Radiobiology

Question 1

What are the three cardinal principles of radiation protection?

Answer 1

Time
Distance
Shielding

Question 2

What is absorbed dose?

Answer 2

mGy/Rad

Radiation the patient has receieved

Question 3

What is equivalent dose?

Answer 3

Incorporates absorbed dose and radiation type
Eqd=AbdxWr
WrXR=1 Wralpha=20

Question 4

What is the effective dose?

Answer 4

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

Question 5

What is the minimum distance an operator must stand from the x-ray tube?

Answer 5

3 metres unless using appropriate PPE

Question 6

What is the genetically significant dose?

Answer 6

Dose to exposed individuals of reproductive age averaged over the entire population of reproductive age

Question 7

What does proper use of collimation provide?

Answer 7

Reduced off focus radiation

As well as reduced scatter because less tissue is being exposed

Question 8

What is the purpose of a grid?

Answer 8

Minimize scatter reaching the image detector

Question 9

What is the minimum source to skin distance for mobile radiograpjy?

Answer 9

30 cm

Question 10

How often should collimation and light beam congruency be checked according to SC35?

Answer 10

annually

Question 11

What is positive beam limitation?

Answer 11

Radiographer must ensure that collimation is adequate by collimating the radiographic beam so that it is no larger than the IR

Question 12

What is half value layer?

Answer 12

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

Question 13

What is grid cut off?

Answer 13

A decrease in the number of transmitted photons that reach the IR because of some misalignment of the grid

Question 14

What does off-level grid cut off look like?

Answer 14

Decreased density across image

Question 15

What does off-center grid cut off look like?

Answer 15

Decreased density across image

Question 16

What does off-focus grid cut off look like?

Answer 16

Decreased density at edges

Question 17

How often is grid performance checked in accordance to SC35?

Answer 17

Annually

Question 18

If a grid is placed upside down, where is grid cutoff on the image?

Answer 18

Decreased density at edges of image

Question 19

How often should PPE be examined in accordance with SC35?

Answer 19

Annually

Question 20

What does the lead lining in the tube provide?

Answer 20

Radiation protection for the patient and imaging personnel from off-focus, or leakage radiation by restricting emission of xrays to area of primary beam

Question 21

What is the minimum SSD for mobile and stationary fluoroscopy?

Answer 21

Min. SSD fir stationary is 38cm

Min. SSD for mobile is 30cm

Question 22

What is the entrance skin exposure and what is it measured in?

Answer 22

Measurement of radiation output at the point of skin entry for common x-ray, and fluoro procedures. mR, mGy or C/kg

Question 23

How does kVp effect scatter?

Answer 23

Increasing kVp inceases scatter to the IR, scatter in general is reduced.

Question 24

What is a controlled area?

Answer 24

An area that is occupied only by the occupationally exposed

Dose limit of 20 mSv per year

Question 25

What is an uncontrolled area?

Answer 25

An area that is occupied by the public | Dose limit of 1 mSv per year

Question 26

What is the led equivalency for Pb aprons at: 100kVp, 100-150kVp and 150kVp or higher?

Answer 26

100kVp- 0.25mmPb 100-150kVp- 0.35mmPB 150kVp or higher- 0.5mmPb

Question 27

What is linear energy transfer?

Answer 27

The average energy deposited as ionizing radiation passes through a medium Ass LET increases chances of biological response increase because more energy is being deposited

Question 28

What is relative biologic effectiveness?

Answer 28

The relative capabilities of radiation with differing LETs to produce a particular biological response

Question 29

What is the oxygen enhancement ratio?

Answer 29

ratio of the radiation dose required to cause a particular biologic response of cells or organisms in any oxygen-deprived environment to the radiation dose required to cause an identical response under normal oxygenated conditions

Question 30

What is the oxygen enhancement effect?

Answer 30

Oxygen enhances the effects of ionizing radiation on biologic tissue by increasing tissue sensitivity

Question 31

What is indirect ionization?

Answer 31

Photon interacts with water, causing ionization which forms free radicals. Free radicals continue to interact with other atoms causing indirect radiation.

Question 32

What is direct ionization?

Answer 32

Photon directly interacts with DNA

Question 33

What is deterministic/non-stochastic effect?

Answer 33

Severity increases with increased radiation dose | Threshold value exists

Question 34

What is stochastic effect?

Answer 34

Incidence increases with increase dose Linear non-threshold Usually occurs with low LET rad

Question 35

What dose response relationship does diagnostic radiation follow?

Answer 35

Linear non-threshold | no exposure is without risk but small dose has very low risk

Question 36

What are somatic effects?

Answer 36

Biological damage from ionizing radiation to body cells

Question 37

What are genetic effects?

Answer 37

Stochastic effects from damaged genes