Radiobiology Flashcards
What are the three cardinal principles of radiation protection?
Time
Distance
Shielding
What is absorbed dose?
mGy/Rad
Radiation the patient has receieved
What is equivalent dose?
Incorporates absorbed dose and radiation type
Eqd=AbdxWr
WrXR=1 Wralpha=20
What is the effective dose?
mSv/Rem
Incorporates absorbed dose, type of radiation, and the sensitivity of the organ
Represents the stochastic health risk to the whole body
EffD=AbDxWrxWt
What is the minimum distance an operator must stand from the x-ray tube?
3 metres unless using appropriate PPE
What is the genetically significant dose?
Dose to exposed individuals of reproductive age averaged over the entire population of reproductive age
What does proper use of collimation provide?
Reduced off focus radiation
As well as reduced scatter because less tissue is being exposed
What is the purpose of a grid?
Minimize scatter reaching the image detector
What is the minimum source to skin distance for mobile radiograpjy?
30 cm
How often should collimation and light beam congruency be checked according to SC35?
annually
What is positive beam limitation?
Radiographer must ensure that collimation is adequate by collimating the radiographic beam so that it is no larger than the IR
What is half value layer?
The thickness of a designed absorber required to decrease the intensity of the primary beam to 50% its initial value.
Measured annually in accordance to SC35
What is grid cut off?
A decrease in the number of transmitted photons that reach the IR because of some misalignment of the grid
What does off-level grid cut off look like?
Decreased density across image
What does off-center grid cut off look like?
Decreased density across image