4. Tissue Response to Radiation

Question 1

what is the equivalent dose

Answer 1

absorbed dose weighted for relative biological effectiveness

Question 2

what units is the equivalent dose measured in

Answer 2

sieverts (Sv)

Question 3

what are the weighting factors for x-ray/gamma/e-, neutrons, protons, and alpha particles

Answer 3

x-rays = 1
protons = 2
neutrons = 2.5-20
alpha = 20

Question 4

what is the difference between equivalent dose and absorbed dose

Answer 4

no difference, just different units

Question 5

what is the effective dose

Answer 5

equivalent dose weighted for biological sensitivity of tissues

Question 6

what units is the effective dose measured in

Answer 6

Sieverts (Sv)

Question 7

how do you calculate the effective dose for various tissues

what should it add up to

Answer 7

take tissue weighting factor and multiply by equivalent dose in Sv and add it up for different tissue categories

add up to 100% or 1.0

Question 8

what is radiation damage

Answer 8

ionising radiation causes damage molecules that regulate cell processes

Question 9

what happens in terms of repair occur when there are low doses

Answer 9

cell repair can rapidly occur

Question 10

what happens in terms of repair occur when there are high doses

Answer 10

cell death results

Question 11

what happens in terms of repair occur when there are extremely high doses

Answer 11

cells cannot be replaced quickly enough

Question 12

out of the following rank them from most to least sensitive to radiation

skin, reproductive organs, blood forming organs, nervous system, muscle

Answer 12

most
blood forming organs
reproductive organs
skin
bone and teeth
muscle
nervous system
least

Question 13

what is the latent period

Answer 13

time between radiation exposure and the appearance of an effect

Initial effects subdue for a while during latent period but later there is increase in manifest illness

Question 14

the latent period falls between what two stages in terms response

Answer 14

between early response and late response

Question 15

what does the latent period depend on and how does it affect it?

Answer 15

dose

higher dose = earlier acute response

Question 16

what is the predromata and how long dose it last

Answer 16

early effect and it is diminished during latent period (hr-wks)

Question 17

as dose increases, the onset of effects gets ___ but severity of defects ___

Answer 17

shorter

increases

Question 18

what are deterministic and stochastic effect

Answer 18

deterministic = tissue reactions

stochastic = chance damage

Question 19

for deterministic effects

what is its dose levels
how long is its latency period
does it have a threshold dose
what is its biological mechanism
sample clinical effects

Answer 19

med-high dose
short (days-weeks) latency period
yes it has a threshold dose
predominantly cell death mechanism
skin lesions, cataract

Question 20

for stochastic effects

what is its dose levels
how long is its latency period
does it have a threshold dose
what is its biological mechanism
sample clinical effects

Answer 20

low dose
long (years) latency period
no it does not has a threshold dose
predominantly cell damage mechanism
cancer, inherited defect in offspring

Question 21

what do deterministic and stochastic effects depend on in its severity

Answer 21

deterministic = respond to certain dose

stochastic = severity is the same but risk changes based on factors eg age, gender, risk factors

Question 22

what is the difference between somatic and hereditary/germline effects

Answer 22

Somatic cell = single cell, only affects one organ/part of tissue, not inherited

Germline = gametes, carried by whole body

Question 23

what are examples of deterministic effects

Answer 23

acute radiation sickness
milky lens/cataracts
blood forming deficiency
permanent infertility
cell death
skin lesions/burns
hair loss

Question 24

what are examples of stochastics effects

Answer 24

cancer

Question 25

what does the dose response model assume

Answer 25

that the long term biological damage (ie cancer risk) is directly proportional to dose

Question 26

evidence of increased risk of cancer is about ____ mSv in the dose response model why dont we know the lower limit

Answer 26

100mSv Cant do experiment as unethical and low end has background radiation as well so trend could be anything for lower limit

Question 27

what are the 4 great line extrapolations for the linear no threshold model

Answer 27

supra-linearity linear-quadratic linear threshold hormesis

Question 28

how many grays constitutes as mild radiation exposure

Answer 28

1-2Gy

Question 29

how many grays constitutes as moderate radiation exposure

Answer 29

2-6Gy

Question 30

how many grays constitutes as severe radiation exposure

Answer 30

6-8Gy

Question 31

what is acute radiation syndrome (radiation sickness)

Answer 31

result of receiving a large amount of ionising radiation in a very short time

Question 32

what are some early symptoms of radiation sickness

Answer 32

nausea and vomiting dizziness headache fever

Question 33

what are some later symptoms of radiation sickness

Answer 33

``` dizziness and disorientation weakness, fatigue hair loss blood in vomit and stool infections, poor wound healing low blood pressure ```

Question 34

For severe/higher doses the time taken for early effects to develop ___ and the Latent period also gets very ____, get effects ____

Answer 34

shortens shorter early on

Question 35

what is the mean lethal dose

Answer 35

amount of ionising radiation taht will kill 50% of a population in a specified time

Question 36

as the mean lethal dose increases what happens to how the proportion of the population is affected

Answer 36

As dose goes up the effects are not too significant but larger dose is affecting larger proportion of pop