounding aspongy, lighter interior. Long bone has acentral cavity containg bone marrow. Boneis composed chiefly of calcium,phosphorous and a fibrous substancecollagen.Like other connective tissues, it hascells fibres and ground substance (for moredetails refer chapter1). It has also inorganicsubstances in the form of mineral salts whichcontribute about two third of its weight. Asexplained earlier, bone is developed by twomethods viz membranous and endochondral.Bone is the primary structural element ofthe human body. Bones form the buildingblocks of the skeletal system (see the figure)which protects the internal organs, provideskinematic links, provides muscle attachmentsites, and facilitates muscle actions and bodymovements. Bone is hard due to presenceof inorganic substances but it has a degreeof elasticity due to the presence of organicfibres. Since bone is a living tissue, it can

INTRODUCTION repair itself if it is properly aligned afterfracture. The major factors that decides thestress bearing capacities of bone are:

1. The composition of bone.

2. The mechanical properties of the tissuescomprising the bone.

3. The size and geometry of the bone,

4. The rate of applied loads with magnitudeand direction.

1. The skeleton is made of 206 bones. Althoughindividual bones are rigid but the skeleton isflexible and allows the human body a hugerange of movement. Bones can be classifiedas per their shapes as :

1. long and short bones

2. irregular bones

3. flat bones and

4. sesamoid bones

The locations of these types of bones are:(a) Long and short bones: They are in the

limbs. For examples, humerus in upperarm, radius and ulna in forearm;femur, tibia and fibula in lower limbare long bones while metacarpal and

CLASSIFICATION OF BONES

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metatarsal bones of hand and footrespectively are small bones (refer tofigure of skeleton)

(b) Flat and irregular bones are in the skull,back bone and the limb girdles.

(c) Sesamoid bone is buried in the tendon

and free surface is covered witharticular cartilage. It has two functions(1) to reduce friction when it rubs overbony surface, (2) to alter the pull oftendon to which it is attached. Thelargest sesamoid bone is ‘patella’ of theknee joint.

Cranium

Clavicle

Thoracic cage

Sternum

Ribs

Vertebral column

Humerus

Ulna

Radius

Carpal bonesMetacarpal

bonesPhalanges

Femur

PatellaTibia

Fibula

Tarsal bonesMetatarsal bones

Phalanges

Pelvis

Cranium

CervicalVertebrae

Scapula

Ribs

ThoracicVertebrae

Lumbar vertebraInnominate

boneSacrum

Coccyx

Femur

PatellaTibia

Fibula

Tarsal bonesCalcaneus

Metatarsal bonesPhalanges

Anterior View Lateral ViewSk l l S

Neck

Head

Trunk

Limb

Skeletal System

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1. All organs of the body are formed of tissues.A tissue is a collection of similar type of cellswhich are associated with some intercellularmatrix (ground substance) governed bysome laws of growth & development. Boneis made of connective tissue. Bone bindstogether various structures of the body. Boneis a composite material with various solidand fluid substances, besides cells, anorganic mineral matrix of fibres and aground substance, it has inorganicsubstances in the form of mineral salts whichmake it hard and relatively rigid. However,organic components provide flexibility andresilience. The density and composition ofbone varies with age and disease whichresults into degrading of mechanicalproperties.

2. The bones consist of two types of tissuesas shown in ‘cut section view’. The compactbone tissue is a dense material forming theouter shell of bones and the diaphyscal regionof long bones. The outer shell is calledcortical. The other tissue consists of thinplates (trabeculae) in a loose mesh which is

Diaphyscal Region

Periosteum (outer membrane)

Cortical

Cancellous

Endosteum (membrane forbone marrow)

enclosed by the cortical bone tissue. This iscalled cancellous, trabecular or spongy bonetissue. A dense fibrous membrane surroundsthe bone and it is called periosteum(epithelium tissue as explained in chapter 1)the periosteum membrane covers the entirebone except the joint surfaces which arecovered with articular cartilage. It is themost sensitive part of the bone.

1. Material can be homogeneous or non-homogeneous. Homogenous material hassame composition in all directions. Bone is anon homogeneous material as it has differentcompositions in different directions as itconsists of various cells, organic and inorganicsubstances laid in uniform manner. Materialcan be isotropic having mechanical propertiessame in all directions or anisotropic withmechanical properties different in differentdirections. Bone is anisotropic material as itsmechanical response depends upon thedirection of the applied load. For examplecompressive strength is more than tensilestrength and tensile load capacity is more thantransverse load capacity of the bone. Bonehas both liquid and solid constituent, hence ithas viscoelastic properties which is timedependent i.e., the mechanical response ofthe bone is dependent on the rate of loadingof the bone. Bone can stand rapidly appliedloads much better than gradually appliedloads.

2. Mechanical properties of metals, concreteand polymers are found out by testing thespecimen under tensile, compression andbending load by universal testing machineand torsional load by torsion testing machine.Similar tests can be performed on bonespecimen for bulk properties. It can also beperformed separately for cortical andcancellous part of the bone.

3. The stress and strain diagram for the corticalbone under tensile loading is shown in thefigure. The stress and strain diagram has

COMPOSITION OF BONE

Cut Sectional View of Bone

MECHANICAL PROPERTIES OF BONE

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three distinct regions. The part ‘OA’ is elasticregion and the slope of this line is equal tothe elastic modulus (E) of the bone whichis 17 GPa (109 pascal). In the intermediateregion (AB), the bone exhibits non linearelasto-plastic material behaviour. Now thebone does not retains its original length onremoval of load (possible in region OA) anda permanent yielding takes place. On removal

O.010 .020 .030

50

100

128

150

Str

ess

: (M

pa) A

B

C

Perm anentstra in

0

Strain :

of load, the specimen follows path BO’instead BAO and there is a permanent strainof OO′. On loading the specimen will nowfollow path O′B which amounts to higherstrength. This is known as strain hardening.The bone exhibits a linearly plastic materialbehaviour in region BC after yield strength(Point B). The bone fractures when tensilestress is about 128 MPa (106 Pascal) forwhich the tensile strain is about 0.020. Thestress and strain diagram of the cortical bonedepends upon strain rate and the diagram isdrawn for the strain rate of 0.05 per second.It has been seen that a specimen of bonewhich is loaded rapidly, has a greater elasticmodulus and ultimate strength than aspecimen which is loaded slowly. This hasbeen shown in the figure. We also know that

Stress and Strain of Cortical Bone: Tensile Loading

resilience energy is the area under the stressand strain diagram. Hence absorbed energyincreases with rapidly loading. It has beenseen that bone tissues are subjected to astrain rate of about 0.01 per sec duringnormal activities.

Fast and Slow Loading

Resilience Energy = Area Under

Curve

Area I > Area II

Stress

Fast Loading

Slow Loading

Strain

I

II

4. Bone is an anisotropic material. Hence itsstress-strain behaviour depends upon theorientation of bone with respect to thedirection of loading. Bone is stronger (largerultimate strength) and stiffer (larger elasticmodulus) in longitudinal direction (along longaxis) than transverse direction (vertical tolong axis).

Stress

Strain

Longitudinal

Load ing

Transv

erse

Load ing

Bone fails in brittle manner at lower loadduring transverse loading as compared to

Fast and Slow Loading

Longitudinal and Transverse Loading

ε'

σ

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the longitudinal loading. Stress and straindiagram for these loadings is given in thefigure. The values of ultimate strength andelastic modulus are given in the table.

LOADING ULTIMATE ELASTICMODE STRENGTH MODULUS

LONGITUDINAL → 17 GPa

× TORSION 133 MPa

× COMPRESSION 193 MPa

× SHEAR 68 MPa

TRANSVERSE → 11.5 GPA

× TENSION 51 MPa

× COMPRESSION 133 MPa → SHEAR

MODULUS(G)= 3.3 GPa

5. Cancellous bone: The distinguishingcharacteristics of the cancellous bone is itsporosity. Hence cancellous bone has lowerdensity depending upon porosity. Thestress-strain of cancellous bone dependsupon porosity and the mode of loading. Incompressive loading, stress and strain inelastic region varies linearly upto a strainabout 0.05 and after this yielding occurswhen the trabeculaes begin to fracture.Yielding occurs at constant stress untilfracture, showing a ductile materialbehaviour. However on tensile loading,cancellous bone fractures abruptly, showinga brittle material behaviour. The capacity toabsorb energy is higher in compressiveloading than in tensile loading.

+ Stress ( )

Te ns ile Lo ad ing

+ Stra in ( )

– S tress ( )

– S tra in ( )

Low D e nsity

H ig h D en sity

C o m press ive Load in g

0 .2 0 .1 0 .050 .15

25

ULTIMATE STRENGTH, E AND G OF BONE

Compressive and Tensile Loading

6. Factors affecting strength: Factorsaffecting the strength or structural integrityof bone are:

(a) Area: Larger is the bone, the larger isarea upon which the internal forces aredistributed and the smaller is theintensity of stresses.

stress (σ) = Force

Area of bone

or Force = σ × Area of boneHence, bone with larger area canwithstand more force for a given valueof maximum permissible stress.

(b) Geometry of bone: The bone can besolid or hollow tube. The moment ofinertia & polar moment of inertia ofsolid and hollow tube are:

(I)Solid =4D

64

π,

(IP) Solid =4D

32

π

(I)hollow =4 4( – )

64

D dπ

and (IP)Hollow =4 4( – )

32

D dπ

Hence for equal cross sectional areaISolid < IHollow and (Ip)Solid < (Ip)Hollow.According to bending moment equa-tion, applied bending moment

(M) =permissibleI × �

D/2or M ∝ I

which shows that hollow bone can takemore bending load for given σ permis-sible. Similarly, applied torsion

����

perm ×

/ 2PI

D

τ

which shows that hollow bone can takemore torsion load for given τ permis-sible as compared to solid bone.

σ

σ

ε ε

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PREFIXES

(c) Reduction in Density: The strength ofbone decreases with reduction ofdensity which may result due to skeletalconditions such as osteoporosis, withageing or after period of disease.Certain surgical treatments may alterthe geometry of the normal bone whichmay reduce the strength of the bone.Screw holes or other defects in the bonealso reduce the load bearing capacityof the bone as stress concentration atthese locations of defects increasesloading to failure.

Bone

Screw ho leNormal stress Stress

concentration

σ1 1 A σ2 2 A

σ σ

∴ σ σ

1 1 2 2

1 2

1 2

A = AAs A > A

<

1. When a bone is subjected to an external load,it develops internal force to counteract bysome elastic deformation which disappearson the removal of the load and the boneregains its original shape. If the applied loadis high and it generates stresses in the bonewhich are larger than the ultimate strengthof the bone, the bone fractures. Fracturescaused by pure tensile loads are observed inbones having a large proportion of cancellousbone tissues. On other hand, fractures causedby compressive loads are seen in theverterbrae of an aged person whose boneshave weakened due to ageing. Such fractureare generally seen in the diaphyscal regionsof long bones. Bones have oblique fracturepattern under compressive fracture. Long

Stress Concentration

BONE FRACTURES AND TRACTION

bone fractures are usually caused by bendingor torsional loading. Bones have spiraloblique fracture pattern when they arefractured under excessive torsional loading.Bending fractures are usually identified bythe formation of butterfly fragments.Professionals like athletes and distant runnersgenerally suffer bone fractures caused byfatigue. Fatigue fracture of bone occurs whenthe wear and tear caused by repeatedmechanical stress is more than the naturalability of the bone to repair itself. Bone failurecan be (1) Fracture–loss of continuity of abone (2) Dislocation– loss of continuitybetween the articulating surface of a joint(3) Subluxation–early stage which may leadto dislocation (4) Sprain– a partial tear of aligament.

2. Fracture can be classified as under:

(a) Depending on plane of the fracture

(i) transverse fracture

(ii) spiral fracture

(iii) oblique fracture: angle with long axis

(iv) commuted fracture: more fragments

(v) compression fracture: eg fracture ofthoracis spine results in decreasedlength

(b) Communication with exterior

(i ) Simple or closed: No communicationwith exterior through the skin

(ii) Open or compound: There is acommunication between fracture andthe skin or mucous membrane

(c) According to the cause of fracture

(i) Traumatic fracture

(ii) Pathological fracture due to weaknessresulting from tumour or infection

(iii) Stress or fatigue fracture–due torepeated stress

(d) According to number of fracture

(i) single

(ii) multiple

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(e) According to wholeness

(i) complete

(ii) incomplete

3. The treatment of fractured bone can be doneby:

(a) Reduction: It is to bring the fracturedsegments in alignment. It can be

(i) Closed reduction: It is performedfrom outside the body. Themethods are (1) Closedmanipulation (2) Gravity: Theapplication of plaster of Parisincreases weight and provides sideto side stability (3) Tractionprovides both reduction andimmobilization.

(ii) Open reduction: where closedreduction is impossible.

(b) Retention: It is to immobilse a fracture.The methods are :

(i) Traction: It can be (1) traction bygravity (2) skin traction (3) skeletaltraction. Traction is always opposedby counter-traction, that is the pullmust be exerted by something, sothat traction can actually work,otherwise it will simply drag thepatient down instead of providingtraction to the fractured bone. Themethods of skeletal tractions are (1)fixed traction (2) continuous orsliding traction (3) combinedtraction.

(ii) Plaster: Plaster of paris is used forencasing in plaster the wholecircumference of limb.

(c) Rehabilitation: The main aim offracture treatment is not only to providecomplete union of the fracturedsegments but also to bring back thenormal function of the limb as soon as

possible. Proper exercise, crutches andphysiotherapy are used for rehabilitationof the patient.

4. In cases of complete fractures, bone screwplates or rods of compatible metals (cobalt,silicon) are used for holding in place twoparts of the bone as shown in the figure.The size of screw should be sufficient towithstand the shear stress developed due toweight of the patient. Formula for diameter(d) of screw can be calculated by formula::

permissible τ = 2

Weight

dπ where τ is shear

stress.

Plate

Screw

Plate

5. Different arrangements of rope andpulleys are used as traction devices. Thesingle rope- pulley arrangement gives atraction device which pulls the leg towardsright by applying a horizontal force on theleg as shown in the figure. In this case,the traction force in horizontal directionis equal to W = mxg, where m is mass inpan and g is coefficient of acceleration dueto gravity [9.81 metre/sec].

W

T

T = W

T

W

Plate for Bone Reduction

Single Pulley Traction

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T1 cos β = 2T1 cos α or cos β = 2 cos αAs angle α is fixed and known, angle β canbe found out. Also W2 is known, we can findout T1 and T2 from equation (iii) amd (iv).

T sin 1 α

2T 1

W 2

T1

T2

T1

cos α

T sin 1 αα

α

w 1

w 2

B βT2

A

W 1

A

T 2

T 1

l B

8. Two direction traction (Method II): Foranalysis of the coplanar force system of theabove two directions traction, consider ABis horizontal, weight of leg is W with lengthl and centre of gravity at c as ‘l1’, frompoint A.

ΣPx = 0, T1 cos α = T2 cos β ... (i)ΣPy = 0, T1 sin α + T2 sin β = W ... (ii)

ΣMA = 0, Wl1 = T2 sin β × l ...(iii)

If b is given and also values of W, l, and l1

are known, T2 can be found out from

equation (iii), T1 can be also found out from

remaining equations.

The three pulleys arrangement as shownin figure, exerts a horizontal force whosemagnitude is twice that of weight put inthe pan.

Three Pulleys Traction

W

2T

T= 2W

T

TT

W2T

6. Single and three pulleys arrangementprovides traction in one direction only.However there are requirements whentraction is to be given in two directions ofthe fracture at two places. The two sucharrangement of cable-pulleys system havebeen shown in the figures. Each arrangementis nothing but the system of coplanar forcesystem. Each system is in equilibrium whichgives three equations of equilibrium. Usingthese equations, three unknowns can befound out.

7. Two direction traction (Method I): Firstconsider the free body diagram of leg (AB)as shown in above figure with assumptionthat AB is horizontal and point B is also centreof gravity of leg (weight W

1) having distance

‘l’ from A. Now applying the equations ofequilibrium, we have

ΣPx = 0, T1 cos β = T2 .... (i)ΣPY = 0, T1sin β = W1 ...(ii)

If we consider pulley near point AΣPx = 0, T2 = 2T1 cos α ...(iii)

If we consider weight panΣPY = 0, T1 = W2 ...(iv)

From equation (i) and (iii), we have

Two Direction Traction (Method I)

Free Body Diagram

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Fill up the gaps1. Bone is a ________ tissue

(a) strong (b) living

2. Bone has also --------------- substance whichis not present in the cells of soft tissues(a) inorganic (b) organic

3. Hardness of bone is due to ----------------substance while elasticity is due to ---------substance. (a) inorganic and organic(b) organic and inorganic

4. Bone ________ repair itself

(a) cannot (b) can

5. Patella is a ------------ bone (a) sesamoid(b) irregular

6. Skull has ------------------ bones

(a) irregular (b) short

7. Outer shell of bone is ---------------(a) cortical (b) endosteum

8. ------------- tissues are the ends at the bone(a) cancellous (b) endosteum

9. Bone is a ------------- material (a)homogeneous (b) non homogeneous

OBJECTIVE TYPE QUESTIONS

10. Bone is a ---------------- material(a) isotropic (b) anisotropic

11. Bone can absorbs-------------- energy duringrapid loading (a) more (b) less.

12. Bone has --------------------- strength inlongitudinal loading as compared totransverse loading (a) more (b) less

13. Bone has ------------- strength in tension ascompared to compression.

(a) more (b) less

14. Bone strength -------------------- with density(a) increases (b) decreases

15. Solid bone has ---------- strength in bendingand torsional loading as compared to hollowbone for some cross sectional area.(a) more (b) less

16. Strain hardening give--------- yield strengthto the bone (a) less (b) more

17. ---------- is to bring the fractured segmentsin alignment (a) reduction (b) abduction

18. ---------- is to immobile a fracture(a) retention (b) detention

Two Direction Traction (Method II)Free Body Diagram of Leg

A

W 1

α

C

β

W 1

A

T 1 T2

l

B

W

α

C

l

W

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1. (b) 2. (a) 3. (a) 4. (b) 5. (a) 6. ( a)7. (a) 8. (a) 9. (b) 10. (b) 11. (a) 12. (a)

13. (b) 14. (a) 15. (a) 16. (b) 17. (a) 18. (a)

ANSWERS

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Keep your face toward the light and the darkness will never be able to closein on you.

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1. Soft tissues include skin, cardiovasculartissues, articular cartilage, muscles, tendonsand ligaments. All soft tissues are compositematerials. Collagen and elastin fibers are thecommon components of soft tissues andthey have most important propertiesaffecting the overall mechanical propertiesof the soft tissues in which they exist.Collagen is a protein in shape of crimpedfibrils which are joined together into fibers.Fibril can be considered as a spring andevery fibre as an assemblage of fibril springs.The function of collagen is to withstand axialtension. As collagen fibers have high aspectratio (length to diameter ratio), they are noteffective to withstand compressive loads.collagen fiber acts like a mechanical springas it stores the energy supplied to it bystretching the fiber. When the load isremoved, the stored energy is used to returnto the unstretched state. The individualfabrics of the collagen fibers are submergedin a gel-like ground substance consistinglargely of water. Since collagen fibersconsists of solid and water substance, itshows viscoelastic mechanical properties.

INTRODUCTION 2. Elastin is another fibrous protein and itsproperties are similar to the properties ofrubber. Elastin fibers consists of elastin andmicrofibril. Elastin fibers are highly extensibleand the extension is reversible even at highstrain. In other words elastin fibers have alow elastic modulus. The mechanicalproperties of soft tissues depend upon thegeometric configuration of collagen fibersand there interaction with elastin fibers.Collagen fibers have comparatively highermodulus and show viscoelastic mechanicalbehaviour.

1. Both tendons and ligaments are fiberousconnective tissues (Refer to para 23 ofchapter 1). Ligaments are supporting tissues.They join bones and provide support to thejoints for stability. Tendons are connectivetissues and they join muscles to the bones.Another function of tendons is to help inexecuting joint motion by transmittingmechanical force from muscles to bones.Both tendons and ligaments are passivetissues i.e., they can not generate force bycontraction as done by muscles.

TENDONS AND LIGAMENTS

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2. Tendons have higher modulus of elasticity(Stiffer) to stand higher stresses with smallstrain. They also have higher tensilestrength. Hence at joints where space islimited, tendons enable the attachments ofmuscles with the bones. Since tendons cansupport large loads with small strains, hencetendons enable the muscles to transmit forcesto the bones without wasting energy in itsstretching.

M uscles

Bone 3 (Pa te lla)

Tendons (Join bone and m uscle)

Bone 1 (Fem ur)

L igam ents (S upport B one 1 and 2 )

Bone 2 (Tibia)

3. The mechanical behaviour of both tendonsand ligament depends upon theircomposition which vary considerably ineach direction of loading. The stress andstrain diagram for a typical tendon is asshown in the figure. As collagen fibers oftendon require very little force to straightenand rubber like elastin fibers of tendon alsodo not require very high force, we get alarge strain (upto 0.05) with a small appliedforce. The curve is flat in this portion. Thetendon becomes stiffer after this as thecrimp is straightened. Hence stiff andviscoelastic nature of the collagen fibersbegin to take higher load with slight strain.Tendons are tested to function in the bodyupto ultimate strains of about 0.1 andultimate stresses of about 60 MPa.

Str

ess

() σ

Strain ( )0 0 .075 0.05 0 .075 0.1

Stress-strain Diagram : Tendon in Tension

60 M

pa

As the area under the curve is small, hence atendon does not absorb much energy ofmuscles and maximum energy is passed onto the bones.

4. As a tendon has a viscoelastic nature, itsproperties are dependent upon the rate ofloading. When a tendon is stretched rapidly,there is less time for the ground substanceto flow, hence a tendon becomes stiffer.However, a tendon can release to originalshape in a slow manner on unloading. Tendontakes more energy on stretching during rapidloading and releases less energy on slowunloading. The hysteresis loop of loadingand unloading is shown in the figure. Someenergy is dissipated in tendon during loading& unloading process.

Attachment: Tendons and Ligaments(Knee Joint: Femur, Tibia and Patella)

Stress ( )σ

Strain ( )0 .025 .05 .075 .1

Hysteresis Loop – Loading and Unloading

Loading

Un load ing

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5. Ligaments are also composite materialscontaining crimped collagen fiberssurrounded by ground substance. Ligamentscontain a greater properties of elastics (elasticfibers) which contribute to their higherextensibility but lead to lower strength andstiffness. Ligaments are viscoelastic liketendons and exhibit hysteresis on loading &unloading. Ligaments rupture at a stress ofabout 20 MPa, yield at about 5 MPa anddeform at strain of about 0.25. Some energyin ligament is dissipated in causing the flowof fluid within the ground substance.

Stress ( )σ

Strain ( )0 .1 .2 .3

Loading

Un load ing

20 M Pa

1. Muscles are connective tissues and they arethree types. Skeletal, smooth and cardiac(refer chapter1). Smooth muscles (unstriped& involuntary) line the internal organs andcardiac muscles form the heart.Skeletalmuscle (striped & voluntary) is attached toat least two bones via tendons in order tocause and control the movement of one bonewith respect to other bone. When musclefibers contract under the stimulation of anerve, the muscle exerts a pull on the bonesto which it is attached. The development oftension in the muscle has been possibly onlydue to contraction of muscle fibers. Themuscle contraction can take place as a resultof muscle shortening (concentriccontraction), or muscle lengthening(eccentric contraction) or without any

apparent change in length of the muscle(static or isometric interaction).

2. The contractile element (motor unit) consistsof many sarcomere elements connected ina series arrangement as shown in the figure.

M yo s infila m e n t

A c tinfi la m e n t

S C b id

The muscle force is generated within thesesarcomeres by lengthening or shortening ofthe muscle. The force and torque developedby a muscle depend upon number ofsarcomeres (motor units) within muscle,number of sarcomeres utilized, the mannerof change of length of muscle, the velocityof muscle contraction and length of the leverarm of the muscle force. Two differentforces are generated in a muscle. Thecontractable elements of the muscle produceactive tension due to the voluntary musclecontraction. The passive tension isdeveloped within the connective muscletissues when the muscle length surpassesits resting length. The net force is theresultant of these two forces. A typicaltension versus muscle length diagram isgiven in the figure.

Ten

sion

Resting Length

Shorten ing Lengthening

T = Net Tension1

T = Passive Tensionp

T = Active Tensiona

Lengthlo

SKELETAL MUSCLES

Hysteresis Loop : Ligaments

Skeletal Muscle : Contractile Element

Active, Passive and Tension Versus Muscle Length

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At resting, length to the number of cross-bridges between filament is maximum.Hence active tension (Ta) is maximum &passive tension (Tp) is Zero. On lengtheningof muscle, the filaments are pulled apartresulting in reduction of number of bridges.Hence active tension (Ta) reduces. At fullextended position, active tension (Ta)becomes zero.

3. The outcome of muscle contraction is alwaystension. Hence a muscle can only exert a

OBJECTIVE TYPE QUESTIONS

Fill up the gaps1. All soft tissues are ---------materials

(a) composite (b) complex

2. Collagen and ------------ fibers are thecommon component of soft tissues(a) elastin (b) rubber

3. Skin, cardiovascular, articular cartilage,muscle, tendon & ligament are ----------tissues (a) soft (b) ductile

4. Collagen fiber acts like a mechanical--------(a) lever (b) spring

5. Collagen fiber shows------------ mechanicalproperties (a) elastic (b) viscoelastic

6. Tendon and ligament are fiberous --------tissues (a) connective (b) elastic

7. Ligaments are ---------------- tissues(a) supporting (b) active

pull and it can not exert a push. A muscle isalso named according to the function itperforms. A muscle is called ‘agonist’ if itcauses movement through concentriccontraction. An ‘antagonist’ muscle controlsthe movement by eccentric contraction.Hence the biceps during flexion of the forearm is ‘agonist’ as the length of muscledecreases and the bicep during extension ofthe forearm is ‘antagonist’ as the length ofthe muscle increases.

8. Muscles are joined to bone through ------------- (a) ligaments (b) tendons

9. Tendon and ligament give ------------ loopduring loading and unloading (a) complex(b) hysteresis

10. The outcome of muscle contraction isalways------------- (a) compression (b)tension

11. Muscle is -------------- if it causesmovement by concentric contraction (a)agonist (b) antagonist

12. Muscle is --------- if it controls movementincreasing its length (a) agonist(b) antagonist

13. Muscle force is generated in ------- (a)sacromere (b) nerves

14. Muscle can exert -------- force only(a) pull (b) push

1. (a) 2. (a) 3. (a) 4. (b) 5. (b) 6. (a) 7. (a)

8. (b) 9. (b) 10. (b) 11. (a) 12. (b) 13. (a) 14. (a)

ANSWERS

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Though, God's ways of operating may perplex us at times, if we trust, in duetime, we will understand.

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1. The site where two or more bones cometogether whether or not there is movementbetween them, is called a joint. The primaryfunction of joints is to provide mobility tothe musculoskeletal system. In addition toproviding mobility, a joint must also possessa degree of stability. Different joints havedifferent functions to perform. Therefore,the joints have varying degree of mobilityand stability depending upon functions to beperformed. Joints are formed to giverequired mobility. Mobility can be triaxial(motion in all three planes) or uniaxial(motion in only one plane). Shoulder joint(ball and socket) is a triaxial joint, Here highmobility is achieved at the cost of lowstability. Elbow joint (pivot joint) is a uniaxialjoint. It has less mobility (one plane only)but more stability (less vulnerable todislocation). A joint may have no mobility,The connecting bones of the skull form suchjoints and they have extreme stability.

INTRODUCTION

1. Joints can be classified according to tissuesthat lie between the bones.

(a) Fibrous joints: The articulating surfacesof the bones are joined by fibroustissues. The joint has very littlemovement which depends on the lengthof the collagen fibers connecting thebones. The connecting bones of theskull form such joints.

Periosteum (m embrane)

Suture (fibrous tissue)

Bone

Fibrous Joint

TISSUES BETWEEN JOINTS

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(b) Cartilaginous joints : It can be primaryor secondary. A primary cartilaginousjoint is one in which the bones are unitedby a plate of hyaline cartilage (For thistype of cartilage, refer chapter 1). Thejoint between the first rib andmanubrium is a primary cartilaginousjoint. A secondary cartilaginous joint isone in which the bones are united by adisc of fibrocartilage and the articulatorsurface of the bones covered with athin layer of hyaline cartilage.Intervertebral joints are secondarycartilginous joints. The amount ofmovement possible depend on thephysical qualities of the fibrocartilage.

Fibrocartilaginous disc

(c) Synovial joints : The articular surfaceof the bones are covered by a thin layer

Bone I

Articularcartilage

Bone II

Capsule with synovial membrane

inside

Synovial fluid inside joint

cavity

of hyaline cartilage separated by a jointcavity. This arrangement permits greatdegree of freedom of movement. Thecavity of the joint is lined by synovialmembrane which covers the one endof the articular surface of the first boneto that of the second bone. The

synovial membrane is protected on theoutside by a tough fibrous membranewhich is called the capsule of the joint.The articular surfaces are lubricated bya viscous fluid which is called synovialfluid. In certain synovial joints like kneejoint, discs or wedges of fibrocartilageare interposed between the articulatingsurfaces of the bones which are calledarticular discs.

2. Joints can also be classified accordingto the relative motion between thebones forming a joint, synarthrodialjoint does not permit any motion and itis a fibrous joint. Amphiorthrodial jointallows slight relative motions betweenthe bones and it is nothing but acartilagious joint. Diarthrodial jointspermit varying degree of relative motionand they are synovial joints.

1. Synovial joints can be classified accordingto the arrangement of articular surface andnature of movement that are possible by thejoints. The joints are:

(a) Plane joint: In these joints, the articularsurfaces of the bones are flat whichpermit the bones to slide one upon other.The sternoclavicular and acromioclav-icular joints are plane joints.

Sternoclavicular Joint

Acrumiolavicular Joint

Sternum Clavicle

Scapula

(b) Hinge joint : It is similar to the hingeson a door i.e. the bones fold & unfold

Intervertebral Joint (Cartilaginous Joint)

Synovial Joint

TYPES OF SYNOVIAL JOINTS

Plane Joint

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Hinge Joint

themselves. Flexion is folding of bones(coming nearer) and extension isunfolding of bones (moving away).Elbow, knee and ankle joints are hingeJoints.

Elbow Joint

E lbow Joint m ovem ent

Radius

U lna

Humerus

(c) Pivot joint : These joints are like awheel on an axel. Rotation is the onlymovement possible in these joints. Theatlanto–axial and superior radioulnarjoints are pivot joints.

Atlas (firs t cerv ica l ve rtebrae )

Boney P ivo t

Axis (second cerv ica l ve rtebrae)

(d) Condyloid joints : The bones have twodistinct convex surfaces whicharticulate with two concave surfacesin these joints. These joints permitflexion, extension, abduction, adductionwith small rotational movement. The

knuckle joints or metacarpophalangealjoints are condyloid joints.

H AND

M e ta ca rpa l

Ph alan ge

M e taca rpa l

Ph alan ge

H AND

(e) Ellipsoid joints: There is an ellipticalconvex articular surface that fits intoan elliptical concave articular surface inthis type of joints. Flexion, extensionabduction and adduction can take placein these joints. The wrist joint is aellipsoid joint.

Radius Ulna

Scaphoid Lunate Triquetral

Movements

Concave elliptical surface

Convex elliptical surface

(f) Saddle joints: The joint resembles asaddle on a horse’s back. The articularsurfaces are concavo-convex. Flexion,extension, abduction, adduction androtation are possible in this joint.Carpometacarpal joint of the thumb is asaddle joint.

Pivot Joint

Ellipsoid Joint

Condyloid Joint

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Concavo convex a rticu larsurface

M etacarpal o f thum b

Sadd le shape concavo convex a rticu lar surface

Trapezium

(g) Ball & socket joints: In this joint, onebone has a ball shaped head and other

bone has a socket like cavity in whichthe head of first bone fits. The jointpermits all movements like flexion,extension, abduction, adduction, medialrotation, lateral rotation andcircumduction. Shoulder and hip jointsare ball and socket joints.

Scapu la o f shoulder

Concave glenoid fossa (socket)

Humerus

OBJECTIVE TYPE QUESTIONS

Fill up the gaps1. A site where two or more bones come

together, whether or not there is a movementbetween them is called---------------(a) skeleton (b) joint

2. The primary function of a joint is to provide-------- to musculoskeletal system(a) safety (b) mobility

3. Joint is required to provide -------- besidesmobility (a) stability (b) safety

4. Motion in all time planes is called--------

(a) trimotion (b) triaxial

5. Motion in one plane is called---------

(a) monomotion (b) uniaxial

6. The connecting bones of the skill form a---- joint (a) fibrous (b) fixed

7. Cartilage joint has bones united by a -------of fiberocartilage (a) ligament (b) disc

8. Synovial joint has articular bone surfacesseparated by a --------- filled with synovialfluid (a) cavity (b) pouch

9. ------- fluid reduces wear and tear of articularbone surfaces (a) lubricating (b) synovial

10. Intervertebral joint is a -------- joint(a) cartilaginous (b) fibrous

11. Synovial joint has ------- degree of freedomof movement (a) greater (b) lesser

12. Amphiorthrodial joint permits------- relativemotion between bones (a) slight (b) varyingdegree of

13. Diorthrodial joint permits ------- relativemotion between bones (a ) slight (b) varyingdegree of

14. Synovial joint of plane variety has thearticular surfaces of the bones which are------- (a) flat (b) sliding

15. A joint which is like a wheel on an axel is------ joint (a) hinge (b) pivot

16. A saddle joint has reciprocally --------articular surfaces (a) convex (b) concavo-convex

17. A ellipsoid joint has--------- articular surfaces(a) concavo-convex (b) elliptical

18. A condyloid joint has two distinct -------surfaces which articulate with two distinct------ surfaces(a) f lat, flat (b) convex, concave

Saddle Joint

Ball and Socket Joint

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ANSWERS

1. (b) 2 .2 .2 .2 .2 . (b) 3 .3 .3 .3 .3 . (a) 4 .4 .4 .4 .4 . (a) 5 .5 .5 .5 .5 . (b) 6 .6 .6 .6 .6 . (a)7 .7 .7 .7 .7 . (b) 8 .8 .8 .8 .8 . (a) 9 .9 .9 .9 .9 . (b) 1 0 .1 0 .1 0 .1 0 .1 0 . (a) 1 1 .1 1 .1 1 .1 1 .1 1 . (a) 1 2 .1 2 .1 2 .1 2 .1 2 . (a)

1 31 31 31 31 3..... (b) 1 4 .1 4 .1 4 .1 4 .1 4 . (a) 1 5 .1 5 .1 5 .1 5 .1 5 . (b) 1 6 .1 6 .1 6 .1 6 .1 6 . (b) 1 7 .1 7 .1 7 .1 7 .1 7 . (b) 1 8 .1 8 .1 8 .1 8 .1 8 . (b)

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There is always some good in every situations, all you have to do is look for it.

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1. The vertical column is also known as spine,spinal column or back bone. It is the controlaxis of the body. It supports the body weightand transmits it to the ground through thelower limbs. It is the most complex part ofthe human muscleoskeletal system. Itsprincipal functions are to protect the spinalcord, to support the head, neck and upper

INTRODUCTION limbs; to transfer loads from the head andtrunk to the pelvis; and to provide flexibilityto carry out a variety of movements. It canbe divided into five regions viz. cervical(neck), thoracis (chest), lumbar (lowerback), sacral and coccygeal regions. Thethoracis and lumbar regions of spinal columnform the trunk of the body while sacral andcoccygeal regions join with pelvis and formparts of pelvic girdle.

N e c k

C h e s t

B a c k

P e lv ic g ird le

C e rv ic a l V e rte b ra e (7 )

T h o ra c ic V e rte b ra e (1 2 )

L u m b a r V e rte b ra e (5 )

S a c ra l V e r te b ra e (5 )

C o c c y g e a l V e rte b ra e (4 )

P e lv isS pina l C olum n

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1. The vertical column is made up of 33vertebraes which include 7 cervical, 12thoracic, 5 lumbar, 5 sacral and 4 coccygeal.In the thoracic, lumbar and sacral regions,the number of vertebrae corresponds to thenumber of spinal nerves and each nerve lyingbelow the corresponding vertebrae. Incervical region, then are eight nerves, theupper seven lying above the correspondingvertebrae and the eight below the 7th

vertebrae. In the coccygeal region there isonly one coccygeal nerve.

2. The vertebrae are also grouped accordingto their mobility. The moveable or truevertebrae include 7 of cervical, 12 ofthoracic and 5 of lumbar vertebrae whichhave intervertebrae disks in between forfacilating rotating movement. Hence theseare 24 movable (true) verterbrae and nineunmovable (false) verterbrae which are insacrum and coccyx region. Twelve thoracicverterbrae have ribs attached to them.

3. There are 24 movable verterbrae and theyform amphiarthrodial joints with thefibrocartilaginous interposed between eachpair of vertebrae. The fibrocartilaginous discsperform following functions.

(1) Sustains loads transmitted fromsegments above

(2) Act as shock absorbers

(3) Eliminate bone to bone contact

(4) Reduce the effects of impact forces bypreventing direct contact between theverterbraes. The intervertebrae discpermits articulation of each verterbraewith the adjacent verterbrae in theseplanes. Hence the entire spinal columnfunctions like a single ball and socketjoint. Flexion and extension, lateralflexion and rotation of body is possibledue to the structure of spinal column.

4. At the superior end, spinal column has twoimportant joints with head. The atlanto-occipital joint is the joint between the firstcervical vertebrae (called atlas) and theoccipital bone of the head. This is a doublecondyloid joint (refer chapter 6) The jointpermits movement of the head in the sagittalplane and lateral plane. The atlanto axial jointis the joint between the atlas and the axis(first and second verbetrae). This is a pivotjoint which permits head to rotate in thetransverse plane.

5. The movement of head and neck is provided,controlled and coordinated by a musclegroup viz. prevertebrals (anterior), hyoids(anterior) sternocleidomastoid (anteriorlateral) scalene (lateral), levator scapulae(lateral) suboccipital (posterior) and spleni(posterior). The spine gets its stability fromthe inter vertebral discs and from thesurrounding ligaments and muscles. Thediscs and ligaments provide passive stabilitywhile muscles give active support. Themuscles of the spinal column exist in pairs.The anterior portion of spine is connectedto abdominal muscles viz. the rectusabdominis, external obligue and internalobligue. These muscles can do flexion &maintain the spine in proper position. Thereare three layers of posterior trunk musclesviz. the erector spine, the semispinalis andthe deep posterior spinal muscle groups.These muscles provide trunk extension asthey are located at posterior position of thespine. The effect of gravity is also overcomeby these muscles. The quadratus lumborummuscle helps in lateral trunk flexion. Thepelvis and lumbar spine is stabilized by thismuscle. The lateral flexion of the trunk iscarried out by the abdominal and posteriormuscles. The rotational movement of theturnk is controlled by the simultaneousaction of anterior & posterior muscles.

ANATOMY OF SPINAL COLUMN

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1. When head flexes in meridian plane, exteriormuscles exert force to support the head.There is also compressive force exerted onthe first cervical vertebrae at the atlanto-occipital joint.

Muscle

Spinal cord

A

B

W

O

R

F

a

b

FBD

2. Let F is muscle force & R is reaction at thejoint. We get a three forces system which isconcurrent at joint O. Hence we can applyLami’s theorem on the force system.

sin (180 – + )

W

β α = cos

R

α = sin (90 )

F

+ β

Where α is angle with horizontal of muscleforce and β is angle of reaction of joint withhorizontal.

sin ( – )

W

β α =cos

R

α = cos �

F

∴ R = cos

sin ( – )

W αβ α

= cos

sin cos – cos sin

W αβ α β α

=sin – tan cos

W

β α β

Similarly F =sin

sin( – )

W ββ α

=cos

sin cos – cos sin

W ββ α β α

= cos tan –sin

W

α β αIf we have W = 50 N, α = 30° & β = 60°

Then R =50

sin 60 – tan 30 cos 60

=50

3 1 1–

2 23×

=50 3 2

2

× × = 88 N

Similarly F =50

cos30 tan 60 – sin 30

=50

3–1/ 2

2

= 50 N

Hence muscles must apply 50 N force tosupport the head and reaction forcedeveloped at the joint is 88 N.

1. Neck: It can rotate in horizontal plane. Itcan do lateral bending. It can also do flexionand extension in meridian plane.

R ight Left

Ex ten tion F le xion

R ight Left

Latera l B ending

F le xion & Ex tens io n

R ota tion

MOVEMENTS OF NECK AND SPINE

Movements of The Neck

ANALYSIS OF FORCE SYSTEM

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2. Spine: Spine can do flexion and extensionin meridian plane. It can also do lateral

bending. It can also have rotationalmovement in horizontal plane.

Rotation

Lateral Bending

Flexion Extension

Movements of Spine

OBJECTIVE TYPE QUESTIONS

Fill up the Gaps1. The primary function of spinal column is to

protect the ----- of the body

(a) posture (b) spinal cord

2. Neck has ---- cervical vertebraes.

(a) six (b) seven

3. Chest has -------- thoracic vertebrae

(a) Thirteen (b) twelve

4. Back has ---- lumbar vertebrae

(a) five (b) four

5. The spinal column has ---vertebrae

(a) 24 (b) 33

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6. There are -------- movable vertebrae

(a) 24 (b) 33

7. Each movable vertebrae has fibrocartilagi-nous --------- interposed between each pairof verterbrae.

(a) plate (b) disc

8. Movable vertbraes form -------- joints

(a) amphiorthrodial (b) rotatable

9. Thoracic vertebraes have ------ attached tothem. (a) ribs (b) abdomen

10. The interverbetrae disc permits ----- of eachverbetrae with the adjacent vertebrae in threeplanes. (a) articulation (b) rotation

11. Entire spinal column functions like a single------- joint. (a) ball and Socket (b) plane

12. The joint between first cervical vertebraeand the occipital bone of the head is -----

(a) ‘atlanto’ occipital (b) vertebro occipital

13. The atlantoaxial joint is between the firstvertebrae and --------- vertebrae

(a) 3rd (b) 2nd

14. 9 unmovable verterbraes are in -------

(a) Back (b) Pelvic girdle

15. Chest is ------------ region

(a) cervical (b) thoracic

16. Back is ---- region. (a) thoracic (b) lumbar

17. The thoracic and lumbar regions of spinalcolumn form the ------ of the body.

(a) chest (b) trunk

18. Sacral and coccygeal regions join to form------- (a) shoulder girdle (b) pelvic girdle

19. Ligament and discs provide ------- stability

(a) active (b) passive

20. Muscles provide ------- stability

(a) active (b) passive

21. The load from head to pelvis is conveyedby -------

(a ) chest bones (b) spinal column

22. The protection to spinal cord is provided by------- (a) chest bone (b) back bone

23. Intervertebrae discs permit-------contactsbetween adjacent vertebrae.

(a) smooth (b) no

24. In coccygeal region, there is-------nerve/nerves

(a) one (b) four

ANSWERS

1. (b) 2. (b) 3. (b) 4. (a) 5. (b) 6. (a)

7. (b) 8. (a) 9. (a) 10. (a) 11. (a) 12. (a)13. (b) 14. (b) 15. (b) 16. (b) 17. (b) 18. (a)19. (b) 20. (a) 21. (b) 22. (b) 23. (b) 24. (a)

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INTRODUCTION

1. The upper and lower limbs were evolvedbasically for bearing the weight of the bodyand for locomotion as it is seen inquadrupeds (eg. cows and dogs). Thereforethe two pairs of limbs are formed on thesimilar basic pattern. The evident similaritiesof upper and lower limbs are :

Upper limbs Lower limbs

1. Shoulder griddle 1. Hip girdle2. Shoulder joint 2. Hip joint

3. Arm with humerus 3. Thigh with femur4. Elbow joint 4. Knee joint

5. Forearm with 5. Leg with tibiaradius and ulna and fibula

6. Wrist joint 6. Ankle joint

7. Hand with 7. Foot with(a) Carpus (a) Tarsus

(b) Metacarpus (b) Metatarsus(c) 5 digit (c) 5 digit

2. Due to the evolution of erect posture in man,the function of weight bearing was takenover entirely by the lower limbs. As a resultof this removal of function of load bearing,the upper limbs (specially the hands) becamefree. Hands were gradually evolved into theorgans having greater manipulative skill. Theupper limbs started performing differentfunctions. Hence the apparent differencebetween the upper and lower limbs is as aresult of the difference of functions.

Evolution

The division of the upper limbs with bonesand joints are:

Change of Posture

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3. The forces involved on various joints canbe classified as (1) internal forces (2)external forces. Internal forces aredeveloped in muscles and joint reactions.External forces are gravitational force andmechanical applied forces. To apply theprinciples of statics to analyze the mechanicsof human joints, following assumptions aremade :

(a) Only one muscle groups controls themovement of joint

(b) Muscle attachment is at a joint whichis known

(c) The line of action of muscle tension isknown

(d) Proper point of joint at which joint canrotate is known

(e) Segmental weight of the parts of bodywith their centre of gravity are known

(f) Frictional forces at joints are small &negligible

S.No. Division Bones Joints

1. Shoulder region 1. Clavicle 1. Sternoclavicular2. Scapula 2. Acromioclavicular

2. UPPER ARM Humerus Shoulder joint

(Shoulder to elbow) (scapula humerus)3. Forearm 1. Radius 1. Elbow joint

(Elbow to wrist) 2. Ulna 2. Radius ulna4. Hand 1. Carpus 1. (a) Wrist joint

(8 Carpel bones) (radio - carpal) (b) Inter carpal

2. Metacarpus 2. Carpometacarpal(5 metacarpal bones)

3. 14 Phalanges 3. (a) Intermetacarpal (2 for thumbs & (b) Metacarpophalangeal

3 for each finger) (c) Proximal and distalinterphalangeal

(g) All forces acting on a joint are coplanar

(h) Deformation is small and negligible inmuscles, bones and tendons etc

(k) Dynamic effect is ignored

1. Shoulder joint: It is also calledglenohumeral joint between hemisphericalhumeral head (ball) and the shallowlyconcave glenoid fossa (socket) of thescapula bone. Hence it is a ball and socketjoint which permits variety of movementsto the arm. The movements allowed areflexion and extension, abduction andadduction, outward rotation and inwardrotation. The configuration of the articularsurfaces of this joint makes the joint moresusceptible to instability. The stability of thejoint is due to the presence of ligaments andmuscles. Ligaments are glenohumeral andcoracohumeral while the major muscles ofthe joint are :

MECHANICS OF THE SHOULDER

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(1) deltoideus

(2) supraspinatus

(3) pectoralis major

(4) coracobrachialis

(5) latissimus dorsi

(6) teres major

(7) teres minor

(8) infraspinatus

(9) subscapularis

Scapula

Glenoid fossa (socket)

Humeral head (ball)

Humerus

Shoulder joint

Rotation(Horizontally)

Flexion and Extension (Sagitally)

Abduction (Laterally)

Rotation (In Abduction)

Elevation Circumduction

Movements of the Shoulder

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2. The shoulder girdle consists of the clavicle(collarbone) and scapula (shoulder blade).The acromioclavicular joint gives smallsynovial articulation between acromion ofthe scapula and the distal clavicle.Coracoclavicular ligaments join these twobones. The sternoclavicular joint is a saddlesynovial joint and it gives articulationbetween sternum and clavicle. Costoclavicleligaments join these bones and providestability. Both these joints of clavicle withsternum and scapula have layers of cartilage(called menisci) interposed in between thejoints. There are six types of movementpossible as shown in the figure. There are 6

muscles that control and coordinate thesemovements viz. trape = 145, levatorscapulae, rhomboid pectoralis minor,serratus anterior and subclavius.

Sternoclavicula r Joint

S ternum

Humerus

C lavic leScapula

Coraco clavicular ligaments

Acromion of scapula

Articular surface (plane)Costoclavicular

ligaments

Articular surface (saddle)

Acromio-Clavicular

joint

3. The shoulder joint is very susceptible toinjuries like dislocation of the joint & thefracture of the humerus bone. As the headof humerus is relativity free to rotate aboutthe articulating surface of the glenoid fossathe freedom of movement is gained by

reduced joint stability. The humeral head islikely to be displaced if external loading ismore than the strength of the muscles andligaments.

1. Case study 1: Let us take a typical case ofarm stretched fully & holding a weight (Wb)as shown in the figure. Free body diagramof the arm is also shown. The shoulder jointis at point A, deltoid muscle is attached atpoint B; center of gravity of the arm is atpoint C and weight in hand is acting at pointD. The force F is developed by deltoidmuscle at point B which makes an angle αwith horizontal. The reaction R acts at thejoint which makes an angle β withhorizontal. The weight of the arm (W) actsvertically downwards at point C. The weightheld in hand also acts vertically downwardsat point D. The mechanical model of the armis also shown. The distances of point B, C,& D from point A are a, b, and c respectively.Now we have a coplanar force system inequilibrium which gives us three equationsof equilibrium i.e. Σ Px = O, Σ PY = 0 & ΣM = O.

M uscle

Shou lder Jo in tw b

F

C D

BW

W b

A

R

C D

Sternoclavicular and Acromioclavicular Joints

ANALYSIS OF FORCE ON THESHOULDER JOINTS

Arm Abducted Horizontally

Free Body Diagram of Arm

ββ

α γ

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R F

W b

a b

c

W C B A

D

Σ Py = 0, – R sin β + F sin α – W– Wb = 0...(i)

Σ Px = O,R cos β = F cos α ...(ii)Σ MA = 0, – F sin a × a + W × b + Wb × c = 0

... (iii)

If we have been given the value of a = 20,b = 40, c = 60, α = 12°, m = 4 Kg(W = 4× g = 4 × 10 = 40 N), mb= 5 Kg(Wb = 5 ×10 = 50 N) then substituting thesevalues in equations (i), (ii) and (iii)

– R sin β + F sin 12 – 40 – 50 = 0 ... (iv)R cos β = F cos 12 ... (v)– F sin 12 × 20 + 40 ×40 + 50× 60 = 0

∴ F = 4600

20 sin12× = 4600

20 sin13× = 1080 ...(vi)

From eqn (v) R cos β = F cos 12= 105.64 ... (vii)

From eqn (iv) R sin β = F sin 12 – 90= 129.4 ... (viii)

From eqn (vii) and (viii)tan β = 0.123

∴ β = 7

and R =1056.4

cos7 =

1056.4

0.95

= 1056.5

2. Case study 2: Consider an athlete isstrengthening his shoulder joint by loweringand raising a bar bell with arms straightwhile lying down as shown in figure below.The weight of the bar bell is Wb at a distance

‘b’ from the shoulder joint (point D) and Wais weight of the arms acting at a distance ‘a’from the shoulder joint. Now we can analysethe force system, when the arm is makingan angle θ with horizontal.

M0 = Wa × a cos θ + Wb × b cos θ.

If we take, a = 30 cm, b = 60 cm, Wa = 60N and Wb = 300 N

M0 = 60× 0.30 cos θ + 300×0.60 cos θ = (18 +18) cos θ = 36 cos θ

The moment at the shoulder joint varies asper the angle θ. It is maximum when θ = 0(arm is horizontal) and zero when θ = 90(arm is vertical).

θ

W b

W a

a

b

oo

y

x

w a

w b

o

θ

1. The elbow joint has three bones vizhumerus, radius and ulna. Humerus lies inupper arm while radius & ulna lie in forearm.At the distal (far from root) humerus hascapitulum (rounded head) and spool shapedtrochlea. The humeroulnar joint is a hugejoint formed by humerus (distal) and ulnahaving concave trochlear fossa (cavity) atproximal (root). The joint can make onlyuniaxial rotation which permits flexion andextension. The humeroradial joint is formed

Free Body and Mechanical Model of Arm

MECHANICS OF THE ELBOW

Mechanical Model of Arm

β α

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by the capitulum of the distal humerus andhead of the radius. It is a also a hinge joint.The third joint in this region is the proximalradioulnar joint which is a pivot joint formedby the head of the radius and the radial notchof the proximal ulna. The joint permits theradius and ulna to make relative rotationabout the longitudinal axis of either of thebones. The movement by the joint from thepalm-up to the palm down is called pronationwhile the movement by the joint from thepalm down to palm up is called supination.

Capitulum (rounded head)

Head

Radius

Humerus

Trochlea (spool shaped)

CavityRadial no tch

U lna

Flex ion

Extension

Movem ents of the Elbow

Supernation Pronation

Movem ents of the Forearm

2. The muscles coordinating & controlling themovement of the elbow joint are:

(a) Bicep brachii: It is the most powerfulflexor of the elbow joint, specially whenthe joint is in supinated position. On thedistal side, the biceps is attached to thetuberosity of the radius and on theproximal side, it has attachments at thetop of the coracoid process and upperlip of the glenoid fossa.

(b) Brachialis muscle: This flexor hasattachments at the lower half of theanterior portion of the humerus & thecoronoid process of the ulna.

(c) Triceps brachii: The muscle controlsthe extension movements of the elbow.It has attachments of the lower headof the glenoid cavity of the scapula, theupper half of the posterior surface ofhumerus, the lower two thirds of theposterior surfaces of the humerus andthe olecranon process of the ulna.

Triceps

Brachio Radialis

ANTERIOR

Brachialis

Pronator Teres

Tricep Brachii

Anconeus

Supinator

POSTERIOR

Muscles of the Elbow

Bones of the Elbow

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(d) Pronator teres and supinator muscles:The pronator teres is attached to thelower part of the inner condyloid ridgeof the humerus, the medial side of theulna and the middle third of thehumerus, the medial side of the ulna andmiddle third of the outer surface of theradius. As the name suggests, itperforms pronation. The supinationmuscle has attachments at the outercondyloid ridge of the humerus, the

neighboring part of the ulna and theouter third of the radius. The musclecontrols supination. The coordinatedrelaxation and contraction of theopposing muscles enables to controlmovement of the limbs. To raise theforearm, the biceps (two rooted muscle)contracts and shortens while triceps(three rooted muscles) relaxes. To lowerthe forearm, the reverse occurs.

Tricepsin resting

phase

Biceps in resting phase

Forearmat rest

Tricepscontracts

B icepsreplaces

Forearmhalf lower

Tricepsre laxes

Bicepscontracts

Forearmhalf ra ised

Tricepsback inrestingphase

Biceps backin resting phase

Forearm back rest

Tricepsfu lly

re laxed

Biceps fullycon tracted

Forearmfu lly raised

Raising of Forearm Lowering of Forearm

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3. The elbow joint : The elbow joint is a synovialjoint of the hinge variety. A ligamentouscapsule encloses an articular cavity filled withsynovial fluid. The synovial fluid is a thickand viscous substance. The primary functionof synovial fluid is to provide lubrication tothe articulating surfaces which reducescoefficient of friction, thereby frictionalforces acting against movements are reducedconsiderably. The synovial fluid alsonourishes the articulating cartilages . Besidesabove two functions, the synovial fluid helpsin distributing the forces acting on the jointto a large area. All forces acting on the fluidare transferred to the fluid as liquid pressurewhich is uniform in all directions. Thecomponents of the fluid pressure along the

horizontal get cancelled and the verticalcomponents get added up, resulting into avertical force on the joint. The elbow joint iscontinuous with the superior radioulnar joint.The humeroradial, the humeroulnar and thesuperior radioulnar joints together are knownas cubital articulations. The long axis of thearm makes an angle of about 170° with thelong axis of the forearm when the forearm isextended and supinated. The elbow joint issusceptible to fractures and dislocations.Fractures occurs at the epicondyles of thehumerus and coronoid process of ulna.Another elbow injury that happens frequentlyis tennis elbow, which occurs due to repeatedand forceful pronation and supinationmovement of the elbow.

Elbow Joint

Humerus

Radius

UlnaSynovial Cavity

Humerus

Radius

Ulna

Capitulum of humerus articulates with head of radius

Trochlea of humerus articulates

with trochlear notch of ulna

Head of radius articulates with

radial notch of ulna

Lateral epicondyle

Radial collateral ligament

Humerus

Capitulum

Annular ligament

Radius

Ligaments

Epicondyle of Humerus

Olecranon

Coronoid Process of ulna

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4. The radioulnar Joints : The radius and theulna are joined to each other at the superiorand inferior radioulnar joints. Supination andpronation (rotary movements of the forearmalong the long axis) are possible due to thesejoints,. It is a pivot type synovial joint.Pronation and supination movements aresimilar to turning a door handle, moving ascrew or opening a lock. The head of radiusarticulates with the radial notch of ulna inthe joint.

Notch o f u lna

U lna

Articular d isc

Head of radius

annular ligament

oblique cord

Radius

In te rosseus m embrane

1. Let us take a typical example of the arm inwhich elbow is flexed to a right angle andan object is held in the hand. The freebodydiagram of the forearm is shown indicatingforces and reaction acting on it inequilibrium. The mechanical model of theforearm is also shown to convert it to asimple mechanics problem. As shown in thefigure, W = weight of the forearm acting atC (Centre of gravity of the forearm), Wb =weight of the body held in the hand at pointD, F = Force exerted by the biceps muscleon the radius at point B and R = reactionforce at the elbow joint at point A. Let thedistance AB = a, AC = b and AD = c. Theforce system on the forearm is a coplanar

FORCES ON THE ELBOW JOINT

The Radioulnar Joint

force system and we get three equations ofequilibrium

i.e. Σ Px = 0, Σ PY = 0 and Σ MA = 0

Σ PY = 0, – R + F = W + Wb ...(i)Σ MA = 0, F × a = W× b + Wb × c

or F = bW b W c

a

× + ×

If we take mass of forearm 2 kg (W = 2× g ≈20 Ν), mass of object 5 kg (Wb = 5 × g ≈ 50 N),a = 5 cm, b = 15 & c = 40 cm

∴ F =20 15 50 40

5

× + ×

=3 0 0 2 0 0 0

5

+ = 460 N

∴ R = – 20 – 50 + 460

= 390 N2. The above example indicates that the muscle

force and reaction at joint are considerablylarger than the weight of the object. Both F& R can be brought down if distance ‘a’ islarge i.e. distance between joint & point ofattachment of the muscles. However nearerattachment of muscle to the joint helps inquick motion of the forearm w.r.t joint.

3. If the muscle force is not acting vertical thenmuscle force (F) will have a rotationalcomponent acting vertically up (as in theprevious example) and a translationalcomponent (stabilizing or sliding dependingon flexed position). If muscle force (F) isacting towards upper arm (making angle θwith vertical) then F cos θ is rotationalcomponent and F sin θ is stabilisingcomponent acting towards joint. Now ifmuscle force (F) is acting away from theupper arm (making angle θ with vertical),then F cos θ is rotational component andF sin θ is sliding or destabilising component.

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A B

W W b

(a) Arm F lexed at righ t ang le

A

R F

W W b

(b) Free body D iagram of Forearm

A F

R B

C D

W W b

a

b

c

(c) M echan ical M ode l

BDC

DC

F = Rotational effect of A

F cos = Rotational effect at A�

F sin = Stabilising effect at A�

F cos = Rotational effect at A � F sin = Destabilising effect at A �

F cos q

q F

F sin qB

F cos q

F sin qB

qF

A

A

R

A

R

B

F

R

4. In practice, biceps muscle is not the onlymuscle exerting force on the forearm in theflexed position. The brachialis and thebrachioradialis muscles are also exertingforces. The mechanical model of the forcesystem is still a coplanar force system asshown in the figure. As we have threeequations of equilibrium, hence the systemis determinate for only three unknown. Thethree equations are ΣPx = 0, ΣPy = 0, andΣMa = 0

ΣPy= 0, F1 + F2 sin θ2 + F3 sin θ3

=R sin α + W + Wb ...(i)

R F 1

F 2F 3

A B

θ3

a 1a 2

a 3 c

W b

αC β3

θ2

B 2 B 3

W

D

b

ΣPx =0, R cos α = F2 cos θ2 + F3 cos θ3..(ii)ΣMA =0, F1× a1 + F2 sin θ2 × a2 + F3 sin θ3 × a3

= W × b + Wb × c ...(iii)The muscle forces F1, F2, and F3 are

proportion to their areas i.e., A1, A2 and A3

F1 A1 = F2 A2 = F3 A3

F2 =1

2

A

A F1 = K2 F1

F3 = 1

3

A

A F1 = K3 F1

From eqn. (iii)F1 × a1 + F1 K2 × a2 sin θ2 + F1 K3 xa3sin θ3

= W × b + Wb × c

∴ F1 =1 2 2 2 3 3 2sin sin

bW b W c

a K a K a

× + ×+ θ + θ

Force Analysis of Forearm

Rotational and Translation Components

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1. The wrist joint: This is a synovial joint ofthe ellipsoid variety. It is also called as radiocarpal joint. There is an elliptical convexarticular surface (formed by triquetral, lunateand scaphoid) that fits into an ellipticalconcave articular surface (formed by radiusand ulna) as shown in the figure. Themovement of flexion, extension, abductionand adduction can take place but rotation isimpossible.

Radius Ulna

Scaphoid

Lunate Triquetral

2. The knuckle joint: It is also called asmetacarpophalangeal joint. The joint is asynovial joint of the condyloid variety. Thejoint has two distinct convex surfaces (onmetacarpal bone) that articulate with twoconcave surfaces (on phalanx). Themovements possible are flexion, extension,abduction, adduction and small amount ofrotation.

JOINTS OF HAND

M etacarpa lPhalanx

M etacarpa l

Phalanx

3. The thumb joint: It is also calledcarpometacarpal joint. It is a synovial jointof the saddle variety. The joint has thearticular surfaces which are reciprocallyconcave convex and resemble a saddle on ahorse’s back. The joint permits flexion,extension, abduction, adduction and rotation.

Metacarpal of thumb

Trapezium

Knuckle Joint

Wrist Joint

Thumb Joint

OBJECTIVE TYPE QUESTIONS

Fill up the gaps1. Upper & lower limbs are formed on --------

basic pattern (a) similar (b) dissimilar

2. Due to evolution of erect posture in man,the function of weight bearing was takenaway by the ----- (a) foot (b) lower limbs

3. Shoulder region has clavicle and -------bones(a) scapula (b) humerus

4. Upper arm has ----------- bone

(a) Humerus (b) Radius

5. Forearm has radius and ------ bones

(a) humerus (b) ulna

6. The joint between humerus and scapula is

____________ joint. (a) glenoscapular(b) glanohumeral

7. The joint between clavicle and scapulais ---------- (a) acromioscapular

(b) acromioclavicular

8. Clavicle bone and scapula are also knownas ---------- and -------- (a) shoulder blade,

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collar bone (b) collar bone, shoulder blade

9. Clavicle bone & sternum form -----joint

(a) Clavicular sternal (b) sternoclavicular

10. The primary function of synovial fluid is toprovide -------- to the articulating surfaces(a) support (b) lubrication

11. The synovial fluid also ----------- thearticulating cartilages.

(a) nourishes (b) support

12. The joint between humerus with both radiusand ulna is called ------- joint

(a) elbow (b) radioulnar

13. The joint between radial and ulna is called

-------- (a) ulnaradial (b) radioulnar

14. The shoulder girdle consists of the collarbone and -------- (a) scapula (b) clavicle

15. Ligaments are ------- tissues (a) passive (b)active

16. Muscles are ----------- tissues (a) passive(b) active

17. The movement of the elbow joint iscoordinated & controlled by -------

(a) ligaments (b) muscles

18. Radius is joined with ------- to ulna(a) ligaments (b) muscles

19. The radioulnar joint permits----------movement of the forearm along the long axis(a) rotational (b) abduction

20. The wrist joint is a synovial joint of -------variety (a) ellipsoid (b) condyloid

21. The knuckle joint is a synovial joint of

--------- variety (a) ellipsoid (b) condyloid

22. The thumb joint is a synovial joint of

---------- variety (a) saddle (b) plane

23. Radiocarpal joint is a ----------- joint(a) wrist (b) knuckle

24. Metacarpophalangeal joint is a ---------- joint(a) wrist (b) knuckle

25. Carpometacarpal joint is a --------- joint

(a) knuckle (b) thumb

ANSWERS

1. (a) 2. (b) 3. (a) 4. (a) 5. (b) 6. (b)7. (b) 8. (b) 9. (b) 10. (b) 11. (a) 12. (a)

13. (b) 14. (a) 15. (a) 16. (b) 17. (a) 18. (a)19. (a) 20. (b) 21. (a) 22. (a) 23. (b) 24. (b)25. (b)

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Knowledge is a collection of facts. Wisdom is knowing how to apply knowledge.

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INTRODUCTION

1. The lower limb in its basic design is similarto the upper limb because both of them wereused earlier for locomotion. Each limb has agirdle (shoulder or hip girdle) by which it isattached to the axial skeleton. The hip girdle

supports three main segments of the lowerlimb: (a) proximal (thigh) (b) a middle (leg),(c) a distal (foot). Each segment moves atits proximal joint. Lower limb has specializedfor support and locomotion. The lower limbis therefore bulkier and stronger than upperlimb

2. The parts of the lower limb are:

S.No. Parts Bones Joints

1. Gluteal region (covers the Hip bone Hip jointside and back of the pelvis)

2. Thigh 1. Femur 1. Knee joint(Hip to knee) 2. Tibia 2. Tibia fibular joint

3. Patella4. Fibula

3. Leg 1 Tibia 1. Ankle Joint(knee to ankle) 2 Fibula 2. Subtalar and transverse tarsal

3 Talus joint 4 Calcancus

4. Foot (Heel to toes) 1 Tarsus 1. Tarsometatarsal (TM) joint(7 tarsal bones)

2. Metatarsus 2. Intermetatarsal (IM) joint(5 metatarsals)3. 14 Phalanges 3. Metatarsophalangeal (MP)

(2 in great toe and3 in toes (4)) 4. Interphalangeal (IP) joint

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3. The hip bone is made of three elements(ilium, pubis and ischium) which are fusedat the acetabulum. Two hip bones form thehip girdle which articulates posteriorly withthe sacrum at the sacroiliac joints. The bonypelvis includes the two hip bones, a sacrumand a coccyx. Hip joint has articulationbetween the hip bone and femur.

4. The fibula of the leg does not take part inthe formation of knee joint. Patella (knee cap)is a large sesamoid bone developed in thetendon of quadriceps femoris. It articulateswith the lower end of femur anteriorly andtakes part in the formation of knee joint.

1. The pelvis consists of the bones viz. ilium,ischium, pubis and sacrum. At birth, threebones are distinct. In adults these bones arefused and synarthrodial joint is formed whichpermits no movement. The pelvis is locatedwith spine at centre and one femur bone ateach end. Any movement of spine or femurbone will result into the movement of thepelvis. Hence there is no muscle whoseprimary function is to move the pelvis.Movements of pelvis are resulted by themuscles of the trunk and the hip.

2. The hip joint is formed by the femoral headfitting well in to the deep socket of theacetabulum. The transverse and teresfemoris ligaments of the hips support andhold the femoral head in the acetabulum asthe femoral head moves. The stability of thehip joint is resulted from its constructionwhich also permits wide range of motionsfacilitating walking, sitting and squatting.The joint permits flexion and extension,abduction and adduction, and inward andoutward rotation. The movement iscontrolled and coordinated by ligaments,muscles and bony structure, and shape of

the hip. The articulating surfaces of thefemoral head and the acetabulum are linedwith hyaline cartilage. These two form adiarthrodial joint which is a ball and socketjoint. Derangement of the hip can producealtered force distributions in the jointcartilage, leading to degenerative arthritis.

C u p s h ap ed Ac etab ulu m

H e misp h erial He ad o f F em u r

Isoc h iu m

Iliu m

Sa crum

H ip J o int

F e m ur

Hip Joint

3. The muscles of the hip joint can be dividedinto (1) hip flexer (psoas, iliacus, rectusfemoris, pectineus and tensor fascia) tocarry out activities such as running orkicking (2) hip extensors are gluteusmaximus and hamstring muscles(biceps femoris-semitendinosus, semimembranosus). The hamstring muscles alsowork as knee flexers (3) Hip abductormuscles providing for the inward rotationof the femur. They are gluteus medius andgluteus minimus. The gluteus medius alsostabilises the pelvis in the frontal plane (4)Hip adductor muscles are adductor longus,adductor magnus and gracilis muscles (5)Outward rotation of the femur is providedby small deeply placed muscles.

1. Case study 1: To understand the stabilityof the hip joint, consider a man who isbent forward and lifting a weight (Wb). Asshown in the figure, the man’s trunk isflexed by an angle α as measured fromthe vertical.

MECHANICS OF THE HIP

FORCES ON THE HIP JOINT

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w b

A B

R

C

W

F

(w + wm b)

Vertica l Vertica l

D

a

b

l

α

W + Wm b

R F A

w l w l

B

C

α θ

The forces acting on the lower limb of theman is shown in the figure. Weight (Wm +Wb) is total ground reaction acting at pointD of the feet where Wm = weight of manand Wb weight being lifted. Wl is the weightof both legs including the pelvis which isacting at point C. F is the force exerted bythe erector spinae muscle supporting thetrunk and acting at the point A. R is thereaction at the union of the sacrum and thefifth lumbar vertebrae (point B). Amechanical model of man’s lower body withforces is illustrated. Assume the force F isacting at angle α to the vertical. Also assumeshortest distance of A, C and D from B isa, b, and c as shown on the model.

Σ ΜΒ = 0, F × a + Wl× b = (Wm + Wb) × c

∴ F =( ) –m b lW W c W b

a

+ ×

Also R sin θ = F sin αand R cos θ = F cos α – Wl

– Wm– Wb

If α = 30°, a : b : c = 1 : 4 : 6 ;w1 = 40% of Wm ; and Wm = Wb

F =

6 4( ) – (0.4 )

11 11111

m m mW W W+ ×

= 12 Wm = 1.6 Wm

= 10.4 Wm

R sin θ = F sin 30 = 10.4 × Wm × 1

2

= 5.2 Wm

R cos θ = 10.4 Wm cos 30 – 0.4 Wm – 2Wm

= (9.152 – 24) Wm

= 6.752 Wm

R = 2 2 2[(5.2) + (6.752) ] mW

= 2 7 04 45 59mW . . .+= 8.52 Wm

θ = tan–1 57It can be seen that muscle force (F) is 10.4times and reaction at joint is 8.52 times theweight of the man when trunk is flexed for30° from the vertical.

2. Case study 2: While walking and running,the body weight is momentarily taken by oneleg. For the single leg stance, the forcesacting on the leg are shown in the figure. Fis the muscle force exerted by the abductormuscle. R is the reaction force developedby the pelvis on the femur. Wm is the weightof the man which acts on the leg as a normalforce by the ground. Wl is the weight of theleg. Let α and β are angles made by F andR with the horizontal. A mechanical modelof the leg with forces acting on it is alsoshown. A is point of rotation of the hip joint;B is point where the hip abductor musclesare attached to the femur; C is the centre ofgravity of the leg where Wl is acting, and Dis point where ground reaction force (= Wm)is acting upwards, The distance from pointB to A, C and D are a, b and c as shown inthe figure. α and β are the angles of F andR from horizontal while θ 1 and θ2 are theangles of femur neck and femur shaft withthe horizontal. The forces acting on the legform a coplanar force system which willgive us three equations of equilibrium (ΣPx = 0, ΣPy = 0, ΣM = 0)

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F R

D

W l

W m

From horizontal α = ang le o f Fβ = ang le o f R

FB D C

α

β α

B

F

R

A

C

W l

W m

D

Fem ora l neck

Fem ora l shaft

a

b

c

θ2

θ1 θ1 = Fem ur neck ang le

θ2 = fem ur sha ft angle

(a cos – b cos θ1 2θ )

D

B

C

A

(a cos – c cos θ1 2θ )

w l

F

Σ MA = 0, F sin α × a cos θ1 – F cos α × asin θ1 – Wl × (a cos θ1– b cos θ2) + Wm × (acos θ1 – cos θ2) = 0

F =m l 2 1

1 1

( – ) cos – a (a – ) cos

a (sin cos – cos sin )mcW bW W Wθ

θ�

� � �

= m l 2 m 1

1

( – ) cos – a ( – ) cos

sin ( – )

CW bW W W

a

θα θ

If we take a : b : c = 1 : 4 : 10, θ1 = 45° θ2=80°, α = 75° and Wl = 18% of Wm, then we get

10 4– 0.18 cos80

15 15

1( – 0.18 ) cos75

151

sin (75 – 45)15

m m

m m

W W

W WF

× × − =

×

=(10 – 0.72) 0.174 – (1– 0.18) 0.259

0.5 mW× ×

Mechanical Model of Leg

One Leg Stance Forces Acting on a Leg

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=9.28 0.174 –.82 0.259

0.5

× ×× Wm

=1.6 – 0.21

0.5 mW×

= 2.78 Wm

Hence force exerted by the abductor muscleis 2.78 times the weight of the man.

Σ Px = 0, F cos α – R cos β = 0or R cos β = F cos αR cos β = 2.78 Wm cos 75 = 0.72

Σ Py = 0, F sin α – R sin β – Wl + Wm = 02.78 Wm – R sin β – 0.18 Wm + Wm = 0or R sin β = 3.6 Wm

R = 2 23.6 0.72+ × Wm

= 12.96 0.52+ × Wm = 3.67 Wm

Also tan β =3.6

0.72 = 5

or β = 78.7°Hence the reaction force at the hip joint is3.67 times the weight of the man and itmakes angle of 78.70 with the horizontal.

3. Case study 3: In the last case study of oneleg stance, we have considered the free body

O

A

F

R

G

β

W – Wm l

α

LG Sh ifted to le ft as

we ight ofle ft side we ight of righ t s ide

Centre line

O

β

O

x

R

y α

β

F W – Wm l

Single Leg Stance

diagram of the leg and mechanical model ofone leg in solving the magnitude of muscleforce (F) and reaction at the joint (R). Asimpler approach for finding F and R is toconsider the free body diagram of the bodyminus the right leg (as shown in the figure)with the left leg on the ground.

The weight of the man minus left leg (= Wm– Wl) does not act at middle line but now itshifts from centre towards a point at leftside of CG point (left side is heavier thanright side as shown in the figure). F ismuscle force at A and R is reaction at hipjoint at point B. Now we get a concurrentforce system which meet at point O. Wecan apply lami's theorem for finding solution.

sin (90 )

F

+ β =

sin (90 – )

R

α

= –

sin (180 – )m lW W

+ α β

cos

F

β =cos

R

α=

sin ( – )m lW W

β α

∴ F =( – ) cos

sin ( – )m lW W β

β α cos β

F =( – ) cos

sin ( – )m lW W α

β αIf we take Wl = 18% Wm, α = 75° andβ = 78.7°

F =( – 0.18 )

sin (78.7 – 75)m mW W

cos 78.7

= 0.82 .196

0.0645mW ×

= 2.49 Wm

R =0.82 0.26

0.0645

× Wm= 3.3 Wm

4. Case study 4: In one leg stance, if a mancarries dumb bell in each hand, we can findmuscle force (F) and hip joint reaction (R).In the free body diagram of the upper body

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with load Wb in each hand and weight= (Wm – Wl) is acting at CG is shown as inearlier case. The force F and reaction R willbe having higher value due to extra loads inthe hand. If we consider three weights Wb,(Wm–W1) and Wb as shown in the figures,the equivalent of these three weight (Wm +2Wb– Wl) will act at point CG′ which willbe towards the left of the center line andthe right of CG. Now we have three forcesystem viz. F, R and Weqv(Wm + 2Wb – Wl)which are concurrent and Lami’s theoremcan be applied for a solution. If we considerthe angle of muscular force makes sameangle α with horizontal as in the last case,the new angle β′ of the reaction will begreater than β of the last case since CG′has shifted towards the right of the man.

Single Leg Stance with Equal Weights in Hands

F =cos

sin ( – )eqvW′β ×

′β α

=cos ( 2 – )

sin ( – )m b lW W W′β × +

′β α

R = cos

sin ( – )eqvWα ×

′β α

=cos ( 2 – )

sin ( – )m b lW W Wα× +

′β α

It can be seen that carrying loads by usingboth hands helps in bringing the equivalentweight closer to the midline of the body andit is effective in reducing requiredmusculoskeletal forces.

5. Case study 5: In the right leg stance if aman carries dumb bell in the left hand, wecan consider upper body less right leg. Theweight of the upper body (Wm– Wl) actingat CG′ as explained in earlier cases will shifttowards the left of the man (at CG′′) due tothe extra load Wb. Hence the length of thelever arm of total gravitational force (Wm–Wl +Wb) with respect to the right hip jointwill increase. To counter balance the largerclockwise moment resulting fromgravitational force, the abductor muscle hasto exert larger force ‘F’ so that it givesstabilising anticlockwise movement at theright hip joint. It can be seen that a shift ofcentre gravity from CG′ to CG′′ towardsthe left of the man will decrease the angle β′to β′′ between R and the horizontal. Thefree body diagram of the upper body andthe action of forces have been shown in thefigure. We have now three force systemwhich are concurrent and solution can beworked out by applying Lami’s theorem.

F =cos ( )

sin ( – )eqvW′′β

′′β α

=cos ( – )

sin ( – )m b lW W W′′β × +′′β α

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R = cos ( )

sin ( – )eqvWα

′′β α

=cos ( – )

sin ( – )m b lW W Wα +

′′β α

It can be seen that shifting of CG′ to CG′′(towards left) will decrease the angle fromβ′ to β′′ for the reaction. The supportingmuscle force F required at the hip joint isgreater when load is carried on the oppositeside of the body as compared to the forcerequired to carry the loads by using bothhands. If the load is carried on the sameside i.e., right side, the supporting muscleforce required at the right hip joint is lessbut the muscle force required at the left hipjoint is greater.

6. Lever approach: The lever approach can beused for calculation of hip joint forces. It isan approximation method. Assumptions are:

(1) all forces are vertical

(2) all anatomical angles are neglected

(3) 1/3 of body weight (Wm) consists oflower limbs and upper body consistsof 2/3 of the body weight. Hence dur-ing single leg stance, the weight of up-

per body and one leg is equal to 5

6 Wm.

(4) The ratio of dm (distance of muscleforce from the joint) and dw (distanceof the point where net weight is act-ing) equal to 1:3. As shown is in thefigure.

1 /3 w m

2 /3 w m

dwdm

R 5/6w m

F

dwd m

RF

56

W m

Right Leg Stance Lever Approach : One Leg Stance

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F × dm = 5

6 Wm × dw or

F = 5

6 × Wm × w

m

d

d =

5

6 ×

3

1. Wm

= 2.5Wm.

If man weighs 1000 N, Then,

F = 2.5 × 1000 = 2500 N and

R = 2500 – 1000 = 1500 N.

7. Pathological hip joint: The angle offemoral neck from normal is about 125°. Invalgus deformity, the femoral neck bendsor twists outward and the angle becomes

Norm al

d m

θ = 125°

d ’m dG

Wθ >125°

d ’m d m<Valgus

F

56

d”m d G

θ < 125° W

Varusd dm>

F

65

greater than 125°. The moment arm of themuscle force (dm) decreases to dm'. Henceabductor muscle force (F) has to increase

to provide stabilising moment to balance themoment development by the weight of upperbody and one leg during single leg stance asF × dm' –5/6W × dG. As F has increased whileweight does not change, reaction (R) at thejoint will also increase. In varus deformity,the femoral neck bends or twists inward andthe angle of femur neck with normalbecomes less than 125°. This will increasedm to which will result in decrease ofabductor muscle force (F) as

dm″ × F =5

6 Wm× dG. Similar effect takes

place if femoral neck is longer than usual.However bending stresses in the femoralneck increase in various deformity or whenfemoral neck is longer than usual.Therefore, femoral neck is more susceptibleto fracture.

8. Other factors affecting hip joint: Peoplewith weak hip abductor muscles or painfulhip joints usually lean towards the weakerside and walk with an abductor gait. Leaningthe trunk sideways towards the affected hipshifts the centre of gravity of the body closerto the affected joint. The shifting of CGresults into the reduction of the moment armof the body weight. This reduces therotational action of the moment of the bodyweight. Hence we require lower magnitudeof abductor muscle force (F) to stabilise themovement due to the weight. Abductor gaitcan also be corrected more effectively witha cane held in the hand opposite to the weakhip joint as shown in figure on next page.The reaction on the cane acts opposite tothe body weight and that too with a biggermoment arm from the hip joint. The abductormuscle force (F) reduces as F × dm = W×dG– Rcane× dcane. The lower F means lowerhip joint reaction (R).

Pathologic Hip Joint

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1. The knee is the largest joint in the body. It isalso a most complex joint. The complexityis the result of fusion of three joints in one.It is formed by fusion of the lateralfemorotibial, medial femorotibial andfemoropatellar joints. It is a compoundsynovial joint, incorporating two condylarjoints between the condyles of femur (thighbone) and tibia (leg bone) and one saddlejoint between the femur and the patella. Thefemorotibial has two distinct articulationsbetween the medial and lateral condyles of

Abduction Gait

MECHANICS OF THE KNEE

Effect of Cane

the femur and the tibia. These articulationsare separated by layers of cartilage, calledmenisci (fibrocartilaginous discs). Thelateral and medial menisci prevent bone tobone contact between the articulatingsurfaces of the femur and the tibia and theyalso work as shock absorbers. Thefemoropatellar joint is the articulationbetween the anterior end of the femoralcondyles and the patella which is a floatingbone kept in position by the quadricepstendon and the patellar ligaments. The patellaalso protects the knee from impact relatedinjuries and enhances the pulling effect of

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quadriceps muscles on the tibia throughpatellar tendon. The stability of the knee jointis provided by (1) ligaments (2) menisci (3)muscles crossing the joint. Flexion andextension are chief movements. Thesemovements take place in the uppercompartment of the joint above the menisci.They differ from the ordinary hingemovement in two ways (1) The transverseaxis around which these movements takeplace is not fixed. During extension, the axismoves forward and upwards and in thereverse direction during flexion, (2) Thesemovements are invariably accompanied byrotations. Rotatory movements at the kneeare of a small range. Rotations take placearound a vertical axis and are permitted inthe lower compartment of the joint, belowthe menisci. Muscles producing movementsat the knee joints are:

Movement Principal Muscles

1. Flexion 1. Biceps femoris

2. Semitendinosus

3. Semimembranosus

2. Extension 1. Quadricep femoris

3. Medial rotation 1. Popliteus

of fixed leg 2. Semimembranosus

3. Semitendinosus

4. Lateral rotation Biceps femoris

of flexed leg

2. The knee is a weak joint because the articularsurfaces are not congruent. The tibialcondyles are too small and shallow to holdthe large and convex femoral condyles inplace. The femoropatellar articulation is alsoquite insecure because of the shallowarticular surfaces and the outwardarticulation between the long axis of the

meniscus

���������������� biceps femorishead

of fibula

����������Tibial collateraligament

Lateralcondyle

MedialcondyleMedialmeniscus

Tibia

anteriorborder of tibia

Front view

Femur

Fibularcollateralligament

Lateralmeniscus

Femur

biceps femoris

fibula

Quadricepstendon

Patella

bicepsfemoris

Patellar ligament

Cruciate ligamentsCapsular ligaments

Quadriceps

patella

Tibia

Qukadriceps femorls extending knee

Quadriceps

patella

Posterior (Back view) Bicep femoris flexing knee

Patella

Lateral (side view)

Tibia ligaments

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thigh and of the leg. The stability of the jointis maintained by cruciate and collateralligaments and muscles crossing the joint. Theleg may be abnormally abducted (genuvalgum or knock knee) or abnormallyadducted (genu varus or bow knee).Common injuries are (1) injury to menisci(2) injury to cruciate ligaments (3) injury tocollateral ligaments.

3. Another leg bone on the outerside of tibia isknown as fibula. It acts as support to thetibia but does not take any part in the kneejoint formation. The front portion of the kneejoint is formed by patella which articulateswith the lower part of the femur and upperpart of the tibia. The patella moves up anddown with contraction and relaxation of thethigh muscle while straightening and bendingthe joint. The movements of the joint aresmooth and painless as long as there is notrauma or irregularity in their articularsurfaces. Any physical or nutritional traumamay cause degeneration of the articularsurfaces or loose body formation. Thesechanges are associated with pain andirregular movements at the joint and furtherdegeneration of the joint.

4. Case study 1: To determine muscle force‘F’ acting in patellar tendon, reactions Raxialand Rshear on the tibial plateau when a manweighing 1000 N is slowly climbing the stairsas shown in the figure. Let θ is angle madeby the tibia with horizontal, t = distancebetween patellar tendon from the patellofemoral joint, S = horizontal distancebetween ground reaction and the patellofemoral joint. Assume the weight of thelower leg and any effect of fibula arenegligible. We have now a system ofcoplanar force system and we get threeequations of equilibrium i.e. ΣMj = 0, ΣPx= 0, ΣPy = 0, ΣMj = 0, F × t – 1000 × S = 0

or F = 1000 × S

t

ΣPx = 0 (along the long axis of the tibia)Raxial = 1000 cos θ + F

Σ PY = 0, Rshear = 1000 sin θIf we take t = 60 mm, s = 200 mm and

θ = 60°, then

F = 1000 × 200

60 = 3333.3 N

Raxial = 1000 ×1

2 + 3333.3

= 3833.3 N

Rshear = 1000 × 3

2 = 866 N

5. Case study 2: A man is wearing a heavyboot and doing lower leg flexion and

Free Body Diagram of Lower Leg

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extension exercise from a sitting position asshown in the figure. We draw the free bodydiagram of lower leg as well as mechanicalmodel of the leg. F is the magnitude of forceexerted by the quadriceps muscle on the tibiathrough the patellar tendon.R is the reaction on the tibiofemoral joint atpoint 0. The patellar tendon is attached tothe tibia bone at point A. The CG of the lowerleg is located at point B. The CG of the bootis located at C. The distance of point ABand C from point O are a,b and crespectively. The tibia makes an angle of αwith horizontal and the muscle force makesangle of β with the long axis of the tibia. Weresolve the forces along the tibia axis (x-axis) and vertical to the tibia axis (y-axis)

Fx = F cos βFy = F sin β

R

F

w b

αwl

C

b

aA

C

β0

y x

Ry

w ly

w lx

α

w byw bx

Fy

B

R X

F y

θ

Wbx = Wb sin αWby = Wb cos αWlx = Wl sin αWly = W1 cos α

Taking moment about point 'O' which is ΣMO

= 0

F sin β × a – Wl cos α × W

b cos α × c = 0

or F = ( ) cos

sinl bb W c W

a

+ αβ

Now Σ Px = 0

R cos θ – F cos β + Wb sin α+ Wl sin α = 0

Now, ΣPy = 0

R sin θ = F sin β – (Wb + W

l) cos α.

2 2[ cos – ( ) sin]b bR F w w= α − +

[ 2sin ( ) cos ]b bF W Wβ + + α

Exercising Knee Joint

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R2 = 2 2( )b lF W W+ +

–2 ( ) sin ( )b lF W W+ α + β

6. It can be seen that normal component of F(quadricep muscle force = F sin β) tries torotate the tibia about the knee joint while itstangential component (= F cos β) along thetibia axis tends to move the tibia towardsthe tibiofemoral joint. If θ is small, F cos θis more and more muscle force is wasted tocompress the knee joint. If θ is large, F sinθ is large and a larger portion of the muscletension is used to rotate the tibia or lowerleg about the knee joint.

7. It can be seen that the patella bone providesanterior displacement of the quadriceps andpatellar tendons thus lengthening the momentarm of the muscular force by increasing theangle β. As shown in the figure, muscularforce F make angle β1 when patella is presentand angle β2 when patella is absent. Themoment arm is AB sin β1 with patella > ABsin β2 without patella as β1> β2. Decreasingof moment arm results into the quadricepsmuscle to exert more force than normal torotate the lower leg about the knee joint.

β1 2 > β

P a te lla

Bβ1

P a te lla re m o ve

F F

Bβ1

A

K n ee w ith p a te lla K n ee w ith o u t p a te lla

8. It can be seen that quadriceps muscle goesover the patella while getting connected tothe femur and the tibia. The patella and themuscle form a rope pulley arrangement. Thelarger is the tension in the muscle, the largeris the compressive force or pressure, thepatella exerts on the femoropatella joint.

Now we have three forces F , F and R whichare concurrent at point 0 with angles of theforces are α, β and v respectively with thehorizontal. We can apply Lami’s theorem forfinding a solution.

R

O

β

α

F

v

β

F

F

α

R

O

v

sin ( )

F

β + γ =sin (180 – ( )

F

α + γ

= sin(180 – –

R

β α

sin ( )

F

β + γ=

sin ( )

F

α + γ =

sin ( – )

R

β α

or R =sin ( )

F

α + γ sin (β–α)

or R = sin ( )

F

β + γ sin (β–α)

and sin ((β + γ) = sin (α + γ) or sin β cos γ + cos β sin γ = sin α cos γ +

cos α + sin γ or sin β + cos β tan γ = sin α + cos α tan γ

or tan γ (cos β –cos α) = sin α – sin β

or γ = tan–1 sin – sin

cos – cos

α ββ α

Functions of Patella

Patella Pressure on patellofemoral Joint

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1. The ankle joint consists of a deep socketformed by the lower ends of the tibia andfibula into which is fitted the upper part ofthe body of the talus. The talus is able tomove on a transverse axis in a hinge likemanner. The shape of the bone and thestrength of the ligaments and the surroundingtendons make this joint strong and stable.

2. The ankle joint complex consists of threejoints i e. tibiotalar, fibulotalar and tibiofibular.The tibiotalar joint (ankle joint) is a synovialjoint of the hinge variety. The articulation isbetween the spool like convex surface ofthe trochlea (structure serving as pulley) ofthe talus and the concave distal end of thetibia. The tibiotalar joint is the articulationbetween the external malleolus (roundedbony) of the tibula and the medial and lateralsurfaces of the trochlea of the talus. Thedistal tibiofibular joint is the articulationbetween the internal malleolus of the tibiaand the external malleolus of the fibula. Theankle permits flexion and extension in sagittalplane, inversion and eversion, inward andoutward rotation, and pronation andsupination movements are possible about thefoot joints such as the subtalar andtransverse joints between the talus andcalcaneus.

MECHANICS OF THE ANKLE

Ankle Joint

3. Case study: Consider a man standing ontiptoe of the foot as shown in the figure.The ground reaction equal to weight of theman is acting vertically unwards at point ‘A’F is the magnitude of the force exerted bythe archilles tendon and it makes angle αwith the horizontal at point B. R is themagnitude of reaction exerted by the tibiaon the talus at the ankle joint (point ‘C’).

It makes an angle β with the horizontal. Nowwe have three force system and these forceshave to be concurrent during equilibrium.We can apply Lami’s theorem to find thesolution.

sin (90 )

F

+β=

sin (180 – )mW

α + β = sin (90 – )

R

α

cos

F

β =sin ( – )

mW

α β = cos

R

α

∴ F =cos

sin –mW β

α β

and R =cos

sin ( – )mW α

α β

Ankle Joint

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Fill up the gaps

1. The hip bone is made of ______ elements

(a) two (b) three

2. There are ______ hip bones (a) two (b) three

3. The thigh bone is ___________

(a) Tibia (b) femur

4. Lower limbs and upper limbs have a _____by which they are attained to axial skeleton(a) girdle (b) joint

5. Tibia and ______ are leg bones (a) femur(b) fibula

6. The hip joint is formed by the femoral headfitting well into the deep socket of the_______(a) acetabulum (b) sacrum

7. The _______ of the leg does not take part inthe formation of knee joint (a) tibia (b) fibula

8. Patella is also known as ______ (a) kneecap (b) force deflector

9. Patella is a large _______ bone developed inthe tendon of quadriceps femoris

(a) sesamoid (b) irregular

10. Acetabulum has a shape of ______

(a) cup (b) plane

11. In varus deformity, the femoral neck bendsor twists ______ (a) inward (b) outward

12. In valgus deformity, the femoral neck bendsor twists (a) inward (b) outward

13. The angle of femur neck with vertical isgreats than 125° for ______ and less than125° for ______ (a) valgus, varus (b) varus,valgus

OBJECTIVE TYPE QUESTIONS

14. The femoral neck is ______ susceptible tofracture in varus deformity (a) more (b) less

15. A man with weak hip abductor muscle orpainful hip joint usually lean ______ theweaker side (a) toward (b) away

16. Leaning towards the painful side whilewalking is called _______ (a) abductor gait(b) crippled gait

17. The largest joint in the body is ______(a) knee (b) hip

18. The most complex joint in the body is _____a) knee (b) hip

19. The knee joint is a complex joint formed bythe thigh bone, leg bones and _____(a) patella (b ) talus

20. The ankle joint formed by the tibia and fibulaas they form socket into which is fittedupper part of the _____(a) calcaneous(b) talus

21. Patella also ________ the moment arm ofthe muscular force during extension(a) shortens (b) lengthens

22. The knock knee is an abnormality of the kneejoint when the leg is abnormally -----(a) adducted (b) abducted

23. The bow knee is an abnormality of the kneejoint if the leg is abnormally ---------(a) adducted (b) abducted

24. Cane is held -----side of the painful hip jointto reduce the abductor muscle force

(a) same (b) opposite

ANSWERS

1. (b) 2. (a) 3. (b) 4. (a) 5. (b) 6. (a)7. (b) 8. (a) 9. (a) 10. (a) 11. (a) 12. (b)

13. (a) 14. (a) 15. (a) 16. (a) 17. (a) 18. (a)19. (a) 20. (b) 21. (b) 22. (b) 23. (a) 24. (b)

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Accept God's advice gracefully as long as it doesn't interfere with what youintend to do.

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1. The blood has carriers of fuel supply. Theblood has ability to transport waste materialsto predestined destinations. The blood alsocontains a mechanism for repairing smallsystem punctures and a method for rejectingforeign elements from the system. Man isable to sustain life because the blood issupplied to all systems of the body. Thecirculating blood supplies oxygen andnutrients to the cells of the body. The heartis a very important organ in the body whichacts as a pump to circulate the blood in thebody. The failure of heart is the cause ofmany deaths. There are many techniquesand instruments to measure functioning ofheart and to diagnose any of itsmalfunctioning for treatment so as to avoidits failure. The cardiovascular systemconsists of heart, distribution system (arteriesand arterioles), diffusing system (capillariesin contact with cells) and collecting systems(veins), The cardiovascular system is aclosed hydraulic system. Blood pressure,

INTRODUCTION flow and volume are measured by usingengineering techniques.

1. The cardiovascular system or the bloodvascular system is a closed hydraulicsystem. The blood consists of plasma andcorpuscles. The red corpuscles, whitecorpuscles and thrombocytes are suspendedin the plasma. There are about 4.5 to 5.5million red blood cells per cubic millimeterof blood. There is about 3.5 to 5 litres/minblood circulating in normal adult at rest. Theblood circulating system consists of:

(a) Heart: The circulation of blood ismaintained within the blood vessels bythe rhythmic pressure in the trunkvessels exerted by the contraction andexpansion of the heart. The heart actsas a pump whose elastic muscular wallscontract rhythmically to developpressure to push the blood through thevascular system. The heart contracts

WORKING PRINCIPLE OFCARDIOVASCULAR SYSTEM

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Blood Circulation Systemically

continuously and rhythmically, withoutrest, about 1,00,000 times per day. Theaverage heart rate is 75 beats per mini.e., each cycle of beat is completed in0.8 seconds.

(b) Distribution system: The blood issupplied to all cells of the body throughdistribution system which consists ofarteries, arterioles and capillaries. Eachartery bifurcates to smaller arteries untilsmaller type (arterioles) is reached. Thearterioles feed into the capillaries whereoxygen is supplied to the cells andcarbon dioxide is removed from thecells. The oxygen depleted blood movesto venules.

(c) Diffusing system: It consists of finecapillaries which are in contact with thecells of the body. Capillaries take blood

from arterioles and transference ofoxygen to cells and carbon dioxide tothe blood takes place through capillaries.The oxygen depleted blood fromcapillaries moves to vein. Tissuemetabolism is the process by whichcells take oxygen from blood and giveout carbon dioxide to blood.

(d) Collecting system: It consists of veins.It collects blood which is depleted ofoxygen and which contains wasteproducts of metabolic processes fromvarious organs. The blood is taken backto heart which sends it to lungs forreoxygenation and then the recirculationof oxygenated blood to all systems ofthe body. The veins differ from arteriesin having valves to control the directionof flow towards the heart.

Vena Cava

Aorta

Right Lung

Cor

onar

y si

nus

InferiorVena Cava

PulmonaryVein

Tricus pid Valve

Sem ilunarva lve

PulmonaryArtery

MitralValva

Aorticva lve

Tissue

Left A triumLeft

ventricle Left Lung

Tissue

Right At rium

Right Ventricle

Superior Vena Cava

CO2

O2

CO 2

O2CO 2

CO 2

O 2

O 2

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VeinCapilla ries B igger Arte ry

TissueArterioles Sm alle r Artery

Co llecting system

Diffusing system

Distr ibu tion system

Venu le

2. The organs which are supplementing thefunctioning of cardiovascular system are:

(a) Lungs: The blood with carbon dioxideand air intake reach lungs whichprovide a region of interface for thetransfer of oxygen to the blood fromair and removal of carbon dioxide fromthe blood to the air.

(b) Kidney/liver and spleen: These organshelp in the removal of waste products

Blood Circulation

Distribution, Diffusion and Collecting System

and in maintaining the chemical qualityof the blood.

1. The heart can be considered as a pair oftwo stage pumps working in series with eachstage of the pumps arranged physically inparallel. However the circulating bloodpasses through from first stage to second

THE HEART: WORKING ANDSTRUCTURE

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stage. The heart has two halves viz. theright heart and the left heart. The right heartis a low pressure pump while the left heartis a high pressure pump. The right heartreceives blood from inferior venacava andsuperior venacava veins and pumps it to thelungs. The blood flow through the lungs iscalled the pulmonary circulation. The leftheart receives blood from the pulmonaryvein. The left heart acts as a pressure pumpand it pumps the blood for the systemiccirculation which has a high circuitresistance with a large pressure gradientbetween the arteries and veins. The musclecontraction of the left heart is larger andstronger as it is a pressure pump while theright heart is a volume pump with lessercontraction. However, the volume of bloodhandled by each pump is same as they areworking in series. The cardiac muscles formthe wall of the heart. The structure issomewhat in between striped and unstriped.The muscles are not in the control of “will”.The muscles contract rhythmically and theyare immune to fatigue. The muscles receivetheir own blood supply from the coronaryarteries.

2. The deoxygenated blood enters the storagechamber of the right heart which is calledthe right atrium. The coronary sinus alsobrings the deoxygenated blood aftercirculating through the heart by the coronaryloop and empties it into the right atrium.When the right atrium is full, the right heartcontracts and it forces blood through thetricuspid valve into the right ventricle. Nowthe right ventricle contracts, the tricuspidvalve closes and the pressure in the ventricleforces the semilunar pulmonary valve to openso that the blood can flow throughpulmonary artery into the lungs. The bloodis oxygenated in the lungs.

3. The oxygenated blood enters the left atriumfrom the pulmonary vein. The blood ispumped into the left ventricle through mitral

(also called bicuspid) valve by thecontraction of the left atrium muscles. Whenthe left ventricular muscles contract, thepressure increases and it closes the mitralvalve. The pressure further increases and itforces the aortic valve to open, permittingthe blood to rush into the aorta. The outwardflowing of the blood from the right and leftheart takes place synchronously. Thepumping cycle can be divided into two partsviz. systole and diastole. Diastole is the periodof dilation when the left and right atrium arefilled with blood. Systole is the period ofcontraction, of the left and right ventriclemuscles when the blood is pumped into theaorta and the pulmonary artery. Once theblood has been pumped into the arterialsystem the muscles relax resulting in adecrease in pressure in both ventricles. Thein a outlet valves close and inlet valves opento restart a new cycle of the heart. Thevolume of blood is about 5 to 6 litres in aman and the heart pumps about 5 litres permin during resting. Hence heart can circulatecomplete blood in about one min. However,during running or heavy exercise thecirculation rate is increased considerably. 120mm Hg (Mercury) is the average bloodpressure during systole which is called “highblood pressure”. 80 mm Hg is the averageblood pressure during diastole which is called“low blood pressure”. A healthy person has120/80 blood pressure which means systolicpressure = 120 mm Hg (it is gauge pressure,which gives absolute pressure = 120 + 760

mm = 880 mm Hg ≈880

1000 × 13.6 × 9.81 =

117.4 kpa) and diastolic pressure = 80 mmHg (It is gauge pressure. The absolutepressure = 80 + 760 = 840 mm of Hg =

840

1000 × 13.6 × 9.81 = 112.07 kpa). The rise

of the blood pressure or the fall of the bloodpressure from the normal blood pressure

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indicates malfunctioning of heart or anyblockade in the arterial system.

4. Structure of the heart: The walls of theheart are composed of a thick layer of cardiacmuscle which is called myocardium.Myocardium is covered externally by theepicardium and lined internally by theendocardium. The heart is divided into fourchambers by septum. Septum is a thin wallwhere it divides atrial portion into right andleft atrium. Septum is a thick wall where itdevides ventricular portion into right and leftventricle. The superior venacava opens intothe upper part of the right atrium. Theopening does not have any valve. It returnsthe deoxygenated blood from the upperportion of the body. The larger inferior venacava opens into the lower part of the rightatrium. It has non functioning valve at theopening. The deoxygenated blood from thelower portion of the body enters through it.The coronary sinus brings blood aftercirculation from the heart and it has anopening between superior and inferior venacava. The right ventricle is connected withthe right atrium through the atrioventricularorifice which is guarded by the tricuspidvalve. The tricuspid valve consists of threecusps. The right ventricle is connected tothe pulmonary artery through pulmonaryorifice which is guarded by the pulmonaryvalve. The valve consists of three semilunarcusps. The four pulmonary veins, two from

Myocardium

Endocardium

Pericardial Cavity

Aorta

Fibrous pericardium

Epicardium

Parietal SerousPericarduim

Diaphragm

each lungs, open into the left atrium. Theopening has no valve. The left atrium isconnected to the left ventricle through theatrioventricular orifice which is guarded bythe mitral valve. The left ventricle isconnected to the aorta through the aorticorifice which is guarded by the aortic valve.It consists of three cusps. The walls of theleft ventricle are three times thicker than thewalls of the right ventricle as to withstandthe six times higher pressure in the leftventricle as compared to the right ventricle.As the ventricle has to perform strongerpumping work, its walls are thicker than thewalls of the atrium and its surfaces areridged. The shape of right ventricle iscircular while it is crescentic for the leftventricle.

Pu lm onary Va lve

Tricuspid Va lve

R igh t Ve ntricle

R igh t Atrium

Su perio r Ve na C ava

In fe rio r Ve na C ava

Blood

D eoxygena ted B lo od

R A R V

5. Valves of the heart: The valves of the heartmaintain unidirectional flow of the blood. Italso prevent the regurgitation of the bloodin the opposite direction. There are fourvalves in the heart which consist of a pairHeart : Walls and Layers

Heart Structure and Blood Flow

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PREFIXES

of atrioventricular valves and a pair ofsemilunar valves. The atrioventricular valvesare a tricuspid valve having three cuspsguarding right atrioventricular orifice and abicuspid valve (mitral) having two cuspsgaurding the left atrioventricular orifice. Thesemilunar valves are the aortic andpulmonary valves, each having threesemilunar cusps as shown in figure.

Pu lm on ary Valve

Ao rtic V alve

T ricuspid Va lve

B icusp id Va lve(M itra l va lve )

Atrioventricular valves are made of a fibrousring to which the cusps are attached. Theseare flat and project into the ventricular cavity.The valves are closed during ventricularsystole. The tricuspid valve has three cusps.

Fibrous ring

Cusp

Papillary Muscle

It can admit the tips of three fingers. Thebicuspid (Mitral) valve has two cusps. It canadmit the tips of two fingers. The bicuspidcusps are smaller and thicker than those ofthe tricuspid valve. The atrioventricular valvehaving 3 cusps is shown in figure.

Four Valves of the Heart(Cut portion and Atria Removed)

Semilunar valves are the aortic andpulmonary valves. They are called semilunarvalves because their cusps are semilunar inshape. Both valves are similar to each other.Each valve has three cusps which areattached to the vessel wall. The cusps formsmall pockets with their mouth facing awayfrom the ventricles. The valves are closedduring ventricular diastole when the cuspsexpand in the ventricular cavity.

6. The conducting system of the heart: Theheart contracts rhythmically at about 70beats per minute in the resting adult. Therhythmic contractile process originatesspontaneously in the conducting system andthe impulse travel to different regions of theheart so that both atriums contract first andtogether which is to be followed later by theboth ventricles contracting together. Theslight delay in the passage of the impulsefrom the atria to the ventricles permits timefor the atria to empty their blood into theventricles before the contraction of theventricles. The sinoatrial node (SA) islocated superior to the right atrium (fullthickness of myocardium) where theexcitation of the heart contraction is initiated.Sinoatrial (SA) node is also called pacemakerand it is a special group of excitable cells.Once initiated, the cardiac impulse spreadsthrough the atrial myocardium to reachthe at rioventricular (AV) node. Theatrioventricular node is situated in the lowerpart of the atrial septum just above thetricuspid valve. From AV node, the cardiacimpulse is conducted to the ventriclesby the a t r ioventricular bundle. The

Atrioventricular Valve

The Aortic Valve

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atrioventricular is the only muscularconnection between the myocardium of theatria and the myocardium of the ventricles.The atrioventricular bundle descends to thelowest part of the ventricle septum. At theupper part of the septum, the atrioventricularbundle divides into two branches, one foreach ventricle. The right branch movesdown on the right-side of the ventricularseptum and emerges at the anterior wall ofthe right ventricle where it joins with thefibers of the purkinje. The left branch of thebundle pierces the septum and passes downon the left side of the septum beneath theendocardium. The left branch further dividesinto two branches which ultimately join withthe fibers of the purkinje of the left ventricles.The conducting system not only generatesrhythmical cardiac impulses but alsoconducts these impulses quickly throughoutthe myocardium of the heart. It is essentialso that the different chambers of the heartcan contract in a coordinated and efficientmanner. The SA node creates an impulse ofelectrical excitation that spreads across theright and left atrium. The right atriumreceives the early excitation as it is nearerto the SA node. This excitation causes theatria to contract. A short time later, theexcitation simulates the AV node. After a briefdelay the activated AV node initiates animpulse into the ventricles through thebundle of HIS. The bundle branches takethe impulse to the fibers of purkinje in themyocardium. The contraction occurs in themyocardium and the blood is pumped intopulmonary artery and aorta from the rightand left ventricles. The heart rate is controlledby the frequency at which the SA nodegenerates impulses. But the nerves of thesympathetic nervous system and the vagusnerve of the parasympathetic nervous systemcause the heart rate to quicken or slow downrespectively. The effects of the sympatheticand vagus nerves are in opposition to eachother but the result is additive if they bothoccur together in opposite directions. The

action of these nerves is called their tone.The nerves affecting the rate of the heartare controlled by the brain. The heart rateincreases when a person is anxious,frightened or when a person indulges intoovereating or has respiration problems orhigh blood pressure.

SA Node (Pacem aker)

AV Node

Bund le o f H IS

R igh t bundle b ranch

Purk in je fibers

Left bundle b ranch

1. Surrounding the cells of the body are bodyfluids which are ionic and they provideconducting medium for electric potential.The cells of nerve and muscle which arerequired to generate biopotential, have a semipermeable membrane. The membrane hasunique characteristic to permit ions of somesubstances to pass through it while othersare blocked on its surface. The body fluidshave prinicpal ions of sodium (Na+),potassium (K+) and chloride (Cl–). Themembrane permits potassium and chlorideions to enter inside the cell while it blockssodium ions. In order to maintain the balanceof ions inside and outside the cells, there ishigher concentration of sodium ions atoutside which is equal to higherconcentration of chloride ionsat potassiumions of inside the cell. Though ionic balancefrom the concentration point of view isachieved but the charge imbalance exists with

The Heart : Conduction System

RESTING AND ACTION POTENTIAL

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positive charge at outside and negativecharge at inside. The biopotential is rangingfrom –60 to –100 mV. It is called the restingpotential of the cell and cell in the restingstate is called to be polarized. Whenmembrane is excited by any externalenergy, the characteristics of themembrane change. The membrane nowpermits more sodium ions to enter into thecell.The movement of positive chargedsodium ions constitutes an ionic current flow

which lowers the charge barrier built acrossthe membrane due to positive sodium ionsand negative chloride ions. The reductionof the charge barrier accelerates thepassage of sodium ions in the cells. Thepotassium ions which have higherconcentration during the resting state insidethe cell, start moving out of the cell buttheir passage is not as rapid as that of

Polarisation of a Cell

sodium ions. The net result is more positiveions inside the cell. This potential is knownas action potential. Its value is about +20mV. The process of a cell gaining an actionpotential on excitation is known asdepolarization. When the rush of sodium ionsinside the cell stops, the ionic current doesnot flow and the membrane again becomesimpermeable to chloride and potassium ions.The sodium ions inside the cell are quicklytransported to the outside by a process calledsodium pumping and cell is again polarizedto the resting potential. This process isknown as repolarization.

2. The curve showing the potential inside thecell with respect to time during restingpotential, depolarization and repolarization,is called wave form of the action of potential.The cycle time varies from the cell to cell.

Depolarisation of a Cell

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In nerve and muscle cells, repolarization isfast after depolarization and cycle iscompleted in short time (about 1 millisecond). On other hand, the cell of the heartrepolarizes very slowly and cycle takes moretime (about 150 to 300 millsec). Thewaveform of action potential does not dependupon the intensity of the stimulus. Howeverthe stimulus must be strong enough toactivate the cell. After the completion of thecycle, there is a short time during which thecell can not be excited. This period is calledthe absolute refractory period and it lastsabout one millisec. After the absoluterefractory period, the cell can be excited bya very strong stimulus during a period oftime which is called a relative refractoryperiod. The relative refractory period lastsfor much longer time as compared to theabsolute refractory period.

3. Each excited cell generates an actionpotential and current begins to flow. Theother cells in the neighbourhood of theexcited cell also get excited and the actionpotential begins to travel which is calledthe propagation of the action potential. Therate at which it propagates is called

40

30

20

10

0

–10

–20

–30

–40

–50

–60

–70

–80

Bio

pote

ntia

l

Depo la risation Repo la risationAbso lu te and Re la tive

Refractory P eriod

Tim e (m illi seconds)

Waveform of the Action

propagation rate or conduction rate. Theconduction rate depends upon the type ofcell and diameter of muscle or nerve. Theconduction rate is faster in nerves (about 2to 140 meter/sec) while it is slow in heartmuscle (0.03 to 0.4 meter/sec.)Thebiopotentials generated by the muscles ofthe heart give electrocardiogram (ECG) Thebiopotential generated by the neuronalactivity of the brain is called the electroencephalogram (EEG). The biopotentialassociated with muscle activity constituteelectromyogram. (EMG)

1. The biopotentials generated by the musclesof the heart with time is called the electrocardigram. The action potential starts froma point called the pacemaker or sinoatrial(SA) node which is located near the top ofthe right atrium. The action wave formpropagates in all directions along the surfaceof both atria. The waveform reaches thejunction of the atria and the ventricles. Thewaveform terminates at a point on thisjunction which is called the atrioventricular(AV) node. The propagation of excitation is

THE ELECTROCARDIOGRAM (ECG)

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delayed at AV node so that the ventriclescan be filled up with the blood from the atria.Once the period of delay is over, theexcitation is spread to the all parts of theventricles by the bundle of His. The fibersin the bundle (called Purkinje fibers), branchout into two parts to initiate action potentialsimultaneously in the myocardium of theventricles. The action potential moves fromthe inside to the outside of the ventricularwalls. The waveform terminates at the tipof the heart. The depolarization iscompleted. After 0.2 to 0.4 sec, a wave ofrepolarization starts in which neighbouringcells play no part but each cell returns to itsresting potential independently.

2. If the biopotential is recorded from thesurface of the body, the curve is obtainedwhich is called ECG. A typical ECG is asshown in the figures. If prominent featuresof the curve are given alphabeticdesignations, we can explain the eventsrelated to the action potential propagationwith the help of these features. Thehorizontal portion right of the point P isconsidered as the baseline or equal potentialline. The wave P represents depolarizationof the atrial myocardium. The depolarizationof ventricles and the repolarization of theatria take place simultaneously which isindicated by QRS part of the curve. The

Biopoten tia lP

R

Q S

J T

U

Tim e

ECG Waveform

wave T represents the repolarization of theventricles. The after potential in the ventriclesis given by the U wave. The P–Q part ofthe curve shows the period of the delaycaused to excitation wave at the AV node.The ECG helps in the diagnosis ofmalfunctioning of the heart. Longer cycletime or slow heart is called bradycardia whileshorter cycle time or fast heart is calledtachycardia. The cycles must be evenlyspaced otherwise a patient has arrhythmia.If the duration between P and R is greaterthan 0.2 second, it suggests the blockage ofthe AV node. If any feature of the curve ismissing, it indicates a heart block.Electrocardiography is the instrument usedto record ECG. The cardiac disorder,specially those involving the heart valves cannot be diagnosed by the ECG and othertechniques like angiography (X-ray photosafter injecting contrasting medium into theblood stream) and echocardiography(Ultrasound measurement of the heart) areused.

1. The beating of the heart and the pumpingof the blood is associated with thegeneration of sounds. The technique oflistening to sounds produced by the heart

HEART SOUNDS

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and blood vessels is called auscultation. Thephysicians are trained to diagnose the heartdisorders by listening to the sounds. Thestethoscope is the device used to listen tothe sounds. The “lub-dub” are two distinctsounds that are audible by the help of astethoscope with each heart beat. The lubis produced when the atrioventricularvalves close and prevent any reverse flowof the blood from the ventricles to atria.The lub is also called the first heart soundand it occur at the time of the QRS part ofthe ECG. The “dub” sound is produced bythe closing of the pulmonary and aorticvalves. The “dub” is also called the secondheart sound and it occurs about the time ofthe end of the ‘T’ wave of the ECG. Thethird sound is sometimes produced aftersecond sound by the rushing of the bloodfrom the atria to the ventricles.

1. The heart has to develops sufficient pressureto circulate blood from heart (1) to lungsand back for oxygenation of the blood (2)to all body systems with the help of the

P

R

T

Q SBiopoten tia l

Tim e

Heart Sound

Th irdSecondFirs t

Heart Sound and ECG

distribution, diffusion and collection systemof the blood. The blood pressure has to besufficient high to overcome the resistanceof the arterial vascular pathways. The flowmust not stop at any cost and even remotestcapillaries must receive sufficient bloodwhich further pass it into the venous system.The other requirement of the blood vascularsystem is that the system must be capableto dampen out any large pressure variation.Our body is equipped with a monitoringsystem which can sense and take correctivesteps by regulating the cardiovascularoperations to maintain proper flow.Therefore in our body, pressure is maintainedwithin a relatively narrow range and the flowis kept within the normal range of the heart.

2. Determining an individual’s blood pressureis a standard clinical measurement. Bloodpressure values in the various chambers ofthe heart and in the peripheral vascular systemhelp in diagnosis of functional integrity ofthe cardiovascular system. First we have tounderstand the two basic stages of diastoleand systole with each heart beat. The pumpedblood from heart has the blood pressurewhich is a function of time (1) in the aorta

BLOOD PRESSURE

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(dotted lines) (2) in the left atrium (dot circlelines) (3) in the left ventricle (full lines ) (4)pulmonary artery (–00– 00) (4) rightventricle (–m–m–) which are shown in thefigure. The events of the heart are alsocorrelated with the features of the ECG inthe same figure.

3. During systole, the output of the blood fromthe left ventricle is high in the beginning andthe blood pressure in the aorta increases tothe maximum (120 mm Hg). The blood

Blood Pressure Variations With Time

pressure falls as the blood moves furtheraway in the blood vascular system. Thesystolic period is completed with the closingof the aortic valve to prevent any back flowof the blood from the aorta to the leftventricle. The dichrotic notch (sudden stopin the drop of pressure) indicates the closureof the aortic valve in the figure. Atvial systolelasts for 0.1 sec and ventricle systole lastsfor 0.3 sec. The arterial pressure graduallydecreases with further flow of the blood into

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the distributing and diffusing system. Theduration of cardiac cycle is 0.8 sec at theheart rate of 72 beats per min.

4. The pressure of the pulsating blood changesas it moves through the arteries. The bloodgets dampened and reflected by the walls ofthe arteries. The pressure and volume alsoget changed when any artery is branchedinto smaller arteries. In smaller arteries andarterioles, the pressure decreases to 60 to

Typical Blood Velocity and Pressure

30 mm Hg and the blood also loses itsoscillatory character when the blood flowsthrough the capillaries into the venoussystem, the pressure drops down to 15 mmHg. The chief seat of peripheral resistanceis arterioles. In venous system, the pressurefurther decreases to 8 mm Hg in the venulesand to 5 mm Hg in the veins . The pressureis as low as 2 mm Hg in the vena cavaNormal mean pulmonary artery pressure is15 mm Hg.

1. The blood pressure is considered a goodindicator of the status of the cardiovascularsystem. The blood pressure is measuredby an indirect method using asphygmomanometer (sphygmos = pulse). Inthis method, the occlusive cuff is inflateduntil the pressure exerted by the cuff on theforearm artery is above the systolicpressure. The pressure of the cuff is nowslowly lowered. When the systolic pressurebecomes higher than the occlusive pressure,the blood in the forearm artery can spurtsunder the cuff and causes a pulpable pulsein the wrist. Audible sounds generated bythe flow of blood and vibration of the vessel

under the cuff are heard through astethoscope. The audible sounds are alsocalled korotkoff sounds. No blood spurts inthe artery till the occlusive pressure is higherthan systolic pressure. On lowering of theocclusive pressure, the blood starts to spurtas and when occlusive pressure becomeslesser than systolic pressure. Themanometer pressure at the first detectionof the pulse, indicates the systolic pressure.As the pressure in the cuff is decreased, theaudible korotkuff sound decreases and atone point, it suddenly stops. The manometerpressure at the point when sound stops,indicates the diastolic pressure.

MEASUREMENT OF BLOOD PRESSURE

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130120110100

9080706050403020

D iasto lic P ressure

Cuff P ressure L ine

Syphgmo m anometer Cuff

S tethoscope

Hand Bu lb

Systolic Pressure

2. The indirect method as described above iseasy to use and can be automated. Howeverit does not provide continuous recording ofpressure variation. It also fails when theblood pressure of a patient is very low.Methods for direct blood measurementprovide continuous recording of the bloodpressure and they are more accurate thanthe indirect method. They require howeverthat a blood vessel be punctured in order tointroduce the sensor. The pulse pressure isthe difference between systolic and diastolicpressure. Mean atrial pressure is diastolicpressure plus one third of pulse pressure.

3. Tension in the wall of blood vessel: Ablood vessel can be considered a thincylinder as thickness of the blood vessel issmall as compared to its internal diameter(diameter > 15 × thickness of the wall). Ifthe internal pressure in the blood vessel is

Blood Pressure Measurement

P1, σ = stress developed, D = diameter ofvessel, t = thickness of the wall, then forequilibrium.

D

t

σ σ

P i

P1 × D = 2 × σ × t

or σ = 2ip D

t∝ P1r where r = radius, t =

thickness and taken constant.

Hence the stress developed in the bloodvessel is proportional to the product of theinternal radius and pressure.

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4. Example: Let us find the stress in the bloodvessels if 1 mm Hg = 130 N/m2 for (1) anaorta having mean internal pressure 110 mmHg, t = 1.2 mm and diameter of 2.4 cm (2)a capillary having mean pressure of 20 mmHg, t = 0.5 µm and diameter of 10 µm (3)the superior vena cava having mean internalpressure of 10 mm Hg, t = 0.15 cm anddiameter of 0.03 m.

As found out σ = pi × 2

D

t

Case 1 : σaorta = 110 130 .024

2 0.8012

× ××

= 143 KN/m2

Case 2 : σcapillary =–520 130 10

2 0.5 10

× ×× ×

Case 3 : σvenacava = 510 130 0.03

2 0.15 10

−× ××

= 26 KN/m2

1. Blood flow is highest in the pulmonary arteryand the aorta as the blood leaves the heartfrom these two points. The flow at thesepoints is called cardiac output. The cardiacoutput in a normal adult at rest varies from3.5 to 5 litres/min. The stroke volume is theamount of the blood that comes out duringeach heart beat. If heart beat = 80 per minand cardiac output = 4 litres /min, then stroke

volume = 4

80 = 0.05 litres/beat. Similarly

cardiac index (n) is defined as the cardiacoutput per min per sq meter body surfacearea. The typical value of n is 3.3 litres/m2/mm. The mean circulation time (≈ 60 sec)can be obtained by dividing cardiac outputto the total amount of blood circulation. Inthe arteries, blood flow is pulsatile. Duringcertain parts of the heart beat cycle, the

BLOOD FLOW

blood flow can occur in reverse direction.The elasticity of the walls of the bloodvessels helps in smoothing out the pulsationand pressure of the blood. The capillariescan enlarge or constrict under the influenceof certain drugs or when exposed to lowtemperatures. The blood flow reduces duringvascoconstriction of the capillaries. Theblood flow increases during vasodilation ofthe capillaries. Hence the status of thecirculatory system can not be determinedby measuring only blood pressure as it varieswith the flow resistance of the capillaries.The basic theory of circulatory function is:

(a) The blood flow to each tissue of thebody is always precisely controlled inrelation to the tissue needs.

(b) The cardiac output is controlledprimarily by the local tissue flow.

(c) The arterial pressure is independent oflocal blood flow or cardiac output.

(d) Veins besides transporting blood backto heart from the tissues, act asreservoir of blood. The veins cancontract and expand as venous wallsare thin which permit the veins to holdmore blood or less blood dependingupon the requirement of varioussystems.

(e) Circulatory shock is caused bydecreased cardiac output. It can be dueto cardiac abnormalities that decreasethe ability of heart to pump blood. Itcan be also due to the factors thatdecrease the vanous return flow. Themost common cause is trauma to thebody as hemorrhage is caused by thetrauma.

2. As we have seen in chapter 2, Newtonianfluids obey Newton’s viscosity equation andviscosity does not change with the rate ofdeformation. Non Newtonian fluids do notfollow the linear relationship between shearstress and the rate of deformation i.e.

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τ ≠ µdu

dy. Blood is also a non Newtonian

fluid. The Reynold number is the ratio of

inertial forces to viscous forces Re = µ

VDρ

where ρ = density, V = velocity D =diameter and µ = viscosity. When Reynoldsnumber is large, inertial forces are large ascompared to viscous forces and the inertialforces tend to diffuse the fluid particles,causing intense mixing of the fluid, whichis characteristic of turbulence. In bloodflowsituations, laminar flow continue to occurat Reynolds number as high as 10,000.Hence the blood flow is laminar in the bloodvascular system except only in the aortaduring a small fraction of each cycle when

(Shear s tress)

P lastic Flu id

Ideal P lastic

Non Newtonian F luid

New ton ian Flu id

D ilatan t F lu id

τ µ =

Inviscid & Idea l Flu id

τ µ =

(Strain Rate )

dudy

dudy

dudy

τµ

= a

nd n<1

dudy

and n > 1

τ n

n

S tenosis

Fluid Classifications

Separation of Blood FLow

flow is turbulent. The turbulent blood flowmay also arise due to a stenosis orobstruction in the circulatory system.Stenosis may also take place in the valves.

3. Synovial fluid: Articulating cavity ofsynovial joint contains synovial fluid. A kneejoint configuration is shown in the figure.Jointing bones have articular cartilage at theirends. Cartilage is collagen rich tissue whichhas two main properties. Firstly it canmaintain shape and secondly it providesbearing surfaces at joints. Cartilage hasporous nature. Joint cartilage has a very lowcoefficient of friction (less than 0.01). Thesqueezc film effect between cartilage andsynovial fluid is considered to give lowcoefficient of friction. Hence the effectiveviscosity of the synovial fluid near thearticular cartilage is abnormally high. There

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is also possibility of increasing concentrationof suspended particles (hyaluronic acidmolecules) in synovial fluid due to filtrationin porous cartilage and its surfacetopography which provide boosted jointlubrication. The articular surfaces areprotected due to the boosted lubrication.

Fem ur

Articular Cartilage

Tibia

Fibu la

Articulating Cavity w ith synovial flu id

4. Special characteristics of blood flow are: (a) the Reynolds number of the blood is high

(range 10,000) which results into a largerentry length (the length in which 99% ofthe final velocity profile is achieved). Inmost cases in the blood vessels the fullydeveloped flow is never reached as theblood vessels start branching before thisstage is attained.

(b) The blood is flowing through the bloodvessels which have different properties. Thereason for the different properties is thatthe blood vessels are formed of differentsubstances such as elastin, collagen andsmooth muscles.

(c) Unusual large bifurcation or branching ofthe blood vessels. There are million of bloodvessels in the blood circulating system.

(d) The blood vessels have to bend into unusualcurvature in the blood circulating systemwhich leads to secondary flow in some cases.

(e) The turbulent flow may arise due to a stenosisor obstruction in the circulating system. Itmay also be due to the defective valves.

(f) The blood has unusual pulsating nature

which arises from rhythmic action of theheart. The pressure and volume increaseduring systole which gradually decreaseduring diastole.

(g) The blood has unusual fluid properties. Theblood consists of millions of differentcorpuscles suspended in the plasma. Thesecorpuscles can deform when these arerequired to pass through the blood vesselshaving diameter smaller than their own.

(h) The blood vessels can contract or enlargeas explained earlier. The veins can enlargeto act as reservoir to store more blood.

5. Hagen-poiseuille flow: The flow of bloodin arteries was investigated by the physicianPoiseuille. He considered laminar flowthrough a horizontal round blood vessel asshown in the figure. The flow moves incylindrical laminae.

Cylindrical Laminae

The equilibrium of a cylinder of radius r andlength dx is considered with pressure P atright and P – δP at left when the blood flowis from right to left. The net pressure forceat the ends must be equal to the shear force.

P πr2 – ( P + δp) πr2 – = τ 2πr.dx

or τ = dp

dx 2

r...(i)

maximum shear stress τ = – dp

dx

2

R when r = R.

Knee Joint : Synovial Fluid

Laminar Flow Through Round Artery

Velocity Profile : Laminar Flow of Blood

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The velocity distribution can be obtained by therelationship

τ = µdU

dy

but y = R – r∴ dy = – dr

Using this, we get τ = µdU

dr...(ii)

Putting value from eqn. (ii) in eqn. (i)

dU

dr=

τ dP

dxr

or U =1

4µ dP

dx r2 + A (on integrating)

Condition; r = R then U = 0

hence A = – 1

4µdp

dx R2

∴ U =1

dp

dx (R2– r2)

The velocity profile in a fully developed laminarartery flow is a paraboloid of revolution. At thecentre line (r = 0), the velocity is maximum.

U max =1

4µdp

dxR2

or U = Umax 1–

2r

R

Total discharge (Q) through the artery

Q = dq∫ = 0

2R

rdrπ∫ .Umax

2

21–

r

R

Q = 2 π Umax

2

4

R =

dP

dx

R4

The average velocity (Umean) is given by

Umean = 2�

Q

R =

1

dP

dx

R2 = max

2

U

6. The proper functioning of all parts of thebody depends on adequate supply of bloodto these parts. If the blood supply to anypart is reduced by a narrowing of the bloodvessel, the function of that part can beseverely affected. Incase the blood flow ina certain vessel is completely blocked dueto blood clot or thrombosis, the tissues inthe area supplied by the blood vessel willdie. The brain stroke takes place when theblood vessel of the brain is blocked. Theheart attack similarly takes place when thereis an obstruction in the coronary arteries thatsupply blood to the heart muscle. A reductionin the blood flow of the coronary arteriescan cause a severe chest pain which is calledangina pectoris. A clot in the blood vesselsin the lung is called an embolism.

7. Blood flow cannot be measured easily. Theblood flow meters are based on the principleof (1) electromagnetic induction (2)ultrasound reflection (3) radiographicprinciple (4) dye dilution (5) chamberplethysmography. The magnetic andultrasound blood flow meters actuallymeasure the velocity of the blood stream. Atransducer is used that envelope an excisedblood vessel to measure the mean velocityof the blood stream. The flow of the bloodcan be worked out. In an ultrasonic bloodflow meter, a beam of ultrasonic energy isused to measure the velocity of flowingblood. A pulsed beam is directed through ablood vessel and transit time is measured.Transit time is shortened if blood flow is insame direction as that of the pulsed beamotherwise transit time is lengthened. Inradiographic method, blood is made visibleby X-rays by the contrast medium and themovement of the blood can be measured.The dye dilution method measures the bloodflow instead of the blood velocity as done

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by the earlier described methods. The dyeis injected at a constant infusion rate I (gms/min). A detector measures the dyeconcentration down stream. Concentrationincreases and finally reaches a constant valueCo (gms/litre). The blood flow F (litres/min)= I /Co. In chamber plethysmography the

venous occlusion cuff is inflated to stopblood return from the veins of the forearm.Arterial flow causes the increase in volumeof the forearm segment which the chambermeasures. The flow of the blood isproportional to the change in the volume ofthe chamber.

Blood F low

N

S

V

M agnet

B lood Vessel

Vo ltage induced is p roportiona l to the

veloc ity o f the b lood

A co lumn o f conductive b lood

D

Flow

Signal w ith frequency (F)

Dopp le r shift o f frequency (Fb)

is p roportional to veloc ity of the b lood

Detecto r detects s igna l’s carry ing frequency F + Fb o r F – Fb depend ing direction o f

Flow

Magnetic Flow Meter

Blood Flow Meter

Dye Dilution Method

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Plethysmograph

8. Solved example: A patient has cardiacoutput of 4.2 litres/min and heart rate of 84beats/min and a blood volume of 5 litre. Findout (1) the stroke volume (2) the meancirculation time (3) the mean velocity in theaorta if it has a diameter of 32 mm.

The stroke volume = Cardiac output/min

beats/min

= 4.2 litres/min

84 beats/min= 0.05 litres

The circulation time = The blood volume

cardiac output/min

= 5litre

4.2 litres/min

= 1.19 min

Flow = Area × mean velocity = AV

∴ Velocity = Flow

A = 2

4.2 litres /min

4

DArea =

= –3/

2

4.2 10 min

0.32�

4

×

2

4.2 4 10

(0.032)

× ×π ×

–3

–4

4.2 4 10

10.24 10

× ×π × ×

= 5.22 m/min

1. Diabetes is a chronic and incurable disease inwhich excess sugar is present in the blood.Sugar (glucose) is necessary to provide energyto cells of the body. Insulin produced by thepancreatic cells of the body that convert theglucose in the blood into energy. In diabetes,the pancreatic cells produce little or no insulinor the body does not respond properly to theinsulin, resulting in glucose levels building upin the blood. The body loses its primarysource of energy. Excess blood sugar levelsover a period of time harm the eyes, kidneys,heart, nerves and blood circulation to limbsbesides starving the cells of the body.

Diabetes and Blood Sugar

DIABETES AND BLOOD SUGAR

O cclus io n

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Fill in the gaps

1. The blood has carrier of ---------- supply(a) fuel (b) water

2. The rhythmic pressure is maintained by thecontraction and expansion of the -----------(a) artery (b) heart

3. The heart beats without rest about 1,00,000times per ------------ (a) day (b) week

4. The average heart rate is ------------ beatsper min (a) 75 (b) 150

5. Arteries, arterioles and capillaries form ---------- systems (a) diffusing (b) distribution

6. The veins form ------------- system

(a) dispatching (b) collecting

7. The left heart receives blood from thepulmonary ----- (a) vein (b) artery

8. The ----- heart is larger and stronger as it isa pressure pump (a) left (b) right

9. The -------- heart is a volume pump

(a) left (b) right

10. The heart is divided into four chambers by ------ (a) epicardium (b) septum

11. The inferior and superior vena cava openinto ------ atrium (a ) left (b) right

12. The right atrioventicular orifice is guardedby ---------- valve. (a) tricuspid (b) dicuspid

13. The pulmonary orifice is guarded bypulmonary valve which consists of ---------semilunar cusps (a) two (b) three

14. The left atrioventricular orifice is guardedby the ------------- valve (a) mitral

(b) tricuspid

15. SA node is also called --------- (a) pulsemaker (b) pacemaker

16. The propogation of excitation is delayed atAV node so that--------can be filled up withthe blood from the -------- (a) atria, venacava (b) ventricles, atria

OBJECTIVE TYPE QUESTIONS

17. The sympathetic nervous system ----- theheart rate (a) quickens (b) slows down

18. The Vagus nerve of the parasympatheticnervous system ---- the heart rate

(a) quicken (b) slows down

19. The ---- state of a cell is called polarised

(a) resting (b) action

20. The process of gaining an action potentialon excitation is called -------(a) polarisation(b) depolarization

21. After sodium pumping the cell is -------- tothe resting potential (a) depolarized

(b) repolarized

22. The dub sound is introduced by the heartby the closing of the valves (a) atrioventricular (b) semilunar and aortic

23. The 'lub' sound is produced by the heart bythe closing of the ------ valves (a) atrioventricular (b) Semilunar and aortic

24. The lub is the -----heart sound (a) first

(b) second

25. The dub is the -- heart sound (a) first

(b) second

26. The first heart sound occurs at the time ofthe -------- part of the ECG (a) PQR

(b) QRS

27. The second heart sound occurs at the ---------- of the ‘T’ wave of the ECG (a) start(b) end

28. The blood pressure is measured by an indirectmethod using a -----manometer (a) cuff

(b) sphygmo

29. ------- pressure is the difference betweensystolic and diastolic pressure (a) pulse

(b) heart

30. The systolic period is completed with theclosing of the -------- valve (a) mitral

(b) aortic

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31. The systolic period starts with the closingof the valve (a) mitral (b) aortic

32. The action potential is about --------- millivolt(a) –70 (b) +20

33. The resting potential is about ---------millivolt(a) –70 (b) +20

34. The walls of the left ventricle is -------timesthicker than the walls of the right ventricle(a) two (b) three

35. The pressure in the left ventricle can be ----------times higher than the right ventricle(a) four (b) six

36. The walls of --------- are thicker and ridgedas composed to the wall of --------

(a) ventricle, atrium (b) atrium, ventricle

37. The delay line is at ------- node (a) SA

(b) AV

38. From the AV node the cardiac impulse isconducted to------- (a) the bundle of His

(b) The purkinje fibre

ANSWERS

1. (a) 2. (b) 3. (a) 4. (a) 5. (b) 6. (b) 7. (a)

8. (a) 9. (b) 10. (b) 11. (b) 12. ( a) 13. (b) 14. (a)15. (b) 16. (b) 17. (a) 18. (b) 19. (a) 20. (b) 21. (b)

22. (b) 23. (a) 24. (a) 25. (b) 26. (b) 27. (b) 28. (b)29. (a) 30. (b) 31. (a) 32. (b) 33. (a) 34. (b) 35. (b)

36. (a) 37. (b) 38. (a)

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1. Respiration consists of two phases viz.inspiration and expiration. Inspiration andexpiration are accomplished by the alternateincrease and decrease of the capacity ofthoracic cavity. The respiration rate is 16 to20 per minutes in adults. It is faster inchildren and slower in the aged. Duringinspiration, air is taken in the lungs and theblood is oxygenated. During expiration, thelungs eliminate carbon dioxide in a controlledmanner. Oxygen is required to sustain lifeas oxygen combines with hydrogen, carbonand other nutrients in order to generate heatand energy. This is called the process ofmetabolism which is taking place in the cells.Carbon dioxide and waste are produced fromthe metabolism. The respiration is the entireprocess of taking in oxygen as a part of airfrom the atmosphere, transporation ofoxygen to the cells and transportion ofcarbon dioxide from the cells to theatmosphere.

1. The right and left lungs are elastic bags whichare soft and spongy. They are located in aclosed cavity which is called thoracic cavity.The right lung has three lobes while the leftlung has two lobes. The lungs can shrink toone-third or less in volume. Air enters intothe lungs through the air passage formedby the nasal cavities, pharynx, larynx,trachea, bronchi and bronchioles. Thetrachea (wind pipe) connects the larynx(voice box) to the left and right bronchus.The epiglottis is a valve above the larynxwhich prevents any liquid or food fromentering into the larynx. Each principalbronchus enters into the corresponding lung.Each principal bronchus on entering the lungdivides into secondary bronchus whichpasses to a lobe of the lung. A secondarybronchus gives off tertiary bronchi. Eachtertiary (segmental) bronchus goes to astructurally and functionally independent

To attain knowledge, add things everyday. To attain wisdom, remove thingsevery day.

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INTRODUCTION THE RESPIRTORAY TRACT

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unit of a lung which is called a bronchopulmonary segment. From here, the airconducting tubes are called bronchioles.Further branching and reduction in size leadsto terminal bronchioles and respiratorybronchioles. The respiratory bronchiole isconnected to alveolar sacs (small air sacs)which are attached in the wall of the lungs.The alveoli receives deoxygenated bloodfrom pulmonary artery and sand oxygenatedblood to heart through pulmonary vein. A

respiratory unit is composed of respiratorybronchiole, alveolar ducts and alveolar sacs.The amount of alveolar air replaced by newatmospheric air with each breath is only

2

3rd alveolar air.

Expired air contains 2/3 rd alveolar air and1/3 rd dead space air (150 ml) i.e., air innasal passage, pharynx trachea and bronchi.

The Respiratory Tract

Soft plate

Epiglottis valve

Larynx (vocal cord)

Left bronchus

Left lung

Diaphragm

Nasal cavity

Hard plate

Oral cavity

Pharynx(throat)

Right bronchus

Right lung

Trachea (wind pipe)

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Bronchus, Alveolar and Capillary Network

1. The thoracic cavity has a single entranceat the top through the trachea. The capacityof the thoracic cavity can be increased byelongating its dimensions in all direction.This results in air under atmosphericpressure entering into the lungs through thetrachea. The size of thoracic cavityincreases due to

THE MECHANICS OF RESPIRATION (1) the movement of diaphragm up anddown which increases vertical diameter (2)the movement of the rib cage up and downwhich increases lateral diameter. Thediaphragm is a bell shaped muscle locatedat the bottom of the thoracic cavity. Thediaphragm on contraction movesdownward and enlarges the thoracic cavity.At the same time muscles lift the rib cage

v ein

sa c s

R ight P rin cipa lB ro nc hu s

T ra ch ea

S ec on da ryB ro nc hu s

Le ft P rinc ipa lB ro nc hu s

Ter tia ryB ro nc hu s

Term inal B ro nc hu s

R es piratory B ro nc hu s

O x y ge nated bloo d toha rt th ro ugh

pu lm on ary v ein

P ulm o na ry v e nule

A lv eola r s ac

A ir

C apilla ryC apilla ry

A lv eola r s ac s

A lv eola r du cts

P ulm o na ry A rter iole

D eox yge nate d bloo dfro m p ulm o nary

A rtery

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and sternum. The geometry of the rib cageis such that on its lifting, it increases thethoracic cavity. As thoracic cavity increasesin volume, a negative pressure is created inthe lungs. The negative pressure is relievedby air rushing into the lungs from theatmosphere. The lungs themselves arepassive organs in the inspiration process.

Diaphragm contracts

& moves down

Diaphragm

New position of diaphargm

Thoracic diameter increases vertically

Rib cage moves up

Sternum

Rib lifted

Rib

Thoracic diameter increase laterally

Vertebrae

The expiration process is also passive and itstarts with the release of the diaphragm andrib cage muscles. The volume of thorociccavity reduces and a positive pressure isdeveloped in the lungs which forces air outof the lungs into atmosphere. Duringinspiration, the pressure inside the lungs isnegative (about–3 mm Hg). Duringexpiration, the pressure inside the lungs ispositive (about +3 mm Hg)

2. Deoxygenated blood is brought by thesuperior and inferior vena cava into the rightatrium, from here it moves into the rightventricle. The blood is pumped to the lungsfrom the right ventricle through pulmonaryartery. The blood in the lungs passes through

the pulmonary capillaries which are locatedin the walls of the alveolar sacs. Here oxygenis taken up by the red corpuscles which formoxyhemoglobin. Simultaneously carbondioxide is liberated from the blood cellswhich is pushed out to the atmosphere byexpiration. The blood pressure in thepulmonary artery is about 20 mm Hg whenblood is pumped by the right ventricle andblood pressure is about 4 mm Hg whensuperior and inferior vena cava brings bloodto the right atrium. The interchange ofoxygen and carbon dioxide takes place inthe capillary surface of the alveoli. Thecapillary surface is more than 75% surfaceof the alveoli (80 m2).

3. The oxygenated blood from the pulmonarycapillaries is carried through the pulmonaryveins to the left atrium. The blood from theleft atrium moves to the left ventricle whichpumps the blood into the aorta at highpressure (about 80 to 120 mm Hg) so thatthe blood can be circulated through all theparts of the body. The blood gives out oxygenat the cells of the tissues. The deoxygenatedblood is collected by the venous systemsinto the superior and inferior vena cava.

4. The flow of the air in the respiratory systemis usually laminar. However, during heavybreathing or when there is any obstructionduring breathing, the flow of the air canbecome turbulent. The Reynolds number atwhich the flow of the air becomes turbulentis as high as 50,000. When Reynolds numberis small, viscous forces dominate overinertial forces. If Reynolds number is lessthan one, inertial forces can be neglected.Low Reynolds number flow is thecharacteristic of air flows in alveolarpassages of diameter less than a few hundredmicrons.

5. Some of the terminology used for therespiratory measurements are:

(a) Hypoventilation: Insufficientventilation to maintain normal partial

pressure of carbon dioxide (2CoP )

Descent of Diaphragm

Antero Posterior Expansion

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(b) Hyperventilation: Abnormallyprolonged, rapid or deep breathingwhich produces the condition of overbreathing

(c) Dyspnoia: Shortness of breath ordistress in breathing usually associatedwith serious disease of lungs.

(d) Hypercapnia: Excess amount of lungcarbon dioxide in the system whichresults from inadequate ventilation.

(e) Hypoxia: It is shortage of oxygen dueto inadequate ventilation

(f) Compilation work: The work requiredto expand the lungs against elasticforces.

(g) Compliance: The volume increase oflung per unit increase in lung pressure.(the compliance is expressed as litresper cm H2O. Compliance of the normallungs is 0.22 litres per 1 cm of H2O).

(h) Airway resistance: It is the resistanceof the air passage and expressed as cmof H2O per litre per sec.

1. Lung volume and capacities are determinedso as to find out the condition of thebreathing mechanism. Certain definitions areused to define the parameter related to thebreathing mechanism are:

(a) The tidal volume (TV): It is thevolume of gas inspired or expiredduring each normal respiration cycle.It is the volume between andinspiratory level and expiratory level.The tidal volume is about 500 mL fora normal adult.

(b) Inspiratory Reserve volume (IRV): Itis the extra volume that can be inspiredabove the tidal volume. The normalvalue of IRV is about 3000 ml.

(c) Expiratory Reserve Volume (ERV): Itis the extra volume that can be expired

by forceful expiration at the end of thetidal volume. The normal value is about1100 ml.

(d) Residual Volume (RV): It is the volumeof air remaining in the lungs despiteforceful expiration. The normal valueis about 1200 ml.

(e) Inspiratory capacity (IC): It is themaximum volume of air that can beinspired after reaching the endexpiratory level. IC = TV + IRV. Thenormal value is about 3500 ml.

(f) Functional residual capacity (FRC) :If the volume of air remaining in thelungs at the end expiratory level. FRC= RV + ERV or FRC = TLC – IC. FRCcan be regarded as the baseline fromwhich other volumes and capacities arespecified. The normal value is about2300 ml.

(g) Vital capacity (VC): It is the maximumvolume of gas that can be expelled fromthe lungs by forceful expiration after amaximum inspiration. It is infact thedifference in volume of the maximuminspiration and the residual volume. VC= IRV + TV + ERV. The normal valueis about 4600 ml.

(e) Total lung capacity (TLC): It is theamount of gas contained in the lungs atthe end of a maximum inspiration. TLC= TV + IRV + ER + ERV. The normalvalue is about 5800 ml.

(f) Respiratory minute volume: It theamount of air inspired during one minuteof rest. It can be obtained by multiplyingthe tidal volume (TV) by the numberof respiratory cycles per minute.

2. Solved Example

(a) If a person has TLC = 6 litres and thevolume of air left in the lungs at theend of maximum expiration is 1.2 litres,then find the vital capacity (VC) of theperson.

THE VOLUME AND CAPACITIES

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End insp ira to ry leve l

End expiratory levels

VC

RV

ERV

TV

Tim e

Volum e (capacity)

FRC

TLC

IRV IC

Here TLC = 6 litres

RV = 1.2 litres

We know VC = TLC – RV

= 6 – 1.2 = 4.8 lires

(b) A man is doing exercise. The volumeof air expired and inspired during eachrespiratory cycle changes from 0.5 to3.5 litres. What does this value indicateand what is this value called?

The man inspires and expires the tidalvolume during each normal respiration.Hence 0.5 litre indicates the tidal volume.During exercise, he requires maximumvolume of air that can be inspired afterreaching the end expiratory level. Hence3.5 litre is the inspiratory capacity. Theinspiratory reserve volume = IC – TV =3.5 – 0.5 = 3 litre.

(c) It is given that 1.2 litre of air remains inthe lungs despite forceful expiration.The man can expire 1.1 litre by forcefulexpiration at the end of the tidal volume.The inspiratory capacity is 3.5 litre.Find FRC, TLC and VC.

Given : Residual volume (RV) = 1.2 litre

Extra reserve volume (ERV) = 1.1 litre

Inspiratory capacity (IC) = 3.5 litre

∴ FRC = RV + ERV = 1.2 + 1.1 = 2.3litre

∴ TLC = FRC + IC = 2.3 + 3.5 = 5.8 litre

∴ VC = TLC – RV = 5.8 – 1.2 = 4.6 litre

1. The most commonly used instrument forthe measurement of respiratory volume isthe recording spirometer. All the volumes andcapacities of the lungs can be measuredexcept the residual volume, functionalresidual capacity and total lung capacity.The instrument consists of a movable bellinverted over a chamber of water. The bellcontains air above the water line which is tobe breathed. To simplify the measurement,the bell is counterbalanced by a weight toensure air inside the bell remains atatmospheric pressure and the amount of airin the bell is proportional to the height of thebell above the water line. As the patientbreaths into the tube connected to the air

Lung Volumes and Capacities

THE VOLUME, CAPACITY ANDMEASUREMENT

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under the bell, the bell moves down withinspiration and moves up with expiration.The height of the bell above the water linecan be calibrated to the volume of the airbreathed in and out.

2. A gas analyzer is used along with aspirometer to measure the residual volume,FRC and total lung capacity. Followingtechniques are used:

(a) The closed circuit technique: It involvesrebreathing from a spirometer chargedwith a known volume andconcentration of helium (marker gas).After considerable breathing so that thecomplete mixing of gas in spirometerand pulmonary gases can be assumed,the residual volume (RV) of the patient

Spirometer

can be found out by a gas analyser byfinding the volume and concentrationof the helium.

(b) The nitrogen wash out technique: Itinvolves the inspiration of pure oxygenand expiration into an oxygen purgedspirometer. After breathing, the gasremaining in the lungs is 78% nitrogen.On breathing of pure oxygen, oxygenwill mix with nitrogen in the lungs. Onexpiration, a certain amount of nitrogenwill wash out which can be measuredwith expired breath. A washout curvecan be obtained with each breath fromwhich the residual volume (RV)capacity can be found out.

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Nitrogen ana lyser

M outh piece

O ne wayvalve

Pure oxygen (O )2

O xygen (O )2

N itrogen (N )2

Carbon diox ide (Co )2

Counter we igh t

Sp irom eter

3. The functional residual capacity (FRC) canbe measured by using a bodyplethysmograph. It is an airtight box inwhich the patient is seated. The patientbreaths air from within the airtight boxthrough a tube provided inside the box. Thetube has a shutter to close off the tube andan airflow transducer. Pressure transducersmeasure the pressure inside the box and inthe breathing tube on the patient's side ofthe shutter. Now total air is sum of the airinside the box (Vb) and the air in the patient'slungs (VP) i.e. Vt =Vb + VP . Since the boxis airtight and

dVt = o, hence

dVb = – dVp.

We also know that if temperature isconstant, then PV = constant is applicablefor air in box as per the Boyle’s law. Nowduring expiration, the Vp (Volume of lungs)

decreases (dVP is negative)resulting increase

in box volume i.e., bv∆ is positive. Increase

in box volume results in the decrease of thepressure in the box (as PV = constant).Similarly during inspiration the volume oflungs increases and the box volumedecreases which results into increase in thepressure in the box. Now the shutter in thebreathing tube is closed and airflow in themouth is stopped. The pressure transducerin the tube measures the mouth pressurewhich is almost equal to alveolar pressure.The changes in mouth pressure correspondto the changes in box volume whichcorrespond to the volume of lungs duringexpiration and inspiration. If the test isperformed at the time of end of expiratorylevel, the intrathoracic volume must be equalto the FRC.

Nitrogen Washed Out Technique

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Pressure Transducer to m easure

a ir p ressure in breathing tube

Breathing tube

Air pum p

Air

Shutter

Patien t

A ir T igh t box

Pressure transducer to m easure p ressure

in box

Body Plenthysmogram

4. Airway resistance measurements:Resistance of the air passages is calledairway resistance. To determine airwayresistance, intra-alveolar pressure andairflow measurements are required. The intraalveolar pressure is measured in cm of H2Oand the flow in litres per sec. The bodyplethysmograph can be used to measure intraalveolar pressure (Pia) and airflow (f)

Air resistance is ______

R = ia atmP P

f

− where Patm = atmospheric

pressure.

1. Artificial ventilation is used whenever patienthas reduced breathing or respiratory failure.During respiratory failing, we use deviceswhich can supply oxygen and remove carbondioxide so that normal partial pressure ofoxygen (Po2) and carbon dioxide (Pco2) canbe maintained. The devices for the artificialventilation consist of a mask breathing valveand self filling bag. The working of the deviceis as shown in the figure. The breathing valve

is designed to permit fresh air or oxygen tothe patient and expired air is conducted tothe atmosphere. The self filling bag functionsas a hand pump. On squeezing, it suppliesfresh air or oxygen for inspiration and laterfills with fresh air or oxygen by self expandingduring expiration.

V a lve O pe ns

M ask

V a lve C loses

Fresh A ir o r oxygen

S e lf F il ling b ag

S q ueeze d

M ask

Fresh A ir

Valve C loses

Valve opens

ARTIFICIAL VENTILATION AND VENTILATORS

Inspiration

Expiration Artificial Ventilation

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2. Ventilators: It is used when artificialventilation is required for a longer time. Thefunction is to ventilate the lungs of a patientin a manner as close to natural respiration.The ventilators can be negative pressure typein which the flow of air to the lungs isfacilitated by generating a negative pressurearound the patient’s thoracic cage. Otherventilators are positive type in whichinspiratory flow is developed by applyingpositive pressure (Pressure > atmosphericpressure) at the airways. During the

expiratory duration, the inspiratory flowdelivery system stops the positive pressureat the exhalation system and simultaneouslyit opens the valve to allow the expired air tothe atmosphere. The positive pressureventilators are preferred over the negativepressure ventilators. Ventilaters used duringanaesthesia are small and simpler while thoseused during intensive care are morecomplicated and capable of giving accuratecontrol over a wide range of respiratoryconditions.

OBJECTIVE TYPE QUESTIONS

Fill in the gaps1. Inspiration and expiration are two phases of

---------- (a) Hybernation (b) Respiration

2. The air is taken in the lungs during ---------(a) Inspiration (b) Expiration

3. Carbon dioxide is eliminated from the lungsduring ----- (a) inspiration (b) Expiration

4. The lungs are located in the closed cavitywhich is called -----cavity. (a) thoracic (b)bronchus

5. The lungs can shrink to --------- in volume(a) half (b) one third

6. The nasal cavities, pharynx, larynx, trachea,bronchi and bronchioles form------------

(a) air passage (b) lungs

7. The wind pipe is called ---------- (a) Trachea(b) larynx

8. The voice box is called ------ (a) trachea(b) larynx

9. The thoracic cavity has a single entrance atthe top through the------ (a) trachea (b)larynx

10. The descent of diaphragm increases thethoracic capacity ------(a) laterally (b)vertically

11. The movement of the ribcage upwardsincreases the thoracic capacity -------- (a)

laterally (b) vertically.

12. As the thoracic capacity increases -------pressure is created in the lungs (a) positive(b) negative

13. During respiration, the lungs are ------ organs(a) active (b) passive

14. The blood in the lungs passes through thepulmonary ------which are located in thewalls of the alveolar sacs (a) capillaries (b)arterioles

15. The blood passes through the pulmonarycapillaries to the pulmonary ---------(a) Veins(b) venules

16. The flow of the air in the respiratory systemis usually ----- (a) turbulent (b ) laminar

17. The blood flow becomes turbulent ifReynolds number is -------- than 50,000. (a)higher (b) lesser

18. Low Reynolds number flow is thecharacteristic of the air flow in -------------passage (a) alveolar (b) respiratorybronchus

19. The respiratory volume can be measured by---------- (a) volume meter (b) spirometer

20. A-------- is used along with spirometer tomeasure residual volume (a) gas analyser(b) volume analyser

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ANSWERS

21. Functional residual capacity can be measuredby ---------(a) spirometer (b) bodyplethysmograph

22. Artificial ----------- is used whenever patienthas reduced breathing (a) lungs (b)ventilation

1. (b) 2. (a) 3. (b) 4. (a) 5. (b) 6. (a) 7. (a)8. (b) 9. (a) 10. (b) 11. (a) 12. (a) 13. (b) 14. (a)

15. (b) 16. (b) 17. (a) 18. (a) 19. (b) 20. (a) 21. (b)22. (b)

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While this door is closing, another door is opeing. It is our job to go find thatdoor.

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INTRODUCTION MECHANICS OF KIDNEYS

1. The kidneys are a pair of excretory organssituated on the posterior wall of the abdomenjust below the diaphragm, one on each sideof the vertebral column. They remove wasteproducts of metabolism, the excess of waterand the excess of salts from the bloods. Theyalso maintain pH value. Each kidney is beanshaped. Each kidney is about 11 cm long, 6cm broad and 3 cm thick. The left kidney isa little lengthier and narrower than the rightkidney. The kidney is about 150 gm innormal adult. The kidneys are also calledrenes from which the deriative renal andnephron have been derived. The redcorpuscles of the blood supple oxygen tothe tissues of the kidney. In return thekidneys remove waste products from theblood plasma and regulate the compositionof blood plasma.

1. Each kidney consists of one to three millionof tiny functional units which are callednephrons. Each nephron consists of a clusterof capillary loop which is called theglomerulus which opens into a collectingtubule. The renal arteries carry blood fromthe aorta into the glomerular capillary tuftthrough arterioles. The blood pressure in theglomerulus capillary tuft is about 70 to 90mm of Hg. The flow of blood is controlledby the arterioles by the amount ofcontraction. Due to the pressure the wastewater and salt in the plasma of the bloodpass through the thin walls of the capillariesinto the glomerulus, from where they moveinto the tubule. The glomerulus filtrate alarger quantity of fluid, about 180 litres perday which consists mainly of water and othersubstance besides the body waste. A large

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amount of water and other substance arereabsorbed by kidney tubules and wastewhich is called urine (about 1 to 1.5 litresper day) is passed to bladder through ureter.The total blood flow through the kidneys isabout 1200 millilitre per min whileextracellular fluid (fluid outside cells) is about15 litres out of total body fluid of 40 litrewhich means that intra cellular fluid volumeis 25 litres (fluid inside the cells). The bloodplasma and extra-cellular fluid are inequilibrium which ensures that the amount

Working of Nephron

Blood from rena l a rte ry

G lom eru la r cap illa ry

tu ff

Tubu le

Arteriole

Peritubular cap illa ry

To Ve in

Ure te r

of blood equivalent to extra-cellular fluid canpass through the kidneys once every 15mins. Hence the composition of bloodplasma and extra cellular fluid is closelyregulated by the kidneys. Special aspects ofblood flow through the nephrons–.

(a) The glomerular capillary tuff has highblood pressure which helps in filtering.

(b) Low pressure in the peritubular capil-lary which permits fluid being absorbedcontinually into the capillaries.

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2. Uremia is urine in blood which is a renalmalfunction. In acute renal failure, urineformation stops as kidneys fail to performexcretory or regulatory function on the

blood. The renal failure results in changesin the body fluid due to the progressivedecrease in the number of functioningnephrons. Due to decrease in number of

Blood Flow Through Kidneys

The Respiratory Tract

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Principle of Dialysis

functional nephrons, the clearance of urea,creatinine and other metabolic wasteproducts in the plasma of the blooddecreases which is called reduction in theglomerular filteration rate (GFR). Thekidneys become less effective as regulatoryorgans. Uremia is the clinical state resultingfrom renal failure. Uremia affects otherorgans of the body as certain substancesthat accumulate in the blood are toxic. Theartificial kidney (Dialyzer) is used which isa mechanical device to remove theaccumulated waste products in the blood.

1. The artificial kidney is a dialyzing unit whichoperates outside the patient’s own body. Itreceives the blood from the cannulated arteryof the patient through a plastic tube. Thedialysate consists of electrolyte solutions ofdesirable composition. The dialysis occursacross a membrane of cellophone. Afterdialysis, the dialyzed blood is fed to anappropriate vein of the patient through a tube.The dialyzing membrane has small

preforation (diameter of about 5×10–9 m) andwaste products of the blood are able to passthrough the membrane into the dialysate fluidbecause of the existence of a concentrationgradient across the membrane. Themovement of waste products from the bloodto the dialysate results in clearing of theblood and dialysate with waste products isdiscarded. To speed up the dialysis either apositive pressure is applied to the bloodcompartment or a negative pressure iscreated in the dialysate compartment.

Dia lysate M em brane Blood

W aste Products

Fill in the gaps

1. Kidneys are a pair of ------- organs(a) urinating (b) excretory

2. Kidneys remove ------- products from theblood (a) waste (b) all salts

3. The ---- kidney is a little lengthy andnarrower than the -----kidney (a) right left(b) left, right

4. The kidneys are also called --------(a) beans(b) renes

5. The kidneys regulate the -------- of the bloodplasma (a) concentration (b) composition

6. Each kidney consists of million of functionalunits which are called ----------(a) neutrons(b) nephrons

7. The capillary loop of nephron is called----------- (a) tubule (b) glomerulus

8. The glomerulus opens into ---------(a) tubule(b) ureter

9. The urine is passed to the bladder through -------------- (a) tubule (b) ureter

10. Uremia is ------in blood which is a renalmalfunction (a) plasma (b) urine

11. Artificial kidney is also called ---------------(a) Analyzer (b) Dialyzer

12. The dialyzing membrane has small ---------(a) charge (b) perforation

13. Due to existence of the concentrationgradient across the membrane, the wasteproducts are able to pass through the

OBJECTIVE TYPE QUESTIONS

THE ARTIFICIAL KIDNEY (DIALYZER)

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1. (b) 2. (a) 3. (b) 4. (b) 5. (b) 6. (b) 7. (b)8. (a) 9. (b) 10. (b) 11. (b) 12. (b) 13. (a) 14. (a)

15. (b) 16. (b) 17. (b) 18. (a) 19. (b) 20. (b) 21. (b)

ANSWERS

membrane to --------(a) dialysate (b) urine

14. To speed up the dialysis either a --------pressure is applied to the blood compartmentor a -------- pressure is created in thedialysate compartment (a) positive, negative(b) negative, positive

15. The composition of the blood plasma andextra celluar fluid is closely --------by thekidney (a) monitored (b) regulated

16. The blood pressure in the glomeruluscapillary tuff is about ------------ (a) 10 mmHg (b) 70 mm Hg

17. The glomerulus filtrate about ----------- fluidper day (a) 1.5 litres (b) 150 litres

18. A large amount of water and other substanceof the filtrate are reabsorbed by kidney ---------- (a) tubules (b) ureter

19. The kidneys function on the blood----------to remove waste products and to regulatecomposition (a) corpuscles (b) plasma

20. The -------supply oxygen to the tissues ofthe kidney (a) plasma (b) red corpuscles

21. The kidneys are located ---------thediaphragm on the posterior wall of theabdomen (a) above (b) below

Page 136: Fundamentals of biomedical engineering

1. Prosthesis is a fabricated substitute for amissing part of the body as a limb, heartvalve, eyes and tooth. Cybernetics is thestudy of self organizing machines andmechanical brains. The emphasis is todevelop prosthetic devices for humanenhancement. Prosthetics are hot area ofresearch. Artificial hands and legs givewearers a better quality of life. Degenerativeretinal diseases result in the death of the rodsand cones (the cells responsible for lightdetection). The scientists are working onways to restore functional sight to thosewho have become blind through disease. Thebionic eye system is made of a 3 mm chipimplanted into the retina and a pair of virtualr-eality style goggle containing a video camera.The goggles convert the video pictures intoan infrared image. Dextra is an artificial handsystem which is being developed. It cancontrol up to three fingers by recording themovement of muscles in the remaining partof the arm as a person thinks about movinghis hand. Robotic devices are also beingdeveloped to help the handicapped and alsoto enhance the strength of a normal person.The Berkeley lower extremity exokeleton(Bleek) is a device which is being developed.

When I was sick, I didn't want to die. When I race, I don't want to lose. Dyingand losing, it's the same thing.

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INTRODUCTION It can calculate how to distribute weight sothat wearer feels little or none of it. A soldierwho can carry huge loads without gettingtired would be more useful on any battlefield. A Fireman who needs to climb stairswith heavy equipment or a rescue workerwho needs to take supplies into areas wherevehicles can not go are other applications ofBleek.

1. Human ambulation or gait is one of the basicneed of independent functioning. It iscommonly affected by other diseaseprocesses or injury. The terminology usedto describe gait is :–

(a) Gait Cycle: It commences when theheel of the reference extremity contactsthe ground and ends when the heel ofthe same extremity contacts groundagain. The gait cycle consists of twoperiods of stance, two periods of swingand two periods of double support.

(b) Stance phase: It is the interval inwhichthe foot of the reference extremity is incontact with the ground. For example,when we consider the right lower ex-tremity as reference extremity, the leftlower extermity is in swing phase while

GAIT ANALYSIS

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the right lower extremity is in stancephase. A single gait cycle contains rightand left stance. Stance phase consti-tutes 60% of the gait cycle.

(c) Swing phase: It is the interval inwhichthe foot of the reference extremity doesnot contact the ground. Therefore asingle gait cycle contains right and leftswing phase. The swing phase consti-tutes 40% of the gait cycle.

(d) Double support phase: It is the inter-val in which body weight is transferredfrom one foot to the other and both right

and left feet are in contact with theground at the same line. There are twodouble support phases in a gait cycle.

(e) Stride: Two steps consisting of a rightstep and a left step comprises a stride.Step length is the distance from thepoint of heel strike of one extermity tothe point of heel strike of the secondextremity. Stride length is the distancefrom the point of heel strike of one ex-tremity to the point of heel strike of thesame extremity.

Stance phase left Swing phase right Double support phase

Double support phase Stance phase right Swing phase left Double support phase

Gait Cycle

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(f) Units: Each phase of gait has been di-vided into units. The stance phase hasunits of (1) heel strike (2) footflat (3)mid stance (4) heel off (5) toe off.Swing phase has units of (1) accelera-tion (2) midswing (3) deceleration.

(g) Ground reaction and moments: Theground reaction vector (R), flexionmoment (FM), extension moment(EM), plantar flexion moment (PM) and

dorsal flexion moment (DM) have beenshown in the figure for various unitsof stance phase. The ground reactionvector (R) changes from a positionanterior (in heel strike) to posterior (inflat foot) which changes the directionof moment at knee from counterclockwise to clockwise. The directionof moment changes in each unit ofstance phase.

Step Length and Stride Length

Unit of Stance Phase

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1. A prosthesis has three major parts :

(a) The interface which consists of socket,any additional suspension and body op-erated controls.

(b) The skeleton which replaces the lostlimb segment. The skeleton is given alimb–like appearance. It is a system oflevers separating the artificial joints.

(c) The artificial joints are required to workas natural joints. They are designed tolimit, modify and assist the movements.

2. All movements to the prosthesis are giventhrough interface. The skeleton provides notonly a realistic appearance but alsoincorporates a system of levers by whichpower/movement is transmitted to the joints.The joints are to perform the controlfunction.

3. Prostheses for lower limb: The lower limbbears the body weight. It is required to givesupport and balance to the body. It has tobe strong and capable to provide mobility inthe movements during gait cycle as under :

(a) Midstance: The body weight duringstanding erect passes throguh the imagi-nary line joining centre of ankle, thecentre of rotation of the knee and thecentre of trochanter (behind hip). Thisis known as trochanter-knee-ankle or

TKA line as shown in figure. The limbcan be considered to be made of threelevers. The thigh and shin are verticaland foot complex is horizontal. Theankle joint is the junction of the hori-zontal and vertical levers. If it is con-trolled, then the natural limitation ofextention at knee and hip can be usedto stabilise these joints when the bodymass is acting on the extensor axis as-pects of the joints. A prostheses hasmechanical stops to provide thisstabilty. We will get greater stability ifthe joint lies on the extenor side of theweight axis but then the flexion at thebegining of the swing phase will be dif-ficult to be initiated.

Trochanter

TK A line

knee

ankle

(b) Heel-Strike: The stance phase duringwalking starts with the contact of theheel with the ground. The ground re-action is at the posterior end when the

PROSTHESES: CLINICAL REQUIREMENTS

Movement During Stance Phase

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heel striks the ground. The shin there-fore tends to rotate forward causingunwanted knee flexion. This rotation ofthe shin has to be counteracted by themechanism of the prostheses.

R = The ground reaction of heel-strike

R

Heel Strike

(c) Toe off: A similar reverse action oc-curs at toe off as the ground reactionis at the anterior end of the horizontal.The shin therefore tends to rotate back-ward impeding flexion of the knee.

Toe-off

R = The ground reaction a t toe o ff

(c) Swing phase: During this phase, thesocket exerts force through the skel-eton to the joints which activate theirmechanism to propel the prostheses for-ward.

(d) Alignment Device: A good prosthesisdepends upon a well fitting socketwhich is properly aligned with the foot

and the interposing joint mechanism inboth the swing and stance phase. Thealignment device must permit (1) tilt-ing of the socket in any direction fromthe vertical (2) movement of the socketrelative to the foot in any horizontal ofthe joint axis in a horizontal plan direc-tion (3) rotation (4) proper calibrationfor the adjustment purpose.

4. Prostheses for Ankle-Foot: The clinicalrequirements for the prostheses during thegait cycle are :

(a) Stance phase: The prostheses shouldallow plantar flexion without foot stopat heel contact so that the ground reac-tion is located anteriorly towards theankle axis. This alleviates the forwardrotation of the shin and stabilises theknee. The stabilisation of knee allowsand assists the shin to become verticalwhen the body passes over the foot.Some doriflexion of the foot is requiredbefore the heel rises to prevent exces-sive knee stability.

(b) Swing phase: The prostheses must belight as the ankle foot complex is at theextremity of the limb. It must rise of attoe off with knee flexion to clear theground. During swing phase, it shoulddorsiflex.

Single Axle Ankle Joint

Solid-Ankle Cushionded Heel Foot (Sach)

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5. Knee Joints: Knee joints fall into two gorups:(1) A below knee prosthesis (2) An aboveknee prosthesis. In a below knee prosthesis,the stump is too long and patient can retainhis useful natural knee. In an above kneeprosthesis, the amputation is high enough,permitting the artificial knee joint to beincoporated in prosthesis. The clinicalrequirements of this type of prostheses are:

(a) Stance phase: The prosthesis must per-mit little flexion during full extension whilein midstance. It must support the bodyweight while in flexion. It must extend ifrequired even while supporting the bodyweight. It should be durable.

(b) Swing phase: The prosthesis can flex attoe off so as to allow the heel to risefreely and clear the ground. Howeverexcessive rise due to inertial force is tobe prevented. It must develope force todecelerate the shin and foot when it ischanging from flexion to full extension.

1. Three types of prostheses are available to abelow knee amputees viz. (1) conventional(2) patellar tendon bearing. (PTB) and

(3) protheses tibiale supra condylienne.Earlier, only conventional type of prostheseswas available which has a shank which holdsa foot ankle assembly and a socket. The socketcannot provide any supporting force on theanterior aspect. The weight is born by thestump on its medial and lateral aspects and thethigh. A simple hinge joint connects the thighcorset to the socket. With the present trend ofan extension of the patellar tendon bearingbelow knee prostheses commonly known atPTB has been developed, a below knee stumpcan not be subjected to much pressure at thedistal end due to shearing stress developingbetween soft tissues and the cut end of thebone. After careful consideration of thecomplete biomechanical problem, the fulladvantage of weight-bearing capabilities of thepatellar tendon is taken in fabrication of thisprostheses. A cuff is provided for thesuspension. To do away even with thesuspension straps and also to increase theweight bearing on the patellar tendon, aprostheses properly known as PTC(Prostheses Tibiale supra condylienne) hasbeen developed. Here the socket is aligned withthe knee in flexed position and the suspensionis achieved by an extension of the socket soas to completely enclose the patella and themajor portion of the femoral condyles.

A BELOW KNEE PROSTHESES

Patellar Tendon

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2. Earlier nearly all prostheses for below kneeamputation had jointed side steels on eitherside. This is nothing but a simple, uniaxial,elevis mortice-and-tenon or box joint towhich a lock is fixed. Since natural knee isnot a simple uniaxial joint and there isdifference between working of natural andartificial joint, there is a tendency toexaggerate the movement between the stumpand the socket which is known as piston

action. In below knee amputation, the nautralknee can largely provide the control for boththe stance and swing phase.

1. For the above knee amputee, the naturalcontrol of knee joint is lost. The prosthesesmust have stance and swing phase controls.It is common to provide simple locks to

AN ABOVE KNEE PROSTHESES

Below Knee Amputee

Below Knee Prostheses

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prevent flexion or elastic straps over the frontof the knee to help accelerate the shin ascontrols. More complex mechanisms maybe more effective but they lead to weightproblem and poor reliability. In simple form,the artificial leg for an above knee prosthesesincorporates a manual locking type of thigh

turntable as shown in the figure. Theprostheses does not permit all naturalmovements like foot inversion and eversion,and turning of the foot or toes upwards. Toavoid the stump socket tending to slip overthe stump, a torque opposing knee flexionis provided in the artificial leg to increasethe stump to stump socket friction.

Lock

Turn table

2. Uniaxial knee Joint: It is for the aboveknee prosthesis. In its simplest form, it is atransvers bolt about which shin rotates onthe thigh pioce. Mechanical stops are placedat full extension and upto 120° flexion. Somebasic joint mechanisms can be added whichmodify its actions as under :

(a) Stance phase mechanism: Some inherent stability is incorporated in theprostheses employing the ground reac-tion force to extend the knee againstthe extension stop while in errect posi-tion.

(b) A simpler lock which engages automati-cally when standing up.

Transverse bolt

An Above Knee Prostheses

Uniaxial Knee Joint

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(c) Stabilising arrangement with frictionsurface to support the body’s weightwhen knee joint is flexed upto 30°.

(d) Swing phase helping mechanism asknee lock adversely affects the swingphase.

(e) Elastic straps over the front knee orknee mechanism with spring inside toassist the shin forward by the recoilafter flexion. They act as acceleratorfor the shin.

(f) Variable swing phase controls: Werequire unimpeded swing in the middleranges and progressively greaterintermittent friction at each end of theswing phase. Both hydraulic andpneumatic controls are available. Bothoperate the same way with one or twocylinders with piston travels unimpededuntil near the end of piston stroke. Itthen forces air or liquid through anorifice (restricted opening) thusproviding damping and resistance. Thepneumatic swing controls are lighter.

1. Paraplegics have paralysis of both lowerextremities and generally the lower trunk. Acommon garden wheel chair provides themdesirable mobility. However they do needregular exercise for the fitness of the body.The assessment of the functional capacityof a paraplegic is important for periodicfollow up during medical rehabilitationprogram. The assessment contributes toestablishing the patient's physical fitness.Arm cycloergometry has been found to bevery suitable for the wheelchair users withnormal upper limbs. An arm exercise withsome work load is accompanied by a largerrise in the heart rate, higher blood pressure,increased pulmonary ventilation and oxygenconsumption. It is also found that reciprocal

REHABILITATION OF A PARAPLEGIC

propelling is more convenient thansynchronous propelling. As shown in thefigure, there is a force-couple going to theopposite direction with only axial movementof the trunk in the horizontal plane is the netresult in the reciprocal mode while there is asignificant bending movement of trunk in thesagittal plane in the synchronous mode.

F

Reciprocal

F

2F

M

Synchoronous

1. The arrhythmia means abnormal rhythm ofthe heart. Rhythmic action of the heart isinitiated by regularly recurringelectrochemical impulses originating at thenatural cardiac pacemaker located at the SAnode. Each pacing impulse spread ever thesurface of the atria to the AV node. After somedelay at the AV node, the impulse is conductedto the ventricles (Refer chapter 10). A normalsinus rhythm (NSR) depends on the proper

Mode of Propelling

CARDIAC PACEMAKER

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functioning of the pacemaker (SA node) andconduction of the impulses. Any change inthe NSR is called an arrhythmia. SA nodemay temporarily or permanently fail due tosome diseases and no impulse originates fromSA node. The pacing function is taken overby some other cells near AV node. Howeverin that situation the heart is paced at a muchlower rate and such condition is calledbradycardia or slow heart. In this situation,the heart can not provide sufficient bloodto meet the body's demands.

2. A pacemaker system is a device capable ofgenerating pacing impulses like a naturalpacemaker and delivering the pacing impulsesto the heart. All pacemakers have a pulsegenerator and electrode. Pacemakers can be(1) asynchronous (fixed rate) (2) demand typesynchronous (3) atrial-synchronous (4) rateresponsive pacemaker. The asynchronouspacemaker generates impulse at a uniformrate regardless of what is going on in the heart.The oscillator controls the pulse output circuitand impulse is given to the heart throughelectrode.

1 2 3 41 Power pack2 O scilla to r3 O utpu t c ircuit4 E lectrode

1. Asynchronous pacing is also calledcompetitive pacing as the fixed rate impulsemay take place along with the natural pacingimpulses of the heart. Hence both impulsescompete to control the heart beat. The aboveproblem is overcome in the synchronouspacemaker. The artificial pacemaker does notcompete with the natural pacing impulsesof the heart. A demand type synchronouspacemaker has a timing circuit, an outputcircuit electrode and a feedback loop. The

ASYNCHRONOUS PACEMAKER

timing circuit runs at fixed rate which islower than the natural pacing rate of theheart. Hence pacemaker remains at stand bymode. The pacemaker takes over when thenatural pacing rate of the heart falls below

the fixed rate set on the pacemaker. The atrialsynchronous is used where the conductionsystem of the heart fails specially the AVnode. The SA node generates impulse whichstimulates the atria. The impulsecorresponding to atrial contraction (the Pwave of the ECG) is detected by theelectrode of the artificial pacemaker whichtriggers with appropriate delay an impulsesimilar to natural AV node which has failed.Often atrial synchronous pacemaker iscombined with the demand pacemakersystem so that the combined pacemaker cando the jobs of defective natural pacemakerand defective AV node. The rate responsivepacemaker has a sensor which converts thephysiological variables of the patient toelectric signals which are fed into thecontroller circuits. The pacemaker isprogrammed to control the heart rate as perthe electric signal generated by thephysiological variables. The controllerdecides whether artificial pacing is requiredor the artificial pacing in place of naturalpacing. If it is not required, the artificialpacing remains in the non functional state.The pacemakers can also be grouped asinternal pacemakers and externalpacemakers. Internal pacemakers arepermanently implanted in patients who haveeither failed SA node or have suffered frompermanent heart block. The external pacemakers have external wearable pulsegenerator connected to electrode located onthe heart. These pacemakers are used ifpatients have temporary heart irregularitiesor if patients are undergoing cardiac surgery.

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Demand Type Synchronous Pacemaker

CARDIOVASCULAR PROSTHETIC ANDORTHOTIC DEVICES

1. Pump oxygenerator. It is used to performthe hearts pumping action and the lungsoxygeneration function during cardiacsurgery. It consists of a pump formaintaining arterial blood pressure and anoxygenerator which can oxygenate blood byremoving carbon dioxide. The pump andoxygenerator are connected in series. Theyare connected either between the right atriumand a femoral artery or between the superior

and inferior vena cava. Rollers or multiplefingers pump is used which regularly pressthe squeezable tubing carrying blood so thatnecessary arterial pressure and pulsatingmotion are provided to the blood withoutany physical contact of the pump and theblood. The oxygenerator can be film typeor membrane type. In film type, the rotatingdisks provide large surface area to the bloodexposed to oxygen. In the membraneoxygenator, the blood is made to flowthrough the tubes made of membrane whichis permeable to oxygen and carbon dioxide.

Pump Oxygenerator

Impulse allowed =Ia

Impulse pacemaker = Ip

Impulse heart = Ih

Ia = Ih when Ih > Ip

= Ip when Ip > Ih

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2. Artificial heart. It is small blood pump ofbiocompatible material which can replace adeceased heart. The pump is implanted onthoracic cavity and it is operated inside fromany electrical or pneumatic device. Theartificial heart can be used as a permanentreplacement or as a temporary measure untila suitable natural donor heart is planted.

3. Aortic balloon system. It is a cardiacassistance device. It is a sausage shapedballoon that can be inserted into aortathrough a femoral artery. The balloon isconnected to an external apparatus whichcan inflate or deflate the balloon by supplyingcarbon dioxide or sucking out carbon dioxidefrom the balloon. Consider the balloon in theinflated state in the aorta which is permittingsome blood to flow past it. As the ventriclecontraction starts, suction action is appliedto the balloon which causes it to collapse.The ventricle will require now less effort topump the blood to replace the volumeoccupied earlier by the balloon. As the aorticvalve of the ventricle closes, the balloon isexpanded by supplying of carbon dioxide tothe balloon. As the balloon expands, it pushesthe blood from the aorta to the rest of thebody. The balloon performs much of thework which is normally done by the leftventrical.

4. Defibrillator. The heart is able to pumpblood through precisely synchronized actionof the heart muscles. The rapid spread ofimpulse on the surface of the atria causesatria to contract together and pump bloodinto the ventricles. After a delay of impulseat AV node, the ventricles are synchronouslystimulated to pump blood to the pulmonaryand systemic cirulatory systems. Ifsynchronism is lost, then this condition isknown as fibrillation. Fibrillation leads to thenormal rhythmic contraction of either theatria or the ventricles being replaced by rapidirregular contraction of atria or ventrieles.Atrial fibrillation is the fibrillation of atriawhile ventricular fibrillation is the fibrillation

of the ventricles. Atrial fibrillation leads toinadequate pumping of the blood butventricular fibrillation more dangerous asthis leads to failure of blood pumping anddeath of the patient. The most successfulmethod of defibrillation is the application ofan electric shock to the heart. The electricshock is able to stimulate all muscles of theheart simultaneously. All the cells of the heartmuscle enter their refractory period togetherat the end of the electric shock, after whichnormal heart action may resume. Generallyelectric shock of intensity 6 ampere,frequency 60 HZ for duration of 0.25 to 1sec is applied. Nowadays DC (direct current)defibrillation is used, in which a capacitor ischarged to a high DC voltage which israpidly discharged through electrode acrossthe chest of the patient. There is possibilityof accidentally application of the defibrillatoroutput during ventricular repolarization (Twave) which may cause ventricularfibrillation. To avoid this problem, specialdefibrillator is used which has synchronisingcircuitry to ensure the output occursimmediately after R wave but before T wavecan occur. Such defibrillator is calledcardioverter which is a combination of thecardio monitor and the defibrillator.

1. Hemodialysis is nothing but an artificialkidney and it is a widely used as a prostheticdevice for the patient having acute renalfailure. It is a mechanical device to removethe accumulated waste products in the blood(Refer chapter 12).

1. Is a therapeutic device which assist a patientin ventilating his lungs. The ventilator is usedwhenever any patient has reduced breathing

HEMODIALYSIS

VENTILATORS

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or respiratory failure. The ventilators havebeen covered in details in chapter 11.

1. In order to periodically check a patient'sprogress and make vital decisions at timesof crisis, the exact reproduction of the ECG,arterial blood pressures and other variablesare required. The principal display device forpatient monitoring is the cathode ray tube(CRT). The patient monitoring display devicecan be of two types of CRT displays viz.(1) conventional or bouncing ball (2) nonfade display. In conventional or bouncingball display the method uses oscilloscopewith the horizontal sweep driven by a slowsweep generator which makes the electronbeam to move from left to right at apredetermined selectable rate. ECG signalsare applied to the electron beam to move upor down vertically. As the electronic beammoves up and down at high speed in verticaldirection with constant horizontal sweepfrom trace to trace, the display appears as acontinuous wave form which moves fromleft to right. As the electron beam movesacross and forms a pattern on the screen ofCRT, the earlier portion of the waveformbegins to fade away and ultimatelydisappears. The ability of trace to remainvisible for some duration on the screen ofthe CRT is called persistance. The duration

of persistance depends on the phosphorouscoating of the screen. CRTs withpersistance of about 1 second are available.As ECG wave form may occur at a rate of60 events per min, the persistance of 1 secwill allow only one cycle of waveform visibleon the screen. In this also, the last portionof waveform will be brighter than the earlyportion of the waveform. The temporarydisplay of such nature makes diagnosis adifficult task. The problem has beenovercome in the nonfade display. In thismethod the electron beam rapidly scans theentire surface of the CRT screen in atelevision like raster pattern. The brightnesslevel is kept a very low brightness level sothat raster is not visible. A method called Zaxis modulation is used so that the beam isbrightened only when a brightening signalis applied to the CRT. The brightening signalis generated only when the electron beam isat a location that contains a part of thedisplayed waveform. The brightening signalproduces a dot on the screen. Each timewhen electron beam scanned the screen, aseries of dots are produced on the screenwhich have ECG pattern. Since dots areproduced so close together and the scan isso rapid that the dots appear as a continuoustrace. In addition to nonfade display, theongoing heart rate, systolic and diastolic,blood pressure and the patient’s temperatureare displayed as numerical readouts.

OBJECTIVE TYPE QUESTIONS

Fill in the gaps

1. Arrythmia means-----------rhythm of theheart (a) normal (b) abnormal

2. The natural cardiac pacemaker is located atthe --------(a) AV node (b) SA node

3. The impulse of conduction is delayed at-------- (a) AV node (b) SA node

4. A normal sinus rhythm (NSR) depends onthe proper functioning of --------- (a) AVnode (b) SA node

5. If no impulse originates from SA node, thepacing function is taken over by some othercells near -------(a) AV node (b) septum

PATIENT MONITORING DISPLAYS

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6. Bradycardia is a condition in which heart ispaced at -----rate (a) slower (b) faster

7. All pacemakers have a electrode and ------(a) pulse generator (b) electric circuit

8. The fixed rate pacemaker is called---- (a)synchronous (b) asynchronous

9. Asynchronous pacing is also called-------pacing (a) harmonious (b) competitive

10. The problem of the competitive pacing hasbeen overcome in ---------pacemaker (a)synchronous (b) asynchronous

11. The timing circuit of the demand typesynchronous pacemaker runs at fixed ratewhich is --------- than the natural pacing rateof the natural heart (a) lower (b) higher

12. The controller of ------- pacemaker decideswhether artificial pacing is required in placeof the natural pacing (a) synchoronous (b)rate responsive

13. The heart’s pumping action and the lung’soxygenation function during cardiac surgeryis performed by the---------- (a) pumpoxygenerator (b) artificial heart

14. The pump oxygenerator has ----- and ---------- (a) roller pump, oxygenerator (b)dialyzer, oxygenerator

15. The oxygenerator can be film type or -----type (a) membrane (b) screen

16. Artificial heart is a small blood pump of ------------- material which can replace adecreased heart (a) strong (b) biocompatible

17. Aortic baloon system is a cardiac --------device (a) assistance (b) boosting

18. Atria and ventricles are required to --------simulated one after another (a)asynchronously (b) synchronously

19. ------------ leads to the normal rhythmiccontraction of either atria or the ventriclesare replaced by the rapid irregular twitching(a) fibrillation (b) defibrillation

20. The most common method of defibrillationis the application of ---------- (a) an electricshock (b) blood infusion

21. A device combining the defibrillator andcardiomonitor is called -------------- (a)cardioverter (b) cardio defibrillator

22. Hemodialysis is nothing but a --------- (a)artificial kidney (b) artificial bladder

23. Artificial ventilating the lungs of a patient isdone by --------- (a) Ventilator (b)Respirator

24. The principal display device for patientmonitoring is the ---------- (a) CRT (b)Display tube

ANSWERS

1. (b) 2. (b) 3. (a) 4. (b) 5. (a) 6. (a) 7. (a) 8. (b)

9. (b) 10. (a) 11. (a) 12. (b) 13. (a) 14. (a) 15. (a) 16. (b)

17. (a) 18. (b) 19. (a) 20. (a) 21. (a) 22. (a) 23. (a) 24. (a)

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History teaches everything including the future.

INTRODUCATION

1. Orthosis is a greek ward which means‘making straight’ or ‘correction ofmaladjustment. Hence orthosis is the sciencethat deals with making & fitting oforthopedic appliances. The desiredoutcomes of orthosis intervention areachieved by selected application andtransmission of forces through the orthosisappliance. The desired outcome of optimalcontrol, corrected stabalization or assistancefrom orthosis is achieved through variuosdesign principles. While selecting an orthoticdevice, the goals of the orthosis areconsidered. Also the degree of freedom tobe atained and the forces required to beachieved from the orthotic device for thedesired outcome are considered.

2. While selecting an orthotic device, we haveto consider the kinematic characteristics ofthe defective joint or segment including ananalysis of degree of fredom. We have toevaluate before selecting an orthosis for ajoint segment, its translation and rotationsabout various axes. Although we try to

correct one or two of the six potential degreeof freedom of rotation through theapplication of orthotic device but anawarenesess of all inherent motions andrelative relatiionship between connectedsegments is essential for maxmising theeffectiveness of the orthosis.

THREE FORCE SYSTEM

1. The goals from orthosis can be achievedthrough selected application of forcesdeveloped by the orthotic device. The appliedparallel forces are required to be balancedout by using a three points loading system.In the figure, a three force system is appliedon the lower limb. The three force systemis such that F

B = F

A + F

e and F

A × D

1 = F

c ×

D2. If two posterior pressure pads at A and

C in a hip-knee-ankle orthosis are placed atdistance D

1 and D

2 from anterior pressure

pad B then force in pad ‘B’ is twice of theequal forces in A & C when D

1 = D

2. Both

bending moment diagram and shear forcediagram are important for designing andachieving the intended goal of the orthosis.

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Shear fo rce d iagram

Bend ing mom ent d iagram

FA

FC

FB

D1

D2

1. A very throughtful orthosis device can beprescribed to a person with neurologicinvolvenment so that he may access moreefficient movement patterns and may reduceresidual gait disability. Three basic functionaltasks are essential for lower limbs forefficient and successful ambulation. Theyare (1) weight acceptance (2) one leg stancesupport (3) swing phase (limbadvancement). The above process musthappen in smooth manner and the limb mustremain stable. It must be able to absorb theimpact of superincumbent body weight and

ORTHOSIS FOR GAIT DISABILITY stand all moments developed during forwardmovements of the limb and the body. Thefunction of single limb support involves thatthe body can carryout forward movementon the weight bearing limb. The limb has toperform this task over a reduced area ofsupport on the ground. The swingadvancement involves removal of weightfrom the limb and its forward progressionuntil next step is initiated. The groundclearance is an essential element of thefunctional task of the limb during swing limbadvancement. The funtional task, gaitsubphase and critical events for a normalgait cycle are as tabled below :

Function task Gait subphase Critical events

1. Weight acceptance 1. Initial contact 1. Heel first contact2. Loading response 2. (a) Hip stability

(b) Controlled knee with 15°flexion

(c) 10° Ankle plantar flexion2. Single limb stance 1. Mid distance 1. Controlled tibial progression

2. Terminal stance 2. (a) 10° dorsiflexion of ankle joint(b) Heel rise from ground(c) Trailing limb position

3. Swing phase 1. Preswing 1. 40° knee flexion2. Initial swing 2. (a) 15° hip flexion

(b) 60° knee flexion3. Mid swing 3. (a) Hip flexion to 25°

(b) Zero ankle dosiflexion4. Terminal swing 4. Knee extention to neutral

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2. The goals of orthotic prescriptions are toimprove the biomechanics of gait. Primaryemphasis is on the more commonlyprescribed lower limb braces. The orthosisaims to achieve biomechanical alteration ofhuman movement in upright function. Awide range of ankle-foot orthosis (AFO)designs are used in treating the person withneurologic involvement. Braces are capableof providing some degree of control duringstance, swing or both phases of gait. Theuse of knee braces, taping or foot orthosiscan be beneficial treatment duringstrengthening programme to achievedynamic control and balance at thepatelloferroral joint at knee. Supportivewrapping and bandaging techniques arebeneficially used for athletics. Adhesivestrapping and protective padding techniquesare commonly accepted as orthotic treatmentto orthopaedic patients.

1. Spinal cord disease or injury causesparaplegia. This results in the loss of physicalfunction like standing and walking. Theability to stand and walk is considered mostimportant in the individuals’s potential toreturn to a normal life style. There has beenan increase in the research and developmentof rehabilitation technology, enabling moreparaplegic patients to stand and ambulate.The ability of a person with paraplegia tostand upright imparts several physiologicalbenefits. They include improvement in bloodcirculation, reduction in spasticity andretardation of osteoporosis. The jointcontractures and kidney malfunction are alsoprevented. The ability to stand and walk alsoimparts psychological benefits as person

PARAPLEGIC ORTHOTIC WALKINGSYSTEM

Knee Brace Knee Taping

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with paraplegia may feel himself a normalperson having standing and walking ability.The most commonly used orthotic systemsfor the paraplegic patients are (1) bilateralKAFO (knee-ankle-foot orthosis) (2)HKAFO (Hip-knee-ankle-foot orthosis).KAFO requires a large energy expenditurefor the patients to walk. HKAFO forparaplegic gait allows ambulation at a lowerenergy cost. Two major designs of HKAFOare hip guidance orthosis (HGO) andreeiprocating gait orthosis (RGO) as shown

in the figure. These orthotic systems aresimilar as the patient is braced from the midtrunk to the feet and the knee and anklesimmobilized in a neutral position. Theseorthosis permit hip flexion and extention butprevent hip adduction. The RGO is designedto be worn inside the patients clothes. Thepatient requries assistance of roller orreciprocating roller while walking wearingRGO. However HGO is worn outside thepatient’s clothes and the patient walks withthe assistance of crutches.

Trunk Band

Pe lv ic Band

Th igh cu ff

Knee cuff

Anklecuff

M etal footp la te

H ip Jo int

Dual cab lesystem

Pelv ic Band

Kneecuff

HGO RGO

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Fill in the gaps.1. Orthosis means --------- of maladjustment.

(a) correction (b) reduction

2. --------- is a science that deals with makingand fitting of orthopaedic appliances.

(a) prostheses (b) orthosis

3. We try to correct one or two of the --------potential degree of freedom of motionthrough the application of orthotic devices.(a) four (b) six

4. The goals from orthosis can be achievedthrough selected application of ---------developed by the orthopic device. (a) forces

OBJECTIVE TYPE QUESTIONS

(b) movements

5. The biomechanics of gait can be improvedby ---------. (a) orthosis (b) prostheses

6. Suppertive wrapping and bandagingtechniques are used by ---------

(a) orthopaedic patients (b) athletics

7. Addesive strapping and protective paddingtechniquel are used by ---------

(a) orthopaedic patient (b) athletics.

8. Three basic functional tasks are essential forlower limbs for efficient and successful

---------. (a) ambulation (b) stance

ANSWERS

1. (a) 2. (b) 3. (b) 4. (a) 5. (a) 6. (b) 7. (a)8. (a)

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1. Biomaterial is a synthetic material used toreplace a part of a living system or tofunction in intimate contact with livingtissues. Therefore biocompatibility isacceptance of an artificial implant by thesurrounding tissues and by the body as awhole. The success of implant dependsupon–

(a) Acceptance of the implant by thesurrounding tissues.

(b) Implant is nontoxic and noncarcinogenic.

(c) The material of implant must have highmechanical strength

(d) Implant faces varying loads and henceit should have high fatigue life

(e) The material should be chemically stableand inert

(f) Implant should have sound engineeringdesign

(g) Appropriate molecular weight andmolecular weight distribution (weightof implant & its density)

(h) Material should be easy to be fabricatedand processed for large scaleproduction.

2. Biomaterials can be (1) Polymers (2) Metals(3) Ceramics and (4) Composites. Nylon,silicone rubber, polyster and poly tetra-fuoroethylene are polymers commonly beingused as biomaterials. Polymers are resilentand easy to be fabricated but they deformand degrade with time. Titanium & its alloys,Cobalt and Chromium alloys, stainless steel,Gold, Silver and Platinum are commonbiocompatible metals. Metals are strong,tough and ductile. However, metallicimplants are difficult to be produced andthey are like to corrode. Aluminium oxide,Calcium phosphates and carbon are commonbioconspatible ceramics. Ceramics are inert,strong and highly biocompatible. Howeverceramics are brittle and they are not resilent.Carbon fibers reinforced polymers and bonecement are biocompatible compositematerials. They are tailor made and strongbut difficult to be made.

3. The uses of biomaterials are :–

(a) Replacement of damaged or diseasedparts like hip joint, knee joint & heartvalves etc.

(b) Assistance in healing as done bysutures, bone plates and intramedullaryrod etc.

You spend the first two years of your kids' lives teaching them to walk and talkand the next 16 years telling them to sit down and be quiet.

INTRODUCTION

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(c) Assistance in functioning as by cardiacpacemaker and intraocular lens etc.

(d) Correction of functional abnormality.Example : Cardiac pacemaker.

(e) Cosmetic correction. Example: chinaugmentation, augmentation mamoplasty.

(f) Assistance in diagnosis: Probes andcatheters are made of biomaterials.

(g) Assistance in treatment eg. cathetersand drains of biomaterial.

4. As explained above, the success of implantdepends upon various factors. Also if 'f'is failure and 'r' is reliability, then r = l – f.The total reliability of implant havingmultiple modes of failure (f

1 f

2 ... to f

n)

can be given as:

r = (l – f1) (l – f

2) ... x (l – f

n)

= r1 × r2 ... x rn

Most pure metals generate a severe tissuereaction. The reason is that metals have highfree energy and they tend to lower their freeenergy by oxidation/corrosion. This is thereason that vanadium steel can not be usedfor implants.

5. Stainless steel : The austenite stainless steelsuch as 316 stainless steel (molybdenum insmall percentage) and 316 L stainless steel(carbon up to 0.08% only) are mostcommonly used for implants. These steelsare non magnetic and corrosion resistant.The austenite stainless steel is prone to workhardening and it has to be heat treated aftercold working. 316 L stainless steel has 17to 20% chromium, 12 to 14% nickel & 2 to4% molybdenum. The inclusion ofmolybdenum enhances resistance to pittingcorrosion. Nickel stabilizes the austenite(α) phase at room temperature. It alsoenhances corrosion resistance. The austenitephase stability of steel is influenced by bothNickel & Chromium contents as shown inthe figure. The implants of these steels aresuitable as temporary implants such asfracture plates, screws and hip nails.

Austen ite phase

25

20

15

10

5

Nic

kel

Ferite phase

25 20 15 10 50

Chron ium

6. Co Cr alloys : These are mainly two typesof cobalt - chronium alloys viz (1) CastableCo Cr Mo alloy (2) Wroughtable by forgingCo Cr Mo alloy. The castable is used fordentistry and artificial joints. The wroughtCo Cr Mo alloy is used for makingprostheses suitable for heavy loaded jointslike hip and knee. The wrought Co Cr Moalloy has good fatigue and ultimate strengthand it is used where we require long servicelife. The cast Co Cr Mo alloy (F – 75) hasmainly 22 to 33% Cr, 5 to 7% Mo, 2.5% Niand balance Co while wrought Co Cr Moalloy (F 562) has mainly 19 to 21% Cr, 9 to10.5% Mo, 33 to 37% Ni and balance Co.

7. Titanium and Alloys : Titanium is used forimplant as it has low density and goodmechanical properties. Titanium (alsoaluminium) evokes minimum amount oftissue reaction as it forms a tancious oxidelayer which resists further diffusion of metalions to oxygen gas at the interface. Whilemaking implant, titanium has to be processedin an inert atmosphere. Titanium is anallotropic material. It can exist as a hexagonalclose-packed structure (α phase) upto 82ºCand as a body - centered cubic structure (βphase) above 82ºC. The transformationtemperature changes on addition of alloyingelements which enables the titanium alloysto have a wide range of properties. The mainalloying elements of the alloy are aluminium(5.5 to 6.5%) and vanadium (3.5 to 4.5%).

Effects of Ni and Cr on Phase of Steel

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The titanuim nickel alloys have propertiesof "shape memory effect (SME)". It meansthat the material can gain its original shapeon heating. Therefore these alloys havingSME are used for orthopedic implants,contractile muscles for artificial heart, filterfor vena cava, orthodontic dental archwiresand intracranial aneurysm clips.

8. Dental metals : Dental amalgam is an alloyobtained by mixing silver-tin alloy withmercury. Since mercury is in liquid form,the silver - tin alloy can be mixed in it. Theresultant paste is packed into a preparedcavity of tooth. The final composition ofdental amalgam contains 45 to 55% mercury,35 to 45% silver and 15% tin. The amalgamsets in solid form in one day.

9. Gold : Gold being base metal has highcorrosion resistance but poor mechanicalproperties. Gold and its alloys are used asdental materials as they have durability,stability and corrosion resistance. Dentalfillings of gold can be carried out by twomethods viz. casting and maletting.Mechanical properties of gold can beimproved by adding not more than 25%copper or 4% of platinum.

10. Corrosion of metallic implants : The mainreason of metallic corrosion is its oxidation.A metal in pure form stays in metastableequilibrium. Tissue fluid in the human bodycontains water, dissolved oxygen, chloride

and hydroxide ions etc. Hence metallicimplants have to face a very corrosiveenvironment. Corrosion is unwantedchemical reaction of metallic implant withenvironment. The metals tend to lower theirenergy state by electrochemical reactionwith environment. Oxidation and reductionare two electrochemical reactions. Oxidationis a reaction in which electrons areconsumed. Oxidation reaction is :–

M → M+n + ne ...(I)

Similarly reduction reactions are –

M+n + ne → M ...(II)

2H2O + O2 + 4e → 4.0H ...(III)

4H+ + O2 + 4e → H2O ...(IV)

2H+ + 2e → H2 ...(V)

Equation (III) gives corrosion reactionoccurring at neutral PH solution and metallicimplants are generally corroded accordingto this. It is also seen that variation of oxygenon metal surface leads to corrosion withsites with lower oxygen concentration(cracks, dirt or along screw of implants)become anodes and exposed sites withhigher oxygen concentration becomecathodes. These anodes and cathodes withbody solution connecting them to formelectro chemical cells leading to deteriorationof metallic implants.The tendency of metalsto corrode is given by the standardelectrochemical series of Nernst potentialsas given below :

M etal

e

D irt

Screw in M etal C racks in M etal D ir t on M eta lM etal

e

e e e

e

e

Deterioration Due to Oxygen Concentration Gradient

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S.N. Metal Potential CV Remarks

1 Li+ + 2.96 Anode

2 K+ + 2.92

3 Ca2+ + 2.90

4 Na+ + 2.71

5 Mg2+ + 2.40

6 Ti2+ + 2.00

7 Al2+ + 1.70

8 Zn2+ + 0.76

9 Cr2+ + 0.56

10 Fe2+ +0.414

11 Ni2+ +0.23

12 Sn2+ +0.14

13 Pb2+ + 0.12

14 Fe3+ +0.045

15 H 0.000 Reference

16 Cu2+ – 0.34

17 Cu+ – 0.47

18 Ag+ – 0.80

19 Pt2+ – 0.86

20 Au+ – 1.50 Cathode

These protentials are found out inelectrochemical measurement in which oneelectode is metal and other is a hydrogenelectrode consisting of porous platinum tubethrough which hydrogen is passed. Theprotential of hydrogen electrode is taken asreference i.e. Zero potential. Metal havinghigher protential than hydrogen electrode areknown as noble metals while those havinglower protential are known as base metals.If two dissimilar metals are present in a

solution, then the metal having higherprotential will become anode and galvaniccorrosion starts which is much rapid thancorrosion of a single metal. Hence metallicimplant should be made of a single metalwithout any impurity. Any region of stresswill become anode with respect tounstressed region of the same material asstressed region has higher energy level. Thecorrosion of stressed region starts at theearliest opportunity. Also base metals are lessprone to corrosion.

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M etal Fe++

H 2

+0.44vPorous

p la tinum tube

So lu tionFe++

Fe++

H+

H+

H+

gas

V

OBJECTIVE TYPE QUESTIONS

Fill in the gap

1. ------- is a synthetic material to replace apart of a living system. (a) Biomaterial (b)Biometal.

2. The reliability of an implant is ------- if itdepends upon two factors having probabilityof failures as f1 and f2. (a) f1 × f2 (b) (l – f1)(l – f

2)

3. The acceptance of an implant by surroundingliving tissues is called -------.(a)bioacceptance (b) biocompatibility

4. Metals have high ------- energy. (a) latent(b) free

5. Vanadium steel is no longer used for implantsas it is pron to -------. (a) break (b) corrode

6. Titanium has ------- density. (a) low (b) high

7. Shape memory metals can gain ------- shapeon heating. (a) original (b) small

8. Titanium alloys show -------. (a) shapememory effect (b) good mechanicalproperties

9. Dental amalgam is an alloy obtained bymixing ------- with mercury. (a) silver-copper alloy (b) silver-tin alloy

10. Dental amalgam can set in -------. (a) oneweek (b) one day

11. Mechanical properties of Gold can beimproved by mixing copper not more than ------- percent. (a) 30 (b) 25

12. Oxidation is a process in which electronesare -------. (a) liberated (b) consumed

13. Reduction is process in which electrons are-------. (a) liberated (b) consumed

14. ------- protential is given by the standardelectro chemical series. (a) Faraday (b)Nernst

15. Hydrogen electrode has ------- protential. (a)one (b) zero

16. Gold and silver are ------- metals. (a) noble(b) base

ANSWERS

1. (a) 2. (b) 3. (b) 4. (b) 5. (b) 6. (a) 7. (a) 8. (a)9. (b) 10. (b) 11. (b) 12. (a) 13. (b) 14. (b) 15. (b) 16. (b)

Measurement of Potential Against Standard Hydrogen Electrode

Page 160: Fundamentals of biomedical engineering

1. Polymer as name suggests is many mers(small molecules or repeating units) joiningtogether under suitable condition to form along chain (a heavy molecule). The processof forming a long chain of a heavy moleculefrom small molecules is called poly-merization. The polymerization can be doneby condensation (water is condensed out)or by addition (by rearranging bonds withineach monomer). Polymer can be linear,branched or cross linked as shown in tablebelow .

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Human beings dream of life everlasting. But most of them want it on earth andnot in heaven.

INTRODUCTION

S.N . Type M er

o r Repeating unit L ink ing

1 L inear polym er

2 B ranched polym er

3 C rossed Linked

Polymer can be obtained by linking of onetype of mers (monomers) or more than twotypes of mers. Hence copolymers arepolymers made form two of more types ofmers. The degree of polymerization (DP) isdefined as average number of mers (repeatingunits) per molecule (long chain)i.e.,Molecular weight of polymerization = DP ×molecular weight of mers. The possiblearrangements of copolymers can be :–

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( ) R andoma

( ) A lte rnatingb

( ) B lockc

( ) G raftd

2. Poly dispersity Index (PDI). The ratio ofweight average molecular weight to thenumber average molecular weight of anypolymer is called polydispersity index and isdenoted by PDI.

i.e. PDI = Mw

Mn

where Mw = Weight average molecular

weight

Mn = Number average molecular weight

Mn = Ni Mi

Ni∑∑

= 1 1 2 2

1 2

N M N M ...

N N ...

+ ++ +

where Ni = No. of molecules havingmolecular weight Mi

N1 = Molecules have molecular weight M1

N2

= molecules have molecular weight M2

and so on.

Mw =

2Ni Mi

Ni Mi∑∑ =

2 21 1 2 2

1 1 2 2

N M N M ...

N M N M

+ ++ +

PDI gives an idea about the molecular weightdispersion. Therefore if PDI = 1 i.e.,

Mn = Mw , then no dispersion in thesystem occurs and complete polymerisationhas occurred without formation of otherproducts. So in medicinal application, PDIshould be unity to avoid any side reactionsor side effects due to detachment ofbyproducts weakly adhered in the polymer.

Example: What is number and weightaverage molecular weight of polymer? Twomonodisperse polymer samples with numberaverage and molecular weight (a) 10,000 adn(b) 20,000 were weakly adhered in thepolymer were mixed. Prepare two samplesby taking two parts of (a) and one part of (b)(2) mixture two was prepared by taking onepart of (a) and two part of (b). Calculatenumber and weight average molecular weightof mixture 1 and 2. (UPTU 2005-06)

Solution: Number average molecularweight. The arithmatic mean of molecularweight of all the polymeric chains presentin the polymeric disperse. It can be given astotal mass of polymeric disperse divided bythe total number of molecules present. It is

denoted by Mn

Mn = i i

i

N M

N

ΣΣ =

1 1 2 2

1 2

...

...

N M N M

N N

+ ++ +

Weight average molecular weight. In thisvarious molecular species are takenproportion to their weights. It is denoted by

Mw .

Mw = i i

i

W M

W

ΣΣ =

1 1 2 2

1 2

W M W M ....

W W ....

+ ++ +

But Wi = Ni Mi

Hence M w = 2

i i

i i

N M

N M

ΣΣ

= 2 21 2 2

1 1 2 2

M N M .......

N M N M .......1Ν +

+

Weight average molecular weight can bedetermined by viscosity method orultracentrifuge method. The value of weightaverage molecular weight is always greaterthan number average molecular weight.

Given – MA = 10,000 & MB = 20,000

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Now for mixture (1) having 2A + B, we haveN1 = 2, M1 = 10,000, N2 = 1 and

M2 = 20,000

Mn = i i

i

N M

N

ΣΣ =

1 1 2 2

1 2

N M N M

N N

++

= 2 10,000 1 20,000

2 1

× + ×+ =

40,000

3= 13,333.4

Mw = 2

i i

i 1

N M

N M

ΣΣ =

2 21 1 2 2

1 1 2 2

N M N M

N M N M

++

= ( ) ( )2 2

2 10,000 1 10,000

20,000 20,000

× + ×+

= 2 22 10 4 10

40,000

× + × = 15,000

Now for mixture (2) having A + 2B, we haveN1 = 1, M1 = 10,000, N2 = 2 and

M2 = 20,000

Mn = i i

i

N M

N

ΣΣ =

1 1 2 2

1 2

N M N M

N N

++

= 1 10,000 2 20,000

3

× + ×

= 50,000

3 = 16,333.4

Mw =

2i i

i i

M

N M

ΝΣΣ

=

2 2 21 1 2 2

1 1 2 2

M N M

N M N M

Ν ++

=( ) ( )2 2

1 10,000 2 20,000

1 10,000 2 20,000

× + ×× + ×

=8 810 8 10

50,000

+ ×

=8

4

9 10

5 10

×× = 1.8 × 104

3. During the past few years considerableadvances have been made in the developmentof polymeric materials for use in medicineand surgery particularly for replacements inthe cardiovascular system. A number ofpolymers with proper surface modificationwhich can remain biocompatible for severalmonths are now available. Heart valves,heart-lung devices, catheters, artificialmembranes, pacemaker and blood pump aredevices which are made from polymericbiomaterials. The successful use ofpolymeric implants are improved the qualityof life of many patients. But the state of artof the production of these polymericmaterials for a specific perpose has not beenperfected. New polymeric biomaterials arebeing developed to make good prosthesesdevices which will enable the patientswithout limbs to lead a normal life. Thecommercial polymers can not be used forbiomedical applications. They do not havesufficient purity and reproductibility. Thepolymeric material must meet the need ofthe surgeons as well as the design problemsof the implant. The polymeric material mustmeet the criteria outside and inside of aphysical system. For example chemicalinertness and mechanical strength areoutside criteria for selection of polymer butthe functional characteristics of the polymerwith physiological system are inside criteriafor the selection or designing thecomposition of a polymer.

4. Selection of polymeric biomaterial:Certain sets of information that case help inselection of polymeric biomaterial formaking of an implant can be grouped intotwo categories viz(1) General characteristicsand (2) Special considerations. The generalcharacteristics which a biomedical polymermust have (1) chemical purity (2) goodfabrication methodology (3) adequatemechanical strength (4) no leachable

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impurity (5) easy stretchability. Thepresence of traces of catalyst, residualadditive or other impurities in the polymericimplant may trigger thrombosis formation,protein deposition or giant cell growth orany other unfavourable tissue response.Similarly the fabrication history has greatsignificance and biomedical polymer mustretain its characteristics even afterfabrication. The polymeric material of theimplant is reacted upon by physiologicalenvironment. The implant must functionwithout being itself demaged and withoutcausing adverse effect on the tissuessurrounding it. Hence polymeric biomaterialshould not cause – (1) thrombosis (2) anydistruction of cellular element of blood (3)cancer (4) toxic and allergic response fromtissues (5) adverse effect on immune system(6) depletion of electrolytes (7) fatal effecton enzymes and proteins.

5. Specific considerations mean that apolymeric biocompatible material is designedspecifically to meet the functionalrequirement in the prevalent environmentinside the body. To accomplish this, anunderstanding of the relationship of thestructure and properties of the polymer withrespect to its interaction with physiologicalsystem at molecular level is required. Thespecific considerations for designing are :(a) Type of polymers: certain rigid and

elastometric polymers evoke less tissuereaction and thrombosis formation thanother.

(b) Molecular weight and Molecular weightdistribution: Most of mechanicalproperties of a polymer improve withmolecular weight upto a limiting valueand then remain constant with furtherincrease in molecular weight. Similarlymelting point, elasticity and otherproperties are found to have same trend.

However solubility and brittleness showsreverse trend. Therefore, molecularweight of the polymers should be abovethe limiting value. The properties of thepolymers are also affected by themolecular weight distribution of thepolymers which should not be broad.Incase of broad distribution, polymermay have two molecular weight chainswhich may dissociate and leak into theblood stream causing malfunction.

(c) Crystallization and intermolecularforces : Flexible polymer can be obtainedby keeping the chain separated fromone another otherwise the polymer willbe crystalline and rigid. If crystallisationof the polymer occurs when implanted,stress cracking and stiffening ofpolymer take place. The highlycrystalline polymers like nylon,polyethylene and polypropylene aremade flexible with addition ofplasticisers. However they can undergoextensive molecular rearrangementunder tensile and other stresses and theymay again become crystalline. Due tothis, they can readily crack or developpits. These sites also become areas forabsorption of protein molecules. Thepresence of strong intramolecular forcesfevours crystallisation of linearpolymers which leads to cracks andprotien absorption on the surface of thepolymer.

(d) Mechanical properties: An implant orprostheses device has a mechanicalfunction to perform and hence itsmaterical must have enough mechanicalproperties which depend upon itsprocessing, fabrication, shape, stressand strain relationship and its timedependent changes (creep anddeformation). The properties of apolymer like molecular weight and

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molecular distribution and crystallinity(crystallinity can be prevented byplasticizers) can be controlled whichwill ensure a good performance of thepolymer.

(e) Surface characteristic: The surface ofa polymer which comes directly intocontact with tissues and blood, playsan important role in deciding thebiocompatiblity of the polymer. Whenblood comes in contact with thepolymer, there is a rapid absorption ofplasma protein on its surface.Subsequent interaction results into theabsorption of platelets of the bloodwhich leads to the thrombosisdepending upon the nature of theprimary layer of proteins. Theabsorption of proteins from the plasmadepends upon the type of surface,hemorheological parameters and typesof ionic species present in plasma. Thenature of protein absorbed dependsupon the physical and chemical natureof the surface of the polymer. Smoothsurface of the polymer which is freeof pits, cracks and roughness does notabsorb proteins. The smoothness ofthe surface depends upon themicromolecular structure of thepolymer and also on its surfacetreatment.

1. Polyvinyl chloride (PVC): It is anamorphous and rigid polymer as it has largeside group. It has a high melt viscosity whichmakes its processing difficult. Thermalstabilisers are added to prevent thermaldegradation. Plasticizers are added to makeit flexible. Lubricants are added to increasemelt flow during processing. PVC is usedin film form for blood bags, solution bags

and surgical packaging. PVC tubing is usedin catheters, cannulae dialysis devices andIV administration.

2. Polyethylene (PE) : It is available in manygrades depending upon density as (1) highdensity polyethylene (HDPE) (2) low densitypolyethylene (LDPE) (3) very low densitypolyethyelene (VLDPE) (4) Linear lowdensity polyethylene (LLDPE) (5) Ultra highmolecular weight polyethylene (UHMWPE).HDPE is used for bottles, caps and nonwoven fabric. LDPE is used for packaging,flexible containers and nonwovendisposeables. LLDPE has excellent punctureresistance and therefore it is used forpouches and bags. Extruded tubes are madeof VLDPE. UHMWPE has high density andhigh mechanical properties. It is used fororthopedic implant such as acetabular cupof tibia in hip joint and patellar surface inknee joint.

3. Polypropylene (PP): Thermal and physicalproperties of polypropylene are similar topolyethylene. Polypropylene has a very highflex life and high resistance to environmentstress cracking. It is used for prosthesesfor finger joint, disposable hypothermicsyringes, membrane of blood oxygenator,packaging for devices, containers (solutionand drugs), suture, artificial vascular graftsand non woven fabrics etc.

4. Polystyrene (PS): High impact polystyrene(HIPS), PS foam and general purposepolystyrene (GPPS) are three gradesavailable. GPPS has good transpancy, easeof fabrication, thermal stability, low densityand high modulus. Its ductility, impactstrength and resistance to stress crackingcan be improved with addition of modifier.It is used for vacuum canisters andfilterware. One of the copolymer ofpolystyrene is acrylonitrile butadicne -styrene (ABS) which has good surface

CERTAIN POLYMERIC BIOMATERIALS

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properties and dimensional stability. It is usedfor IV sets, blood dialyzers, diagnostic testkits and clamps etc.

5. Polymethylmeth acrylate (PMMA): It isamorphous and it has good resistance (indilute alkalies and inorganic solution), lighttransparency and excellent optical properties,good weathering properties and goodmachineability. It is used for blood pumpsand reservoirs, IV systems, membranes forblood dialyzer, contact lenses, implantableocular lenses, dentures and bone cements forprostheses fixation etc.

6. Polyesters : Polyethylene terephthalate(PET) is most common polyster which isused for biomedical applications such asvascular graft, sutures and meshes. PET canalso be converted by conventionaltechniques into moulded articles such as

lucer filters, check valves and catheterhousing.

7. Polyamids (Nylons): Nylons are designatedby number of carbon atoms in the repeatingunits. For example Nylon 6 and Nylon 11.The presence of CONH groups providesattraction between chains and improvesphysical properties such as strength. Certainnylons have specific strength which is fivetimes that of steel and they are most suitablefor composites. However nylon ishygroscopic and they lose strength in vivowhen implanted.

1. The applications of polymers as biomaterialshave been elaborated with each type ofpolymer. However some other applicationsare :

S.N. Polymer Application

1. Segmented polyurethane Artificial heart, heart valves,vascular tubing

2. Polyalkyle siloxane Heart valve, hydrocephalusdrain link

3. Segmented copolydimethylesiboxane urethane

Heart valve

4. Perfluoro butynyl ethylecellulose

Membrane of oxygenator

5. Polyalkyle sulfone Membrane of oxygenator6. Hydrogels As grafted surface for polymers

having good mechanicalproperties

7. Silicon rubber withsilica filler and coatedwith free silicon

Cosmetic space filler.

APPLICATION OF POLYMERS

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Fill in the gaps1. Polymer is many ------- joining together as

a chain. (a) mers (b) erms

2. Heavy molecule has a ------- chain ofrepeating unit in a polymer. (a) heavy (b)long

3. Polymerisation can be done by addition and-------. (a) substraction (b) condensation

4. ------- are made from two or more types ofmers. (a) Copolymer (b) twin polymer

5. ------- is average number of mers permolecule. (a) degree of polymerisation (b)degree of saturation

6. The molecular weight of a polymer is 90and of a mer is 15. The degree of polarisationis -------. (a) 12 (b) 6

7. Mechanical properties of a polymer improvewith molecular weight upto a ------- . (a)maxwell value (b) limiting value.

8. ------- is added to a polymer to make itflexible. (a) Elasticiser (b) Plasticizer

9. ------- surface does not absorb protein. (a)Rough (b) Smooth

10. ------- is used for implantable cellular lens.(a) PMMA (b) polystyrene

11. LLDPE has excellent ------- resistance. (a)flow (b) puncture

12. UHMWPE is used for orthopedic implantsuch as ------- surface of knee joint. (a)patellar (b) hip

13. Nylons are designated by number of -------atoms in the repeating unit. (a) hydrogen(b) carbon

14. ------- are added to increase the melt flowduring processing of PVC. (a) lubricant (b)flow activator

15. ------- are added to prevent thermaldegradation of PVC. (a) thermal resistant(b) thermal stabiliser

16. Nylon has specific strength which is -------times that of steel. (a) two (b) five

17. Hydrogels are used as ------- surface forpolymers having good mechanical properties.(a) grafted (b) cleaner of

18. ------- rubber is used for cosmetic implant.(a) silicon (b) butyl

OBJECTIVE TYPE QUESTIONS

1. (a) 2. (b) 3. (b) 4. (a) 5. (a) 6. (b) 7. (b) 8. (b)

9. (b) 10. (a) 11. (b) 12. (a) 13. (b) 14. (a) 15. (b) 16. (b)

17. (a) 18. (a)

ANSWERS

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INTRODUCTION

Whether you're a man or not comes from your heart, not how much hair youhave on your head

1. Ceramics are solids that have inorganicnonmetallic materials as essentialcomponents. They are mainly refractorypoly crystalline compounds usually inorganiclike silicates, metallic oxides, carbides,hydrides, sulfides and selenides. Ceramicshave been used in pottery for a very longtime. Ceramics are brittle and have lowtensile and impact strength. Due to theseweak properties, ceramics could not findmany applications. However ceramics havehigh compressive strength, aestheticallypleasing appearance and relative inertness tobody fluids which have made ceramicsextremely suitable as biocompatible materialsto replace various parts of the bodyparticularly bone, heart valve and dentalcrowns. Ceramics have high specificstrength as fibers and they are increasinglyused as reinforcing components forcomposite biomaterial for tensile loadingapplications such as artificial ligament andtendons. Ceramics have high resistance toplastic deformation and they are nonductilewith zero creep. Hence ceramics are veryprone to fracture at microcracks wherestress concentration takes place. It is very

difficult to find accurate tensile strength ofceramic which varies with the presence ofmicrocacks. Due to this, ceramics have lowtensile strength in comparison withcompressive strength. A flawless ceramicis very strong even in tension. For example,flawless glass fibres are twice stronger thansteel in tension. Ceramics are very hard.Alumina (Al

2O

2) and quartz (SiO

2) are

ceramics having hardness which is little lessthan diamond. Ceramics are insulatorshaving low conductivity of electricity andheat. Ceramics are refractoric materialshaving very high melting points. Bioceramicscan be classified as:

(a) Relatively inert (nonabsorbable)

(b) Semi inert (bio active)

(c) Non inert (biodegradable)

1. As the name suggests, these bioceramicsmaintain their physical and mechanicalproperties by resisting corrosion and wearin the hostile environment in the body tissues.They are (1) biofunctional for lifetime (2)biocompatible (3) nontoxic (4) noncarcinogenic (5) nonallergic (6) non-

RELATIVELY INERT (NONABSORBABLE)BIOCERAMICS

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inflammatory. They are generally used forstructural support implants such as femoralheads, bone plates and screws etc. They arealso used for non structural applications asventilation tubes, sterlization devices anddrug delivery devices. Certain suchbioceramics are described in succeedingparas.

2. Alumina (Al2O

3): It is obtained from

bauxite and corrundum. Natural alumina isknown as sapphire and ruby depending uponcolour due to impurities present. Thestrength of alumina depends upon grain sizeand porosity. The strength is high for lowgrain size and low porosity. Alumina is usedas biomaterial for orthopedics and dentalsurgery. As it is hard it is used for watchmovements and making emery paper / belt.The properties like low friction and wear,and innertness to the in vivo hostileenvironment have made alumina an idealbiomaterial for joint replacement. The mostpopular application of alumina is in total hipprostheses. It has been found that aluminahip prostheses with an UHMWPE (ultra highmolecular weight polyethylene) socket ismore perfect device than metal prostheseswith UHMWPE socket.

3. Zirconia (ZrO2): It is obtained from Zircon

(Zr SiO4). It has high melting point andchemical stability. It can be used as implantfor bone but its properties in these respetare inferior to alumina.It has goodcompatibility with body tissues and it is alsonon active to body environment.

4. Carbons : Carbon has many allotropicforms like crystalline diamond and graphite,noncrystalline glassy carbon andquasicrystalline pyrolitic carbon. Pyroliticcarbon is generally used for surface coatingof implants. The strength of pyrolitic carbonis quite high as compared to graphite andglassy carbon as it has fewer number offlaws and unassociated carbons in theaggregate. Carbon shows excellent

compatibility with tissues and blood. Pyrolitecarbon coated devices are extensively usedfor repairing disceased heart valves and bloodvessels due to high compatibility. Carbonfibers and textiles are used as reinforcementfor composite biomaterials.

1. Bioactive ceramics form strong bonds withsurrounding tissues of the body onimplantation. Surface reactive bioceramicsare (1) bioglasses and ceravital (2) denseand non porous glasses and (3) hydroxy-apatite. The surface reactive bioceramics areused for (1) coating of metal prostheses toincrease the bonding of implant with adjacenttissues (2) reconstruction of dental defects(3) as filler to fill the space created by donorbone, bone screw, excised tumors anddeceased bone (4) as bone plate and screw(5) prostheses of middle ear ossicles (6)replacing or correcting teeth

2. Glass ceramics : They are polycrystallineceramics. In fine grained structure, theyhave excellent mechanical and thermalproperties. Glass ceramics can be bioglassand cervital glass ceramics depending uponcomposition. The formation of theseceramics depends upon the nucleation andgrowth of small crystals and theirdistribution. 1010 to 10 15 nucles per cm3 arerequired to develope a crystal. Certainmetallic agents and ceramics are used fornucleation and crystallisation. The nucleationof glass is carried out at temperatures muchlower than the melting temperature. Thegrowth takes place at higher temperatures.The composition of cervital is similar to thatof bioglass in SiO2 (40 to 50%) and CaO(20 to 30%) but differs in contents of othercomponents (Na2O, P2O5, MgO & K2O).Glass ceramics have a very low coefficientof expansion (it can be negative also) andhigh resistance to surface demage due tocontrolled grain. Their resistance to

SEMI INERT (BIOACTIVE) BIOCERAMICS

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scratching is as high as that of saphire. Theglass ceramic has brittleness which gives ita lower mechanical strength. Therefore theglass ceramics can not be used for implantsubjected to high loads like joint implants.However they are being used as filler forbone cement, dental restorative compositesand surface coating material of implants.

G rowth

Nuclea tionTem p

Tim e

1. Biodegradable ceramics as name suggests,degrade on implantation in the body. Theabsorbed ceramic is replaced by endogenoustissues. These ceramics must have controlledin vivo degradation and their degradedproducts should be easily absorbed by thebody without any toxic effects. The rate ofdegradations varies from ceramic toceramic. All biodegradable ceramics arevariations of calcium phosphate exceptplaster of paris and biocoral. The mostcommon biodegradable ceramics are – (1)aluminium calcium phosphate (2) plaster ofparis (3) coralline (4) hydroxyaptite (5)tricalcium phosphate

Crystallisation of Glass Ceramic

NON INERT (BIODEGRADABLE)CERAMICS

2. Calcium phosphate : It is commonly usedin the form of artificial bone, manufacturingvarious forms of implansts and as porouscoatings on various implants. The mechanicalproperties of calcium phosphate varyconsiderably due to variations in structureand manufacturing processes. Infact ournatural bones and teeth are made of acrystalline form of calcium phosphatesimilar to hydroxyaptite. Hence hydro-xyaptite has excellent biocompatabilety.

3. ALCAP ceramics : Aluminium calciumphosphate (ALCAP) ceramics have uniquecharacteristic that they have a multi-cristallographic structure and the phase ofthe ceramic can be rapidly resorbed onimplantation. ALCAP is prepared from AlO

2

Ca O2 and P

2 O

5. ALCAP has insulating

dielectric properties but it has nopiezoelectric or magnetic properties.

4. Corals: They have structural similarity tobone and therefore they are used for boneimplants. They provide excellent structurefor the ingrowth of bone as their maincomponent calcium carbonate is graduallyresortbed by the tissues. Modified coralsresemble cancellous bone.

5. Tricalcium phosphate (TCP) ceramics:They are used for correction of periodontaldefects and augmentation of boneycontours. The ceramic can be grounded andsieved to obtain desired size particles for useas bone substitutes and also for makingceramic matrix for drug delivery systems.TCP sets and hardens on addition of water.

OBJECTIVE TYPE QUESTIONS

Fill in the gaps

1. Ceramics are -------. (a) ductile (b) brittle

2. Ceramics are mainly refractory polycrystallic compounds usually -------.(a) organic (b) inorganic

3. ------- have been used in the pottery for avery long time. (a) Ceramics (b) composites

4. A ------- ceramic is very strong even intension. (a) sintered (b) flaw less

5. Flaw less glass fibers are ------- strongerthan steel in tension (a) four tinos (b) twice

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1. (b) 2. (b) 3. (a) 4. (b) 5. (b) 6. (a) 7. (b) 8. (a)9. (a) 10. (a) 11. (b) 12. ( b) 13. (b) 14. (b) 15. (b) 16. (a)

ANSWERS

6. ------- has hardness which is little less thandiamond. (a) Alumina (b) Zirconia

7. Ceramics are prone to fracture at -------.(a) edge (b) microcrack

8. Saphire and ruby are natural -------.(a) alumina (b) Zirconic

9. Carbon has many ------- forms.(a) allotropic (b) material

10. ------- is an ideal biomaterial for jointreplacement. (a) alumina (b) quartz

11. Carbon shows excellent ------- with tissueand blood. (a) adjustment (b) compatibility

12. ------- carbon coated devices are extensivelyused for repairing disceased heart bloodvessels.(a) fine (b) pyrolite

13. The glass ceramics can not be used forimplant subjected to -------. (a) movement(b) heavy loads

14. Bioactive ceramics form strong ------- withsurrounding tissues of the body onimplantation. (a) adhesion (b) bonds

15. Biogradable ceramics------- on implantationin the body. (a) adjust (b) degrade

16. Our natural bone and teeth are made of acrystalline form of -------. (a) calciumphosphate (b) TCP

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INTRODUCTION

1. A composite is a non homogeneous materialwhich has two or more distinct constituentmaterials or phases on a scale larger thanthe atomic. It is possible to achieve desiredproperties like flexibility and strength bysuitably combining two or more material asdistinct phases without forming alloy. Thecomposite materials offer a variety ofadvantages in comparison withhomogeneous materials. Considerablecontrol over material properties can beachieved. There is possibility of making stiff,strong and light weight material or highlyresilent and compliant materials. A reinforcedplastic is a composite having two distinctconstituents/phases of plastic and fibre glassbut brass is an alloy (not a composite) as ithas no distinct phases of copper and tin. Afoam is a composite inwhich one phase isempty space. There are existing manynatural composites. Natural composites arebone, cartilage, skin, dentin and wood.Lungs, cancellous bone and wood are alsonatural foam type composites. A compositematerial can be biocompatible if the interfacebetween constituents must not be degraded

by the hostile environment inside the body.The composites are used for dental filling,orthopedic implant with porous surfaces(UHMWPE) and bone cement (reinforcedmethyl methacrylate).

STRUCTURE OF COMPOSITE

1. The desired properties can be obtained bysuitably modifying the structure of acomposite. It is possible to alter thehomogeneous structure of a material byusing other material soas to get annonhomogeneous in a larger scale structure.It is also interesting that the properties of acomposite depends upon (1) the shape ofthe inhomogeneities (2) the volume fractionof constituents and (3) the interface amongthe costituents. One of the constituent canbe in shape of fiber, platetlet or lamina. Theinclusions can also vary in size and shape(spherical, polyhedral, ellipsoidal orirregular). The inclusions can have randomor orderly orientation. The properties of acomposite depends upon the structure. Forsimple structures, it is possible to predictthe properties of the composite. Some ofsimple structures of composites having twoconstituents are as shown in the figure.

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F

Composite Lam inar Fibrous

FF

F F F

The force on the composite materials havebeen indicated. The modulus of elasticity(E) of the composite can be given as : –

E = Ei V

i + Em (1 – Vi)

where Ei = modulus of elasticity of inclusion

Vi = Volume fraction of inclusion

Em = modulus of electricity of the matrix(main material)

It can be appreciated that by using inclusionsof material having high modulus of elasticityit is possible to get a composite material ofhigher stiffness. The shape of inclusion isimportant. In isotropic system, inclusion inshape of platelet or flakes are the mosteffective in creating a stiff composite. Theinclusions in shape of fibers are also effectivebut little less. But spherical inclusions areleast effective.

1. It is very convenient to stiffen or harden asoft material (generally polymers) by theincorporation of particular inclusion. Theshape of inclusions plays an important partin deciding the properties as explainedalready. The stiffness E of a composite is –

E = ( )5 – Vi

3 2

Ei Em

Ei / Em+ + Em

PARTICULATE INCLUSIONS

where Ei = modulus of elasticity of inclusion

Em = modulus of elasticity of matrix

Vi = Volume fraction of inclusion

2. The strength of composite depends upon thebrittleness and duetility of inclusions and thematrix. The fiberous composites fail whenfiber inclusions break or buckle or pullouttake place from the matrix. Carbon fibersare generally used in HDPE as reinforcementto get a composite for knee replacement.Carbon fibers can be also used withUHMWPE to get more stronger composite.Carbon fibers are also used to reduce thetemperature of implant and in improvingmechanical properties like resistance tocreep. Metal wires are used with PMMA.They are also used in bone cement to achievenear about equal strength of the bone.Graphite fibers have been used in bonecement. The metal implants are generallyfound to be much stiffer than bone in totalhip replacement which results into theshielding and resorbing of nearby bone. Thecomposite materials are better alternative tometals for implants. They also help inpromoting healing.

Simple Structures

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1. It is desirable to have voids and cellular solidsin the matrix which will reduce the stiffnessof the composite. Such structures areflexible and they can be seen in seatcustions, filters, sandwich panels(insulation), floating devices and coatings toencourage tissue growth. The stiffiness (E)of the composite is :

E = Es (Vs)2

Es = modulus of elasticity of solid phase

Vs = Volume fraction of solid phase.

POROUS COMPOSITE 2. Porous composite have a higher ratio ofsurface area to volume. Hence more area isexposed to hostile environment in the body.Hence they must be more innert to tissues.Porous composite allows tissue growthwhich is desireable as it allows a relativelypermanent jointing of the implant with thesurrounding tissues. Porous composites areused for implants in bone and artificial rootsof teeth. Porous composites are also usedin soft tissue applications as artificial skin,ligaments and blood vessels.

Fill in the gaps1. A composite is a ------- material.

(a) homogeneous (b) non homogeneous

2. A reinforced plastic is a-------. (a) polymer(b) composite

3. A composite has ------- distinct constituentmaterials or phases. (a) atleast three (b) twoor more

4. Foam is a ------- material. (a) composite(b) polymer

5. Foam has one of its phase as -------.(a) empty space (b) light material

6. A foam type composite has ------ratio ofsurface area to volume. (a) less (b) high

7. The properties of a composite depend upthe volume fraction and shape of the -------(a) matrix (b) inclusions

OBJECTIVE TYPE QUESTIONS

8. ------- inclusions are least effective inimproving properties of a composite.(a) fiberous (b) spherical

9. ------- fibers are used with HDPE to get acomposite for knee replacement (a) metal(b) carbon

10. ------- are used with PMMA for bonecement to achieve near about strength ofthe bone. (a) metal wires (b) nylon filaments

11. Porous composites have ------- ratio ofsurface area to volume. (a) lower (b) higher

12. For implants in bone and artificial roots ofthe teeth ------- composites are used.(a) porous (b) particulate

13. The voids and cellular solids in the matrixwill ------- the stiffness of the composite.(a) increase (b) decrease

1. (a) 2. (b) 3. (b) 4. (a) 5. (a) 6. (b) 7. (b)8. (b) 9. (b) 10. (a) 11. (b) 12. ( a) 13. (b)

ANSWERS

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Endure today's pain today. Do not add it to yesterday's. Nor attempt to shouldertomorrow's.

INTRODUCTION

1. The biogradable has same meaning as otherterms such as absorbable and resorbable.The biogradable polymers are those polymerswhich can be broken down throughhydrolytic mechanism without the help ofenzymes. The biogradable polymericbiomaterials have two major advantageswhich are:

(1) These materials are absorbed by thebody leaving no trace at the implant site.

(2) These materials regenerate tissues andtheir implant is used as temporaryscaffold for tissue regeneration.

TYPES

1. All biogradable polymeric biomaterials canbe divided into eight groups based on theirchemical origin as under:

(a) Biogradable linear aliphatic polyestersand their copoymers. This group ofbiogradable polymers are widely usedin surgery. Polyglycolide polylactide,polycaprolactone and polyhydioxy butyrate are linear aliphatic polysters . Thecopolymers are formed through

copolymerisation of the members of thislinear aliphatic polysters are alsoincluded in this group.

(b) Biogradable copolymers obtained fromcopolymerisation between linearaliphatic polysters and monomers otherthan linear aliphatic polysters.

(c) Polyanhydrides

(d) Polymerisation of orthoesters.

(e) Polymerisation of ester–ethers.

(f) Polysaccharides which arebiodegradable such as hyaluronic acidand chitin.

(g) Polyaminoacids

(h) Inorganic biogradable polymers havingnitrogen - phosphorous linkage insteadof ester linkage.

APPLICATIONS

1. The widely used biomedical application ofbiodegrable polymeric biomaterial has beenin wound closure. These biomaterials arebased either upon the glycolide or the lactidefamily. Their degradation with time andenvironment is vary important. Thesebiomaterials are used as surgical meshes forhernia and body wall repair.

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2. The next largest biomedial application ofbiodegradable polymeric biomaterials is indrug control and release in devices.Polyanhydrides and orthoester polymers arethese types of biodegradable polymers whichare used to prepare a drug depot which wouldlast for a few months.

3. Biodegradable polymeric biomatierialsparticularly totally resourbable compositeshave recently been used in the field oforthopedics as PDS pins for the fixation ofinternal bone fracture.

4. Biodegradable polymeric biomaterials are alsoused as vascular grafts and stunts, nerve

growth conduits, augmentation of defectedbone, ligament and tendor prostheses andintramedullary plugs for total hipreplacement.

5. Biodegradable polymeric biomaterials havea controlled in vivo degradation. The materialmust be biodegradable and its degradedproducts should be easily absorbed by thebody without any toxic effects. The rate ofdegradation of the material should match thedemand of the end use to which it will beput. Bioabsorable sutures is one of suchapplication.

Fill in the gaps 1. Biodegrable polymeric biomaterials are

absorbed by the body leaving ------- traceat the implant site. (a) no (b) some

2. Biodegradable polymeric biomaterialsencourage the tissues -------.(a) destruction (b) regeneration

3. The biodegradable polymeric biomaterialsare widely used for wound -------.(a) closure (b) repair

4. The role of degradation of biomaterial shouldmatch the demand of the end ------- towhich it will be put. (a) use (b) system

5. The degraded products should be easilyabsorbed by the body without any -------effect. (a) unhealthy (b) toxic

6. The biodegradalic polymeric biomaterial cancontrol drug release and it can be used as adrug -------. (a) depot (b) storage

7. Biodegradable polymeric biomaterials can bebroken down through hydrolytic machanism------- the help of enzymes.(a) with (b) without

8. Nowadays, ------- sutures are used insurgery. (a) nylon (b) biogradable

OBJECTIVE TYPE QUESTIONS

ANSWERS

1. (a) 2. (b) 3. (a) 4. (a) 5. (b) 6. (a) 7. (b) 8. (b)

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INTRODUCTION

1. The fixation and maintenance of a stableinterface between the prostheses and tissuesis a most difficult problem of orthopedicjoint prostheses implantation. Frequentprostheses fixation problems are related toinfection, wear and wear particles, looseningof prostheses and failure of implants. Thefailure of implants can be (1) mismatch ofproperties of tissue and biomaterial (2)wrong design of implants (3) impropersurgery and fixation (4) post surgicalimproper care (5) loosening of implant.Prostheses fixation can be mechanical orbone cement fixation.

2. Mechanical fixation : Bolts and nuts ( tofix femoral components to the femur bonein total hip prostheses) and metal pegs (tofix acetabular coresponent with metal tometal bearing surfaces) are the mechanicalmethods of fixation of prostheses. Thismethod of fixation and bearing surfaces havemany drawbacks like (1) massive tissuereaction (2) harmful release of wearparticles during metal to metal friction and(3) stress concentration around the holes

resulting into loosening of fixation. Thepassive mechanical fixation is a bettermethod of fixation in which press fit is usedto fix the femoral ceramic stems of a hipjoint instead of bolts and nuts. The large sizeof the stem also helps in distributing thestresses on a large area. The passive fixationalso includes the formation of a membraneat the interface of the bone and implantwhich prevents any relative movementbetween them or loosening of joint.

3. Bone cement fixation : Bone cement ismade of PMMA (polymethyl methacrylate)powder and MMA (methyl methacrylate)monomer liquid. When the powder and liquidare mixed, the monomer liquid wets thepolymer powder particle surfaces and linksthem by polymerisation. The mixture has adough state when it is injected into theprepared intramedurally cavity. Theprostheses is then placed over the cementas shown in the figure. The setting time ofthe bone cement takes 5 to 15 minutes. Theproperties of cured bone cement arecomparable to those of acrylic resins(compressive strength atleast 70 Mpa).

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Syringe

Bone cem ent

Fem ur

Prostheses

Dough injection Prostheses fixa tion

Bone cem ent

The use of a mesh reinforcement (a wirecoil) around a prostheses in bone cement

Prostheses

M esh reinfo rcem ent

Bone cem ent

fixation helps in decreasing the stress on thebone cement.

Fill in the gaps1. Bolts and nuts are the mechanical methods

of fixation of -------. (a) prostheses (b)bones

2. The press fit used for the fixing of femoralstem of a hip joint is a ------- mechanicalfixation. (a) passive (b) tight fit

3. The bone cement consists of PMMA ------and MMA -------. (a) powder, liquid (b)liquid, powder

4. The bone cement takes ------- minutesto polymerise and set. (a) 30 – 40(b) 5 – 15

OBJECTIVE TYPE QUESTIONS

5. The wire coil with the bone cement fixation

of prostheses helps in the ------- of the stress

on the bone cement. (a) increase (b)decrease

6. The large size of stem in passive mechanical

fixation helps in -------the stresses on thelarger area. (a) localising (b) distributing

7. The passive mechanical fixation also induces

the formation of a ------- at the interface ofthe bone and implant. (a) membranes (b)

void

1. (a) 2. (a) 3. (a) 4. (b) 5. (b) 6. (b) 7. (a)

ANSWERS

Bone Cement Fixation Mesh Reinforcement

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One can enjoy life a lot more by saying yes than by saying no.

INTRODUCTION

1. The body produces various physiologicalsignals. The accessibility to these signals isimportant because (1) they can be internal(blood pressure) (2) they may emanate fromthe body (infrared radiation) (3) they maybe derived from a tissue sample (blood ortissue biopsy). All physiological signals canbe grouped into the flowing categories – (1)biopotential (2) pressure (3) flow (4)dimensions ( for example : imaging), (5)displacement (such as velocity, force, andacceleration) (6) impedence (7) temperatureand (8) chemical concentration andcomposition.

2. The transducer is a device that converts oneform of energy to another. A transducerconverts a physiological signal to an electricoutput. The transducer should respond onlyto the targeted form of energy present inthe physiological signal and it must excludeall other energies. The transducer shouldinterface with the living system in such away that it should extract minimum of energyand also it should not be invasive.

1. Physiological signals are generated by thebody during the functioning of variousphysiological systems. Hence physiologicalsignals hold information which can beextracted from these signals to find out thestate of the functioning of thesephysiological systems. The process ofextracting information can be very simpleas feeling the pulse to find the state of heartbeats and it can be complex which mayrequire analysis of the structure of tissueby a sophisticated machine. Depending ontype of energy, the physiological signals canbe:

(a) Bioelectrical signals: These signals aregenerated by nerve cells and musclecells. The source of these signals arecells which undergo change of statefrom resting potential to action potentialunder certain conditions. The changeof potential in many cells generate anelectric field which fluctuates and in thisprocess it is to emit bioelectric signal.ECG and EEG are obtained from thebiosignals from heart and brainrespectively.

SOURCES OF PHYSIOLOGICAL SIGNALS

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(b) Biomechanical Signals: These signalsare generated by some mechanicalfunction of a physiological system.These signals are related to motion,displacement, pressure and flow of thephysiological system. The respiratoryphysiological system functions with themovement of chest which can beanalysed.

(c) Bioacoustic Signals: These are createdby the physiological systems which aredealing with the flow of blood and air.The flow of the blood in the heart, theopening and closing of chest inrespiratory system generate uniqueaccoustic signals.

(d) Biomedical Signals: Weak magneticfields are generated by various organslike heart, brain and lungs whilefunctioning. Magneto encephalographis obtained from the biomagneticsignals from the brain.

Sources of Physiological Signals

(e) Biochemical signals: The informationis obtained by chemical measurementsfrom the living tissues or analysis ofthe samples obtained from the body.The concentrations of variousconstituents in the blood and themeasurement of partial pressure ofoxygen and carbon dioxide inrespiration are found out by this method.

(f) Bioimpedence Signals: The impedenceof the skin depends upon thecomposition of skin, blood distributionand blood volume through the skin. Themeasurement of impedance helps infinding the state of skin and functioningof various physiological systems. Thevoltage drop by the tissue impedenceis nothing but a bioimpedence signal.

(g) Bio optical Signals: These signals areproduced by the optical variations bythe functioning of the physiologicalsystem. The blood oxygenation can bemeasured by measuring transmitted andreflected light from the blood vessel.

EEG (Nervous system)

Electrooculogram (occular system)

ECG (cardiovascular system)

Blood pressure (cardiovascular system)

Blood flow (cardiovascular system)

Respiratory parameters (Respiratory system)

Phonocardiogram (heart sounds)

Electromyogram (muscular system)

Pulse rate (cardiovascular system)

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1. Transducer is a device which converts oneform of variable or energy into another formof variable or energy. Generally, transduceris required to convert physiological variablesinto electrical signals which are easier to beprocessed. The relationship between inputand output variable can be linear, logarithmicor square. The transducer can be active orpassive depending upon conversion of nonelectrical variable into electrical signal. The

active transducer directly converts inputvariable into electrical signals while passivetransducer modifies either excitationvoltages or modulates the carrier signals. Thepassive transducers are externally poweredwhile active transducers are self generatingand requrie no external power.

1. Modern digital computers make theapplication of these transducers absolutelyvery essential. Type of transducer, principleof operation and typical applications aretabled as under :–

TRANSDUCER

ACTIVE TRANSDUCERS

S.N. Type Principle of Operation Typical Application

1 Moving Coilgenerator

Motion of Coil in a magneticfield induces a voltage.

Measurement of :(a) Velocity(b) Vibration

2 Photovoltaic A voltage is generaten in asemiconductor for junction(solar cell) when simulated byradiant light energy

Light variation ismeasured as currentoutput of cell. Physiolo-gical signals modulatelight intensity.

3 Thermocouple When the junction of twodissimilar metals is heated andother is cooled, then an emf isgenerated across the juctions.

Measuring of:(a) temperature(b) heat flow(c) radiation

4 Piezoelectriceffect

An emf is generated whenan external force is appliedto a crystalline material likequartz :

M etal AM etal B

Jauction 1

Jauction2

Thermo voltage

(a) Sound(b) Vibration(c) Acceleration(d) Pressure

variation.

P – S i

– +N i – S i

Silicon solar cell

+

+ + + +

– – – –

Force

Vp

Measurements of

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1. The passive transducer consists of a usuallypassive circuit element which changes itsvalue as a function of the physical variabledeveloped by physiological signal to bemeasured. There are only three passivecircuit elements that can be used to changevoltage at the output of the cercuitaccording to the physical variable : (1)resistors (2) capacitors and (3) inductors.The passive transducer is part of a cercuitnormally an arrangement similar to awheatstone bridge which is powered by anac or dc excitation.

2. Principle of Wheatstone Bridge. The circuitis as shown in the figure. These are fourresistances R1, R2, R3 and R4 connected toa DC source (V0). The voltmeter (V)indicates the difference of potential betweenjunction ‘A’ and ‘B’. The value of potential

at junction ‘A' = V0 – V0 2

1 2

R

R R+ and at

junction ‘B’ = V0 – V0 4

3 4

R

R R+ : It can be

seen that if R1 = R2 = R3 = R4 = thenpotential at junction ‘A’ and ‘B’ is same

0

2

V

and voltmeter reading will be zero.

Any variation in resistance in any of armwill vary the potential between junction ‘A’and ‘B’ which can be read by the voltmeter.In unbonded strain gauge, the arrangementis made such that resistance in arms R1 andR4 is reduced by ∆R and resistance in thearms R2 and R3 are increased by ∆R whichgives potential at junction ‘A' = V0

1–2

R R

R

+ ∆ and at junction ‘B’ = V0

–1–

2

R R

R

∆ . Hence there is a potential

difference equal to R

R

∆ between junction

‘A’ and ‘B’ where ∆R depends upon the

variable input.

R 1

R 3

R 2

R 4

A

B

V o+

3. Potentiometer : An ordinary potentiometercan be used to convert displaement orrotary motion into a change of resistance.In linear displacement potentiometer, thereading of the voltmeter at point ‘C’ = v/l× l1 which depends upon the position ofthe pointer ‘C’. Similarly rotationaldisplacement potentiometer, the pointer ‘C’rotates as per the input variable.

V

l1

A

C

B + –

lm oving po in ter c’

V

A B

C

O

+ –

V

V

4. Strain gauge : The resistance of a resistiveelement is proportional to length andinversely proportional to area i.e.,R = r l/A(r = resistivity, l = length and A = area). If atensile force is applied to extend its lengthand reduce area, then resistance of theresistive element will increase. Similarly if

PASSIVE TRANSDUCERS

Resistive Passive Transducers

Linear Displacement

Rotational Displacement

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compressive force is applied, its resistancewill decreases. We define gauge factor as

the ratio of R

R

∆ to

L

L

∆ i.e., gauge factor

G = /

/

R R

L L

∆∆ . The strain gauge can be (1)

unbonded and (2) bonded in order to obtainsufficient resistance for each arm (four armsof wheatstone bridge). Several turns of thinwire are used between two posts (refer tofigure). Four posts are mounted on stationarypart and other four posts are connected tothe transducer which can move to right orleft with respect to the stationary part. If

moving part moves to right, resistiveelements R2 and R3 are relaxed tension. Asexplained in the principle of wheatstone, thechange of resistance is indicated by thevoltmeter which depends upon the linearmovement of the transducer. In the bondedstrain gauge as shown is the figure, a thinresistance wire is shaped in a zigzag mannerand it is cemented between two paper / foilcovers.

The compact strain gauge can be easilycemented to the surface of a structure / bodyand any change in surface dimension isindicated by the change of the resistance ofthe strain gauge.

Top Cover

Strain gauge w ire

Bottom Cover

R 1

R 2

R 3

R 4

Resistance a rm (m any tu rns o f w ire)

M oving part

S ta tionary m em ber

R 1

R 3

R 2

R 4

V

Unbounded Strain Gauge and Connectivity

Parts of Bonded Strain Gauge Bonded Strain Gauge

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5. Solved Example (strain gauge). A straingauge (l = 0.1 meter) is bonded to a surface(Area = 4 cm2) having modulus of elasticityE = 200 G N/m2. The strain gauge unstrainedresistance is 200 ohm and gauge factor (G)= 10. When load is applied, the resistancechanges by 0.01 ohm. Find the stress andload applied.

Gauge factor G =/

/

R R

L L

∆∆

∆ L = R

R

∆ ×

L

G =

0.01

200 ×

0.1

10 = 0.5 × 10–6 m

ε = strain = L

L

∆ =

–60.5 100.1×

= 0.5 × 10–5

Stress σ = ε × E= 0.5 × 10–5 × 200 × 109

= 1 × 106 N/m2

Force = σ × A = 1 × 106 × 4 × 10–4 = 400 N

1. Variable induction : The property ofinductance is varied in the cercuit to changethe output voltage in accordance with theinput variable. The inductance L = n2 Gµ(n = number of turns in coil, G = formfactor of coil and µ = permeability of corematerial inside the coil). Though inductioncan be varied by any of these threeparameters, but generally arrangement ismade to change the permeability to achievevariation in induction of the cercuit as perthe variable input. In the passive inductiontransducer, the core is made of a softmagnetic material which changes theinduction of the coil when it is moved insideor outside, thereby the output of ac signal ischanged as per the displacement of the corein the coil.

Core

Co il

AC S igna ls

2. Variable reductance : In this, core remainsstationary inside the coil but the air gap inthe magnetic path of the core is varied tochange the net permeability, thereby varyingthe output signal as per the input variable(displacement).

Air gap

D isp lacem ent

P late iron

Co ilCore

O utpu t

3. Linear Variable differential transformer(LVDT). The transducer consists of atransformer with one primary and twosecondary windings. The secondarywindings are connected as shown in thefigure so as that their induced voltagesoppose each other. If the core is positionedin central position as shown in the figure,the voltage induced in both secondarywindings is equal and opposite, thereby theoutput voltage is zero. If the core is movedupwards, the voltage in secondary 1 isgreater than voltage in secondary 2. Similarlythe voltage in secondary 2 will be greaterthan voltage in secondary 1 if the coremoves down. The output voltage will varyas per the movement of the core which ischanging as per input variable.

Fixed AC vo ltage

Prim ary

D isp lacem ent

Secondary1

Secondary 2O utpu t

LVDT

Induction Displacement Transducer

Variable Reductance Transducer

LVDT

INDUCTIVE PASSIVE TRANSDUCERS

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PASSIVE CAPACITANCE TRANSDUCERS

1. Variable capacitance : The capacitance (C)of a capacitor having two parallel plates ofarea ‘A’ which are separated by a distance

‘d’ is : C = Εo Εr A

d (Ε0 = dielectric

constant of free space and Εr = relativedielectric constant). The capacitance can bechanged by varying any of the parametesbut it is parameter ‘d’ (separation betweenplates) which is usually changed in thetransducer. In the linear displacement typecapacitance transducer, one plate ofcapacitor is fixed while other plate ismovable to change the capacitance as perthe input variable. In the angulardisplacement capacitance transducer, oneplate is fixed while other plate rotates tochange the capacitance as per the inputvariable.

Fixed p late

d M oving p late

Capacitance increases

M ovement

Capacitance decreases

Capacita tion

D isp lacem ent ‘d’

Variation of Capacitance with Displacement

Fixed p la te

M ovable

θ

Capacitance

Angu la r d isplacement ( )θ

1. The physiological state of an individual isindicated by his body temperature. It hasbeen seen that a person in shock has reducedblood pressure in circulating system whichresults into low body temperature. Infectionand illness are usually reflected by a highbody temperature. Special heated incubatorsare used for maintaining the body temperatureof infants. The temperature of the joint ofan arthritic patient is closely linked with theamount of local inflammation. Thetemperature can be measured by (1)thermocouples (2) thermistor and (3)radiation and fiber optic detectors. Theprinciple of thermocouple has already beenexplained in para 5 of this chapter.

2. Thermistors: It is a shortened word forthermo and resistor which means that theyare semi conductors having a high negativetemperature coefficient. The resistance of

Variation of Capacitance with Angular Displacement

TEMPERATURE MEASUREMENT

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thermistors decreases as temperature increasewhile resistance increases as temperaturedecreases. The resistance of thermistor canbe given as

RT1 = RT01 0

1 1–

T Te

β

where RT0 are resistance

at T1 and T0, β = temp coefficient.Thermistors can be formed into disks, beads,rods or any desired shapes. Thermistorprobes are available with resistance from afew hundred ohms to several megohms. Mostthermistor thermometers use the principle ofwheatstone bridge to obtain a voltage outputwhich varies as per input temperature.

3. Infrared thermometers: Our skin isperfect emitter of infrared radiation and theenergy emitted is proportion to the bodytemperature. A device sensitive to infraredradiation can measure the emitted energyfrom a patient without clothing (roomtemperature 21ºC) and directly indicates thebody temperature. Such type ofthermometers can detect areas of poorcirculation, locate breast cancer or otherunknown sources of heat in the body. Thethermograph is an infrared thermometerincorporated into a scanner which can beused to scan entire surface of body or somepart of body like a television camera. Theinfrared energy detected in scanning is usedto modulate the intensity of a light beam sothat to get the image on the photographicfilm in which the brightness depends on thedetected infrared radiation. The image iscalled a thermogram.

4. Transduction principle & applications:Biomedical transducer consists of two parts:(1) sensing element and (2) transductionelement. A detector or sensing element is thatpart of a transducer which responds to aphysical phenomenon or its change. Atransduction element transforms the outputof a sensing element to an electrical output.Hence transduction element acts as asecondary transducer:

5. Transduction principle : Several basicphysical variables and the transducersavailable for measurement are listed asunder :

S.N. Physical Transducer

Variable

1 Displacement (a) Variableresistance

(b) Variableinductance

(c) Variablereluctance

(d) LVDT

(e) Variablecapacitance

(f) Unbon-ded straingauge

2 Velocity MagneticInduction

3 Surface strain strain gauge

4 Force/Pressure (a) Unbon-ded straingauge

(b) Piezo-electric

5 Temperature (a) Ther-mocouple

(b) Ther-mistor

6 Light/infrared (a) Photo-voltaic

(b) Photo-resistor

7 Magnetic field Hall effect

In medical applications, the physiologicalvariable can be transformed into one of thephysical variable (as listed in the table) whichcan be measured very conveniently. This isknown as transduction principle.

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6. Force transduction : A force summingmember is used for the conversion ofphysical variables. The force can betransformed into (1) surface strain (figure‘a’) (2) displacement (figure ‘b’) (3) outputvoltage in LVDT (figure ‘c’) (4) photoresistivity (figure ‘d’).

Strain gaugeForce

Figure (a)

T ra n sd u ctio n w ith s tra in g a u g e

D isp lacement

Force

Figure (b)

T ra n sd uc tio n in D isp la cem en t

Force

O utpu t voltage

ACgenera to r

CoreFigure (c)

Transduction in output voltage

Force

Screen

lam p Photo resistorFigure (d)

Transduction in variable resistivityForce Transducer with Transduction

7. Transduction for displacement, velocityand acceleration : The parameters ofdisplacement (D), velocity (V) andacceleration are interlinked as under :

V = D

t

∂∂ where t = time

A = V

t

∂∂ =

t

∂∂

2

2

D D

t t

∂ ∂ = ∂ ∂ we can also write above relations as under

D = V t∂∫ = 2A t∂∫∫V = A t∂∫If we know one out or three variable, thenwe can find out other two variables bydifferentiation or integration. Thoughvelocity and displacement transducers arereadily available, but their applications inbiomedical are difficult. Thereforedisplacement and velocity are measured byindirect methods like magnetic or opticalmethods.

8. Pressure transduction : Pressure ismeasured using diaphragm which getsdeformed under pressure. The deformationis measured with the help unbonded straingauge or LVDT. The output of these devicesvaries as per input pressure variable. Thetransducers using flat or corrugateddiaphragms are designed to work on theprinciple of variable capacitance orreluctance. The diaphragms are usually formoderate pressure ranges and bourdon tubesare used for high pressure ranges. Thediaphragm type transducers infect measuregauge pressure (the blood pressure at oneside of diaphragm which gets deformedagainst atmospheric pressure). The absolutepressure can be measured if there is avacuum at one side of the diaphragm.

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Encoded Disk

Fluid pressure

D iaphragm

New position o f d iaphragm

Atmospheric p ressure

Deflected d iaphragm

Fluid

Deflection due to fluid flow

Fluid

9. Analog to Digital transduction: Digitaldata can be easily processed by computerswhich require that the output of transducersor instruments should be in digital form. Ifthe output of a transducer is not in digitalform, a device to convert the output fromanalog to digital form has to be used.Generally transducers contain encoded disks

or rulers with digital pattern which arephotographically transformed on them.These patterns can be decoded with the helpof a light source and photodiode or phototransistor. The encoded disk rotates and adigital signal indicating its position is obtainedin digital form.

Corrugated DiaphragmFlat Diaphragm

Bourdon Tube

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Electrode

R

C

+ –

Body e lectrode

R

Biopotential Electrode Interface

10. Biopotential electrodes:The biopotentialelectrodes can be grouped as under :

(a) Microelectrodes: They measurebioelectric potential near or within asingle cell. Their tips are sufficientlysmall to penetrate a single cell to getthe potential from the cell.

(b) Body surface electrodes: Theseelectrodes do not penetrate the skinor cell but they are fixed on thesurface of the body to measure thepotential. ECG, EEG and EMG areobtained by using these electrodes.The floating electrodes are the latest

version of these type of electrodes whicheliminate direct contact of metal with skinby use of electrolyte paste or jelly, therebypermitting conductive paste between metaland skin.

(c) Needle electrodes : These electrodes aredesigned to penetrate the skin to recordEEG potential of a region of the brain orEMG potential of a muscle. They are infactsharp and small subdermal needles to easilypenetrate the scalp for EEG. They arerequired to penetrate up to surface at somedepth of the skin which is parallel to brainor muscle.

M etal

Lead w ire

Skin

E lectro ly te paste

Floating Type Body Surface Electrode

OBJECTIVE TYPE QUESTIONS

Fill in the gaps

1. ------- is a device which converts oneform of energy into another. (a)Transducer (b) biomechanism

2. The ------- transducer directly convertsinput variable into electrical signal. (a)active (b) passive

3. The ------- transducers are externally powered.(a) active (b) passive

4. The ------- transducers are self generating.(a) active (b) passive

5. The resistance of resistor element is ------- tolength and ------- to area. (a) proportional,

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ANSWERS

1. (a) 2. (a) 3. (b) 4. (a) 5. (a) 6. (b) 7. (b)8. (b) 9. (a) 10. (b)

inversely proportional (b) inverselyproportional, proportional

6. The wheat stone bridge principle is used in------- strain gauge to find out input variable.(a) mercury (b) unbonded

7. In LVDT, the induced voltages of twosecondary windings ------- each other.(a) add (b) oppose

8. ------- are semiconductor having a highnegative temperature coefficient(a) thermocouples (b) thermistors

9. A transducer consists of sensing element and------- element. (a) transduction(b) amplifying

10. The ------- element acts as a secondarytransducer. (a) sensing (b) transduction

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If you can find humour in anything, even in poverty, you can survive it.

INTRODUCTION

1. Signal processing (same as signalconditioning) has a rich history and itsimportance is evident in diverse fields likeradar, data communication, nuclear sciencesand biomedical engineering. In applicationslike EEG or systems for speech transmissionor speech recognition, we like to extractsome characteristic parameters. Alternativelywe may like to remove interference such asnoise from the signal or to modify the signalto present it in a form which is more easilyinterpreted by an expert. Also a signaltransmitted from input to output stage or

over a communication channel is corruptedin a variety of ways like distortion, fadingand insertion of background noise. In suchcases, processing of the signals is essential.

2. To understand signal processing and itsrequirement, we take the example of wheatand the process involved in converting thewheat into flour. We have to process thewheat in the first stage and then analyse theflour we get. Depending upon the graderequired for the flour, we filter the contentsand reprocess the whole thing till the wheatis transformed into flour of the requiredgrade. Signal processing may be seen in asimilar manner.

TransducerS ignal

Processing D isp lay

Signal Processing in Instrumentation

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1. The purpose of signal processing is toprocess the signals from the transducersinorder to prepare them to operate displayingor recording devices suitably. The part ofinstrumentation system that is provided toamplity, modify or transform the electricoutput of the transducer is called signalprocessing system. It also includes anydevice which is used to combine or relatethe outputs of two or more transducers(multiplexing). The input and output of signalprocessing system are electrical signals butthe output signals are generally modified withrespect to the input signals.

2. The transducer output is generally notsuitable to be coupled to the display unitdirectly. The signal processing has to be doneon the signals generated by the transducerswhich consists of amplification, filteringaveraging, matching of impedance of thetransducer to the display unit. Signal filteringis a process to reduce the undesirable signalssuch as noise. Averaging of repetetive signalsis carried out in order to reduce noise if itcannot be done by the method of filtering.Transformation of signal is done to convertthe input signals from the time domain tofrequency domain which can be furtherprocessed or conditioned in a easier way.

METHOD OF SIGNAL PROCESSINGSIGNAL PROCESSING INBIOINSTRUMENTATION 1. Signal amplification : The signals

generated by the transducers are very weak.Amplifiers are used to increase the level orto boost the amplitude of the signals tomatch the requirements of the recording ordisplay units. Amplification also increasesthe resolution and sensitiveness of theinstrument. The bioelectric signals oftencontain components of extremely lowfrequencies. In order to achieve a faithfulreproduction of the signals, the amplificationmust have excellent frequency response inthe subaudio frequency range.

2. Filtering : It is a device or circuit whichamplifies some of the frequencies presentin its input and attenuates or blocks otherfrequencies which are not required. Filterscan be classified as (1) high pass filters (2)low pass filters (3) band pass filter and (4)band stop filters. High pass filters onlyamplify the frequencies which are abovecertain value. Low pass filters only amplifythe frequencies below a certain value. Bandpass filter amplify frequencies which arewithin a certain band. Band stop filtersamplify all frequencies except those incertain band.

Noise signa l

0 40 50 80 120Frequency

60 80 120H igh pass filter

(frequency > 60)

s igna l

Inpu t O utpu t

High Pass Filter

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5 35 40 60

Low pass filter (frequency < 40)

No isesigna l

Frequency5 35

Inpu t O utpu t

Filters can also be classified as passive oractive filters. Passive filters use passivecomponents such as resistor, capacitor andinductors. Active filter use amplification inaddition to passive components. The filterscan also be classified as analog and digitalflitters. An analog filter processes analoginputs and its output is analog. A digital filterprocesses digital data and generates digitaldata output. Analog filters are based onmathematics operators and digital filtersrequire no more than addition, multiplicationand delay operations. Certain instruments useanalog to digital conversion to convert asignal to digital form which can be furtherfiltered by employing high speed digitalcomputing. All measuring and recordinginstruments pick up some degree of noisesignal of 50 Hz from power lines and nearbyoperating machineries. The noise signals of50 Hz can be attenuated by the applicationof low pass filter which permits frequenciesbelow 50 Hz to pass through. Such filtersare called ‘Notch’ filters

3. Signal averaging : Filtering is effectivemethod to remove noise signals incasetransducer signals and noise signals do notoverlap. Noise signals having frequencieshigher than 100 Hz in ECG signals can beeasily blocked by employing a low pass filtercercuit with a cut off frequency value of

100 Hz. However if noise signals havefrequency range of 50 Hz to 100 Hz, thenuse of a low pass filter cercuit with a cutoff frequency values of 50 Hz will attenuatesome components of ECG signals which cannot be permitted. Signal averaging is theappropriate technique for such case. It is adigital technique of separating a repetitivesignals from noise without introducing signaldistortion. The requirements from the signalsand noise before employing signal averagingare – (1) The signal waveform has to berepetitive and signal must occur more thanonce at regular intervals (2) The noise hasto be random and non periodic (3) Thetemporal position of signal wave form canbe accurately ascertained. Each new signalwaveform or curve is made to align (curvefitting) with previous signal waveform sothat repetitive signal are added up. The signalstrength is increased a number of times thesignal waveforms are added. However noiseis random in occurrence and it has mean ofzero. ECG signals are corrupted by randomnoise signals which are broadband. Noisesignals can not be removed by filter cercuitswithout the loss of some part of ECGsignals. The technique of signal averagingis employed by first identifying the QRScomplex of ECG signals.

Low Pass Filter

HIGH PASS FILTER

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Response 1

Response 2

Response 3

P

R

Q S

T

Averag ing o r to ta l response

Signal averaging of this noisy signal requiresa way to time align each of the QRScomplexes of the signal responses as shownin the figure. The time at which eachstimulus occurs is considered as thereference time and the values for eachresponse are summed upto get the totalresponse at the reference time. By repetitivesumming, it is possible to enhance the signalto noise ratio. Signal averaging is commonlyused with ECG, EEG and EMG and it isperformed on a computer. The techniqueinvolves digitizing signal, storing in memoryand locating the stimulus.

4. Digital transformation: Until recently,signal processing has been commonlycarried out using analog equipment. Forexample, a biopotential amplifier is to receivea weak electrical signal of physiologicalsystem and increase its amplitude so that itcan be conveniently further processedrecorded or displayed. Generally suchamplifications are is the form of voltage

amplifications as they are suitable forincreasing the voltage level of signal. Thecomputers offer tremendous advantages inflexibility and speed. Hence signal processingemploying digital computers are beingincreasingly used now adays. In analogsignal amplitude and time are varyingcontinuously over its respective intervals. Ina digital signal, amplitude and time take ondiscrete values. An analog signal can beconverted into digital form by followingprocesses – (1) sampling (2) quantising and(3) encoding. In sampling operation, onlysample value of analog signal at uniformlyspaced discrete instant of time are retained.In quantizing operation, each sample valueis approximated to the nearest level in a finiteset of discrete level. In the encodingoperation, the selected level is representedby a codeword that consists of prescribednumber of code elements.

Analog S ignal Sam pling Q uantiz ing Encod ing D ig ital

s igna l

Signal Averaging

Analog to Digital

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Fill in the gaps1. The transducer output is ------- to be coupled

to the display unit. (a) suitable (b) notsuitable

2. High pass filter only amplify the frequencies------- the certain values. (a) below(b) above

3. Low pass filters only amplify the frequencies------- the certain value. (a) below (b) above

4. Low pass filters attenuating noise signals of50 Hz are called ------- filter. (a) notch(b) blotch

5. The signals can not be separated from noisebye filtering in case noise and signals have------- frequencies. (a) overlapping(b) different

OBJECTIVE TYPE QUESTIONS

6. The method of ------- signals is used forECG and EEG. (a) filtering (b) averaging

7. In averaging, the waveform of the responseis made to ------- with the waveform of theprevious response. (a) oppose (b) align

8. Sampling, quantising and encoding are usedto convert signal z to ------- signal. (a)digital, analog (b) analog, digital

9. Signals are transformed from -------domainto -------domain. (a) time, frequency(b) frequency, times

10. ------- filters have components as resistors,capacitors and inductors in the theircercuits. (a) active (b) passive.

ANSWERS

1. (b) 2. (b) 3. (a) 4. (a) 5. (a) 6. (b) 7. (b)8. (b) 9. (a) 10. (b)

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Learn from the mistakes of others. You can't make them all yourself.

INTRODUCTION

1. The photographic film had been the principalmeans for acquisition and storage of imagefor many years. In recent times, computershave become the frontmost devices for aprocessing, transferring, storing anddisplaying images. The computers and digitalimaging processing techniques haverevolutionised the way the medical imagesare produced and manipulated. Medical datacan be acquired by imaging systems likecameras, which can be fed into computers.The computers can perform mathematicaloperations to produce images having goodquality and can highlight aspects of imageswhich are required for diagnosis. The imagescan also be stored, retrieved or transmittedto remote sites through telephone lines orany other communication means.Radiography, computed radiography,ultrasound, magnetic resonance and otherimaging systems can be considered ascameras or vision devices which areconsidered means that can transfer an imagefrom one surface to another. The cameracan be also visualised as a pin hole device

through which all elements of the originalimage must pass through to the final image.An image can be processed without anyregard to the type of camera used fortransferring the image.

ELEMENTS OF DIGITAL IMAGEPROCESSING SYSTEM

1. The digital image processing system consistsof (1) acquisition (2) storage (3) processing(4) communication and (5) display. Twoelements are basically required to acquiredigital images. The first element is a sensorwhich produces output signal proportionalto the input level of energy to which it issubjected. The input energy can be x-rays,ultrasound, radiation or changing magneticfield etc. The second element is calleddigitizer, which converts the electrical outputof the sensor into digital form. The storagemethods of digital images can be classifiedas (1) short term storage devices likecomputer memory (2) on line storage withfast recall such as magnetic disks and (3)archival storage for infrequent access likemagnetic tapes and optical disks. Processing

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of digital images involves processing ofprocedures known as algorithms whichperforms various mathematical operationson the medical data obtained form inputdigital images. Image processing ischaracterised by specific solution. Thetechnique varies from application toapplication depending upon the method ofacquisition of the image. However thepowerful hardware and basic software tostart different image processing systems ofthe computer remain same. These aresupplemented by the specialised software toprocess the image depending upon themethod of acquisition. Communication indigital imaging system involves localcommunication between image processingsystem and transmission of medical datafrom one point to another in remote area.The display devices of the image processingsystems are monitors and TV systems.

O bject

Im age Acqu isition

S to rage (optical disk, v idiotapes,M agne tic

tapes & disks)

C om m unica tion

D isp lay (T V c am era &

film p rin t)

P rocess ing (com pu ter)

Elements of An Image Processing System

RASTER AND FRAME BUFFER OFA COMPUTER

1. The screen of a computer consists of a largenumber of minute subdivisions which are

called picture elements or pixels. A framebuffer of a computer consists of a largecontinuous pieces of computer memory.There can be one memory bit for each pixelin the raster. The memory bit can be eitherin zero (0) or one (1) state. If a particularpixel is activated, the corresponding bit inthe frame buffer is changed from zero (0)to one (1). A 320 × 320 raster has 64,000pixels. Since each pixel has one bit in a singlebit plane, therefore 64,000 memory bits arerequired in a single plane. A single bit planeyields a black and white display. Colour orgrey level can be achieved by usingadditional bit planes. Hence the intensity ofeach pixel on the raster is decided by thecombination of the pixel value in each of bitplane. The pixel value in single bit can betwo i.e., zero or one. If there are four bitplanes, then there can be 24 = 16combinations and the resulting binarynumber is interpreted as an intensity tonebetween zero and 15 (i.e., 24 –1= 15). Theraster is an analog device and it requires an

electrical voltage. The digital data of framebuffer is converted into an analog voltagethrough a digital to analog convertor (DAC).In a 4 bit plane, the value between zero

(dark) to 15 (full bright) on each pixel canbe got by the digital to analog convertor. Acolour frame buffer can be implanted withthree bit planes one for each primary colour

like red, green and blue. Other colours areobtained with their combinations.

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1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1

1 1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 1 1 1 1

O ne b it plane bu ffe r (zero o r one)

Screen (b lack and wh ite )

00

0 0

0 0

0 0

0 000 0

0 00 00000 0 0 0 0

1 1 1 1 1 1 1 0 0 0 0 0 0

D ig ital toana log convertor

4 bit p lane fram e bu ffe r

Screen / R aste r (tona l va lue zero

b lack to 15 full b righ t)

Each Picel of Screen With Tonal Value From Frame Buffer(zero for black and one for white)

4 Bit Plane Buffer

1. The image on the human eye or on a TVscanner (having light sensitive surface) istwo dimensional. The real world whichsurrounds us is made of three dimensions.The two dimensional (2D) intensity imageis generated by the projection of threedimensional (3D) scene. However the 2Dimage contains information about thebrightness of each pixel. The 2D image is

scanned by some means to provide acontinuous voltage output that is proportionalto the light intensity or brightness of theimage on the surface. The output voltagef(x,y) is sampled at the discrete number of xand y points of the image (pixel / pictureelements) which are converted into numbers.The numbers correspond to the grey levelsof intensity corresponding from black (zerobrightness) to white (highest brightness)

VISION PROCESSING

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intensity. In case of colour images, theintensity value is combination of threeseparate arrays of numbers i.e., each arraygives the intensity value of each of the basiccolour viz red, blue and green colour. Thisis called digitization process and the imageis transfered into a 2D image from the lightsource to the light sensitive surface and laterinto an array of numbers which aredependent on the local image intensities atthe corresponding x and y positions on thelight sensitive surface. It can be seen thatfirst step of vision precessing istransformation of light energy to array ofnumbers which is the language ofcomputers. A vidicon tube or charge coupleddevice (CCD) are light sensitive transducerswhich are used for transformation of lightenergy. The tube is a type of sensor with itssurface coated with a photosensitivematerial. The resistance of the sensor isinversely proportional to the light intensityfalling on it. An electric gun emittingelectrons is employed to produce a flyingspot scanner. The scanning of the sensor isdone repidly from left to right and top tobottom. The scanning produces a timevarying voltage which is proportional to theimage intensity of the scanned spot. Thecontinuously varying output voltage is fedto an analog to digital convertor (ADC). Thevoltage amplitude of the ADC is periodicallysampled and converted to the array ofnumbers. A typical ADC will produce 36digital frames consisting of 256 × 256 (or512 × 512) pixels per seconds.

Transferring of Image to Numbers

4 0 4 2 6 0 5 0 9 8 3 6

Scene Charge coup led device

Tim e varying voltage

Analog to d igita l convertor

Array of num bes

1. When 3D objects are projected on 2D sensorsurface of the camera, a lot of information,disappears which means such trans-formation is not one to one. Reconstructionof objects of a 3D scene from only one imageis difficult as it involves recapturinginformation of 3D original scene from thecaptured depictions of 2D image. The aimis to recover a full 3D scene from this 2Dimage as it is done in computer graphics i.e.a 3D representation which is dependent onthe coordinate system of the object. Theintensity of the image can be synthesisedusing standard computer graphic techniquesfrom such a representation. The imagereconstruction process involves two taskswhich are (1) to recover the information lostin 2D projection of the scene and (2) tounderstand image brightness. Theinformation available in the 2D image is thebrightness of the different pixels, which isproportional to the reflection, illuminationand orientation of the object with respect toviewer and light source. In computers, themethod of image processing uses digitalimage functions. These are represented bymatrices since coordinates are integernumbers. The image functions have rangeR = f (x,y), {1< x < xmand 1< y < y

n} where

xm and y

n are image coordinates. The range

of image function value is limited as thelowest value is black and the highest valueis white. The image function has also greylevel values in between black and white

IMAGE RECONSTRUCTION

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values. The quality of a digital imageimproves in direct proportion to the spatial,spectral, radiometric and time resolution.The spatial resolution depends upon theproximity of neighbouring image samplingpoints in the image plane. The spectralresolution is dependent upon the band widthof light friquencies captured by the sensor.On other hand, the radiometric resolutiondepends on the number of grey levelsbetween black and white values. The timeresolution is dependent on the intervalbetween two successive sampling. Theimage is processed by a computer bycarrying out image digitization, sampling andquantization. In image digitization, the imagefunction f (x, y) is sampled into a matrixwith ‘M’ rows and ‘N’ columns. A continuesimage function f (x,y) can be sampled usinga discrete sampling points in the image plane.The sampled image function F

s (x, y) is the

product of the f (x, y) and S (x, y) (sampledfunction). The Fourier transform of thesampled image is the sum of periodicallyrepeated fourier transform F (u, v) of theimage. The transition between the value ofimage function (brightness) and itsequivalent is known as quantization. If ‘K’is the number of levels of quentization and‘b’ is the number of bits used to express thethe brightness of pixels, then k = 2b.

1. Several algorithms of digital imageprocessing are used with technique brownas single image pixel point operations. Itperforms manipulation on sequentialindividual pixels rather than large arrays. Thegeneral relation utilizing discrete single pixelpoint process for an entire image array is :

O (x,y) = M [ f (x, y)]

Where f (x, y) = input image pixel at x and y

O (x, y) = output image pixel at x and y

M = linear mapping function which converts

input brightness value to output brightnessvalue. It is time consuming and wasteful ofcomputer resources incase the above typeof operation is to be performed on a largeimage at every pixel. A look up table (LUT)is an alternative technique to map largeimages. A LUT stores an intensitytransformation function which is designedin such a way that its output grey level valuesare a selected transformation of thecorresponding input values. Let usunderstand how it is done. We take a 8 bitcomputer which can have input values of256 grey levels (28 = 256). Suppose it has adesigned LUT which gives an output valueof zero for input value between zero and127 and an output value of one for inputvalues between 128 to 255. Then the entirepoint process will result in binary outputimages that have two sets of pixel i.e., zeroand one. Similarly LUT can be designed togive other selected outputs for thecorresponding input values.

0 1 2 126 127 128 254 255 Inpu t

O utput0 1

1. Histogram provides a representation of image

contrast and brightness characteristics. The

brightness histogram hf(z) of an image is a

function which gives the frequency of the

brightness value ‘z’ in the image. The

histogram of an image having ‘N’ grey levels

is given by a one dimensional array having

‘N’ elements. The histogram helps in finding

optimal illumination condition for capturing

an image grey scale, its transformation as

well as proper image segmentation of the

LOOK UP TABLES HISTOGRAM

Look up Table

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object from the background. It can be

appreciated that the change of position of

the object does not affect histogram.

Manipulation of histogram can correct poor

contrast and brightness which can

dramatically improve the quality of the

image.

Fre

quen

cy

B it/P ixe l va lue

1. The goal of computer representation is toachieve image understanding with thehighest processing level. The image datarepresentation consists of lower and upperprocessing levels which are applied bytechnical available procedures by thecomputer, similar to our natural vision. Therepresentation can be :

(a) First level of representation. Therepresentation is iconic and it consistsof images containing original data aboutpixel brightness in the form of integermatrices. Certain prepatory operationsare performed such as highlighting someaspects of the image and manipulation,like filteration or edge sharpening.

(b) Second level of representation. In this,the segmentation of images isperformed i.e., the parts of the imagesare joined into groups that seems tobelong to the same object.

(c) Third level of representation. It isgeometric representation having priorknowledge about 2D and 3D shape ofthe object. The quantification of a shapeis made on the basis of illumination andmotion of the object.

(d) Fourth level of representation. In this,the representation of data is made on

the basis of the relationship models. The

information gained from the images maybe used by semantic nets and frames

i.e., prior knowledge of the relationship

among adjacent regions is usually usedin processing.

Histogram

LEVEL OF IMAGE DATAREPRESENTATION

Image Processing Stages

SceneLocal p rocessing O bject processing In te rpre ta tion

Im age sensing In te rm ed ia te leve lLow leve l H igh level Sem antic descrip tion

LOOK UP TABLE

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GREY LEVEL THRESHOLDING

1. It is a simplest segmentations process. Manyobjects or regions are characterised by fixedreflectivity and light absorption by theirsurfaces. A brightness constant or thresholdcan be fixed so as to segment or separatethe object and its background.

1. Data and an algorithm are two basic relatedparts of any progrmme. An algorithm is afinite set of instructions if followed canaccomplish a particular task. All algorithmsmust have following criteria :

(a) Input — zero or more.

(b) Output — atleast one.

(c) Definiteness — each instruction mustbe clear and unambiguous.

(d) Finiteness — after a finite number ofsteps, each instruction must end.

(e) Effectiveness — each operation mustbe definite and feasible. All instructionsmust be feasible to be carried out. Whilecreating or using algorithm for digitalprocessing, the principle of humanimage perception must be followed. Asan image is to be understood by ahuman, the information should beexpressed using variables which areeasier to perceive like contrast, border,contour and shape texture. Thesensitivity of human senses varieslogarithmically to the brightness of inputsignal. Hence after an initiallogarithmically transformation, theresponse to stimuli, may be treated aslinear. A few examples of algorithmsare :

(a) Algorithm for basic thresholding:Search all pixel of f (i, j) of image f. Animage element g (i, j) of the segmentedimage is an object pixel if f (i, j) > Tand it is a background pixel otherwise.

ALGORITHMS

(b) Algorithm for computing the brightnesshistogram (i) Assign zero value to allelements of the array h

f

(ii) For all pixel f (x, y) of the image f,increase h

f (x, y) by 1.

1. We have seen that digital image is sampledand mapped as a grid of dots and pictureelements (pixels). Each pixel is given a tonalvalue (white, black, shade of grey orcolour ) depending upon brightness whichis represented in binary code i.e., zero andone. The binary digits / bits for each pixelare stored in a sequence by a computer. Inorder to handle large data, data iscompressed and reduced by a mathematicalrepresentation. The bits are then interpretedand read by computer to produce an analogversion for display or printing. The file sizeof a digital image is very large and it requiresvery large memory of the computer, therebytaxing the computing and networkingcapatibilites. Compression is used to reducethe size of image file for storage, processingand transmission. All compressingtechniques are based on algorithms whichare nothing but mathematical shorthand,abbreviating the long string of binary codeof an uncompressed image, thereby creatinga compressed image file requiring lessermemory space. Compression can be doneby either standard or proprietary techniques.Compression can also be classified as eitherloss less compression or lossy compression.The loss less compression abbreviates thebinary code without discarding anyinformation. Hence on decompression,image is bit for bit identical to the originaluncompressed file. The lossy compressionuses a method of averaging or discardingthe least important on the basis ofunderstanding of visual perception.

COMPRESSION

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Fill in the gaps

1. Two elements for acquiring digital imageare sensor and -------. (a) digitizer(b) processor

2. Short term storage device for imageprocessing is computer’s -------. (a) CPU(b) memory

3. The screen of a computer consists of a largenumber of minute subdivisions which arecalled -------. (a) pixel (b) bits

4. A frame buffer consists of a large continuouspieces of computer -------. (a) pixel(b) memory

5. The memory bit can be either in zero or------- state. (a) two (b) one

6. The pixel value in single bit plane can be-------. (a) one (b) two

7. A four bit planes can have -------combinations as output at each pixel.(a) 8 (b) 16

OBJECTIVE TYPE QUESTIONS

8. Incase of colour images, ------- bit planesare required. (a) 4 (b) 3

9. The first step of vision processing istransformation of light energy to array of-------.(a) figures (b) numbers

10. Data and ------- are two basic related partsof any program. (a) a computer (b) analgorithm

11. ------- techniques are based on algorithmsto reduce the image data file.(a) compression (b) shortening

12. Compression can be classified as loss lessor ------- compression. (a) gainless (b) lossy

13. The image is processed by a computer bycarrying out image digitization, sampling and-------. (a) quantization (b) manipulation

14. The scanning produces a time varyingvoltage which is proportation to the image

------- of the scanned spot (a) position(b) intensity

1. (a) 2. (b) 3. (a) 4. (b) 5. (b) 6. (b) 7. (b)8. (a) 9. (b) 10. (b) 11. (a) 12. (b) 13. (a) 14. (b)

ANSWERS

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If the wise does not approve your book, it is bad. If a fool applauds it, it isworse.

INTRODUCTION

1. Conventional x-ray examination techniquesstill dominate the field of diagnostic imaging,although most of the images at present beingproduced are digital. X-rays emanate froma small point source and pass through aportion of the body and onto a detector thatrecords the x-rays that reach the detectoras an image which is called radiograph. X-rays radiation is electromagnetic radiationwhich can ionize the matter through whichit passes as it has high energy content. Theionization can cause damage to DNA andcells in human tissues. However it canpenetrate the body to allow noninvasivevisualization of the internal anatomy of thehuman body. X-rays also exhibit particle likebehavior which are discrete packets of pureenergy. These discrete packets are calledphotons. Inorder to reduce the ill effect ofionization due to x-rays while takingradiography, new x-rays techniques are beingdeveloped to minimise the radiation dose.The chief x-rays methods used in theexamination are radiography, fluoroscopy,tomography and bronchography.

1. When an electron in an atom transits fromouter orbital (higher energy) to inner orbital(lower energy) radiation is emitted. Such atransition of electron can occur, if the atemis in an excited or unstable state and it has avacancy in the inner electron shell to whichthe electron can move from the outerelectron shell. The emitted radiation can bein the visible, ultraviolet, or x-rays portionof the electromagnetic spectrum. Theemitted radiation is called characteristicradiation as its energy content is uniquelycharacteristic of the atomic species thatproduced it.

2. There is an another method available toproduce x-rays. If an electron beam isaccelerated so as to hit a metal target, ashower of radiation is produced by the inter-action. If the electron beam is acceleratedwith enough energy by applying suitablevoltage, the radiation produced is x-rayportion of the electromagnetic spectrum.

3. A vacuum tube device as shown in the figureis used to produce x-rays. The tube containsa tungsten filament (the cathode) and a metal

X–RAYS AND X–RAY TUBE

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target (the anode) which is also made oftungsten. The filament cathode is heated withelectric current. A high voltage is appliedbetween the anode and the cathode. The highvoltage facilitates the electrons of the cathodeto be drawn off and accelerated towards theanode. The accelerated electrons strike theanode. This results into the production ofcharacteristic x-rays (characteristic oftungsten metal). The x-ray tube is completelyenveloped by lead casing on all sides exceptfor a small exit port. The lead casing is usedas the lead can absorb most of the emittedx-rays. Hence x-rays can come out of theport only. These x-rays are used forradiography.

Anode Cathode+

Evacuated tube

Lead lined housingX-rays

+ –

1. X-rays are absorbed by the body in relationto specific density and atomic number ofvarious tissues. In irradiating a volume ofinterest, these absorption differences arerecorded on an image receptor.

1. A high voltage generator as shown in thefigure, supplies the essential power to x-raytube. A collimator is used at the exit port ofthe x-ray tube to limit the extent of the x-ray field. The x-ray exposure is kept forprecise and finite duration by an electronictime switch. The exposure is alsoautormatically terminated after a certainamount of radiation has been received bythe image receptor with the help ofphototiming cercuit. The operator selects alloperating parameters like exposure and doseof radiation from the operator’s console.

X-ray tube

Co llim ato r

+ –

X-ray genera to r

O pera to r conso le

PhotocellG rid

Im age reccp tor

OPERATING PRINCIPLE

RADIOGRAPHY SYSTEM

X-Ray Imaging System

X-Ray Tube

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2. An image receptor is a device which candetect and record an x-ray image. It is placedbelow the patient so that x-ray after passingthrough patient falls on the image receptor.The patient’s anatomy modulates the intensityof the x-ray field as it passes through hisbody. The differential x-ray absorption andtransmission by tissues of the body resultsin an exit radiation beam that varies inintensity in two dimensions. The exitradiation beam reaches a detector whichdetects and records the two-dimensionalintensity distribution. The image receptorsused in diagnostic radiology can be :

(a) Photographic film, coupled with anintensifying phophor screen.

(b) Storage phosphor screen.

(c) Direct digital readout device.

1. X-rays normally can not be detected directlyby the human sense. Hence indirect methodsof visualisation have to be used to see theimage of the intensity distribution throughthe body of a patient. Although x-rays havea much shorter wave length than visible lightbut x-rays can react with photographicemulsions in same way as it happens incaseof visible light. The film exposed of x-rayand carrying an image of the x-rays intensityis processed in the developing solution. Thesensitivity of the photographic emulsion canbe increased by the use of intensifyingscreens which are similar to the fluoroscopicscreens. The screen is kept into closecontact with the film surface so that the filmis exposed to x-rays and also to the lightemitting from the fluorescent screen. X-rayfilm is packed in light-tight cassettes withor without intensifying screens. The one sideof the cassette is made of thin plastic whichcan be easily penetrated by the x-rays.

2. An intensifying screen (fluorescent screen)consists of polyster with plastic coating and

a phosphor layer that absorbs x-rays and inresponse emits visible light. A radiographiccassette consists of a pair of intensifyingscreens with a sheet of double emulsion filmsandwiched between the screens. The filmrecords the visible light image emitted bythe intensifying screens in response toirradiation by x-ray. Two phosphor screensare more efficient in detecting x-ray than asingle screen. However sharpnessdecreases.

1. Storage phosphor or photostimutablephosphor system is used to obtain radiographin digital form which are suitable for computerbased storage and processing. This methodis also commonly known as computedradiography. The method also uses a cassettecontaining a screen coated with phosphorsimilar to that used in conventional screenfilm. However, the phosphor used in theintensitying screens emits visible lightimmediately upon absorption of x-rays whichis called fluorescence. The phophor in PSPsystems responds to irradiation with x-raysby storing electrical charges in a patternmatching to the pattern of absorbed x-raysintensities. The pattern is read later by ascanning laser device. Laser causes localizedheating of the phosphor which leads tostimulation of the metastable trapped charge.The stimulation of the metastable trappedcharge leads to conversion of the trappedcharge into visible light, which is calleddelayed luminescence. The visible light is thenconverted to electric current by a photomultiplier tube which is digitized and storedas a digital image in a computer.This is calledcomputed radiography.

PHOTOGRAPHY OR X–RAY FILM

STORAGE PHOSPHOR SYSTEM(PSP)OR COMPUTED RADIOGRAPHY

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Unused PS P

Recording the x-rays im age

Laser converts x-rays im age to v is ib le ligh t

Erasing by ligh t fo r reuse of PSP

PSP ready for reuse

De layedLum inescence

x-rays field

Laser scann ing

L igh t

1. The direct electronic capture of theradiographic image is the future trend ofdigital imaging. These will be no need forstorage phosphor cassette and subsequentlaser readout or digitization of photographicfilm incase the use of direct digital detector.Concerted efforts are being put up todevelop the direct digital detectors. Thesedetectors will convert the radiographic image(the distribution of intensities in twodimensions) into an electrical signal that canbe digitized. It is being tried to developdetectors having better spatial resolution andless noise than PSP systems. Such detectorscan also be mounted permanently on the x-rays system so as to eliminate cassettehandling by any operator.

Storage Phosphor System or PSP

THE DIRECT DIGITAL DETECTOR

1. X-rays diverge from a point source, travelin straight lines and these can affect aphotographic emulsion. A point source oflight produces shadow of a object in its pathas shown in the figure. Similarly any objectin the path of x-rays casts a shadow whichcan be recorded on the photographic materialas an image. The image formed by x-raysdiffers from the image formed by the lightrays. X-rays can pass through substanceswhich are opaque to light rays. Thereforex-rays can project shadows of structureshidden below the surface of the object andrecord their images also on to aphotographic material.

IMAGE FORMATION

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O bject w ith slot h idden

O bject

Im age (dark) Dark im age

L ight dark

due to h idden s lo t

Dark im age

1. It can be seen that x-rays images are formedby projection i.e., images of objects lying inthe path of x-rays are projected on to aphotographic material. This differs from theway images are formed on the retina of theeye or on the photographic film in a camerawhen light rays travel from the object to therecording medium to produce an imagewhich is called a view of the object. Theradiographic image produced by x-rays is aprojection of the object.

Im a ge

O bjec t

O bjec t

L en s

Im a ge

Image Formation

PROJECTION AND VIEW MAGNIFICATION

View Projection

1. Since the light passes through a lens, theimage produced on the retina or on thephotographic film is smaller than the object.However in the case of a projected image, amagnified image is formed because the x-rays continue to diverge as they pass fromthe object to the recording film. The greateris the distance between the object and thefilm, the greater is the magnification of theimage.

O bject

Im age

x-rays source

FF D

FO D

Magnification

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Magnification = Image Size

Object Size

= Focus to film distance (FFD)

Focus to object distance (FOD)

1. The aim of the radiography is to produce animage as sharp as possible. The factorsleading to image unsharpness are :

(a) Geometry

(b) Movement

(c) Absorption

(d) Photographic factor

2. Geometric unsharpness. Since x-rays arenot originated from a point source but fromsmall area (port of the x-ray tube), this givesrise to geometrical unsharpness to the imageas shown in the figure.

Ob jec t

Im age

Ob jec t

Point so urce x-rays Area source x-rays

G eom etric u nsharpness

The amount of geometrical unsharpnessincreases with increase in source area (focalspot) and increase in object to film distance.Geometrical unsharpness

=Object to film Distance

Object to focus distance × focal spot size

1. This type of unsharpness results due topatient, equipment or film movement duringexposure.

Patien t m ovement

M ovement unsharpness

Movem ent Unsharpness

1. If we consider a spherical object of uniformdensity, absorption will be greatest at thecentre and least at the periphery. The gradualfall off in absorption towards the edges leadsto the image having an ill - defined boundarywhich is called absorption unsharpness.

Im age absorp tion

unsharpness

O bject

Im age absorp tion

unsharpness

2. Photographic unsharpness : Theintensifying screen contains crystals whichfluoresce when irradiated by x-rays. Themain reason of photographic unsharpnessis the spread of light between the crystalsand the photographic emulsion. The spreadof light will be greater with larger crystalsand increased distance between the crystals.

Geometric Unsharpness

Image Absorption Unsharpness

MOVEMENT UNSHARPNESS

ABSORPTION UNSHARPNESS

IMAGE SHARPNESS

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X-rays

FilmG ood photograph ic sharpness

ScreenScreen

Poor photographic sharpness

X-rays

Film

Photographic Unsharpness

QUALITY OF DIAGNOSTICRADIOGRAPHS

1. High quality of diagnostic radiographs canbe achieved by :

(a) Scatter control

(b) Proper radiographic technique

(c) Technical image quality controlprogramme

1. In addition to the x-rays that pass straight

through the body and contribute to theradiographic image, other scattered x-rays

deviating from straight path are absorbed by

the image receptor which blur the image,reduce contrast and increase image noise.

Scattered x-rays do not contain useful

information. Grids are used effectively tocontrol scatter. A grid is a device which is

placed directly in front of the image receptor

and it consists of a series of closely spacedlead strips. The strips are oriented such a

way that x-rays that are scattered from the

tissues are absorbed. Only unscattered x-rays can pass through the grid. Hence grid

filter blocks out most of the scattered

radiation and improves the image quality.

2. Proper Radiographic Technique. Selection

of the appropriate parameters of x-raysmachine produces an optimally exposed

radiograph with acceptable image contrast.

The operators should be well trained to knowproper radiographic techniques.

3. Technical quality control program. The aimis to optimise image quality while keepingthe radiation exposure to patients and staffto minimum. Technical quality controlprogram includes the monitoring of theperformance of radiologists and technicians,patient service times, and other performancemeasures.

1. It is a radiological technique by which thedeeper structure of the body can be studiedunder direct vision on a fluorescent screen.The screen consists of a cardboard which iscoated with a thin layer of fluorescent material,like zinc cadmium sulphide. The screen iscovered with a thin sheet of lead glass throughwhich the light rays can pass. However x-rays cannot pass through the sheet so thatfluroscopic image is protected. When thescreen is actuated by x-rays, light is emittedreflecting the pattern of the organs of the bodythrough which the x-rays have passed. Thefluoroscopic image can be seen moreeffectively in darkness when the eyes are fullyadopted in darkness. The sharpness andcontrast of a fluoroscopic image is generally

SCATTER CONTROL

FLUOROSCOPY

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inferior to those of a good radiogram. The chiefadvantage is that the fluoroscopy is a real timeradiography. Fluoroscopic system allowscontinuous viewing of a time varying x-rayimage and permits live visual evaluation ofdynamic events.

2. Modern fluoroscopy systems use a x-rayimage intensifier as shown in the figure. Theintensifier converts the x-ray energy tovisible light. The intensifier is coupledoptically to a television camera. Thefluoroscopic image is viewed on a cathoderay tube (CRT) or a video monitor.

G rid

Patien t

V ideo monito r

x-ray im age

in tensifie r

TV cam era

Co llim ato r

x-ray tube

O pera tor ’s conso le

x-ray genera to r

1. The faint image of a fluoroscopic screen canbe made brighter with the use of anelectronic image intensifier. The intensifiertube contains a fluorescent screen which iscoated with a special material to act asphotocathode. The electronic imagegenerated on the photo cathode is focussedonto a phosphor screen at the end of thetube by the help of an electrostatic lenssystem. Due to the acceleration of theelectrons by the electrostatic lens system

(25 kv) and output image is smaller than theprimary fluorescent image, but there is ahigh brightness gain in the output imagewhich makes it possible to observe the imagein the normal illuminated room.

2 5kv

Ph ospho r o utp ut scre en

Ele

ctro

stat

ic

lens

sys

tem

M irro r

L en s

Ad ju stab le m irro r

F luo rescen t sc reen w ith ph oto ca tho de

x-ray source

M irro r(+ )

(–)

1. The image quality depends upon following :

(a) Contrast. It is the difference inbrightness of two neighbouring regions.In grey - scale image where signaldifferences are represented by varyingshades of grey or brightness, highcontrast means that two objects ofdifferent composition in the imageappear very light or very dark. In alower contrast image, there is lessdifference in relative brightness.

(b) Noise. It is any signal component in animage that does not convey any usefulinformation. The aim is to have a highersignal to noise ratio to reduce therandom noise.

(c) Spatial Resolution. It is ability of animage to faithfully reproduce smalldetails. It is also called sharpness.Unsharpness (blur) indicates lack ofspatial resolution.

Layout of an Intensified Fluoroscopy System

IMAGE INTENSIFIER

Image Intensifier

IMAGE QUALITY

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1. The superimposition of 3 dimensionalinformation on a single plane of photographicfilm which makes diagnosis confusing anddifficult.

2. The photographic film usually used formaking radiograph has limited dynamicrange which permits the organs that haveonly large variation in x-ray absorptionrelative to their surrounding parts will havesufficient contrast differences on the film.This helps in distinguishing the organs easilyon the radiographs. The bony structures canbe clearly identified while it is difficult todiscern the shape and composition of softtissue organs accurately.

1. Mass miniature radiography is a fluroscopic

image which is photographed by a camera.This method is used for quick survey of

persons for diseases like tuberculosis.

1. This is a radiological technique by whichthe bronchial tree can be visualised with theaid of a radioopaque dyc. The dye used isan loidized oil, called lipoid, (40% dyc iodinein poppy seed oil). It is rarely used todaydue to the advent of CT scanning.

1. Firstly a pre-injection image (mask) is

acquired. The injection of iodinated contrast

agent is then performed. After this, the imagesof specified vessels are acquired. These

images are subtracted from pre-injection

images (mask) of the vessels. This techniquegreatly helps in contrast enhancement as the

subtraction removes the appearance of

stationary anatomy from the resulting imageswhile synthesizing images containing only

contrast in the blood vessels. Each image in

the sequence reveals a different stage in thefilling of vessels with contrast.

OBJECTIVE TYPE QUESTIONS

LIMITATION OF RADIOGRAPHY

MASS MINIATURE RADIOGRAPHY(MMR)

BRONCHOGRAPHY

DIGITAL SUBSTRACTIONANGIOGRAPHY

Fill in the gaps

1. X-rays that pass through body and reach adetector as an image is called ---------.(a) radiograph (b) electrograph

2. X-rays can --------- the matter throughwhich they pass. (a) not disturb (b) ionize

3. The ionization can cause damage to--------- and cells in human tissues. (a) BNA(b) DNA

4. X-ray techniques are being developed to--------- the radiation dose. (a) increase(b) minimise

5. An image --------- is a device which candetect and record an x-ray image.(a) receptor (b) captor

6. X-rays have much --------- wavelength thanvisible light . (a) longer (b) shorter

7. A fluorescent screen consists of polysterplastic coated with a ---------layer.(a) phosphor (b) sulphur

8. Storage phosphor is used to obtainradiograph in --------- form. (a) visual(b) digital

9. The radiograph produced by x-rays is a--------- of the object. (a) projection(b) visulisation

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1. (a) 2. (b) 3. (b) 4. (b) 5. (a) 6. (b) 7. (a)8. (b) 9. (a) 10. (a) 11. (b) 12. (a) 13. (b)

ANSWERS

10. The ratio of image size to object size is---------. (a) magnification (b) clarity factor

11. --------- is used to control the scatterx-rays. (a) filter (b) grid

12. Fluoroscopy allows continuous viewing of--------- x-ray image. (a) time varying(b) stable

13. The intensifier converts x-ray energy to---------. (a) current (b) visible light

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Too many people spend money they haven’t earned, to buy things they don’t want,to impress people they don’t like.

INTRODUCTION

1. A conventional radiograph is a 2 -dimensional image formed by the super-imposition of images from successivelayers of the body in the path of the x-rays The image of one layer is obscuredby the superimposition of the images ofabove and below layers. Tomography isused to overcome this problem. In thistechnique the images of selected layers arerecorded sharply while images of otherlayers are unsharp. The technique involvessome form of movement of the patient orequipment during the exposure. Themovement causes images from theunwanted layers to move relative to thefilm during exposure resulting intounsharpness. However the movementkeeps images from the selected layer arekept stationary relative to the film andthese images are recorded sharply.Tomography involves the synchronisedmovement of any two of three subjectsviz x-ray tube, the film and the patient

while the third subject remains stationary.Exception is autotomography in whichthere is movement of the patient only.

2. Computed tomography is the name givento the diagnostic imaging technique inwhich tissues of the body are digitallyreconstructed from attenuated x-rays dataobtained from many directions in aparticular plane.

PRINCIPLE OF TOMOGRAPHY

1. A tomographic image can be generated byfollowing methods of coordination ofmovement during exposure :(a) The patient remains stationary while the

x-ray tube and the film (or detector)move in coordination. This is mostwidely used method.

(b) The x-ray tube remains stationary whilethe film (or detector) with the patientmove in coordination.

(c) The film (or detector) remainsstationary while x-ray tube with thepatient move in coordination .

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2. When the x-ray tube moves over the patient,the projected images of structures ondifferent levels of the body move withdifferent velocities. The structure which isnearer to x-ray tube will have its imagemoving faster. Similarly farther the structureis to the x-ray tube, the slower its imagewill move as the movement of x-ray tubeand film is linked through a pivot. Hence thefilm moves at the same velocity as imagesof the structures only at the level of thepivot. Only these images are recorded onthe same part of the film throughout themovement. Images of structures on all otherlayers move at a different velocity to that ofthe film and these images are not recordedon the same part of the film throughout themovement. These images are thereforerecorded as blurred. As shown in the figure,the film is pivoted at B layer. When x-raytube moves from T

1 to T

2 position during

exposure, the quality of images at differentlevel of layers are :

X-ray tube a t T position2

M ovement

From T to T1 2

x-ray tube a t T position1

A

B

C

Patien t

B layer is p ivo ted

FilmA B C1 1 1

A

B

C

C B A2 2 2

(a) Images layer B move at the samevelocity as the film and images arerecorded on the same part of the filmthroughout the exposure. The imagesrecorded at point B

1 and B

2 are sharp.

(b) Images of layer A move faster than thefilm. The images of A move from theleft of B

1 to the right of B

2 as shown in

the figure. Images are not recorded on

the same part of the film and imagesare therefore blurred.

(c) Images of layer C move slower thanthe film. Images are therefore blurred.

3. It is possible to record sharp images ofstructures on one layer of the body whichare free from obscuring images from otherlayers. Throughout the movement, there isno change in the magnification of images onthe object plane as this would produce imageunsharpness. For constant magnification,focus to pivot distance must remain constant.The layer recorded sharply is called the objectplane. It is parallel to the film. Generally thefilm is parallel to the table to at the level ofthe plane. If the film lies at angle of the tabletop during the movement, the layer will bevisualised same angle. This technique is calledinclined plane tomography.

4. The height of the pivot above the table topcan be changed which enables to select anylevel in the patient for the tomography. The

level can be varied by two ways. Either thepivot can be lowered or raised above thetable top to the required level in the patient(variable pivot system as shown in thefigure) or the pivot is kept in a fixed positionand table top is raised or lowered to bringthe desired level of tomography to the levelof the pivot (fixed pivot system as shown inthe figure).

Priniciple of Tomography

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Film Film

X-ray tube X-ray tubePivo t a layer P ivo t m oved down

to B leve l

A A

B B

A

B

A

B

X-ray tube

Piovt

A A

BA

Film

X-ray tubePiovt

A A

B B

Film

Tablera ised

5. The simplest type of movement of x-ray tubeand film is linear and parallel to table topwhich is also called line to line. The focusto film distance (FFD) changes during themovement. FFD is least at the midpoint ofthe movement. Linear movement is generally

confined to one direction only which is alongthe long axis of the table. In certaintomography systems, linear movement inother directions parallel to the table isallowed. Linear movements havedisadvantage that they produce unsharpedimages.

T 2 T 1M ovement of x-ray tube

Focus

Film m ovement

Moving Pivot System

Fixed Pivot System

Line to Line

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6. Arc to Arc is the movement when x-ray tubeand the film move in arcs with the centre ofration at the pivot. Throughout themovement, the tube remains parallel to thetube top i.e., the focus to film distance (FFD)remains constant as shown in the figure.

X-ray tube path

T 2 T1

P ivo t

Film path

7. In arc to line movement, the x-ray tubemoves in arc while the film moves in a lineparallel to the table top. During themovement, there is a change in the ratio offocus to film distance to focus to pivotdistance. Hence there is continuous changein the magnification of images of the subjectlayer. This leads to unsharpness of theimages.

Pivo t

Film path

T 2 T1

X-ray tube path

1. Although CT is more sophisticated than plainfilm radiography but the basic principle issame i.e., dense structures of the body blockthe passage of x-rays more than soft tissues.Each point on a CT image (a pixel) representsa small volume within the body (a voxel).Dense structures such as bone are displayedas white while less dense structures aredisplayed as various shades of grey with theleast dense structures are displayed as black.Hounsfield unit (named after the inventor ofCT, Sir Geoffrey Hounsfield) is used to giverelative density of a structure on CT. HU ofcertain structures are :– air = –1500, fat = –40, water = 0 soft tissue = +80, bone =+400 and metal = +2000. Each pixel on aCT image is composed of a shade of greycorresponding to shade or fraycorresponding to the average Hu of the voxelthat it represent. The various shades of greycreate contrast in the image. The eye haslimitation to appreciate few number of shadesof grey. CT image has a large number ofshades of grey. Hence windows are createdto view optimally different structures in thebody as per the limitation of the eye.

1. The elements of digital imaging systemare :

(a) Data acquisition system

(b) Processing unit

(c) Communication

(d) Display

RELATIVE DENSITY OFSTRUCTURE ON CT

ELEMENTS OF DIGITAL IMAGINGSYSTEM

ARC to ARC

ARC to Line

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1. Two elements are required to acquire digitalimages. The first element is detector(sensing device) an electrical signal outputwhich is proportional to the level of x-rayssensed. The second element is called adigitizer which is a device for convertingthe electrical output of the sensing deviceinto digital form. The detectors for CTsystems must have high overall efficiency(so as to minimise the patient radiation dose),large dynamic range (the ratio of the smallestand just detectable signal to the largest signalwithout causing saturation), stable with timeand insensitive to temperature variation.Three types of detectors are commonly usedin CT scanners. They are (1) xenon gasionization (2) scintillation detector likesodium iodide, bismuth germanate andcesium iodide crystals which convert kineticenergy into flashes of light which can bedetected by a photo multiplier. (3) solid statedetector (single crystal (Cd WO

4 and

ceramic Cd2O2S with photo diodes) which

DATA ACQUISITION SYSTEM can detect x-ray photons. The output fromthe detector is variation of electrons (current)as per the intensity of x-rays with the helpof current to voltage converter. Themultiplexing is a device to take readingsfrom two or more analog integers with asingle analog to digital converter. An analogto digital converter is device that accepts acontinuous analog voltage signals as inputand converts them in to digital output signals.The converters can be (1) voltage tofrequency converter with a counter ( voltageis converted into pulses and number ofpulses is portional to voltage) (2) pulse widthconvertor (discharged capacitor is chargedat fixed rate until it is charged to analogvoltage and resulting pulse width isproportional to the analog voltage) (3) upand down integrator converter (the input ofanalog integrator is alternately switchedbetween the analog voltage to be digiticizedand a constant reference voltage and outputof analog integrator is used to charge acapacitor at fixed rate as done in pulse widthconverter.

Data Acquisition

X-rays

from object

e lectrons voltage

Converter

Detecto rCurren t

to voltageAnalog

In tegra to r M ultip lex ing

Computer Analog to d ig ita l

PROCESSING UNIT

1. Computer is used as processing unit.Processing of digital images requiredprocedures which can be expressed inalgorithm form. Therefore most imageprocessing functions can be implemented insoftware of the computer. Some of theprinciple imaging hardware being added tothe computer consists of (1) a digitizer /frame buffer combination for image

digitization and temporary storage (2) anarithmetic and logic unit (ALU) processorfor performing arithmatic and logicoperations at frame rate (3) one or moreframe buffers for fast access to image dataduring processing. Many basic imageprocessing softwares are available which cancombine computer softwares of spreadsheets and graphics to provide solution toall image processing problems.

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2. CT technique generates a two dimensionalpicture in which each picture element (pixel)value corresponds to the attenuationcoefficient of a voxel in the object slice. Theinformation received by the computer fromthe data acquistion system has to beprocessed for reconstructing the pictures.The data received by the computer containsfollowing information :–

(a) Positional information about scanningframe.

(b) The value of absorption or attenuation.

(c) Reference information of x-ray outputfrom the reference detector.

(d) Calibration information which isavailable at the end of each traverse.

3. The reconstruction of images from thescanning data is carried out by the computer.The fundamental of the principle is given bythe mathematical discovery that a twodimensional function can be determined bythe projection of this function from alldirections. The scanned data at anglesuniformly distributed about the origin canreconstruct the images if data is properlyprocessed or projected. The time requiredfor reconstruction is same as that is requiredfor acquiring the data. Mathematicalreconstruction algorithms in software permitreconstruction to start simultaneously as thefirst projection data is received by thecomputer. The reconstruction methodsare :

(a) Interactive methods

(b) Analytic methods with the concept ofback projection.

(c) Analytic methods with the concept offiltered back projection.

1. In this method, an initial guess about the twodimensional pattern of x-ray attenuations ismade. The projection data likely to be given

by this two dimensional pattern (modelpredictions) in different directions are thencalculated which is compared with themeasured data. Discrepancies between themeasured data and predicted model data areused in a continuous iterative improvementof the predicted model array.

2. Inorder to illustrate the methodology ofiterative method to obtain an image ofattenuation coefficients from the measuredintensity data, we suppose the attenuationcoefficients of the first row and second row

by a 2 × 2 object matrix as 2

4

8

6 .

Now we carry out scanning in threedirections i.e., scan I in vertical direction,scan II in diagonal direction scan III inhorizontal direction to find image matrix.Following iterations can be carried out tomatch image matrix to the object matrix :–

(a) Scan I of the object matrix in verticaldirection gives the vertical sums of 6and 14 which is distributed in verticalcolumns with equal weighing i.e., 6/2and 14/2 to get an image matrix.

First Iteration

6/2 14/2

2

4

8

6

0 0

0 0

3

3

7

7

6 14

Object m atrix (om )

Im age matrix (Im )

(b) Scan II of matrix in diagonal directionof object matrix gives attenuations as4, 8 and 8 and image matrix after firstiteration given 3, 10, & 7. Differencesof object and image matrix have valuesof 1, –2 and 1 which are back projectedwith equal weighing diagonally asshown in the figure.

ITERATIVE METHOD

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–2/2

2

4

8

6

3

3

7

7

3

3

7

7

3

7 10 8

1

1

2

4

8

6

4

8

O M IM (scan I)

IM (scan II)

(c) Scan III in horizontal direction ofobject matrix gives attenuations as 10and 10 while scanning of image matrixafter second iteration gives attenuationas

2

4

8

6

2

4

8

6

2

4

8

6

2

4

8

6

10

10

0

0

10

10

O M IM (scan II )

IM (scan II I)

10 and 10. The object and image matrixnow match as difference in values ofelements in both matrices is zero. Nowwe use the final image matrix togenerate image with the help of thecomputer.

1. In this method, the image is reconstructeddirectly from the projection data without anyneed to compare the measured data and thereconstructed model. If projections of anobject in the two directions normal to x andy axes are measured and then this projectiondata are projected back into the image plane,the area of interaction receives their summedintensities. It can be seen that the backprojection distribution is a representation ofthe imaged object. In actual process, the

back projection for all scanned angles iscarried out and the total back projectedimage is made by summing the contributionfrom all the scan angles. This methodgenerally gives a crude reconstruction of theimaged object

Pro jection on ‘y ’

z

y

O bject

Pro jection on ‘x ’

x

Pro jection

z

y

Im age reconstructed

Pro jection

x

1. It is possible that the image can be

reconstructed with the back projection after

data has been filtered first. The backprojected image is fourier transformed into

the frequency domain and filtered with a filter

proportional to spatial frequency upto somefrequency cutoff. These filtered projectiosare used to construct the final back -projected image. The filtering operations canalso be carried out in cartesian coordinatesby using analytic algorithms which areknown as convolution techniques. This isachieved by convolving (filtering) theshadow function with a filter. In principle,

Projection in Normal X and Y Directions

Image Reconstruction

FILTERED BACK PROJECTION

Second Iteration

Third Iteration

BACK PROJECTION

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the blurring effect is removed in theconvolution process by means of a weighing(suitable processing function) of the scan

profiles before back projection. This method

has began found to give a goodreconstruction of the imaged object.

1. Communication in digital image processingis primarily concerned with localcommunication between image processingsystems and remote communication fromone place to another which involvestransmission of image data.

1. Spiral CT scanning was introduced in 1989which was a dramatic development, helpingCT scanning to mature into a true volumeimaging modality. In conventional CTscanning, the patient was required to shiftafter each slice to get a new slice. Therotation of x-ray tube is stopped after eachrevolution to shift the patient for next slice.The rotation of x-ray tube is thereforeintermittent and stoppage of rotation. Tofrequent speed of scanning, spiral CTscannig was introduced. In spiral CTscanning, there is continuous rotation of x-ray tube and shifting of patient, resultinginto much faster scanning rate.

1 2 3 4 5 6 7 8 9S lice

Conventional CT Scan

Spiral CT Scan

1. Conventional CT scanners have a single rowof detectors whch can acquire a single sliceimage per rotation. a multislice CT sysetm incontrast uses multiple detector rows (14, 16,64) which enables it to acquire images ofmultiple slices per rotation. The speed ofgantry is also increased in multisliced CTsystem resulting in an overall increase in scanspeed. These improvements dramaticallyreduce the scanning time, permitting largervolume to be scanned in a much reduced time.This technique also gives higher resolutionand also permitting newer techniques like CTangiography and cardiac CT.

C on ven tio na l C T scan

S p ira l C T scan

Th ick sp ira l C T scan

M ultis lice C T scan

COMMUNICATION

MULTI-SLICE COMPUTEDTOMOGRAPHY

SPIRAL CT SCANNING

Evolution of Multi-slice CT Scan

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Fill in the gaps

1. In computed tomography, the images ofselected layers are records ---------.(a) sharply (b) dimly

2. In computed tomography, some form of --------- of the patient or equipment is carriedout during exposure. (a) relative movement(b) synchoronised movement

3. In computed tomography, the patientremains stationary while the x-ray tube andfilm / detector move ---------. (a) independly(b) incoordination

4. On computed tomography, each pixel ofimage represents a ---------. (a) voxel(b) body organ

5. On computed tomography, bone is displayedas ---------. (a) white (b) black

OBJECTIVE TYPE QUESTIONS

ANSWERS

1. (a) 2. (a) 3. (b) 4. (a) 5. (b) 6. (a)7. (b) 8. (b) 9. (a) 10. (a) 11. (b) 12. (b)

6. --------- is used to give relative density of astructure on computed tomography.(a) Hounsfield (b) Hounmerfield unit

7. --------- are used for processing of imageson computers. (a) CPU (b) algorithms

8. A two dimensional function can bedetermined by the projection of the functionfrom --------- directions. (a) three (b) all

9. Imaging of brain is difficult by using methodof ---------. (a) radiography (b) tomography

10. Xenon is a --------- detector. (a) gasionization (b) x-ray photon

11. --------- detectors convert kinetic energyinto flashes of light. (a) titillation(b) scintillation

12. --------- detectors with photo diodes candetect x-ray photon. (a) photiac (b) solidstate

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The grass may be greener on the other side, but it’s just as hard to cut.

INTRODUCTION

1. Magnetic resonance imaging (MRI) is quiterecent diagnositc imaging that has aroused awide interest for a number of reasons asunder :

(a) It employs a strong magnetic field andradio frequency pulses to provideremarkably clear and detailed picturesof internal organs and tissues, therebyeliminating the need of x-ray radiationas in the case of radiography and CTscan.

(b) It provides very good distinctionbetween adjacent structures andexcellent tissue contrast without injectionof potentially toxic contrast agents.

(c) In MR 1, bone does not interfere withthe signals emitting from the tissueswhich carry the images of the areasunder observation. Previously such areascould not be imaged non invasively suchas brain stem and spinal cord.

(d) MRI can help in detecting diseases ofearlier stages that previously could notbe done with available methods.

2. MRI is unique imaging method becauseunlike the usual method of radiography,radioisotopes and CT scanning, it does notrely on radiation. In this, protons of thenuclei of hydrogen atoms are subjected toradio frequency pulses in a strong magneticfield. The protons get thereby “excited” tohigher energy level. Protons also get“relaxed” to the lower energy level on theswitching off radio frequency pulses. Theprotons emit radio frequency signals whenthey move from “excited” to “relaxed”state. These radio signals can be detectedby a receiver and a computer can furtherprocess the output into an image. In ourbody tissues, protons of hydrogen are mostabundant as hydrogen atoms of watermolecules (H of H

2O). Hence MRI image

shows difference in the water content anddistribution in various body tissues. Eachdifferent type of tissues within the sameregion can be easily distinguished.

PRINCIPLE OF MRI

1. Each nucleus of an atom has either proton(one proton in hydrogen) or combinationof protons and neutrons. Nucleus havingan odd number of combination of protons

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and neutrons possesses a nuclear spin (The

value varies from 1

2 to 1) and magnetic

moment which has both magnitude anddirection. The magnetic moments pertainingto different atoms of a body tissues arerandomly aligned and their net magneticmoment is zero as shown in the figure. When

Y

Z

X

NetM agnetic m om ent = 0

a strong magnetic field is applied, each atomwith magnetic moment experiencesmagnetic torque which tends to align eachmagnetic moment. Majority of atoms aligntheir magentic moments parallel to magneticfield and rest align anti parallel to the appliedfield. This results into a net magneticmoment (M0) created in the body tissue dueto the realignment of its atoms as shown inthe figure. It is this net magnetic momentaccounts for the nuclear magnetic

X

Z

B 0

X

Y

Applied m agnetic field

Tissue has net magnetic m om ent = M 0

that resonance signals on which the imagingis based. Any nucleus having magneticmoment tends to align with applied magneticfield and in this process it starts processingabout the direction of magnetic field asshown in the figure.

Y

B0

X

Z

The processing frequency (Wl) is called

Larmer frequency which is related to thestrength of the applied magnetic field (B

0)

given by Wl = γB0 when γ = constant.

Y

B0

E = Lower energy level

1

E = H igher energy level

2

Z

X

The nucleus has highest energy (E2) when

its magnetic moments align anti parallel to theapplied magnetic field and lowest energy (E

1)

when its magnetic moments align parallel tothe applied magnetic field. The excitationenergy (E) is required to excite a nucleus fromthe lower to higher energy level. Theexcitation energy is given by plank’s equation,

as E = 2

h

π Wl where h = plank’s constant.

In MRI, the excitation energy is given tonucleus by applying radio frequency pulses.

The Method of Encryption

Aligment of Magnetic Moment Due toMagnetic Field

Highest and Lowest Energy Level

Precessing of Nucleus

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2. The body tissue has hydrogen protons(nuclei) which absorb energy from theapplied RF pulses of suitable frequency.Therefore protons are excited to higherenergy level from the lower energy level.When RF pulses are stopped, the absorbedenergy of RF frequency is emitted by thenuclei as the electro-magnetic energy of thesame frequency similar to the source(transmitter). Hence supplyingelectomagnetic energy of the appropriaterotational frequency, the protons or nucleiof hydrogen can be excited from a lowerenergy level (E

1) to higher energy level (E

2).

If the energy supply is stopped, the excitedprotons drop back to lower energy level E

1

(relaxed). In this process, the nuclei emitthe energy absorbed during movement fromE1 level to E2 level. If the RF pulses arerepeatedly applied and removed, the nucleistart resonating between E1 and E2 energylevel. The signals produced during relaxation(move from higher energy to lower energy)is dependent on density of hydrogen, thevelocity of flowing fluid through the tissueand the rate at which the excited nucles arerelaxed. The relaxation parameters aremarked T

1 and T

2. T

1 and T

2 depend on the

physical properties of the tissues whenexposed to a series of pulses atpredetermined time intervals. Differenttissues have different T1 and T2 propertiesbased on the response of their hydrogennuclei to radio frequency pulses in the strongmagnetic field. These differential propertiesare made use of by setting equipment

parameters (TR and T

E ) inorder to generate

images either based on T1 or T

2 properties

of the tissues. Due to this reason, images ofthe tissues are known as either T

1 or T

2

weighted. TR stands for the time to repeat

RF pulses while TE is time to receive echoi.e., time internal between application ofpulse and listening of the signal.

3. Signal intensity pertains to the brightness ofsignal generated by specific tissue. Thetissues that are bright (white) arehyperintense while darker signal tissues arehypointense. The tissues which are inbetween bright and dark are isointense. Thesignal intensity of tissue depends uponwhether image is T

1 or T

2 weighted. For

example, fat is bright on T1 weighted imagesand less bright on T

2 weighted images.

Similarly water is dark on T1 weightedimages and bright on T

2 weighted images.

Similarly gas is dark on T2 weighted images.

4. Spatial encoding of the MRI signal isaccomplished by applying magnetic fieldgradient across the region of interest. Wehave seen that magnetic field changes therotation frequency of nuclei. When RF pulsesare applied, the nuclei having same frequencystart resonating. By sequentially varying thefrequency of RF pulses, nuclei can beselectively excited. There are manytechniques by which MRI information canbe spatially encoded, acquired andtransformed into an image. One of thetechniques used is electron technique inwhich magnetic gradient is rotated to obtainmultiple projections which are fed into acomputer to generate an image.

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5. The components of a MRI system are(1) a magnet (2) gradient coils (3)a transmitter (4) a receiver (5) a computer

and (6) shin coils. The layout of the system

is as shown in the figure.

Im age d isplay system

Computer

Control in te rface

Analog to d igita l

converte r

Static m agnetic

field

Sh in coils

G radien t coils

RF transm itter

Rece iver

M agnet

M agnet

The Components of a MRI System

The Components of a MRI System

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A strong magnet is provided to produce ahighly uniform static magnetic field (1 to 3Tesla) which is 10,000 to 30,000 timesstronger than the earth’s magnetic field. Themagnet can be permanent or electromagnetictype. The magnet is a large and hascylindrical shape with a large aperture atcentre to enclose the sliding table on whicha patient can lie down for imaging. The priceof the magnet is the main cause of highpurchasing and installation cost of MRIsystem. The gradient coils are provided tocreate magnetic field gradient in the tissuesof the body to be imaged for spatial encodingof the signals. The transmitter operates atradio frequency to generate pulse sequenceto resonate the hydrogen protons (nuclei)of the tissues. The receiver is required todetect the MRI signals emitted by nuclei ofhydrogen during relaxation. The output ofthe receiver is linked to the computer. Thecomputer and display system is provided tocontrol the system operation so that imagescan be processed, stored, reconstructed anddisplayed, as and when required. Shin coilsare placed at suitable places to maintain thehomogeneity of the magnetic field.

(b) Exposure to radiation of a patient duringimaging has been completelyeliminated.

(c) The detection of abnormalities thatmight be obscured by bone structurein other imaging systems are possible.

(d) The contrast material used in MRI isless likely to produce allergic reactionas compared to the iodine based materialused in x-ray and CT scan.

(e) The diseases at earlier stages can bedetected in MRI system. It can detectthe functioning of brain and onset ofbrain stroke at a very earlier stage.

(f) MR angiography can provide detailedimages of blood vessels in the brainwithout contrast material.

2. The risks of MRI are :

(a) The strong magnetic field can affectany metallic implant in the body of apatient.

(b) It is generally avoided in the first 12weeks of pregnancy incase of pregnantwomen.

3. The limitations of MRI are :

(a) MRI system is costlier than othersystems like CT scan.

(b) Bone can be better imaged by theconventional x-ray system.

(c) CT scan is preferred for patients havingsevere bleeding or acute trauma.

THE BENEFITS, RISKS ANDLIMITATIONS

1. The benefits of MRI are :

(a) Image of the brain and other headstructure are clearer and more detailedthan the images obtained from otherimaging methods.

OBJECTIVE TYPE QUESTIONS

Fill in the gaps1. MRI eliminates the exposure to --------- of

a patient during imaging. (a) shock (b)radiation

2. In ---------, bone does not interfere with thesignals emitting from the tissues. (a) MRI(b) CT scan

3. MRI can detect diseases at --------- stages.(a) advanced (b) early

4. The protons of hydrogen are excited bysubjecting to --------- . (a) Radiation (b) RFpulses

5. The protons emit RF signals when they

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move from --------- to --------- state. (a)excited, related (b) relaxed, excited

6. --------- generates RF pulses. (a) receiver(b) transmitter

7. RF signals emitted by tissues are detectedby ---------. (a) receiver (b) transmitter

8. The output of the receiver is linked to ---------. (a) transmitter (b) computer

9. The gradient of magnetic field is producedby --------- coils. (a) gradient (b) shin

10. The homogeneity of magnetic field isproduced by --------- coils. (a) gradient (b)shin

11. The signal intensity of tissues depends uponwhether images are T1 or T2 ---------. (a)

1. (b) 2. (b) 3. (b) 4. (b) 5. (a) 6. (b) 7. (a)8. (b) 9. (a) 10. (b) 11. (b) 12. (b) 13. (b) 14. (a)

15. (a) 16. (a)

ANSWERS

linked (b) weighted

12. Spatial enconding of RF signals emitted bythe tissues is obtained by magnetic ---------. (a) homogeneity (b) gradient.

13. MRI system is --------- as compared to CTscan. (a) cheaper (b) costly

14. The high cost of --------- is the main causeof high purchasing and installation cost ofMRI system. (a) magnet (b) computor

15. The strength of the magnet of a MRI systemis about --------- tesla. (a) 1 to 3 (b) 5 to 7

16. The strength of earth’s magnetic field is onegauss and --------- gauss make a tesla. (a)104 (b) 103

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Everyone thinks of changing the world but no one thinks of changing himself.

INTRODUCTION

1. The application of ultrasound in medical fieldis based on the sonar principle as used bybats, ships at sea and anglers with fishdetectors. It is totally non invasiveprocedure. Acoustic waves are easilytransmitted in water but they are reflectedfrom an interface according to the changein the acoustics impedance. Leaving bonesand lungs, all tissues of our body arecomposed of water which can transmitacoustic waves easily. Ultrasound can beused for obtaining images of internal organsby sending high frequency sound waves intothe body. The reflected sound waves(returning echoes) are recorded andprocessed to reconstruct real time visualimages by the computer. The returningsound waves (echoes) reflect the size andshape of the organ and also indicate whetherthe organ is solid, fluid or something inbetween. Unlike x-rays, ultrasound requiresno exposure to ionization radiation. It is alsoa real time technique that can produce apicture of blood flow as it is at the verymoment of imaging.

1. The human can hear sound in the frequencyrange of 20 hertz to 20,000 hertz. As thename suggests, ultrasound has frequencygreater than 20,000 hertz. Diagnosticultrasound has the range of 1 to 10megahertz. Ultrasound travels in the formof longitudinal wave i.e., the particles of themedium move in same direction inwhich thewave propagates. The wave transfers energythrough the motion of regions ofcompression and rarefraction within thewave. The propagation of wave dependsupon the elastic properties of the medium.If pressure change is ∆P and ∆V/V iscorresponding change in the volume of

the medium, than ∆P = – β V

V

where β = modulus of elasticity. The averagespeed of wave in biological tissues is given

by relation C = 0

βρ where ρ

0 = density of

the medium without disturbance. Theaverage speed in tissue is taken as 1540m/sec.

ULTRASOUND WAVE

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2. The intensity of a wave is defined as theenergy which flows per unit time across aunit area perpendicular to the wavepropagation. Intensity (I) = 2π2 ρ0 cf 2 ζ max

for an infinite one dimensional plane wavewhere f = frequency, ζ max = maximumparticle displacement, ρ

0 = density and C =

average speed. Therefore intensity dependsupon the parameters of impressed ultrasoundwave (f and ζ max) and parameters of mediumknown as specific acoustic impedence z (z= ρ0C). Biological tissue is not homogeneousacoustically i.e., ρ

0 and C are not constant

within the meduim. If we consider a planelongitudinal wave propagations frommeduim 1 to medium 2, then the percent ofthe incident wave energy which is reflected

= 2

1 22

1 2

( )100%

( )

Z Z

Z Z

−×

+ where Z1 and Z2 are

acoustic impedence of the medium 1 and 2.

The transmitted energy =

21 2

1 2

2Z Z

Z Z

+

×

100%. The interface separated by thegreatest difference in the speed of sound willprovide the greatest reflection as then thevalue of z1 – z2 is large. This is the reasonwhy it is difficult to visualise bone. Similarlythe acoustic impedance of air and tissue are42.8 gm/cm2 and 16 × 102 gm / cm2 whichresults into a large value of z1 – z2 therebythe interface makes the ultrasound energyreflected completely without any penetration.A special jelly is used therefore to minimisereflected energy from the interface of skinand transducer (in air) so that ultrasoundcan penetrate the body for the imaging oforgans. Hence the ability of ultrasoundwaves to travel through any meduim is

restricted by the properties of that medium.These properties include the density andelastic properties which make up theacoustic impedance specific to that meduim.The transmission is also limited by thetransducer frequency being used. Higherfrequencies have shorter wavelengths(V = fλ where v = velocity, f = frequencyand λ = wave length) and they can penetrateless than lower frequencies.

M edium 1

Z ( × C )1 0 1ρ

Incident

Reflected

M ed ium 2

Z ( × C )2 0 2ρ

Transm itted

3. The velocity of ultrasound in a mediumdepends upon modulus of elasticity anddensity of the medium. The knowledge ofvelocity in a medium is essential in calculatingthe depth to which a wave has potential totraverse before it is reflected. The depth ofpenetration is the product of velocity and timelapsed for the wave to travel from source tointerface and back. As the ultrasound beamencounters tissues of different acousitcimpedance, velocities are altered such thatreturning echoes are received by the receiverat different times and echocs have differentintensities. The differences in time andintensity have useful information. Thisinformation as well as the knowledge aboutvelocity in the tissue are used by the computerto generate the image on the monitor.Transmit power or intensity is manuallyadjustable in the machine. Ultrasound poweris expressed by decible (db).

Incident, Transmitted and Reflected Wave

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1. General rules of scanning are :

(1) ultrasound beam should be directedperpendicular to the object of interest for

optimal visulisation (2) the transducer must

be selected which has the highest frequencyallowable for the penetration required (3) a

full bladder is required for optimal

visualization of the uterus and ovaries (GYN)and (4) scanning of all organs of interest is

to be done in two planes which are

perpendicular to each other. The scanningmodes are : (1) bistable scanning (2) Grey

scale imaging (3) A mode (4) B-mode (5)

M-mode and (6) real time. Bistable scanningdisplays images in black and white. Grey

scale imaging is commonly used in which

an analog to digital scan converter transfersinformation from the receiver to the

computer. Multiple shades of grey enhance

tissue characteristics and make theultrasound image more aesthetic and

realistic. Human eye can discern upto 32shades of grey. Therefore most systemsemploy 32 shades of grey only. A-mode(amplitude mode) displays the amplitude ofindividual echoes as a function of distanceor time on cathode ray tube. The display isshown alongside the image which is helpfulin determining the type of tissue i.e., cystic

SCANNING or solid. B mode (Brightness mode) displaysechoes as individual spots on the screencorresponding to the points of origin in thetissue. Differences in amplitudes ofreturning echoes manifest as differentbrightness of the dots. Using many pixels(picture elements), these numerous dots canbe arranged in such a way as to appear indifferent shades of grey for goodvisualisation. A schematics block diagram ofa B-mode ultrasound imaging system is asshown in the figure. M-mode (motion mode)is nothing but the application of B-mode toa moving structure varying with time. Realtime imaging allows the processing of thegrey scale characteristics and the motionof interfaces. The brightness dots move onthe monitor screen as the actual interfacesEchocardiogram gives the movement ofvalves and other structures of the heartwhich are displayed as a function of time.M-mode technique is used to obtain it. A-mode is used for echoencephalogram whichcan determine the location of the problemof the brain. B-mode is used for diagnosticscanning of the eye. B-mode is also usedfor visualizing various organs and stucturesof human body which include breasts,kidneys, ovaries and tubes. It permitsexamination of foetus as early as the 4-weekstage.

D isp la y m o n ito r

T ran sm it te r a n d

re ce iver

C o m p ute r a n d

a n alo g p ro ce sso r

T ran sd u ce r

Schematic Block Diagram of B-mode Ultrasound

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1. The transducer is a device capable ofchanging one form of energy into another. Inultrasound, the transducer is both sender andreceiver of ultrasound pulses and echoes. Thetransducer converts electrical impulses intoultrasound waves and vice versa. Generallya piezoelectrical crystal is used to create theultrasound waves. As the receiver, thetransducer has many functions likeamplification, compensation, demodulation,compression and rejection. Man-made leadzirconate and lead titanate are also used astransducer. The electricity is applied to thetransducer at a specific pulse rate whichallows waves to travel and echo back to thereceiver. The transducer sends pulse of onemicrosecond duration with the interval of 999microseconds before sending next pulse.Hence the ultrasound scan head is in the“listening” mode for the echoes for most ofthe time. The beam emitted by the transducerhas two fields viz. near field and far field.Near field has width from the transducer’sface to the focal point beyond which the beamdiverges and is called far field. Due todivergence, resolution region is bad in the farfield as compared to the near field.

1. Resolution is the ability of the system toseparate and define small and closelyseparated structure. The resolution canbe: (1) lateral and (2) axial. Lateral resolutionis the ability of the system to separate anddefine small structures in the planeperpendicular to the beam axis. Lateralresolution can be optimised by focussing thebeam at the area of interest and then slowlyincreasing the frequency. If the beam width

is greater than the separation between twoobjects then these objects can not beresolved. Axial resolution is the measure ofthe system to separate and define structuresalong the axis of the beam. It depends uponthe pulse duration. Two neighbouringstructures can be resolved by beam if thewavelength of the beam is less than theiraxial distance between them. However theaverage ultrasound pulse contains two wavelengths. Therefore higher frequencytransducer has to be used to improve theaxial resolution. The frequency can not bemade much higher to have better resolutionas then the penetration of wave falls withincreased frequency.

1. The ultrasound image is formed from theuseful information contained by the echoesof the ultrasound which are reflected backwhile traversing and interacting with thetissues of the body. These interactioncontributes to image formation and imagesvary as the tissues vary themselves. It isimportant to have known values of acousticimpedance (z) and speed of ultrasound inthe particular tissue. The acousticimpedance is a function of the elasticity anddensity of a particular tissue. Materials withhigh acoustic impedance can transmit soundfaster than others. The acoustic impedanceof some materials are :

THE ULTRASOUND TRANSDUCER

IMAGE RESOLUTION

WORKING OF ULTRASOUND

(a) Blood — 1.6 × 105 gm /cm2

(b) Bone — 7.8 × 105 gm /cm2

(c) Fat — 1.4 × 105 gm /cm2

(d) Soft tissue — 1.6 × 105 gm /cm2

(e) Air — 0.004 × 105 gm /cm2

(f) Water — 1.5 × 105 gm /cm2

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2. The ultrasound beam is attenuated whiletraversing through the tissues. The beammay be partly scattered, reflected, refractedor absorbed. The amount of intensityremoved from the beam per unit depth isexpressed as the attenuation coefficient

dB = 10 log10

2

1

I

I

which is a logarithmic

expression of the ratio of intensity of thereturning echoes to the intensity of theoriginal sound beam. As frequency increases,the attenuation coefficient also increases.The beam is generally attenuated one dB permhz and per cm of tissue traversed. Whenthe beam reaches perpendicular to the tissueinterface within the body, the energy isreflected back towards the transducer cumreceiver. The amount of energy reflected isproportional to the difference in acousticimpedance between the structures formingthe tissue interface. These echoes aremanipulated for the reconstruction of thediagnostic image.

3. Another reason of the loss of beam energyis absorption by the way of heat. In order tovisualise internal structure, some form ofcompensation has to be employed. Thedifference in the intensity and amplitude ofreturning ehocs are compensated by themethods known as time gain compensationand depth gain compensation. On applicationof these compensation, equal amplitudes ofechoes are displayed for the tissues havingsame impedances irrespective of the depthtraversed or time elapsed between pulsetransmission and listening of echo.

1. A bed side ultransound machine is about thesize of a small cupboard as shown in the

ULTRASOUND MACHINE

figure. It consists of a computer with adisplay unit, circuitory and a hand heldtransducer. The transducer has the shapeof a microphone. It is meant to send out theultrasound beam and to receive the reflectedsound waves.The reflected sound waves arefed to a computer which with the help ofalgorithms, process them to create theimages.

1. Doppler ultrasound is based on the principlethat sound reflected by a moving target likeblood has a different frequency from theincident sound wave. The difference infrequencies is known as Doppler shift whichis proportional to the velocity of the target.Doppler shift is the useful information withthe echoes which helps in the detection offlowing blood. It also enables to quantifythe velocity of the blood. It is possible togive colour coding to the doppler informationand superimpose it on a real time B-modeimage facility which can help in identificationof blood vessels or blood vessels havingabnormal flow. This technique can also beused to diagnose coronary stenosis.

DOPPLER ULTRASOUND

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1. Ultrasound is relatively inexpensive and noninvasive. It does not expose patients toionizing radiation and hence it is safe. It ispreferrd for children and pregnantwomen. The machine is also comparativelyinexpensive.

ADVANTAGES OF ULTRASOUND DISADVANTAGES OF ULTRASOUND

1. Ultrasound imaging system is highly operatordependent. It cannot be used for full bodysurvey. It can not image air containingorgans or bones. The resolution of theultrasound image is inversely related to thedepth of penetration. The quality of imagedecreases in the case of obese patients.

Dopp le r u ltrasound

Sonar (m arine)

Am plitude m ode

im aging

Am plitude to time m ode

Two d im ensiona l cross sectional rea l- tim e

Evolution of Ultrasound System

OBJECTIVE TYPE QUESTIONS

Fill in the gaps1. The application of ultrasound is based on

the --------- principle. (a) Sonar (b) ultra

2. Acoustic waves are easily --------- in water.(a) replaced (b) transmitted

3. Ultrasound has frequency --------- than20,000 hertz. (a) greater (b) lesser

4. Ultrasound wave travels in the form of --------- wave. (a) transverse (b) longitudinal

5. The average speed in tissues of ultrasoundis taken as --------- (a) 1400 m/s (b) 1540m/s

6. Incident wave at the interface is partlytransmitted and partly ---------. (a) absorbed(b) reflected

7. The intensity of echoes depends upon thecharacteristic of meduim known as ---------. (a) specific density (b) specific impedance

8. Specific impedances depends upon density

and --------- in the meduim. (a) speed(b) pressure

9. If meduim 1 and 2 have impedance of z1

and z2 respectively, then percent reflected

beam depends upon ---------. (a) z1 + z

2

(b) z1 – z

2

10. Penetration of ultrasound wave in the tissueincreases with --------- of frequency.(a) increase (b) decrease

11. A-mode is --------- mode. (a) amplification(b) amplitude

12. B-mode is --------- mode. (a) brightness

(b) biotissue

13. M-mode is --------- mode. (a) mobile(b) motion

14. Piezoelectic transducer can convert electric

energy into --------- energy and vice versa.(a) ultrasound (b) heat

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15. When incident sound wave is reflected from

moving target, its frequency is changedwhich is known as --------- shift. (a) hobbler

(b) doppler

16. Ultrasound is a --------- imaging system.(a) invasive (b) non invasive

17. The quality of image --------- the case of

obese patients. (a) increases (b) decreases

18. Gel is applied between skin and transducer

to --------- impedance. (a) lower(b) increase

19. The change of impedance at bone interface

is --------- and ultrasound wave iscompletely ---------. (a) small, transmitted

(b) large, reflected

ANSWERS

1. (a) 2. (b) 3. (a) 4. (b) 5. (b) 6. (b) 7. (b)

8. (a) 9. (b) 10. (a) 11. (b) 12. (a) 13. (b) 14. (a)

15. (b) 16. (b) 17. (b) 18. (a) 19. (b)

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There is no greatness where there is no simplicity, goodness and truth

INTRODUCTION

1. When a combination of neutrons and protonswhich does not exist in nature, is producedartificially, then the atom is unstable. Suchatom is called a radioisotope. The nucleusof radioisotope tries to become stable byemitting alpha and /or beta particle, whichmay be accompanied by gamma rays(photons radiation). This process is calledradioactive decay. The photons radiationemitted by radioisotopes can be easily imagedby gamma cameras. Suitable radioisotopesas labelled tracers can participate in themetabolism or other body functions andtherefore are carried or concentrated intarget organ. Image quality depends on thetracer concentration in the target area andon the emission dynamics of the radioisotope

used. Hence radioisotopes are invaluabletool in the field of medical diagnosis andradiotherapy.

TYPES OF RADIOACTIVE DECAY

1. Radioisotops can be decayed by: (1) betadecay (2) gamma decay (3) alpha particleemission and (4) decay by electron capture.Beta decay takes place by emission of betaparticles from radioisotope. Beta particleshave a charge and mass equal to those ofhigh speed electrons. Beta particle can bepositrions (β+) or negatrons (β–) as shownin the figure. The equation of formation ofbeta particle can be :–

(a) Neutron → proton + β – (negatron)

Example : 14 C6 → 14 N7 + β –

(b) Proton → neutron + β+ (positron)

Example : 22 Na11

→ 22 Na10

+ β +

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e–

e–

e–

e–

e–1

e–1

e–1

e–1β

+

10P12N

11P11N

Decay

β–

6 P8 N

7 P7 N

Decay

2. Gamma emission involves electromagneticradiation similar to x-rays but it has a shorterwavelength as shown in figure. Gammaradiation takes place with transformation of

nucleus of a radioisotope with emission ofalpha or beta particles. The equation ofgamma radiation (x) is:

131 I61 → 131 × C64 + 3β–1 + γ

e–

e–

e–

e–

e–

e–

e–

e–

x-raysG am m a

Nucleus Nucleus

X-Rays and Gamma Radiation

Imgatron Decay (βββββ–)

Positron Decay (βββββ+)

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3. Alpha particle consists of helium nucleuswith two neutrons and two protons.Radioisotopes having higher atomic weightgenerally decay by emitting alpha particlewhich is known as alpha particle emission.Emission of an alpha particle results indecrease of atomic number by two units andatomic mass by four units. The equation ofalpha emission is: 226Ra

88 → 222 Rn

86 +

4He2++

4. The number of protons in a nucleus can alsobe reduced by the process of electroncapture. This is called decay by electroncapture. In this radioactive decay, one ofthe inner orbital electron is attracted into thenucleus where it combines with the protonin nucleus to form a neutron i.e., e– + p+ =n. Combining results in the loss of one protonand gain of one neutron in the nucleus.Though there is no emission of any particlebut x-rays are emitted due to electron movingfrom inner orbit to nucleus. Iron havingatomic number 55 usually decays by thismode.

e– G am m a e

e–

e–

Electron C aptu re

1. Radioistopes are used as tracers which emitα particle, β-particles or γ-rays. Since theseradiations have different physicalcharacteristics, the manner inwhich theseinteract with other matters also differ.Gamma rays are high energy photons havingneither charge nor mass. The penetratingpower of gamma rays is much greater thanthat of alpha or beta particles. Howeverionizing power of gamma rays is less. Gammarays can produce: (1) photo-ionization (2)compton effect and (3) pair production. Inphotoionization, γ-rays interact with orbitalelectron which is ejected as negatron withenergy equal to gamma rays. The negatroninteract with other atoms to ionize them.Gamma rays having more energy can bescattered by electron after absorbing energyfor ejection. This results into ejection of anegatron and a new photon of lowered energywhich moves in altered direction afterscattering. In pair production, gamma raysinteract with an electron and a positron ofnucleus resulting into emission of negatronand of positron. Alpha particle is a heliumnucleus having two protons and two

INTERACTION OF NUCLEARRADIATION WITH MATTERe

–e

–e

–e

e–

e–

e–

e–

Decay

2P2N

88P138N

86P136N

Alpha Particle Radiation

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neutrons. Alpha particles interact with matterin two ways. In one case, alpha particlesimpart energy to orbital electrons of the atomof the matter but without any ejection. Excitedelectrons emit excess energy as photons. Insecond case, alpha particles cause ionizationof matter by ejection of orbital electrons andleaving behind positive charged atoms. Alphaemitting isotopes are not commonly used astracer in imaging as these isotopes have higheratomic number. Beta particles (positrons andnegatrons) are very small. They have highvelocity resulting higher penetrating power.Beta particles dissipate their energy largelyby ionisation or excitation of the atoms withwhich they interact.

1. The number of atoms in a radioisotope thatdisintegrate during a given time intervaldecreases exponentially with time as shownin the figure. If λ = decay constant,N

o = number of atoms present originally,

N = number of atoms present after time tthen N = Noe

–λt. The time for the half thenumber of atoms to disintegrate is given byt1/2 =0.693/λ

Number ofa tom s (N )

Time

RADIOACTIVE DECAY

MEASUREMENT OF RADIOACTIVITY

1. The measurement of radioactivity isdetermination of the rate of emission of

alpha, beta and gamma rays from theradioisotope. These radiations are alsoknown as ionizing radiations as they arecapable of causing ionization directly orindirectly. The methods commonly used fordetection and measuring radioacitivity arebased on the ionization of the gases like inGeiger-Mullier counter and proportionalcounter, or on the excitation of solids orsolution as in scintiallation counter or oninduction of specific chemical reaction incertain emulsion as in auto-radiography. Inthe Geiger-Mullier counter, alpha and betaparticles enter in the counter tube throughmica window having gases under pressurewith anode and cathode as shown in figurewith potential difference of 800 - 2500 volts.The alpha and beta particles ionize moleculesof the gases which move towardsappropriate electrode under the voltagegradient. The process produced a continuousflow of ions which produces dischargepulses of 10 volt amplitude with duration of50 to 100 microseconds. These pulses arecounted which is a measurement ofradioactivity. In proportional counters, thegradient voltage is kept lower than Geiger-Mullier counter and it requires a preamplifierto avoid reducing the pulse size. Scintillatorcounter uses a chemical to convert radiationenergy into light. When an ionizing particleis absorbed in the scintillator, some of theenergy acquired by the scintillator is emittedas a pulse of visible light or near ultravioletradiation. The light falls on a photomultipliertube resulting in pulse of electrons which is

counted to measure radioactivity.

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+

G lass bead

Tungston anode

G lass jacke t

H igh pressure argon and m ethane gas

Copper cy linder (cathode)

M ica w indow

1. Surgery, radiotherapy and /or chemotherapyare used for the treatment of cancer. It mustbe ensured in radiotherapy that the radiationdose delivered to a patient should beoptimally focused to produce a maximumeffect in the volume of cancerous tissue anda minimal effect in the neighbouring healthytissues. Radiotherapy is carefully planned,simulated, executed and verified. Treatmentplanning is carried by modelling to matchthe absorption characteristics of the radiation

RADIOTHERAPY within the anatomy of the patient. Radiationdata is obtained from dosimetry and patientanatomy is acquired from CT scanners.Algorithms are used with these data andpatient’s anatomy in a computer formodelling. To obtain an optimum treatmentplan, the cancerous cells are irradiated fromseveral directions and for certain durationfor two weeks or so. The outcome obtainedfrom this radiotherapy is a good indicatorof further requirements of radiotherapy forthe patient.

Geiger-Mullier Counter

OBJECTIVE TYPE QUESTIONS

Fill in the gaps1. Radioisotope has -------- nucleus.

(a) unstable (b) stable

2. Photon radiation can be easily imaged by--------- camera. (a) Alpha (b) Gamma

3. Alpha particle consists of --------- nucleuswith two neutrons and two protons.(a) helium (b) hydrogen

4. Gamma radiation is --------- radiation similarto x-rays. (a) light (b) electomagnetic

5. Beta particle has charge and mass equal tothat of high speed ---------. (a) proton(b) electron

6. The --------- is time during which halfnumber of atoms disintegrates. (a) half time(b) half life

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ANSWERS

1. (a) 2. (b) 3. (a) 4. (b) 5. (b) 6. (b) 7. (a)

8. (a) 9. (a) 10. (b)

7. Radioisotopes are used as ---------. (a) tracer(b) medicine

8. Radiotherapy is used for the treatment of---------. (a) cancers (b) malfunctioning

9. The radiation dose delivered to a patient

should be --------- focused on canceroustissues. (a) optimally (b) maximumally

10. --------- uses chemical to convert radiationenergy into light when an ionizing particleis absorbed. (a) Geiger-mullier (b)scintillator

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All violence consists of some people forcing others under the threat ofviolence or death to do what they do not want to do.

INTRODUCTION

1. Nuclear medicine comprises of diagnosticexaminations that helps in obtaining imagesof body anatomy and function. The imagesare obtained by detecting energy emittedfrom radioactive substance injected in thepatient by either intravenously or by mouth.The radiation emitted from the patient issimilar to that emerging during radiographyor CT-scanning. Nuclear medicine imagescan assist in diagnosing diseases, tumors,infection and other disorders in organfunctioning. CT scan, ultrasound andmagnetic resonance provides anatomic orstructural information, where as the primarypurpose of nuclear imaging is to providefunctional data.

1. Gamma camera images the gamma (photon)radiation emitted by radioactive compounds.A small dose of radioactive compound isgiven to patient usually intravenously butsometimes orally so that radioactive materialcan be localised in specified body organsystem. The radioactive compound knownas tracer, eventually accumulates in the organand emits gamma rays. The gamma cameradetects the gamma rays, emitted from thebody of the patient and works with thecomputer to produce images which help inmeasurement and functioning of organs andtissues. Image quality depends on the tracerconcentration in the target area and on theemission dynamics of the isotope used. Theimaging detector of the camera is made of asodium iodide crystal where gamma radiationgets absorbed and causes scintillations (tinyflash of light). These are amplified with photomultiplier and the number of scintillations iscounted electronically. Spatial localization ofthe emitting source is achieved with acollimator. The sum of thousands ofscintillations creates an image that representsthe distribution of radioactivity within an organor system.

EQUIPMENT FOR NUCLEARMEDICINE

OPERATING PRINCIPLE OFNUCLEAR MEDICINE

1. Equipment consists of a spacialised nuclearimaging camera and a computer. Gammacamera is used which is enclosed in ametallic housing designed to facilitateimaging of specific parts of the body. Thecamera is mounted on a metal arm thathangs over the examination table.

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2. The type of tracer to be administered dependson which type of scan is to be performed.Imaging can be done either immediately orafter several days. The tracer that is used isdetermined by what part of the body is understudy. It is because some tracers collect inspecific organs better than others.Depending on the type of scan, it may takeseveral minutes to several days for the tracerto travel through the body and accumulatein the organ under study.

1. The computed tomography principles arealso being used in nuclear medicine whichis then called single photon emissiontomography (SPECT). Single photonemission computed tomography is based ona rotating gamma camera. Whereas in CTscan, the image is formed processing x-rayscoming out from the body after absorptionin the tissues, in SPECT the image isreconstructed using the counted number ofemitted photons from the concentration oftracer in the tissues. Like CT scanning,SPECT also uses rotating gamma camera.

1. Positron-emission tomography is a from ofnuclear medicine that uses cyclotron

during the annihilation of the positron-electron pair. Tracers with short life can beproduced by cyclotron and computertechnology has widely improved. Both havehelped in the development of PET.

PET measures the difference in travel timesof the two quantas. This can be used to givethe location of tracer where annihilationstaking place. PET is an analytical techniquethat provides a way of making in vivomeasurements of anatomical distribution andrates of specific biochemical reactionsspecially in the brain. The use of PET toobtain images requires the integration ofthree components viz (1) radioisotope /tracer(2) PET device and (3) tracer kineticmathematical models. The positron emittersmostly used are carbon-11, oxygen-15 andnitrogen-13 which have half life in range of2 min to 20 min. These tracers are taggedto various metabolically active compoundssuch as glucose or naturally occurringcompounds such as carbon monoxide toimage the brain, heart and tumors. Thetracers are administered to the patientsusually by injection but sometimes byinhalation. Since cyclotron is required toproduce positron emitters or tracers, PEThas a very high cost.

SINGLE PHOTON EMISSIONTOMOGRAPHY

POSITRON-EMISSIONTOMOGRAPHY

Positron-emission Tomography

R in g o f d e te c to r

P h o ton

P h oton

C o m p ute r

D isp lay

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Nuclear Medicine Imaging

Fill in the gaps1. Nuclear medicine image acquired from the

radiation --------- from the body. (a) emitted(b) absorbed

2. In nuclear medicine radioisotope is ---------in the organ. (a) accumulated (b) absorbed

3. The primary purpose of nuclear medicine isto provide --------- data. (a) structural(b) functional

4. --------- camera is used in nuclear medicine.(a) positron (b) gamma

5. SPET is based on a --------- gamma camera.(a) rotating (b) linearly moving

6. PET requires --------- and hence it is costly.(a) camera (b) cyclotron

7. Electron and positron pair produces a pairof --------- travelling at 180º apart. (a) photon(b) neutron

8. Radioisotopes for PET are artificiallyproduced with ---------. (a) generator(b) cyclotron

OBJECTIVE TYPE QUESTIONS

ANSWERS

1. (a) 2. (a) 3. (b) 4. (b) 5. (a) 6. (b) 7. (a) 8. (b)

Scin tilla tion counter

G am m a cam era

Sing le photon emiss ion com puted

tom ography

Positron em iss ion

tom ography (P ET)Tracer

technology

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INTRODUCTION

1. Health data as collected from operatinghealth care systems, institutions or any othermean are inadequate for planning. Data needto be transformed into information byadjusting and summarising thom on basisof some parameters which can be age, sexor area etc. This information can betransformed into intelligence by processingwith experience and perception on social andpolitical values. Health data which is notmodified into health intelligence has no value.A health information system is a system tofacilitate the collection, processing, analysisand transmission of health information whichcan help in organising and operating healthservices and also which can be made usefulfor research and training of health servicepersonnels.

1. The uses of health information are :

(a) to ascertain the health status of thepopulation which can help inquantitfying their health problems. Onbasis of these, medical and healthcareneeds can be worked out.

(b) to ascertain the health status which canbe local, national or international

(c) to ascertain the effectiveness of thehealth services

(e) to ascertain the degree of satisfactionof the beneficiaries from the healthservices

(f) to initiate research incase of outbreakof new disease or health problem.

1. The sources of health information are :

(a) Census : It is carried out in mostcountries at regular interval of 10 years.Population census provides basic datasuch as population by age and sex etc.

(b) Registration of death and birth : Itis mandatory in our country for peopleto register the event of birth and death.Whereas census is an intermittentcounting of population, the registrationof death and birth keeps a continuouscheck on total population.

(c) Notification of Diseases : Theincidence and spread of certain specified

USES OF HEALTH INFORMATION

SOURCES OF HEALTH INFORMATION

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diseases are notifiable. List of notifiablediseases vary from country to country.The primary purpose of notification isto effect prevention and to control theoutbreak of contagious diseases.However notification provides variableinformation about fluctuation in diseasefrequency and warning about likelyspread of a disease from othercountries.

(d) Hospital Records : Data such as bedoccupany rates, duration of stay, cost-effectiveness of treatment policies isuseful in monitoring the use of hospitalfacilities. A lot of useful informationabout health care activities andutilization is available from hospitalrecords. The computerization ofmedical records have enabled healthcare to be more effectively carried out,planned and evaluated.

(e) Sample Registration System : It isinitiated to upgrade the death and birthrates. It is a major source of healthinformation.

(f) Morbidity Registers : They arevaluable source of information aboutduration of illness, fatality and survivalcases. They provide information aboutchronic disease in different parts andnatural course of disease.

(g) Health Manpower Statistics:Information on health manpower is thenumber of doctors, dentists,veterinarians, pharmacists, medicaltechnicians and nurses working inhealth care system. Their records aremaintained by medical councils whichis source of health information.

1. Communication is the basis of humaninteraction. The components of

communication are : (1) sender (2) receiver(3) message (4) channel and (5) feed back.The sender is the originator of the message.All communications must have a singleperson or group of persons as receiver. Amessage is the information which the senderwants to transmit to the receiver. It may bein the form of words, pictures or signs. Thechannel is the media of communicationbetween the sender and receiver. It can beface-to-face communication, masscommunication (TV, radio and newspapers)and folk media (nautanki, Harikatha andBurrakatha). Feedback is the flow ofinformation from the receiver to the sender.Infact it is reaction of the receiver to themessage.

Feed back

Sender M essage

Channe lRece iver

1. The communication can be (1) one-way (2)two-way (3) verbal (4) non verbal (5) formaland informal (6) visual and (6)telecommunication and internet. One waycommunication known as didactive methodinwhich the flow of information takes placein “one-way” from the sender to thereceiver. Two-way communication knownas ocrative method inwhich both the senderand the receiver participate. Non verbalcommunication includes communicationthrough body movements, postures,gestures and facial expression. Formalcommunication follows line of authority andinformal communication uses informalnetwork like gossip circles. The usual formsof communication includes charts, graphs,maps, tables and posters etc. Radio, TV and

COMMUNICATION PROCESS

Components of Communication

TYPES OF COMMUNICATION

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internet are mass communication mediawhile telephone and telegraph are point topoint telecommunication.

1. The barriers of health education between theeducator and general public can be: (1)physiological (2) psychological (3)environmental and (4) cultural. Physiologicalbarriers can be difficulties in hearing orunderstanding expression. Psychologicalbarriers can be created by emotionaldisturbances and level of intelligence.Environmental barriers are produced by noise,invisibility and congestion. Cultural barriersare due to illiteracy, lower level of knowledgeand understanding, beliefs and religion etc.The barriers have to be identified and removedto maintain a good communication.

1. The health communication is nothing buthealth education. It is outward and

downward communication of knowledge.

Health communication is the foundation ofa preventive health care system. The health

communication has to perform the functions

of :– (1) information (2) education (3)motivation (4) persuasion (5) counselling (6)

raising morals (7) health development and

(8) organisation. The primary function ofhealth communication is to impart

information to people about health problems

and ways to maintain and improve their

BARRIERS OF COMMUNICATION

HEALTH COMMUNICATION

health. Education is to educate the public

about prevention oriented approach to healthand problems. Most of major health problems

and premature deaths can be prevented

through proper education. The purpose ofhealth communication is to motivate the

public to translate health information into

their personal behaviour and into their lifestyle for the betterment of their health.

Persuasion is the art of winning friends and

influencing people. Health communicationcan influence the public to improve their life

style for better health. Counselling is a

process that can help people to understandbetter and deal effectively with their

problems. It can improve and reinforce

motivation to change behaviour. Counsellingis an important part of treatment, disease

prevention and health promotion. It helps

people to avoid illness and to improve theirlives through their own efforts. Health

communication can help to raise morale of

the health team to work together persistently.Judicial use of communication media can

contribute to health development.

Communication is the life and blood of anorgaisation. Communication can move

horizontally and vetically. Communication

can maintain intra and inter sectorialcoordination.

OBJECTIVE TYPE QUESTIONS

Fill in the gaps

1. Data which is transformed suitably is---------. (a) intelligence (b) information

2. Information can be transformed into--------- by processing with experience andperception. (a) intelligence (b) plan

3. --------- are carried out in most countries inregular interval of 10 years. (a) sampleregistration system (b) census

4. It is --------- in our country for people toregister the event of birth and death.(a) mandatory (b) social obligation

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ANSWERS

1. (b) 2. (a) 3. (b) 4. (a) 5. (a) 6. (a) 7. (a)

8. (b) 9. (a) 10. (b)

5. The incidence and spread of certain diseasesare ---------. (a) notifiable (b) communicated

6. Sender, receiver, message, channel andfeedback are --------- of the communication.(a) components (b) elements

7. One-way of communication is known as--------- method. (a) dedicative (b) socrative

8. Two-way communication is known as--------- method. (a) didactive (b) socrative

9. Health communication is nothing but health---------. (a) education (b) broadcast

10. TV, radio and newspaper are ---------communication. (a) face to face (b) mass.

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If the same man deceives you twice, then may be you deserve it.

INTRODUCTION

1. Some times, it become essential to monitor

physiological events from a distant place.

Some of such situations are:

(a) Monitoring of astronauts during flight.

(b) Monitoring of patients in ambulance whiletransit to hospital.

(c) Monitoring of patients while obtaining theirexercise electrocardiogram.

(d) Monitoring of patients who are permitted tostay away from the hospital.

(e) Monitoring of animals in their natural habitat.

(f) Transmission of ECG or other medicalinformation through telephone links.

(g) Isolating the patients from electricityoperated measuring equipment such as ECGequipment inorder to prevent any accidentalshock to them.

2. Biotelemetry is a method of measuringbiological paramenters from a distance. It isinfact modification of existing methods ofmeasuring physiological variables to a methodof transmission of resulting data. Thetransmission of data from the point of

generation to the point of reception can bedone in various ways. The stethoscope isthe simplest device which uses this principleof biotelemetry. The device amplifiesacoustically the heartbeats and transmitstheir sound to the ears of a doctor through ahollow tube system. Certain applications ofbiotelemetry use telephone lines fortransmission. However biotelemetry mainlyuses radio transmission by suitablymodifying the biological data. Earlier times,the telemetry could be applied to measure(1) temperature by rectal or oral thermistor(2) electrocardiograms by surface electrodes(3) indirect blood pressure by contactmicrophone and cuff (4) respiration byimpedance pneumograph. However it ispossible now to apply biolemetry to almostall measurements such as (1) bioelectricalvariables eg. ECG, EMG and EEG and (2)physiological variables that requiretransducers eg blood pressure, blood flowand temperatures. The signal is obtaineddirectly in electrical form in bioelectricalmeasurements require external excitation forthe conversion of physiological variables intovariations of resistance, induction orcapacitance. The variations can be calibrated

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to display pressure, flow and temperature.In biotelemetry, the measurements as analogsignals (voltage or current) in suitable formare transmitted which are received anddecoded as actual measurements at thereceiving end. ECG telemetry is thetransmission of ECG, form site of anemergency to a hospital where a doctor caninterpret, the ECG and instruct suitabletreatment for the patient. Patients with heartproblem can wear ECG telemetry unit onthe job which relays ECG data to the hospitalfor checking. ECG telemetry unit is also usedfor monitoring when an athlete runs a raceto improve his performance. Telemetry isalso used for transmission of EEG. It isgenerally used for mentally disturbedchildren. The child wears specially designedthe met known as football helmet orsuperman’s element which has built in

electrodes so that his EEG a can be motoredfor any traumatic difficulty during play.Biotelemetry is also used forelectromyogram (EMG) for studies ofmuscle damage or partial paralysis problem.Biotelemetry is commonly used in bloodpressure, blood flow and heart rate researchon unanesthetized animals.

1. A biotelemetry system consists oftransmitter and receiver. The functionalblocks of a transmitter is as shown in thefigure. Physiological signals are obtainedby suitable transducer which are amplifiedand subjected to modulate the carrierwaves for transmission. The receiverreceives the transmission and demodulatesto separates to separate the signal fromthe carrier waves to display or record thesignal as shown in the block diagram.

Physiolog icals igna ls

B ioe lectricalvariab le

Physiolog icalvariab le Transducer

Excita tion

Am plif ie r Processor M odulator

Carrie r wavegenera to r

Tuner Demodula to r D isp lay orrecord

Biotelemetry Transmitter

Biotelemetry Receiver

BIOTELEMETRY SYSTEM

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1. The modulation of carrier waves can becarried out either by amplitude modulationor by frequency modulation. In amplitudemodulation, the amplitude of the carrierwaves is caused to vary with the informationsignals being transmitted. In frequency

METHODS OF MODULATION modulation, the frequency of carrier waveis caused to very with the informationsignals being transmitted. Amplitudemodulated transmission is susceptible tomodulated transmission is less susceptibleto electrical interference. The amplitudesand frequency modulation are as shown inthe figure.

MULTIPLEXING

Unifo rm amplitude

Am plitude Varies

LowFrequency

H ighFrequency

Carrier Waves

Amplitude Modulation

Frequency Modulation

2. In case transmission carrier is in the formof pulses instead of sine waves, thetechnique of modulation is known as pulsemodulation. If amplitude of the pulses is usedto convey the transmitted information, themethod is called pulse amplitude modulation(PAM). If the width of pulses is varied toconvey transmitted information, the methodis known as pulse width modulation (PWM).

1. When many physiological signals are to betransmitted simultaneously, the method offrequency multiplexing is used. In thismethod, low frequency carrier waves(subcarrier) in audio freqency range areused. The subcarriers are modulated by thephysiological signals which further modulate

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Highest am plitude

Th = highest durationTi= low est dura tion

Lowest am plitude

Th T l

Pulse Amplitude Modulation

OBJECTIVE TYPE QUESTIONS

Fill in the gaps

1. ________ is a method of measuring biologicalparametes from a distance.

(a) Biomeasurement (b) Biotelemetry

2. ________ is a device which acouticallyamplify the heart beats. (a) Stethoscope (b)Acoutiscope.

3. Patients with heart problem can wear _____telemetry unit.

4. _______ helmet is used for mentallydisturbed children to monitor their EEG.

(a) Cricket (b) Football

5. ________ biotelemetry is used for studiesof muscle damage or partial paralysisproblem. (a) ECT (b) EMG

6. In _______ modulation, the amplitude ofcarrier is varied with information signal.

(a) frequency (b) amplitude

7. In _______ modulation, the frequency ofcarrier is varied with information signal.

(a) frequency (b) amplitude

8. If amplitude of the pulses is used to conveythe transmitted information, the method isknown as _____ . (a) PAM (b) PWM

9. If width of the pulses is used to convey thetransmitted information, the method isknown as _______ . (a) PAM (b) PWM

10. When many physiological signal aretransmitted simultaneously, the method of_______ is used. (a) signal multiplexing (b)frequency multiplexing.

Pulse Amplitude Modulation

the RG carrier of the transmitter. Eachphysiological signal is placed on a subcarrierof a different frequency and all subcarriersFrequency multiplexing is more efficient andless expensive as compared to the methodof employing separate transmitter for each

physiological signal. At receiving end,transmission is received and demodulated torecover each of the separate subcarrierswhich are individually demodulated toretrieve original physiological signals.

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ANSWERS

1. (b) 2. (a) 3. (b) 4. (b) 5. (b) 6. (b) 7. (a)8. (a) 9. (b) 10. (b)

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INTRODUCTION

1. There are numerous applications of the digitalcomputer in medicine and its related fields.The ability of the computers to store verylarge quantities of data and to have it readilyavailable for further processing makes themextremely useful in medicine. Computers canalso be used in conjunction with biomedicalinstruments so as to make possible digitalcontrol of all functions of the instruments.Since computer has large data storagecapacity, it is possible to optimize themeasurement conditions of instruments. Theincorporation of computer into instrumentsenables the instruments to have a certainamount of intelligence or decision makingcapability. The most powerful asset of thecomputer is its enormous speed of operation.This is possible as the computer can storeall the necessary instructions and data in itsmemory. Data is processed by centralprocessing unit (CPU) of the computer.

1. In hospital, there are three types of datawhich are required to be acquired,manipulated and archived. Data can be (1)alphanumeric (2) medical images and (3)physical signals. Alphanumeric data consistsof the patient’s name, his address, hisidentification number, the results of hislaboratory tests and his medical history.Alphanumeric data are generally managedand organised into a database. The databasesystem is designed to store large data whichcan be retrieved conveniently and efficientlyto provide the information required. Medicalimages are data obtained from CT scan,magnetic resonance imaging and ultrasound.Image data are generally archived on film.Latest trend is to use picture archiving andcommunication system (PACS) generally.

CHARACTERISTICS OF MEDICALDATA

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M edica l data

A lphanum eric

M ed ica l images

Physica l s ignals

In this system, the data of images is storedin digiticized form on optical disks. The dataof images is distributed on demand over ahigh speed local area network (LAN).Images can be reconstructed graphicallywith very high resolution at different wardsof the hospital with the help of the data.Physiological signals are theelectocardiogram (ECG), the electroenc-ephologram (EEG), and blood pressuretracings. These are physiological signalswhich are monitored during surgery andsuch data is to be processed in real time. Ifthe instrument gives abnormal readings ofthe physiological signals, the computersystem must know immediately and displaythese readings with warning while analysingthe continuous data of physiological signals.

hospital from many sources likedoctor’s reports, laboratory tests andadmission and discharge entries. Thereis also non patient data like accountingrecords, inventory of medicine, recordof hospital staff and inventory of alltypes. It is impossible to store andretrieve quickly such informationwithout the help of a computer.

(c) Data reduction and transformation:Physiological signals are useless in rawform. The data has to be subjected toreduction and transformation by theusage of algorithms in computer toobtain meaningful information. Thecomputer can carry out by datareduction and data transformation whichis used in CT scanning for thereconstruction of image.

(d) Mathematical operations: In medicinemany important variables are calculatedby other variables which are accessibleto instruments. For example, manyrespiratory parameters can becalculated from simple breathing tests.However we can program thecomputer to work with the measuringinstrument to give directly the desiredvariables instead of the variables thatare accessible by carrying outsimultaneous mathematical operations.

(e) Pattern recognition: In order to convertphysiological data (in analog form) intomeaningful form of useful parameters(in digital form) important features ofa physiological waveform or image areto be firstly identified. Computer canmake pattern recognition by identifyingunique features. For example computercan be programmed to search data ofECG signals to identify each of theimportant peaks. The downward slopewhich is most negative between R andS waves of the QRS complex can beeasily identified as shown in the figure.

APPLICATION OF COMPUTER INMEDICINE

1. The applications of computer are :

(a) Data Acquisition : The data outputfrom the instruments is in analog form.The sampling and digitizing as well asidentification and formatting of datafrom the instruments are carried out bycomputer. The computer can beprogrammed to reject unacceptablereadings.

(b) Storage and Retrieval : The computerhas ability to store large quantity of datawhich can be retrieved very quickly.During day to day working, largeamount of data are accumulated in a

Types of Medical Data

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P

R

Q S T B lood

Pr

Tim e

(f) Initiate control : Computer can initiatecontrol over other devices as per theprogramming. The input data can becompared and controlled by providingfeedback to source of the data by thecomputer as shown in figure.

(g) Accuracy : Computer can be used tocontrol the accuracy of a device withinthe upper and lower limits asprogrammed.

(h) Averaging : Computer can easilyaverage continuous data over a certaintime duration. This technique is usedto remove the noise signals from thephysiological signals as it is done inECG.

(j) Calibration : Many devices have to bezeroed and recaliberated after certaintime intervals. Computer is used witha such devices to perform thecalibration autormatically.

(k) Table lookup : Table look up andinterpolation can be performed withcomputer. This procedure can be usedfor the determination of parameterswhich are dependent on more than onevariable.

(l) Formatting, printing and display :Computer process data in digital formwhich can be formatted. The raw datacan be converted into physical datawhich can be printed. Hence no furthertranscribing or processing is required.Computer can present the data in themost meaningful form. Data can bepresented in the form of graphs, chartsand tables.

APPLICATION OF COMPUTER INHOSPITAL

Pattern Recognition

Computer

Patien t Sensor Processor

Control

1. We have seen the applications of computerin medicine on broad basis. Now we seewhat are the specific applications of thecomputer in a hospital which are :

(a) Centralised data of outpatient : Thedata of an outpatient from abinitio tohis admission and discharge includinghis laboratory tests are fed through thecomputers to the central dataprocessing system of the hospital whichhelp in storage, quick retrieval of anyinformation about the patient at any timeand white billing him. It helps in thecoordination of various departments ofthe hospital in carrying out the treatmentof the patient which also reduces thewaiting time for the patient when histreatment involves various departments.

(b) Monitoring of Patients’ treatment :Every hospital has intensive care unitand critical care unit where continuousmonitoring of ECG waveform, blood

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pressure, heart beat temperature andrespiratory rate of every critical sickpatient has to be maintained through thecomputer and the computer gives alarmwhenever there is any abnormality inthe physiological signals of any patient.

(c) Assistance in diagnosis : The computergives clear information on the basis ofthe physiological signals of the patientwhich can be easily interpreted by thephysicians for the diagnosis of thesickness.

(d) Imaging : Computers are used in digitalradiography, computed tomography,magnetic resonance, nuclear medicineand position emission tomography toreconstruct images (by non invasivemethods) of the internal organs of thepatients.

(e) Automation of clinical laboratory : Theblood, urine and other specimen can betested quickly with the help ofcomputer. It is possible with the helpof computer to carry out the laboratorytest and also to feed the test resultsdirectly into database system of thehospital which can be accessed to byany doctor or department.

(f) Inter department communication :Local area network or client/serverenvironment helps in any hospital tocommunicate between one departmentto another department throughcomputer for better coordination.

(g) Biotelemetry: The are many instancesin which it is necessary to monitorphysiological events from a distance.Biotelemetry is the measurement ofbiological parameters over a distance.It is used for special out patients whoare discharged from the hospital butthey require monitoring from thehospital. The monitoring function isperformed by either through radiotelemetry or through landline telemetry.The radio telemetry uses a small radiotransmitter attached to the patient thatcan pick up the ECG and otherphysiological signals which aretransmitted to a receiver at a centralmonitoring system of the hospital. Thelandline telemetry uses a modem andcomputer to transmit the physiologicalsignals through telephone lines to thehospital.

OBJECTIVE TYPE QUESTIONS

Fill in the gaps1. --------- can be used for digital control of

all functions of the instrument. (a) computer(b) circuit

2. Computer has --------- storage capacity.(a) small (b) large

3. Incorporation of computer into instrumentsprovides certain amount of ---------.(a) reliability (b) intelligence

4. Data is processed by --------- of thecomputer. (a) memory (b) CPU

5. In hospital, there are --------- types of datato be handled. (a) two (b) three

6. In PACS, the data of images is stored on---------. (a) film (b) optical disks

7. Physiological signals are --------- in rawform. (a) useful (b) useless

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ANSWERS

1. (a) 2. (b) 3. (b) 4. (b) 5. (b) 6. (b) 7. (b)

8. (a) 9. (a) 10. (b)

8. The computer can make pattern ---------.(a) recognition (b) reconstruction

9. --------- uses a small radio transmitterattached to the patient. (a) radio telemetry

(b) land line telemetry

10. It is possible to monitor physiological eventsfrom a distance by ---------.(a) biocommunication (b) biotelemetry

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We enjoy the moment better by taking it one step at a time

INTRODUCTION

1. Telemedicine as name suggests, is the

application of computer technology and

telecommunication to provide health care

from one place to another. Telemedicine uses

information technology to provide timely

treatment to those in need by

telecommunication of the necessary

expertize, diagnosis and information among

distant located parties. Physicians,

laboratories and patients can be distant

located parties. Telecommunication enables

all parties to interact as they are at one place,

resulting in improved patient care and

management, cost effectiveness and better

utilisation of expertise. Telemedicine includes

hardware, software, medical equipment and

communication link.

TELEMEDICINE APPLICATION

1. Telemedicine can be applied to all medicalspecialities but its main applications are

commonly found in pathology, cardiology,radiology and medical education.

Telepathology is used to obtain an expert

opinion on biopsy reports and microscopic

photos of pathology slides. Teleradiology is

used for telecommunication of radiology

images like radiographs, CT scan, MRI and

nuclear medicine from one place to another

for expert interpretation and consultation.

The problem faced in teleradilogy is the vast

data associated with each image and lack of

standardization of data for transmission.

Telecardiology relates to telecommunication

of ECG, echo cardiography and colour

dopler of patient to experts for advice.

Teleconsultation is used by the hospital or a

patient to consult specialist docters. Tele

education can be used for providing medical

education to junior doctors working at

smaller towns who are professionally

isolated from teaching hospitals. The block

diagram of a typical telemedicine system is

as shown in figure.

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Dish transm itting

Sate llite

D ish rece iv ing

Patien t

O nline ECG

Stored ECG

Radiography

CT Scan

M RI

Patholog ical report

Pa tien t data

Scanner

Data

Server com puter

o f rece iv ing cen tre

Printer

V ideo C lips

Audio m essages

Im ages

Video Conference Arch iv ing

Analys is software

Application software

2. Telemedicine concepts can be :

(a) Store and Forward : In this, informationis compiled and stored. The storedinformation can be in the form of videoimages and clips or laboratory reports.The information in the digital form isstored and forwarded to the experts forinterpretation and advice. The expertscan access the same whenever possibleand they can transmit back their advice.

(b) Real time : In this, real time exchange

of information takes place between two

medical professionals or two centres.

The real time exchange of information

may be in the form of video conference

or it may take place simultaneously with

the examination and imaging of the

patient.

1. Integration of medical imaging devices andimage processing facilities has firstlyevolved picture archiving andcommunication system (PACS).Advancement in information technology hashelped in transmission of medical images toone place to another and PACS has beensuitably modified as shown in the figure. Theimaging devices transmit the acquired

Telemedicine System

PICTURE ARCHIVING ANDCOMMUNICATION SYSTEM

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images through the network using astandardized transmission protocol. Theimages have to be compressed to reduce thedata as well as their time for transmission.Inorder to avoid accidental erasing, digitalimages are stored on a meduim capable ofstoring a large number of images in a readonly memory as data base system to facilitatefast retrieval. Images can be viewed at any“image display station” or “diagnostic workstation”. If required, algorithms can beapplied to the ‘image data’ to enhance certainfeatures or to interprete the clinicalinformation of the images. It is also possibleto attach reports and comments to theimages. A large number of methods areavailable for the transmission of images.Inside the hospital, local area network (LAN)

Picture Archiving and Communication System

X-ray film

Im aging devices Storage D isp lay & T ransfer

CT Scan

Radiography

G am m a cam era

Positron em iss ion tom ography

M RI

Film d ig itizer

U ltrasound im aging

D iagnostic work station

Im age d isplay station

Radio therapy PAC S

Im age arch ive

Term inal

Hard copy

is a good solution. However this has to doneby compression of data through algorithms.This transfer requires compression anddecompression algorithms as well as errordetection and correction devices in thesystem. The transmission of images toremote places has another problem. Thereis complete lack of internationally acceptedstandard to code the images for transmissionand also complete lack of a communicationprotocol for such coded images. The mostappropriate communication protocol is likelyto be “open systems interconnection” (OSI)being developed by ISO. The Americancollage of Radiology (ACR) with the nationalelectrical manufacturers Association(NOMA) have also prepared a standard forimage format and for communicationprotocol for transmission of medical images.

Com m unication

Network

Transm iss ion p rotocol

Im age fo rm at

Archiving

Data base

Storage facility

Im aging devices & processing

Im aging Eqpt

Computer

A lgorithm s

User in terface

D isp lay

Needs of Picture Archiving and Communication System

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The communication of medical imagesrequires (1) an agreement on the format ofrepresentation of the digital image data (2)a communication protocol and (3) eitherLAN within the hospital or any other meanof communication to distant locations. TheACR-NEMA image format containsfollowing information :

M ultip lex ing

Fixed station M ob ile sta tionSate llite

Tx

Re

M icrophone

Speaker

ECG

Charge coup le device/cam era

Audio p rocessor

Demultip lexing

Video p rocessor

Tx

Re

M icrophone

Speaker

ECG

Charge coup le device/cam era

Audio p rocessor

V ideo processor

(a) identification data of the patient

(b) data of the examination and imagingdevice used

(c) image representation data

(d) image pixel data

TELEMEDICINE BY MOBILECOMMUNICATION

ARC-nema Standard Interface

ACR-N EM A standard in te rface

Im aging device

ACR-N EM A standard in te rface

Network in te rface

unit

Im aging equ ipment

Network

Network inte rface

unit

1. Mobile telemedicine is now possible usingmobile communication and satellitecommunication as shown in the figure. Inmoving vehicle which has all necessaryequipment, works as a mobile station. Itobtains colour images, audio signal and

physiological signals such as ECG and bloodpressure etc. from the patient at the placeof sickness which is far away from thehealth care centre. These are transmitted tothe health care centre by the help of mobilecommunication. Multiplexing anddemultiplexing is used to reduce the time fortransmissions. The instruction for thesuitable treatment is sent to the mobile stationfrom the specialists at the fixed station.

Telemedicine by Mobile Communication

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1. The world wide web (www) is an internetresource. It has information producing siteswhich can be accessed by the general public.It is possible to use the world wide web forimparting teleeduction and for otherapplications of telemedicine. However it isbeneficial to have a dedicated link as it offerssecurity to the data and reliability tocommunication due to fewer users using thelink.

1. Medical information systems (MIS) arebeing created on a department basis whichas radiological information system (RIS) or

PAT IENT RECO RD S O F HO SPITALS

RADIO LO G ICA L PAT IENT RECO RD S

IM AG E DATA BAS E

HIS

RIS

PAC S

Comm unica te im ages to wards

O pera ting thea te r

Radio therapy

TELEMEDICINE AND INTERNET

MEDICAL INFORMATION SYSTEM

on a hospital basis such as hospitalinformation system (HIS). These informationsystems are created to contain andcommunicate patient data to any authoriseduser. It is of utmost importance that PACSshould be integrated to RIS and HIS foreffective utilization of all patient data.

1. Medical coding and classification systemsare expected to become increasinglyimportant in the health care sector. They areintegral part of the electronic healthinformation systems. The coding andclassification systems will be used toimprove the quality and effectiveness ofmedical services. Activities connected to thedifferent coding and classification systemsare very important attempts atstandardization which are taking place indifferent countries within the discipline ofmedical information. These activities mustsecure a proper professional and economicsupport. It is also of vital importance thatnational health authorities should participatein these activities so as to establish formalcooperation with professional bodies.

Integrated HIS, RIS and PACS System

OBJECTIVE TYPE QUESTIONS

Fill in the gaps1. --------- is to produce health care from one

place to another. (a) telecommunication(b) telemedicine

2. --------- is used for telecommunication ofimages. (a) teleradiology (b) telepathology

3. --------- relates to telecommunication ofECG. (a) telepathology (b) telecardiology

4. --------- is used to obtain an expert opinionon biopsy reports. (a) telepathology(b) teleconsultation

5. --------- is integration of medical imagingdevices and image processing facilities.(a) PACS (b) MIPS

6. Images have to be --------- to reduce thedata for transmission. (a) modified(b) compressed

7. --------- has a fixed station and a mobilestation. (a) mobile telemedicine(b) telemedicine

8. Inside the hospital, --------- is a good solutionfor transmission of images. (a) WAN(b) LAN

MEDICAL CODING ANDCLASSIFICATION

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ANSWERS

1. (b) 2. (a) 3. (b) 4. (a) 5. (a) 6. (b) 7. (a)

8. (b) 9. (b) 10. (a)

9. The --------- is an internet resource.(a) international wide web (b) world wideweb

10. The most likely communication protocol is--------- for transmission of images. (a) OSI (b) COI

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Sulking about your mistakes only leads to future ones.

INTRODUCTION

1. The collection of data usually called databasecontains information relevant to anenterprise. The primary goal of a data basemanagement system (DBMS) is to providea way to store and retrieve databaseinformation that is both convenient andefficient. Database systems are designed tomanage large quantities of information.Management of data involves both definingstructure for storage of information andproviding mechanisms for the manipulationof information. In addition, the databasesystem must ensure the safety ofinformation stored despite system crashesor attempts for unauthrorised access.Criteria is used to retrieve information fromthe database. The way the data is stored inthe database determines how easy it is tosearch for information based on multiplecriteria. Database is designed such that datashould also be easy to be added and removedfrom the database.

DATABASE ENVIRONMENTS

1. Various possible environments exist for adatabase which can be (1) the mainframeenvironment (2) the client/serverenvironment and (3) the internet computingenvironment. The mainframe environmentconsists of a powerful mainframe computerand multiple dumb terminals which arenetworked in the mainframe computer. Thedumb terminals depend on the mainframecomputer to perform all processing. Clientserver environment consists of a maincomputer, called a server and many personalcomputers that are networked to the server.The database resides on the server. Each userwho wants access to the database on theserver should have his own personalcomputer.

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M ainfram e com puter

Dumb te rm inals

Internet environment is similar to client/server computing. A user must have aninternet connection and a supported web

browser installed on the PC. The webbrowser connects the PC to the web server.

Server DatabaseCorporate in terne t

PC (c lien ts)

In te rne t

W eb server

Database

PC

In te rne t W eb browser

The Mainframe Environment

Client/Server Enviroment

Internet Computing Environment

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1. Database Redundancy : In databasedesign, database redundancy has to beremoved. Redundancy means repetition ofrecords or duplicate records existing in thedatabase. Therefore the duplicate recordsmust be removed during the design ofdatabase using normalization of database.

2. Consistency : It means that the data basemust remain consistent before the start oftransaction and even after the completionof the transaction during the use of thedatabase.

3. Integrity : It means the data base must beaccurate. Integrity of database is accuracy.

4. Anomalies : There are three types ofanamolies during the design of databasewhich are :

(a) Insertion anamolies. They are developeddue to wrong insertion of data.

(b) Updation or modification of databaseanamolies. They are developed whileupdating or modifying the database.

(c) Deletion anamolies. They are developedduring deletion of some data.

ASPECTS OF DATABASE DESIGN

NORMALISING OF DATABASE

1. The anamolies are removed by using theconcept of normalization of the database.The normalising is used to remove both theinconsistency and redundacy of the databasewhile designing database. Normalising ofdata base is carried out step by step by usingnormal forms which can be (1) first normalform (2) second normal form (3) thirdnormal form (4) boyee code normal form(BCNF) (5) fourth normal form (6) sixthnormal form and (7) project join normalform (PJNE) and dynamic key normal form(DKNF). While carrying out first normalform, it is ensured that in the domain of each

relation, only one value is associated to eachattribute and the relation must be in tabularform. Second normal form normalising canbe carried after data has been normalised inthe first normal form and one prime attributekey is selected from the set of such aattributes of relation in such a way that othernon prime attributes are fully functionaldependent on the prime attributes key. Afternormalising for second normal form,normalising for third normal form is carriedout. In this, it is established how otherattributes are partially dependent on theprime attributes key. Similarly other normalforms are applied to normalise the database.

CLIENT/SERVER TOPOLOGIES

1. A single centralised server cannot handlelarge number of clients. Hence a commonsolution is to use the cluster of machinesarranged in some topology. There are varioustopologies of client /server database whichare :– (1) Ring topology (2) centralisedtopology (3) hierarchical topology and (4)centralised plus ring topology. In ringtopology, a number of machines areconnected to one another in the shape ofclosed loop so that each machine isconnected directly to two other machines,one on either side of it. The machinesarranged such in a ring, act as a distributedserver. The ring topology is easy to beestablished but any break in a linkbetween any two machines

Ring Topology

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causes a total breakdown. Centralisedtopology is the most commonly used formof the topology. The topology has typicalclient/server pattern used by the databases,web servers and other simple distributedsystems. All information and function arecentralized into one server with many clientsconnected directly to the server to send andreceive information. Hierarchical topologyhas long history of usage in the field ofinternet. The best known hierarchical systemon the internet is the “domain

Centralized Topology

c

s

c

cc

server

C lien t

name service” where authority flows fromthe ‘root name server’ to the server for theresistered clients. In centrilized plus ring

Hierarchical Topology

Root name server

Server

R

C lien t

cc

c

c

topology, the server itself is a ring but thesystem as a whole including clients is ahybrid. The servers are connected in a ringand other machines are connected to ring.This topology has simplicity of a centralisedsystem with the robusress of a ring.

Centralized Plus R ing Topology

S

S S

S

S

S

c

cc

c

NETWORK SECURITY1. Any system attached to a network is exposed

to a wide range of security threats. Anunconnected system has high security butit has no access. Hence network access andsecurity risk are two opposing requirements.A computer network is interconnection of alarge number of computers to increase theiraccess to data while security is designed tocontrol access. Network security has to bedesigned in such a way that there is a balancebetween open access and security. Securitycan be maintained by: (1) secrecy (2)authentication (3) non-repudiation (4)integrity control and (5) privacy.Cryptography has become one of the maintool for privacy, trust, access control,electronic payments, corporate security andother fields. Cryptography is a method ofhiding information which is intelligible to onlythose we intend to understand it. The art ofdevising ciphers to hide the information iscryptography and the art of breaking ciphersis called crypt analysis. The information ormessage is firstly encrypted so as to convertit to the cipher text. There are many kindsof ciphers to encrypt the messages. Thecipher text is transferred through networkto the intended reader who can decrypt the

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ciplier text to the intelligible message asshown in the figure. Two fundamentalprinciples are followed in cryptography :

(a) All encrypted messages must containsome redundancy.

(b) Some measures must be ensured toprevent active intruders to play backthe old messages.

M essage C ipher text

ENCRYPT

DECRYPT

M essage

2. Patient files on a computer can be accessedby anyone with sufficient know-how. Theintegration of medical information systemthrough network makes it even moredifficult to secure the files againstunauthorised access. Passwords andciphering are used to secure the data.

The Method of Encryption

Fill in the gaps.1. --------- system are designed to manage large

quantities of information. (a) database(b) informative

2. The mainframe environment has a powerfulmain frame computer and multiple ---------terminals. (a) intelligent (b) dumb

3. In client / server environment, the databaseresides on the -------- (a) client (b) server

4. Internet environment is similar to ---------computing. (a) client /server (b) mainframe

5. --------- is the repetition of records.(a) conistency (b) redundancy

6. --------- of database is accuracy.(a) integrity (b) consistency

OBJECTIVE TYPE QUESTIONS

ANSWERS

1. (a) 2. (b) 3. (b) 4. (a) 5. (b) 6. (a) 7. (b)8. (a) 9. (a) 10. (a) 11. (b) 12. (b)

7. --------- anomalies are developed due towrong insertion. (a) filling (b) insertion

8. The anamolies are removed from thedatabase by using the concept of ---------.(a) normalising (b) filtering

9. A balance has to be maintanced between openaccess and ---------. (a) security(b) restricted access

10. --------- are used to encrypt the message.(a) ciphers (b) encryptor

11. The art of breaking ciphers is called---------. (a) cryptography (b) crypt analysis

12. In medicine, --------- and ciphering are usedto secure the data. (a) authentication(b) password

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1. Bill Bryson Black Swan (2004): A Short History of Nearly Everything, Great Britain.

2. Bronzino Joseph D. (Editor-in-chief): The Biomedical Engineering Handbook, CRC Press(Aug 2001).

3. Chaffin. D.B. and Andersons G.B.J. (1991): Occupational Biomechanics, John Wiley andsons, New York.

4. Chaurasia’s B.D: Human Anatomy (2nd Edition), CBS Publishers and Distributors, Delhi.

5. Cromwell Leslie, Weibell Fred J and Pfeiffer Erich A (2004): Biomedical Instrumentationand Measurement (2nd Edition), Pearson Education, Delhi.

6. Crownin Shield R.D. and Brand R.A.: A Physiologically based Criterion on Muscle ForcePrediction in Locomotion, Journal Biomechanics, 14: 793–801 (1981).

7. Das S (1994): A Concise Textbook of Surgery (fifth edition).

8. Digital Imaging in Health Care, Economic commission from Europe, Geneva (1987).

9. Dr. Sinha C.K. (1996): Self Study Guide, Scientific Book Company, Patna.

10. Guha Sujoy K. (Editor) (1947): Trends in Biomedical Engineering, CBME Publication, NewDelhi.

11. John G Webster (Editor): Medical Instrumentation: Application and Design (3rd Edition),John Wiley and sons (Asia) Pvt. Ltd. Singapore.

12. Johnson Dul. J, Shiavl G.E. and Townsend M.A.: Muscular Synergism–A minimum FatigueCriterion for load sharing between Synergistic Muscles, Journal Biomechanics, 17: 663–673 (1984).

13. Karz Douglas S., Math Kelvin R. and Groskin Stuart A.: Radiology Secrets, Jaypee Brothers,New Delhi.

14. Khandpur R.S. (2003): Handbook of Biomedical Instrumentation (2nd Edition), Tata McgrawHill Publishing Company, New Delhi.

15. Kindersley Dorling: Ultimate Visual Dictionary, London.

16. Kirby R. and Roberts J.A.: Introducing Biomechanics, Movement Publications, New York.

17. Life, the Universe and Everything, Hindustan Times Paper, New Delhi (11 April 2006).

18. Nawoczenski Deborab A. and Epler Marcia E.: Orthotics in Functional Rehabilitation ofthe Lower Limb.

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Page 270: Fundamentals of biomedical engineering

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19. Nordin M. and Frankel Y.B. (1989): Basic Biomechanics of the Mulculoskeletal System(2nd Edition), Lee and Pebinger, Philadelphia.

20. Norkin Cynthia C.: Physical Rehabilitation: Assessment and Treatment—Gait Analysis.

21. Radha Krishan P., Subramanyan S. and Raju V. (2005): CAD/CAM/CIM, New Age Publication,New Delhi.

22. Seireg A. and Arvikav R.J. (1973): A Mathematical Model for Evaluation of Force inLower Extermities of Musculoskeletal System, Journal Biomechanics, 6: 313–326.

23. Sharma C.R.: Computer Network, Jaico Publishing House.

24. Siwash Michael: Hutchison’s Clinical Method (19 Edition), ELBS.

25. Sonka Milan; Hlavac Vaclav and Boyle Roger: Image Processing, Analysis and MachineVision (2nd Edition), Vikas Publishing House.

26. Snell Richard S.: Clinical Anatomy for Medical Students (3rd Edition), Little Brown andCompany (Boston) Toronto.

27. Tompkins Willis J. (Editor) (2004): Biomedical Digital Signal Processing, Prentice Hall ofIndia, New Delhi.

28. Vitali Miroslaw, Robinson Kingsley P., Andrew Brain G. and Harris Edward E.: Amputationsand Prostheses, Baillie’re Tindall, London.

29. William M and Lisaner H.R. (1977): Biomechanics of Human Motion (2nd Edition), Saunders,Philadelphia.

30. Wictorian C.H. and Nordin M. (1982): Introduction to Problem Solving in Biomechanics,Lee and Filiger, Philadelphia.

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AA below knee prostheses 132Abduction and adduction 4Absorption unsharpness 199Active transducers 171Advantages of ultrasound 224Agonist 51Airways resistance measurements 119ALCAP ceramics 160Algorithms 192Alumina 159An above knee prostheses 133Analog to digital transduction 178Analysis of force on the shoulder joints 65Anatomical terms and planes 1Anatomy of spinal column 58Antagonist 51Aortic balloon system 138Application of computer in hospital 245Application of computer in medicine 244Application of polymers 156Applications of bernaulli’s equation 29Artificial heart 138Artificial ventilation and ventilators 119Aspects of database design 257Asynchronous pacemaker 136

BBack projection 210Ball & socket joints 55Barriers of communication 237Bernaulli’s equation 29Bioceramics 158Bioelectrical signals 169Biogradable polymeric biomaterials 165Biomedical engineering 34Biopotential electrodes 179Body surface electrodes 179Bone cement fixation 167Bone fractures and traction 43Bronchography 202

CCalcium phosphate 160Carbons 159Cardiac pacemaker 135Cartilaginous joints 53

Cell, DNA and atoms 19Centre of gravity 25Characteristics of medical data 244Circumduction of shoulder joint 5Classification of bones 38Client/server topologies 257Cloning 20Communication process 236Communication 211Composite biomaterials 162Composition of bones 40Compression 192Computed Tomography 204Concentric contraction 50Condyloid joints 54Connective tissue 13Corals 160Corrosion of metallic implants 148

DData acquisition system 208Database design topologies and network security 255Database environments 225Defibrillator 138Dental metals 148Digital image acquisition and processing 186Digital subtraction angiography 202Digital transformation 184Disadvantages of ultrasound 224Doppler ultrasound 223

EEccentric contraction 50Elements of digital image processing system 186Elements of digital image system 207Ellipsoid joints 54Epithelium 13Equation of continuity 29Equipment for nuclear medicine 232Eversion of foot 5

FFibrous joints 52Filtered back projection 210Filtering 182Flexion and extension 3Flow in tube 28Fluid connective tissue 13

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Fluid mechanics 27Fluoroscopy 200Forces on the hip joint 75

GGait analysis 127Gauge pressure 31Glass ceramics 159Gold 148Grey level thresholding 192

HHealth care information andcommunication 235Health communication 237Hemodialysis 138Hinge joint 53Histogram 190Histology 13

IIdeal fluid 28Image formation 197Image intensifier 201Image reconstruction 189Image resolution 222Image sharpness 199Inductive passive transducers 174Infrared thermometers 176Interaction of nuclear radiation with matter 228Inversion of foot 5Iterative method 209

LLaminar and turbulent flow 428Level of image data representation 191Limitation of radiography 202Linear variable differential transformer (LVDT) 174Lock up tables 190

MMagnetic resonance imaging 213Magnification 198Mass miniature radiography 202Measurement of radioactivity 229Mechanical fixation 168Mechanical properties of bone 40Mechanics of kidneys 122Mechanics of lower limbs 74Mechanics of the ankle 87Mechanics of the elbow 66Mechanics of the hip 75Mechanics of the knee 82Mechanics of the shoulder 63Mechanics of upper limbs 62Mechanics 23Medical coding and classification 253Medical glossary 8Medical information system 253Medical terminology 6Metallic biomaterials 146Microelectrodes 179

Movement unsharpness 199Movements of neck and spine 59Multi-slice computed tomography 211Muscular tissue 15

NNeedle electrodes 179Nernst potentials 148Nervous tissue 15Network security 258Newtonian fluids 27Non inert (biodegradable) ceramics 160Non Newtonian fluids 27Normalising of database 257Nuclear medicine 232

OOperating principle of nuclear medicine 232Orthopedic prostheses fixation 167Orthosis for gait disability 142Orthosis 141

PParaplegic orthotic walking system 143Particulate inclusions 163Pascal’s law 30Passive transducers 172Pathological hip joint 81Patient monitoring displays 139Photography or x-ray film 196Physiological signals and transducers 169Physiological systems of the body 16Picture archiving and communication system 250Pivot joint 54Plane joint 53Plastic fluid 27Plate for bone reduction 44Poly disparity index 152Poly methylmeth acrylate 156Poly vinyl chloride 155Polyethylene 155Polymeric biomaterials 151Polypropylene 155Polystyrene 155Porous composite 164Positron-emission tomography 233Principle of MRI 213Principle of tomography 204Processing unit 208Projection and view 198Pronation of forearmProstheses for lower limb 130Prostheses 127Prostheses: clinical requirements 130Pump oxygenerator 137

QQuality of diagnostic radiographs 200

RRadioactive decay 229Radiography system 195Radiography 194

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Radioisotopes and radiotherapy 226Radiotherapy 230Raster and frame buffer of a computer 187Rehabilitation of a paraplegic 135Relative density of structure on CT 207Relatively inert (nonabsorbable) bioceramics 158Rotation of shoulder 4

SSaddle joints 54Sarcomeres 50Scanning 221Scatter control 200Selection of polymeric biomaterial 153Signal amplification 182Signal averaging 183Signal processing in bioinstrumentation 182Signal processing 181Single photon emission tomography 233Single pulley traction 44Skeletal muscles 50Sources of health information 235Speciality area of biomedical engineering 34Spiral CT scanning 211Stainless steel 147Storage phosphor system or computed radiography 196Strain guage 172Structure of composite 162Supination of forearm 5Synovial joints 53

TTelemedicine and internet 253Telemedicine application 249Telemedicine by mobile communication 252Telemedicine 249Temperature measurement 175Temperature 31Tendons and ligaments 48Terms related to movements 3The artificial kidney (dialyzer) 125The biochemical system 18The cardiovascular system 17The digestive system 19The direct digital detector 197

The elbow joint 69The excretory system 19The locomotor system 19The mechanics of respiration 113The nervous system 18The respiratory system 18The respiratory tract 111The ultrasound transducer 222The volume and capacities 115The volume, capacity and measurement 116Thermistors 175Thin tube 29Three pulleys traction 45Tissues between jointsTitanium and alloys 147Torricell’s theorem 30Transducer 171Transduction for displacement, velocity andacceleration 177Transduction principle and applications 176Transgenic animals 20Tricalcium phosphate ceramics 160Type of radioactive decay 226Types of communication 236Types of synovial joints 53

UUltrasound imaging 220Ultrasound machine 223Ultrasound wave 220Uses of health information 235

VVariable capacitance 175Variable reductance 174Ventilators 138Vision processing 188

WWorking of ultrasound 222

XX-rays and x-ray tube 194

ZZirconia 159