basic concepts of medical instrumentation - Engr. Ijlal Haider
94898724 Medical Instrumentation
-
Upload
nguyen-tan-nguyen -
Category
Documents
-
view
23 -
download
0
Transcript of 94898724 Medical Instrumentation
-
Dr Shanthi Vijayaraghavan
Professor , Gastroenterology , SriRamachandra University
Consultant gastroenterologist , Lifeline Hospitals , OMR
-
Overview Endoscopy and new techniques Lasers Diathermy Electrical safety
-
ENDOSCOPY
-
Endo inside
Scopy examination of
Endoscopy looking inside
-
PRINCIPLES OF ENDOSCOPY In all flexible endoscopic system light is
transmitted down the endoscope shaft to illuminate the surface to be examined.
The reflected image is conveyed back to the endoscopist via one of two different modalities
A. Fiber optics
B. Electronics
-
Fiber optic Endoscopy
a fixed lens at the end of the instrument shaft focuses the image on internal fiber optic bundle.
The bundle is 2-3mm wide &has20,000-40,000 fine glass fibers, each approx 10mm dia.
The image undergoes a series of internal
reflection with in each fiber as it is transmitted up the bundle.
-
Electronic Endoscopy
Most endoscopes currently are electronic.
image is reflected onto a charge coupled device [CCD] chip mounted on the end of instrument
chips contain 100,000 to 300,000 pixels.
-
1 Function buttons, e.g., video recorder remote control 2 Freeze button 3 Suction button 4 Air/water button 5 Instrument channel 6 Locking device 7 Angling wheel (right/left) 8 Angling wheel (up/down)
-
Tip of Endoscope
-
Video processor (above) and light source (below)
-
Gastrointestinal Endoscopy
Types of Gastrointestinal Endoscopy
Upper GI Endoscopy
Colonoscopy (Lower GI Endoscopy)
Small Bowel Enteroscopy
Endoscopic Retrograde Cholangiopancreatogram (ERCP)
-
Capsule Endoscopy
-
Capsule Endoscopy
-
Endoscopic Ultrasound The ultrasound probe is
placed at the tip of the scope
Allows ultrasonography of organs from a close distance
Individual layers of the GI wall are visualized as distinct layers
-
Magnification Endoscopy
Principle. Magnification endoscopy, known also as zoom endoscopy, can be used for the detailed endoscopic evaluation of suspicious areas, especially after staining
-
Virtual Endoscopy steps:
3D imaging of the organ of interest (e.g using CT, MRI)
3D preprocessing
3D image analysis
-
Virtual Endoscopy Features Advantages:
there are no restrictions on the movement of
virtual endoscope (it can be moved anywhere
through the body)
avoids insertion of an instrument into a natural
body opening or minimally invasive opening
no hospitalization
Disadvantage:
current virtual endoscopy techniques do not
reveal the look of the tissue surface (3D
imaging techniques do not reveal
-
Latest trend is throw-away endoscopes that feature a miniaturized sensor and downstream video-processing circuitry
-
Delivery systems
Free beam
Optical fiber
Articulated arm
Lens
-
Selected Applications of Lasers in Medicine Diagnostic: Goal is to learn something about the tissue Therapeutic: Goal is to modify the tissue, e.g. kill malignant cells.
-
Lasers in medicine: blood and blood flow in the tissues
Where do we use lasers? (some examples)
destruction ...
treatment (eg. photodynamic therapy in cancer) surgery - the CO2 laser scalpel - removal of lens in cataract surgery of the eye
- caurtery of blood vessels in the retina
- welding of detached retina
imaging ...
skin blood flow (Laser Doppler Flow-mapping) curvature of the front of the eye (corneal topography) blood vessels and nerves of the retina - OCT (optical coherence tomography)
- SLO (scanning laser ophthalmoscope)
laboratory diagnostics ...
blood sample analysis microscopy of tissue samples
-
APC laser coagulation
-
Electrosurgical/Surgical Diathermy Units
Copyright 2007
-
62
Electrolysis (mainly near d.c.)
Neuromuscular effects (mainly 10-100Hz)
Heating (mainly 100KHz-30Mhz)
Physiological Effects of Electricity on the Body
-
63
For a (15-100Hz) current passing between the hands, the following effects are expected:
0.5-1mA Perception
10mA Cant let go
100mA Severe pain. Interference with breathing and heart function
1A Sustained heart contraction
Neuromuscular Effects
-
64
Macroshock:
Large current passing through the skin - a small proportion may pass through the heart
Microshock:
Current applied directly to the heart (e.g. pacing leads, intracardiac temperature/pressure lines).
Neuromuscular Effects
-
65
Na+ Na+ Na+
Cl- Cl- Cl-
_ +
Sodium atoms
created at electrode Chlorine atoms
created at electrode
Ionic Current
The formation of sodium atoms at the negative electrode and
chlorine atoms at the positive electrode causes local chemical
actions which kills the cells.
Electrolysis
Physiological Effects of Electricity
-
Copyright 2007
Some Basic Electrosurgery Facts
Used in about 80% of all surgical procedures
Very effective surgical tool Cutting
Coagulation
Fulguration
-
Basic Principles of Electrosurgery
Current conducted through a complete circuit including the generator, insulated cables, electrodes, and the patient
-
Copyright 2007
Monopolar Electrosurgery
-
Copyright 2007
Bipolar Electrosurgery
Electrosurgical
Unit
Tissue between
tips of forceps
Current
Flow
-
Copyright 2007
Electrosurgery Safety Features
Continuity Monitor
-
Copyright 2007
Electrosurgery Safety Features
Continuity Monitor Verifies that a return electrode is
connected to electrosurgical unit
-
Copyright 2007
Electrosurgery Safety Features
Return Electrode Contact Quality Monitor (RECQM)
-
Copyright 2007
Electrosurgery Safety Features
Return Electrode Contact Quality Monitor (RECQM)
Offers better level of protection than
continuity monitor
Assures that good contact exists between the dispersive electrode and patient
-
Copyright 2007
Dual Plate Return Electrodes
Interrogation current flows
between each plate of the
electrode and the patient. If
one side is partially detached
from the patient, an alarm
will sound.
-
Copyright 2007
Electrosurgical Accidents Skin Burns
Fires, Explosions Prepping Solutions, Surgical Drapes,
Bowel Gas
Oxygen-Enriched Atmosphere
Active Electrode Arc or Spark
Too Much/Too Little Power Delivered
Organ Perforations
-
Copyright 2007
A Misconnection Problem
-
Copyright 2007
Electrosurgical Accidents
Argon Beam Coagulators Gas Embolism
Interference
User Injuries Hand sensation
Alternate pathways
-
Active Electrode Accidents Inadvertent activation of the ESU due
to unintentional switch activation User places active electrode on the patient or
the surgical drape between intended activations
Safety holster not used Audible activation tone volume is set too low
Insulation failure along shaft during procedures, such as tonsillectomy causing burn to tissue inside mouth or to lip
User makes direct contact with nontarget tissue
-
Copyright 2007
Electrosurgical Injuries Return Electrode
Poor Site Preparation
Poor Application technique
Non-uniform Conductivity
Repositioning Patient
Electrode
-
Copyright 2007
Laparoscopic Electrosurgery
Monopolar vs. Bipolar
Current leakage though cannula
Insulation breakage
Fire
-
Copyright 2007
ESU-caused Fires
Heat, sparks, flaming gases
Rarely a device failure a known complication
-
82
Diathermy
Application of High-Frequency Electromagnetic Energy
Used To Generate Heat In Body Tissues
Heat Produced By Resistance of Tissues
Also Used For Non-Thermal Effects
-
83
Heating Effects - Surgical Diathermy
In Surgical Diathermy the heat is concentrated at the tip of the
probe because the current density (A/m2) is very high but at the
plate it is low. Heating will occur at the plate if the contact area
reduces (plate comes loose)
Skin Internal Skin
Current = I
Low
current
density at
return
electrode
Current = I
Very high
current density
at active
electrode
-
Shortwave Diathermy A deep-heating modiality Uses energy that is similar to broadcast
radio waves but has a shorter wave length
The energy is delivered to the body is acutally a high-frequency alternating current, but lacks the properties needed to depolarize motor or sensory nerves.
The Federal communication Commission has reserved the frequencies of 13.56, 27.12, and 40.61 for medical use
-
.
2 units that are commonly used The condenser unit
The conduction unit
-
Condenser unit patient within the actual circuit of the
machines unit 2 insulated plates are place on either side of
the site being treated The flow of electromagnetic energy passes
through the tissues, which act as electrical resistors and produce frictional heating
Heating occurs at depths of 2.5-5 cm but is uneven because of differences in the resistance to energy transportation of various tissues
-
Induction Unit
Does not place the patient directly in the units circuit.
Tissues are affected by radiation emitted form the electromagnetic field created by the electrode
may heat tissues up to 5cm beneath the skin
-
ELECTRICAL SAFETY
-
Hospital Safety
Human susceptibility to electric shock varies & depends on general state of health
position of any electrodes on the patient
dampness of skin
-
Safety Standards
Equipment is designed & built to comply with safety standards, namely BS EN 60601-1
This lays down constructional guidelines for medical equipment which influence the safety of the equipment
-
Safety Testing To BS EN 60601-1
Medical electrical equipment is divided into two classes Class 1
Class 2
And, three types Type B
Type BF
Type CF
-
Leakage Current & Loss of Grounding
MA
INS
PA
RT
AP
PL
IED
PA
RT
M
P
Class 1
A serious hazard due to the simple failure of basic insulation or the loss of ground lead will then produce a deadly situation of the metal case /equipment being at live mains voltage which may flow through the patient.
-
93
Connecting Medical with Non-Medical Equipment
IEC 60601 IEC XXXXX A/P
Functional
Connection
The medical equipment might draw large currents via the I/O portMake sure the I/O port is isolated from the enclosure and the A/P. If it is not or if unsure use an separation device
Electrical Hazards
-
94
N/C
N/
C
Ferrite
Ring
RCD circuit
L
N
I
live
I
Neutral
These sense the difference between currents in the live and neutral leads. If the difference exceed a set level a relay is operated to disconnect the supply
Residual Current Devices (RCDs)
-
95
Electrical Hazards
Incidents of Electrocution in Hospitals
Humidity in the plugs of blood and fluid heaters causing
device failure (Andersen C, Pold R, Nielsen HD. Ugeskr Laeger 2000; 162(6))
Accidental toppling of a fluid container causing spillage onto a
blood pressure monitor (Singleton RJ, Ludbrook GL, Webb RK, Fox MA. Anaesth Intensive Care 1993; 21(5))
Electric shocks to anaesthetists after touching a faulty device
and the chassis of another device simultaneously (Singleton RJ, Ludbrook GL, Webb RK, Fox MA. Anaesth Intensive Care 1993; 21(5))
-
96
Electrical Safety Testing Procedure
Visual Inspection
Earth Resistance
Insulation
Leakage Current
Earth Leakage
Current Touch Current Patient Leakage
Current
Electrical Safety Testing
-
Changed roles
Surgeons become computerized
Engineers, mathematicians and physicists enter the hospitals
-
Thank you