Dosimetry/ Radiobiology

Question 1

What is ‘exposure’ in radiation dosimetry?

Answer 1

the ionization created in air

Question 2

unit for ‘exposure’ in radiation dosimetry

Answer 2

coulomb/ kg

Question 3

What does KERMA stand for

Answer 3

Kinetic Energy Released per unit MAss

Question 4

Unit for KERMAs

Answer 4

Gray

Joules/ kg

Question 5

Does KERMA represent the quantity of radiation absorbed by patients?

Answer 5

No

Question 6

Symbol for radiation exposure?

Answer 6

X

Question 7

Symbol for Air Kerma?

Answer 7

K

Question 8

Symbol for Absorbed Dose of radiation?

Answer 8

D

Question 9

Unit for Absorbed Dose of radiation?

Answer 9

Gray

(Joules/ kg)

Old unit: Rad

Question 10

Difference between ‘absorbed dose’ of radiation in comparison to air kerma?

Answer 10

radiation deposited rather than energy released

Question 11

How is the Absorbed Dose of radiation often quoted?

Answer 11

Entrance Skin Dose

OR

Organ dose

Question 12

Symbol for Equivalent Dose of radiation?

Answer 12

H

Question 13

What is the relationship between absorbed dose and equivalent dose

Answer 13

Equivalent dose = Absorbed dose x Radiation Weighting

Question 14

What is Linear Energy Transfer in Radiation?

Answer 14

How much radiation deposited per unit of distance

Question 15

Unit for Linear Energy Transfer in radiation

Answer 15

keV/ micron

Question 16

What is the radiation weighting factor for:

1. x-ray/ gamma rays
2. beta particles
3. Alpha particles
4. neutrons

Answer 16

1. 1
2. 1
3. 20
4. Variable

Question 17

Unit or Equivalent dose of radiation (H)

Answer 17

Sievert

Question 18

Symbol for Effective Dose of Radiation?

Answer 18

E

Question 19

Term to describe different organs having different sensitivity to radiation?

Answer 19

radiosensitivity

Question 20

The calculation for Effective dose of radiation?

Answer 20

Effective dose =

```
SUM of
organ dose x Radiation Weighting x Tissue Weighting
~~~

Question 21

What is Collective Equivalent Dose of radiation?

Answer 21

total impact on all people exposed to that radiation

Question 22

Unit for Collective Equivalent Dose of radiation?

Answer 22

man-Sieverts

Question 23

How much background radiation are humans exposed to naturally?

Answer 23

2-3mSv/ year

Question 24

What are the main sources of background radiation for humans?

Answer 24

Radionucleides in air (1.2mSV)
Internal Radionucleides (0.2mSv)
External Gamma (0.3mSv)
Cosmic Rays (0.3mSv)

Question 25

What is the predominant source of radiation from radionuclides in the air?

Answer 25

Radon

Question 26

What two pathways does cellular damage from radiation occur

Answer 26

``` Direct pathway Indirect pathway (reacts with water causing free radicals) ```

Question 27

Is single or double-strand DNA Break Worse?

Answer 27

Double strand is much worse and is difficult to repair

Question 28

What do deterministic vs stochastic radiation effects mean?

Answer 28

deterministic: minimum threshold beyond which guaranteed to occur, severity worsens with dose Stochastic: probability increases with dose

Question 29

Examples of deterministic radiation adverse effects?

Answer 29

``` Erythema Hair loss (epilation) Cataracts (may actually be stochastic) Radiation poisoning Depression of bone cell formation ```

Question 30

How are deterministic radiation effects caused?

Answer 30

apoptosis

Question 31

Lag time for stochastic radiation effects

Answer 31

leukaemia: - start after 2 year - peaks about 5-10 years Other cancers: - at least 10-year lag - slowly increases to peak like 40 years later

Question 32

Are sperm of ova more sensitive to radiation?

Answer 32

sperm as they are in process of maturing still in adults

Question 33

Where does most information about risks of radiation exposure come from?

Answer 33

Life Span Study (following A-bomb in japan) | Radiation workers

Question 34

What are the proposed models of radiation risk at low doses?

Answer 34

Linear No Threshold Linear Quadratic Homesis

Question 35

What is the Linear No Threshold model of radiation risk?

Answer 35

Risk directly proportional to radiation exposure, | no safe dose

Question 36

What is the Linear Quadratic model of radiation risk?

Answer 36

Lower risk at a low dose then increases at an increasing rate

Question 37

What is the Homesis model of radiation risk?

Answer 37

Small doses of radiation may be protective, and then risk increases from there

Question 38

Which is the accepted model of radiation exposure risk?

Answer 38

The Linear Threshold is at present (as it's the most conservative)

Question 39

What is the Doubling Dose of radiation?

Answer 39

Radiation dose required to double the number of spontaneous mutations in a given population

Question 40

What is the radiation risk factor/ mSV in the general population?

Answer 40

About 1 in 20,000 per mSv

Question 41

What is the relative radiation risk for children vs adults?

Answer 41

about 2-3 times as likely in children

Question 42

What are some deterministic complications of radiation in pregnancy?

Answer 42

failure to implant organ malformation foetal death mental retardation