Radiation Safety COPY COPY Flashcards
Radiation cataract
Considered deterministic effect in exposure of greater than 2 Gray
It may occur with lower doses, especially in those exposed to higher doses more frequently
Appears on posterior capsule of the lease
Up to 50% radiation workers have them
Absorbed radiation dose
Measure of deposited energy measures in Gray. One Gray is equivalent to energy deposition of one Joule per kilogram
Effective dose corrects for the different sensitivity of various tissues by multiplying the absorbed dose by the tissue weighting factor as well as correcting for the type of radiation
Air kerma
Kinetic energy release Di matter
Energy released from a Xray beam in a small volume of air that isirradiated
Reference air kerma
Air kerma measured at a fixed point in space known as interventional reference point, 15 cm from isocenter on the X-ray tube side of the fluoroscope
May be used as a surpgrate for entrance skin dose
Immediately available st the end of the procedure and serves as best approximation of patient skin dose
Entrance skin dose
Measure of radiation that is absorbed by the skin at the site of Xray beam and skin interface
Dose area product
Also known as the kerma area product
Product of intensity of the radiation beam and the area of the beam
Role of image intensifier
Detects the radiation rhat is transmitted through the patient and in turn allows for an image to be generated. The close the intensifier is to the patient the lower the dose required to generate and imaged and the lower the scatter
What is the main source of radiation to the operator and staff in radio suite
Scatter from the patient
What increases the radiation used
Geometric magnification
Fluorography such as digital acquisition
High frame rate
Pulsed fluoroscopy abd looped fluoroscopy decrease it
Signs of radiation skin injury and dose
Threshold is 2 Gray - transient erythema (several hours)
7 Gray - permanent epilating (several weeks after)
10 Gray - dermal athrophy (late effect with teleangiectasia formation)
Over 10 Gray - skin ulceration
Deterministic radiation effect
Effect that occurs at a specific threshold dose of exposure
Skin injury is the most common
Relation of radiation scatter and distance
Scatter = 1/ distance square
What’s the dose of radiation that’s dangerous in pregnancy
50 mGray is a concern
100 mGray May be grounds to termination
Current international commission of radiological protection recommendations for the occupational equivalent dose limit for the lease of the eye to prevent cataracts
20 mSv per year average over 5 years but not exceeding 50 mSV in a single year
If the operator is standing on the patients right side, what’s the tube position for LAO
X-ray tube near the patient and intensifier on the opposite side. Biggest scatter for the operator on the right side
Similarly - cranial angulation increases the scatter because the tube is near the operator and the intensifier is near the scull
