Section 2

Question 1

What does LET stand for

Answer 1

Linear Energy Transfer

Question 2

What does LET do

Answer 2

energy deposited per length

Question 3

Greater LET means

Answer 3

greater damage

Question 4

What particles have increased LET?

Answer 4

alpha and protons

Question 5

Are the 5 MV x-rays more or less damaging than the 250 kVp x-rays?
More damaging

Answer 5

more damaging

Question 6

What does RBE stand for

Answer 6

relative biological effectiveness

Question 7

Why is RBE important?

Answer 7

damaging ability of radiation relative to 250kVp

Question 8

Recall the formula for RBE

Answer 8

RBE = (dose of 250kVp to produce effect)// (dose of test radiation to produce same effect)

Question 9

Greater than 1 RBE means

Answer 9

more damaging

Question 10

Lesser than 1, RBE means

Answer 10

less damaging

Question 11

Spreading the dose over time

Answer 11

leads to less damage

Question 12

acute exposure refers to

Answer 12

rapid exposure/dose

Question 13

chronic exposure refers to

Answer 13

long lasting duration

Question 14

Fractionation is where

Answer 14

same dose rate but split into fractions (used in RT and rate = Gy/hr)

Question 15

Protraction is where

Answer 15

same dose (Gy), continuously delievered at a lower rate so the overall amount of gray stays the same (longer period of time)

Question 16

Older cells are more

Answer 16

radioresistant

Question 17

Younger cells are more

Answer 17

radiosensitive

Question 18

increased radiosensitivity

Answer 18

causes increased metabolic rate and increased proliferation rate

Question 19

aerobic tissue is

Answer 19

oxygenated

Question 20

Aerobic tissue is more

Answer 20

sensitive than anoxic and hypoxic

Question 21

anoxic

Answer 21

no oxygen

Question 22

hypoxic

Answer 22

low oxygen

Question 23

OER =

Answer 23

dose under anoxic// dose under aerobic

Question 24

OER is always

Answer 24

greater than 1

Question 25

OER is always higher for

Answer 25

low LET radiation

Question 26

For high LET, OER

Answer 26

will be reduced to 1 (approaches it)

Question 27

As we age, our ability to repair our

Answer 27

cells become less effective

Question 28

When do we have high sensitivity to radiation?

Answer 28

Before Birth & elderly

Question 29

What is the excess risk for a foetus?

Answer 29

6% per Gy - for 1Gy, there will be risk of 6%

Question 30

Pre implantation is the

Answer 30

fertilisation (9 day period)

Question 31

Major organogenesis (week 2-8) is

Answer 31

point of development where cells are replicating and specialising main risk is embryonic malformations

Question 32

fetal growth (weeks 8-40) is

Answer 32

prenatal death & congenital abnormalities are negligable - main risk is the nervous system and sense organs

Question 33

dose response relationships describe

Answer 33

effects (risk) vs amount of radiation (dose)

Question 34

What are the 2 kinds of responses?

Answer 34

deterministic and stochastic

Question 35

Deterministic (cause & effect) is

Answer 35

health effects directly related to dose - no uncertainity/ambiguity

Question 36

Stochastic (random) is

Answer 36

occurance by chance & probability increases with dose

Question 37

Linear Non-Threshold

Answer 37

is where risk is proportionate to dose

Question 38

LNT model says that any dose

Answer 38

will produce biological effects - there is no safe dose

Question 39

The LNT model is used to evaluate risk because

Answer 39

it gives the best guess of the worst case scenario NOT because it matches all evidence

Question 40

Radiation Hormesis is where

Answer 40

low radiation doses are beneficial - we do not adopt this model

Question 41

absolute risk is the

Answer 41

actual # of cases in a group (# or %)

Question 42

excess risk is the

Answer 42

observed cases/rate - expected case/rate

Question 43

relative risk is the

Answer 43

observed//expected

Question 44

BERT is a useful tool to

Answer 44

explain how much radiation a patient will receive

Question 45

patients have no

Answer 45

dose limits

Question 46

Why do patients not have dose limits?

Answer 46

benefit > risk

Question 47

public dose limit is

Answer 47

1mSv per year

Question 48

Occupational dose limit is

Answer 48

20mSv/year, averaged over 5 consect. yrs

Question 49

ICRP fundamentals for radiation protection is

Answer 49

justification (benefit > risk); limitation (follow rules); optimisation (ALARA)

Question 50

Limitation & optimisation measures include

Answer 50

time (minimise time near source); distance (maximise distance from source); shielding (lead apron and walls)

Question 51

For scattered and leadkage of radiation, we use

Answer 51

secondary barriers

Question 52

The relative risk model

Answer 52

is where risk increases with age

Question 53

Linear Non threshold is

Answer 53

there is no observable biological response at low doses until a point at which a biological response occurs

Question 54

The radiation hormesis model states that

Answer 54

low dose exposure to a physical or biological agent helps the body & as dose increases, the good effects decrease (graph)

Question 55

Radiation that scatters off a patient in a DR scan is considered to be a

Answer 55

secondary source