Mini C-Arm Credentialing Course

Course Overview

• 1.    Introduction–15 minutes Regulatory requirements

B. Introduction to HHS Policy Manual “Use of Mini C-arms by a Physician other than a Radiologist”

C. Fluoro Policies and Procedures- fluoro time reports, pregnant patients, lead aprons, badges

D.  Radiation Badge procedures, contacts

E.  PACS implementation and archiving of images 

Course Overview Cont’d

• 2.    Course Content – 120 minutesA.   Fundamental properties of X-rays

B.   Discussion of dose and ALARA

C.   Biological effects of radiation

D.   Image formation- Fluoroscopy, KV, mA, contrast, magnification and digital processing

E.   Radiation monitoring

F.   Safe practice- distance, shielding of staff and patients, collimation, hand protection, II protection

Course Overview Cont’d

• 3.    Introduction to the Fluoroscan Mini c-arm - 20 minutes Theoretical

Demonstration

Hands on training

 

• 4.    Written Examination – 20 minutes  Certification based on passing the test

Results forwarded to Chief of Surgery and Chief of Diagnostic Imaging

What is a Mini C-Arm?

• Fluoroscopy system• X-ray tube fixed relative

Image Intensifier by a gantry • Primary beam will not

extend past the Image Intensifier

• Collimators reduce beam area (field size) to reduce scatter

• Shape of the gantry is usually semi-circular “C”

• Flexible gantry positioning

Introduction:A. Regulatory Requirements

• Use of mini c-arm is restricted to extremity imaging and must not be used in other anatomical areas, particularly in children.

• The Mini C-Arms at the Hamilton Health Sciences are approved for the following procedures only:

Wrist – Ankle – Hand – Elbow – Forearm – Tib/Fib

Humerus – Foot – Knee – Femur

Any other possible procedure will require permission and supervision from the radiology department.

B. HHS Policy Manual

• Refer to handout: The Use of Mini C-Arms at HHS by a Physician Other Than A Radiologist

– Physicians may become qualified operators of the mini c-arm by successfully completing a course in Radiation Protection and Principles of Fluoroscopy

– Once qualified, they may use this device in the operating room and minor surgery procedure room. The operator is responsible for safety and use of mini c-arm.

– Standard c-arm requires an M.R.T. to operate

– Qualified operator may use only the mini c-arm for fluoroscopy without an M.R.T.

C. Fluoro Policies and Procedures

1. Lead Protection The Mini C-Arms at HHS may only be operated when every staff member in the procedure room is correctly attired:

- “Lead” protective aprons

- approved radiation monitoring badges.

2. Legal Record

Patient Information MUST be entered into the patient ID page on the Mini C-arm

• Patient Name• Patient Id #• Study description• Physician doing procedure• Accession # will be added by the DI technologist after the

case has been logged in to Meditech (required for PACS)• Documentation procedure. Requisitions are to be left on

machine in an envelope. DI Techs will pick up, enter in to Meditech and download images to PACS

3. Patient Protection

• Patients must be provided with protective lead apparel• For extremity exams this means full apron and thyroid

protection• Female patients of childbearing age (11-55) must be

asked if there is any chance they may be pregnant• If the answer is no then proceed with the examination• If the answer is anything other than no then you must

consult with a radiologist before proceeding with exam- Refer to policy manual Irradiation of Pregnant Patient in Diagnostic Imaging

4. Post Exam Documentation

• For female patients of childbearing age “Not Pregnant” or “Pregnant” must be documented on the requisition (Female patients of childbearing age are age 11-55)

• Documentation procedure. Requisitions are to be left on the Mini c-arm in an envelope. DI technologists will pick up, enter in to Meditech and download images to PACS

5. Radiation Badges

Who Needs to be Badged? Radiation Workers

Definition of a Radiation Worker: X-ray Safety regulation 861 defines an x-ray worker

“ as a worker who as a necessary part of the workers employment may receive a dose equivalent in excess of the limits set out in column 4 of the table”.

Part of the Body Irradiated Exposure Conditions and Comments Dose equivalent Annual Limit (mSv)

Column 1 Column 2 Column 3

X-ray Workers

Column 4

Other Workers

Whole Body or trunk of Body

Uniform Irradaition 50 5

Partial or non-uniform irradiation of body

Limit applies to the EFFECTIVE DOSE EQUIVALENT defined in

Note (a)

50 5

Lens of the eye Irradiated alone or with other organs or tissues

150 50

Skin Limit applies to the mean dose equivalent to the basal cell layer of the epidermis for any area of

skin of 1 square cm or more

500 50

Individual organs or tissues other than the lens of the

eye or skin

Effective dose equivalent applies withan overriding limit on dose

equivalent to the individual organ or tissue

500 50

OHSA Dose Schedule

Safety Code 35

D. Radiation Badge Procedures

Badges are changed quarterly Individuals are responsible to ensure their badge is collected and sent

for reading. Badges are to be kept on-site 2 badges issued for staff doing or participating in fluoroscopy One badge is to be worn at waist level under the apron and the second

to be worn outside the thyroid collar. (see next slide) Badge Reports are reviewed by DI staff, photocopied and given to the

area to post in a prominent location For badge issues, contact Jennifer House or Noella Sconci

To be worn under the lead apron at waist level

To be worn outside the lead thyroid collar

July 1, 2006 HHS changed to Global dosimetry

The change standardized vendors across all sites of HHS, St. Joe’s and McMaster University

E. PACS

• Requisitions are to be left on the Mini c-arm in an envelope

• DI technologists will pick up, enter in to Meditech and download images to PACS

• Reporting dose is an integral part of patient care• DI technologists must also upload the dose report

to PACS

COURSE CONTENTA. Properties of X-Rays

• X-rays and gamma rays are called IONIZING radiation because they have sufficient energy to dislodge the orbital electrons of an otherwise neutrally charged atom, creating an ion pair.

• The electromagnetic spectrum also includes ultraviolet, visible light, Infrared, microwaves and radio waves; they are forms of non-ionizing radiation: radiation that does not have sufficient energy to create ion pairs.

Radiation Quiz…

Ionizing or Non-Ionizing?

Radiation Quiz…

Ionizing or Non-Ionizing?

Radiation Quiz…

Ionizing or Non-Ionizing?

Radiation Quiz…

Ionizing or Non-Ionizing?

Radiation Quiz…

Ionizing or Non-Ionizing?

Photoelectric and Compton Scattering

The two kinds of interactions through which the X-rays deposit their energy are both with electrons.

Electrons…

1. Compton interactions

This has the effect of making the patient’s body a secondary radiation source of scattered X-rays.

Scattered radiation in the forward direction may reach the image receptor at a random location and reduce the contrast of the image. Scattered radiation from the patient is also the predominant source of radiation exposure to the radiology personnel.

Compton Scattering:

2. Photoelectric interaction

General relationship: probability of photoelectric interactions α Z3 , where Z is the atomic number.

- Probability of photoelectric interactions occurring is dependent on the atomic number of the material:

- Conditions that increase probability of photoelectric interactions: low photon energies and high atomic number materials.

- This is a result of the binding energies moving closer to the X-ray energies in the beam.

Photoelectric Interactions

The probability of photoelectric interactions depends on how well the X-ray energies and the electron binding energies match.

Photoelectric interaction occurs between an X-ray and a tightly bound electron. The X-ray must have enough energy to eject the electron from the atom, and the X-ray is totally absorbed.

The probability of photoelectric interactions is affected by the atomic number of the material because the atomic number changes the binding energies.

Photoelectric Interactions

Element Atomic # (Z) K shell L shell M shell

Oxygen 8 0.53 0.01 N/A

Calcium 20 4.04 .35 0.03

Copper 29 8.98 .95 0.07

Molybdenum 42 20.0 2.62 0.41

Tungsten 74 69.5 11.5 2.58

Lead 82 88.0 15.2 3.55

Approximate Electron Binding Energies (keV)

The total attenuation coefficient value for materials can vary greatly because of the effect of photoelectric interactions. A minimum value of approximately 0.15 cm2/g is established by Compton interactions.

100 200 300X-ray Energy (keV)

10

1.0

0.1

Attenuation Coefficient (cm2/g)

Lead - Photoelectric

Iodine

Soft Tissue

Compton - all materials

Photoelectric and Compton Interaction Rates

Photoelectric and Compton Scattering

Half-Value Layer

The half value layer is simply the thickness of material required to reduce the number of X-rays passing through it to one half of the incident number.

Tissue has a HVL of about 4 cm in a typical diagnostic X-ray beam. Therefore a 20 cm thick body would allow only about 3% of the X-rays through it.

50%

25%

12.5%

6.25%

3.13%

100%

0 1 2 3 4 5Thickness (HVL's)

Half Value Layer (HVL)

History

• From the very beginning, many had noted the potential problems associated with repeated exposures to high doses of ionizing radiation.

• Early X-ray devices were nothing more than glass vacuum tubes. Operators would be repeatedly exposed during the course of a days work.

Image copyrighted by Radiology Centennial, Inc.

• Wives and female assistants often served as test subjects to determine if a tube was “ready” for the day’s work.

• Reddening of the skin and burns to the hand were common.

Don’t try this at home!Don’t try it at work either!

Image copyrighted by Radiology Centennial, Inc.

• It was not until the death of Clarence Dally (1865-1904), that people agreed:

• X-rays could kill as well as cure.

• X-rays discovered in 1895 • Radiation survey meters –

not till 1928!

Dally - Thomas Edison’s assistant in X-ray manufacturing and testing.Image copyrighted by Radiology Centennial, Inc.

Anyone remember this? (1920-1960)

Radiation Exposure

• Obvious injuries such as a burns• More subtle biological effects (cellular level)

• The primary cause of cell injury is due to the production of free radicals: OH● molecules generated by the ionization of water.

• Free radicals can form other chemical molecules, such as hydrogen peroxide, sodium/potassium hydroxide, and others.

• These chemicals can directly damage or destroy a cell’s structure, or cell’s DNA.

Cell Damage If the damage is minor, the cell may be able to repair itself. If the

damage is severe, the cell may die outright. The effect, or more appropriately, the risk of injury from radiation exposure depends on several factors:

– The type of radiation (alpha, beta, X, etc.),

– The energy of that radiation,

– The intensity and duration of exposure, and,

– The part of the body being irradiated.

Deterministic Effects

Since the discovery of X-rays, it has long been known that very high exposures to radiation over a short period of time will cause very specific effects, from nausea and reddening of the skin, to death.

“Deterministic effects are predictable dose related effects and have a threshold below which the effects do not occur, for example radiation induced epilation, erythema and necrosis of skin.”

Stochastic Effects

The other known risk is the potential for cancer due to long term and repeated exposures to high doses of radiation.

"Stochastic effects include radiation -induced neoplasm and heritable genetic effects. There is no known threshold for stochastic effects and their severity has no relationship to dose."

B. Dose and ALARAUnits

To evaluate the potential risk we need to be able to measure and quantify radiation exposure. The units commonly used for this are:

1. The Exposure Unit

2. Radiation Absorbed Dose Unit, and

3. Dose Equivalence Unit.

Exposure Unit

The exposure unit, known as the Roentgen or “R”, is defined as that quantity of either X or gamma radiation that will, through ionization, produce a total charge of 2.58E-04 coulombs in one kilogram of air at standard temperature and pressure.

The SI unit for exposure is the Coulomb per kilogram of air.

1 C/kg = 3876 R

Radiation Absorbed Dose

The unit of radiation absorbed dose, or “rad”, refers to the amount of energy from ionizing radiation being deposited in matter. The unit can be used for all types of ionizing radiation.

1 rad = 0.01 Joules of energy absorbed per kilogram of material. The SI unit for absorbed dose is the “Gray” or “Gy”.

1 Gy = 100 rad

Dose Equivalence

• Research has shown that there are different levels of risk of injury, specifically cancer, from exposure to different forms of ionizing radiation: alpha, beta, neutron, X or gamma. Remember, the effect radiation exposure can have on a living cell depends on the type, energy, intensity, duration, and part of the body being exposed.

• Concept of dose equivalence provides a common scale for equating the relative risk from exposure to different forms of ionizing radiation.

Dose Equivalence

The unit for dose equivalence is the “rem”. It is the product of the absorbed dose in tissue multiplied by a modifying factor. This may also be referred to as a quality factor.

For alpha radiation, this quality factor is 20. For beta, X and gamma radiation, this quality factor is 1.

The SI unit for dose equivalence is the Sievert (Sv).

rem = rad x quality factor

1 Sv = 100 rem

ALARA

The fundamental principle of radiation safety is to keep occupational radiation exposures As Low As is Reasonably Achievable.

The three primary ways to apply this principle is through proper application and use of time, distance, and shielding.

C. Biological Effects from Acute Whole Body Radiation Exposure

• 25 – 200 rad (25,000 – 200,000 mrad)– Nausea and vomiting, malaise and fatigue, increase in body

temperature and blood changes.• 200 – 1000 rad

– Hemopoietic Syndrome: Ablation of the bone marrow. Death results within months if untreated.

• 1000 – 2500 rad– Gastrointestinal Syndrome: Desquamation of the intestinal

epithelium. Death results within weeks if untreated.• 2500 rad and up

– Central Nervous System Syndrome: Unconsciousness within minutes to hours. Death results within hours to a few days. There is no treatment.

Skin Related Injury• 300 - 800 rad

– Erythema, a reddening of the skin similar to a first degree burn. Pigmentation changes can also occur, resulting in a lightening or darkening of the exposed area. Full recovery usually occurs.

• 800 – 3000 rad– Effects similar to those of a second degree burn resulting in

ulcerations of the injured area. Wound may become infected.

• 3000 rad and up– Effects similar to a third degree burn. Tissue damage may be

permanent or worse. Necrosis of the tissue may require skin grafts or amputation of the injured area.

D. Image FormationFluoroscopy

• Fluoroscopy: production of real-time X-ray images

• History: First done by W.C. Roentgen when he discovered the “new kind of rays” in 1895.

• For medical purposes - 1896.

• Early fluoroscopy units were equipped with a fluorescent screen consisting of copper activated zinc cadmium sulphide that emitted yellow-green light.

• Fluorescent screen covered with lead glass to protect the observer.

• Only very high doses produced a faintly visible image on screen.

• Examination carried out in a dark room, and radiologist had to adapt his/her eyes for up to half an hour prior to exam.

Fluoroscopy

• The image intensifier revolutionized fluoroscopy.

• Real-time imaging and the ability to position the X-ray field makes fluoroscopy powerful.

• Due to the length of the exams, the exposure rate must be kept very much lower than in common radiography (100–200x)

• The fluoroscopic image is formed using fewer X-ray photons and a high gain. This results in images with higher level of quantum noise and inferior spatial resolution compared to ordinary radiographs.

Fluoroscopic Set up

Types of Fluoroscopic Units

Conventional fluoroscopy

Cardiac Cath Labs

Bi-Plane C-Arm

Cystoscopy & Overtable Tube Units

Digital and Pulse Fluoroscopy

Units with Cine Cameras or Photospots

Mobile C-Arms

Fluoroscopic modes of operation

Manual Mode – allows user to select the exact mA and kV required

Automatic Brightness System (ABS) – this mode allows the machine to drive the kV and mA to optimize dose and image quality

Pulsed Digital Mode – modifies the fluoro output by cutting out exposure between pulses

Automatic Brightness system (ABS)

• Instead of film, the detector is an image intensifier fluorescent screen coupled to a video camera.

• X-ray image can be viewed directly on the TV screen and/or can be captured in digital format and viewed/manipulated later.

• To maintain a constant image quality, an automatic brightness system (ABS) detects the X-ray intensity that is reaching the detector and adjusts the mA and/or kVp.

• Example: if the fluoroscope moves from a thick part of the body to a thin part of the body, the X-ray intensity (mA) is reduced to avoid flooding the detector and to reduce the radiation dose to the patient.

E. Radiation MonitoringFactors that affect Radiation Dose

• Several factors that can effect radiation dose to the patient and the quality of the image are geometrical in nature. – The size of the patient

– The size of the viewing field (collimation)

– The distance from the x-ray tube to the patient,

– The distance of the detector (image intensifier) from the patient and

– The use of a grid

Patient Size

The size of the patient is an uncontrollable variable. A more intense X-ray beam is required, for larger patients or denser regions, in order to pass sufficient X-rays to the detector. Hence an increase in mA or kVp is needed. This also increases the radiation dose to the patient.

Radiation dose is greater for larger patients.

Use as low a mA as possible and as high a kVp as possible to obtain diagnostic image quality with lowest dose.

Collimation

Collimators are used to determine the size of the X-ray field. The larger the field size, the larger the amount of scatter which degrades the image quality. Tightly collimating the X-ray beam to the area of interest reduces the amount of scatter, reduces the volume of tissue exposed and improves the image quality.

Use the tightest collimation possible

Inverse Square Law

• X-rays emanate from the focal spot of the X-ray tube.

• The X-ray beam intensity decreases as the square of the distance from this focal spot.

• The further away the patient is from the X-ray tube, the less radiation per square meter and the less likely a radiation skin burn will occur.

• This is very important in lateral or oblique views since the X-ray tube is usually much closer to the patient than in AP or PA views.

The X-ray tube should be as far from the patient as possible

Image Intensifier

• Similarly, we want the image intensifier (detector) as close to the patient as possible.

• The closer the detector is to the patient (X-ray tube) the more X-rays will be recorded by the detector. Also, magnification and the accompanying distortion of the anatomy and image blur is reduced. This results in better image quality and less dose to the patient.

The image intensifier should be as close to the patient as possible.

Grids

• A grid is composed of parallel strips of lead• When placed in the X-ray beam in front of

the image intensifier the grid tends to filter out the scattered radiation.

• It also stops many direct photons resulting in the need to increase the X-ray intensity.

• This increases the dose to the patient. • If highest resolution images are critical to

the procedure, then grids should be used• If image quality is adequate without it, the

grid should be removed to keep the radiation dose at a minimum.

The use of a grid increases radiation dose

Magnification

There are two methods to magnify an object:

1. Use geometry - move the object away from the Image Intensifier and closer to the X-ray tube.The patient dose rapidly increases due to the inverse square law and detail gradually decreases due to geometric unsharpness.

2. Use electronic magnification - By electronically manipulating a smaller radiation Image Intensifier input area over the same Image Intensifier output area

The use of magnification increases radiation dose

A smaller beam area is projected to the same II output.  The resulting object size is larger, but the image is dimmer due to the less beam input.  The ABS system would sense the brightness loss and boost machine X-ray output.

Electronic Magnification

Use of magnification increases radiation dose

Example: when going from a six inch mode to a four inch mode the radiation output may double.

F. Safe PracticeC-Arm Scatter

The C-Arm gantry is supported in a way that allows a great degree of flexibility in its positioning. Therefore, unlike some conventional fluoroscopy units, it is often difficult to provide shielding for scatter radiation on the unit itself.Therefore, it is extremely important that the operator be adequately shielded with protective

lead aprons, and thought should also be given to where the more intense scatter will occur.

Effect of rotating the X-ray system.  Images taken with the Image Intensifier away from the operator result in higher radiation exposure to the operator's eyes compared to images with the II towards the operator.

C-Arm Scatter

primary beam

leakage from the tube housing

scattered radiation

Primary Beam

• Exposure to the primary beam usually only happens to the patient, or in accidental situations. The risk of exposures can be minimized by good engineering design and safety features such as interlocks.

Leakage Radiation

• Leakage radiation refers to the radiation field around a shielded tube, excluding the primary beam. Leakage can occur around shutter assemblies, collimators, joints, and seams of the tube head assembly.

Scattered Radiation

Whatever the primary beam strikes, such as the patient, detector, or beam stop, it will produce a field of scattered radiation. The scattered radiation field will be much lower in intensity and energy than the primary beam.

Minimize Exposure Time

Your radiation dose is a function of time. A medical X-ray unit may produce dose rates in the primary beam around 4000 R per hour, but is only activated for a fraction of a second.

In fluoroscopy systems the longer the footswitch is kept depressed, the greater the dose.

The LONGER the TIME, the GREATER the DOSE

Maximize Distance

As with all forms of radiation, increasing the distance between yourself and the source of radiation will decrease your dose.Ionizing radiation follows the inverse square law. Doubling the distance decreases the dose by a factor of four. Tripling the distance decreases the dose nine-fold!

Use Appropriate Shielding

Increasing the distance is not always the most practical means of reducing one’s exposure.

Shielding is the most common and usually cost effective means of keeping doses as low as reasonably achievable.

Lead Aprons, etc.

• Lead aprons, in various styles are barriers. Typically, they provide protection equivalent to 0.5 mm lead. Often, they are made from a mixture of materials where the different K edge absorptions give equivalent stopping power to lead but with a lower weight.

• Thyroid collars protect the thyroid area.

• Lead glasses protect the eyes.

A lead apron might protect you from about 97% of the scattered radiation

Of course, it is always easier and much more comfortable to shield the X-ray tube and install a barrier shield than it is to shield yourself.

Image copyrighted by Radiology Centennial, Inc.

Thank you

HGH Contacts

Radiation Safety Officer Dr. Gerald Moran

Radiation Protection Officer Dr. Ian Doris

OR/Mobile Charge tech. Kathy Morreale

Equipment service Pat Connelly

QC &Radiation Safety Jennifer House

Radiation Badges (OR) Theresa McHugh Wanchuck

MUMC Contacts

Radiation Safety Officer Dr. Gerald Moran, PhD

Radiation Protection Officer Dr Carmen Otero

OR/MOBILES Charge tech. Marion Bowslaugh

Senior tech. OR/Mobiles Marilyn Kereliuk

Equipment Service Jay Moffat

QC and Radiation Safety Jennifer House

Radiation Badges/Pb aprons Noella Sconci

Policies Submitted to the Policy Office September 26, 2005 

• Irradiation of Pregnant Patients in Diagnostic Imaging• Pregnancy of X-ray Workers•Fluoro by a Physician other than a Radiologist•X-ray Equipment Breakdown•Code of Practice for Protection from Radiation• Patient Overexposure• Fluoro Time Reports• Guidelines for Holding Patients for X-rays• Mobile Radiography Procedure• Mobile Radiography Policy• X-ray Protective Devices Purchase and Quality Control• X-ray Protective Devices Patient Use• X-ray Protective Devices Staff Use• Repeat Exposure• Radiation Dosimetry for X-ray Workers and X-ray Students• Radiation Dosimetry for Outside Vendors• Use of Mini C-arms•Fluoroscopy by an MRT

Radiation Safety Policies