Mini C-Arm Credentialing Course. Course Overview. 1. Introduction–15 minutes A. Regulatory requirements B. Introduction to HHS Policy Manual “Use of Mini C-arms by a Physician other than a Radiologist”
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A. 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
A. 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
Hands on training
Certification based on passing the test
Results forwarded to Chief of Surgery and Chief of Diagnostic Imaging
Wrist – Ankle – Hand – Elbow – Forearm – Tib/Fib
Humerus – Foot – Knee – Femur
Any other possible procedure will require permission and supervision from the radiology department.
1. Lead Protection
The Mini C-Arms at HHS may only be operated when every staff member in the procedure room is correctly attired:
Patient Information MUST be entered into the patient ID page on the Mini C-arm
Who Needs to be Badged?
Definition of a Radiation Worker:
OHSA Dose Schedule
The two kinds of interactions through which the X-rays deposit their energy are both with electrons.
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.
- Probability of photoelectric interactions occurring is dependent on the atomic number of the material:
General relationship: probability of photoelectric interactions αZ3 , where Z is the atomic number.
- This is a result of the binding energies moving closer to the X-ray energies in the beam.
- Conditions that increase probability of photoelectric interactions: low photon energies and high atomic number materials.
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 depends on how well the X-ray energies and the electron binding energies match.
The probability of photoelectric interactions is affected by the atomic number of the material because the atomic number changes the binding energies.
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.
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.
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Radiology Centennial, Inc.
Don’t try this at home!
Don’t try it at work either!
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Dally - Thomas Edison’s assistant in X-ray manufacturing and testing.
Image copyrighted by Radiology Centennial, Inc.
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.Cell Damage
“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.”Deterministic 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."
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.
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
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
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 remDose Equivalence
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.
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.Skin Related Injury
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.Fluoroscopy
Cardiac Cath Labs
Cystoscopy & Overtable Tube Units
Digital and Pulse Fluoroscopy
Units with Cine Cameras or Photospots
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
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.
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
The X-ray tube should be as far from the patient as possible
The image intensifier should be as close to the patient as possible.
The use of a grid increases radiation dose
There are two methods to magnify an object:
The patient dose rapidly increases due to the inverse square law and detail gradually decreases due to geometric unsharpness.
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.
Example: when going from a six inch mode to a four inch mode the radiation output may double.
Use of magnification increases radiation dose
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.
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.
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
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!
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.
A lead apron might protect you from about 97% of the scattered radiation
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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
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
Radiation Safety Policies