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Radiation biology Flashcards

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1
Q

‘Exposure’

A

ability of X-rays to ionize air, measured in Roentgens

concentration of radiation, in air, at a specific point

ionization produced in a specific volume of air

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2
Q

Absorbed Radiation dose

Radiation dose

A

amount of energy absorbed per unit mass at a specific point (Gy or Rads)

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3
Q

Gy and Rads

A

1 Gy = 100 Rads

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4
Q

Equivalent dose =

A

Dose x weighting factor

weighting factor based on different types of radiation

For Xrays and gamma rays = 1

alpha particles = 20

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5
Q

Effective dose =

A

Type of radiation and type of tissue

Sv

EfD = EqD x Tissue factor

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6
Q

Kerma

A

PRIMARY energy transfer (no scatter, not overall dose)

Can’t measure in body, measure at air entrance point

Entrance air kerma

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7
Q

Kerman and photon energy

low vs high

A

Low energy photon primarily PE, KERMA and entry dose roughly the same

High energy photons pass through, KERMA = MORE than absorbed dose

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8
Q

KAP

A

Kerma x beam area

thought of as total radiation used in exam more than actual dose

INDEPENDENT of source distance

Mag will increase entrance skin kerma but NOT change KAP

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9
Q

Entrance Kerma, KAP and collimation

A

KAP WILL decrease with collimation

Entrance KERMA will increase a small amount 2/2 ABC

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10
Q

KERMA, KAP stochastic and deterministic risks

A

KAP estimate/correlates with stochastic risk

Entrance Air KERMA with deterministic effects

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11
Q

Relative Biologic Effectiveness

RBE calc?

A

Capability of radiation with differing LET’s to produce a biologic reaction

Dose of 250kV x-rays/ Dose in Gy of test radiation

ex: reaction produced by 5Gy of test radiation. It takes 10Gy of 250kV x-rays to produce same effect. RBE = ?

10/5 = 2. Test radiation is twice as good at producing the biologic effect

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12
Q

LET and RBE

as LET increases?

A

directly related to a point. Above a threshold (100keV/micrometer), max damage is being done and more radiation is ‘wasted’

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13
Q

Oxygen Enhancement Ratio

OER at high vs low LET

A

relative effectiveness of radiation to produce damage at different oxygen levels

Tissue is more sensitive to damage in an oxygenated state

Only relevant at LOW LET

HIGH LET will do a lot of damage in low or high oxygenated states (OER = 1. damage without oxygen = damage with oxygen)

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14
Q

Direct vs Indirect ionizing radiation

A

Direct act Directly on DNA

Indirect if they act on water (free radical fucks up DNA later)

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15
Q

Syndrome with most sensitivity to x-rays

A

Ataxia Telangiectasia

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16
Q

‘Instant death of a large number of cells’

A

1000 Gy in a period of seconds/minute

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17
Q

‘Mitotic death’

A

When a cell dies after 1 or more divisions

(a small dose can do this)

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18
Q

‘Mitotic delay’

A

A very small dose (0.01 Gy) just before a cell divides can cause a delay or failure in the timing of the normal dividing

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19
Q

Most sensitive phase

overall sensitivity of phases

A

M phase

M > G2 > G1 > S

(G1 = variable in length)

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20
Q

Law of B and T

cell sensitivity

A

Most sensitive cells = lots of turnover, not much differentiation (Skin, blood, GI tract, reproductive)

Less sensitive, little turnover, lots of differentiation (brain, nerves, muscles)

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21
Q

Most sensitive part of GI tract?

A

small bowel

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22
Q

Survival curve graph

? vs ?

quasi-threshold

A

dose vs cell survival

repair mechanisms = quasi-threshold = shoulder on graph = sublethal damage to the cell

only exists with lower LET radiation curves

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23
Q

effect on blood

A

lymphoctyes = most sensitive

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24
Q

ARS

3 subtypes

4 phases

A

4 phases

GI - latent - syndrome/subtype - recovery/death

Bone Marrow, GI, CNS

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25
Q

ARS

Bone Marrow

Dose

latent period

outcome

A

>2Gy

1-6 weeks

possible to survive

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26
Q

ARS

GI

Dose

latent period

outcome

A

>8Gy

5-7 days

death within 2 weeks

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27
Q

ARS

CNS

Dose

latent period

outcome

A

20-50 Gy

4-6 hours

Death within 3 days

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28
Q

lethal dose 50/30

A

Dose that will kill 50% of people within 30 days

3-4 Gy without treatment

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29
Q

Fetus and radiation

First 2 weeks

A

50-100 mGy may cause fetal loss (all or nothing).

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30
Q

Fetus and radiation

8 - 15 weeks

A

8-15 weeks = MOST VULNERABLE

over 100-200 mGy a/w

reduced head diameter and retardation

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31
Q

Fetus and radiation

childhood leukemia

A

increased risk with just a few radiographs

32
Q

Fetal thyroid

A

BEFORE week 8 does NOT take up iodine

after that = hosed

33
Q

General risk of cancer

A

4-5% per Sv

34
Q

Skin stuff

Early transient erythema

Dose

onset

A

2Gy

Hours

35
Q

Skin stuff

Robust erythema

Dose

onset

A

6 Gy

1 week

36
Q

Skin stuff

Telangiectasia

Dose

onset

A

10Gy

52 weeks

37
Q

Skin stuff

Dry desquamation

Dose

onset

A

13 Gy

4 weeks

38
Q

Skin stuff

Moist desquam/ulceration

Dose

onset

A

18Gy

4 weeks

39
Q

Skin stuff

Secondary ulceration

Dose

onset

A

24 Gy skin dose

>6 weeks

40
Q

Hair

temporary epilation

A

3Gy

21 days onset

41
Q

Hair

Permanent epilation

A

7 Gy

21 days

42
Q

Cataracts

anterior vs posterior

A

senile cataracts = anterior

radiation cataracts = posterior lens

43
Q

Cataracts latent period

A

20 years after exposure

44
Q

Cataracts acute exposure

A

2.5 Gy

45
Q

cataracts annual dose rate limit

A

0.15 Gy/year

46
Q

Sterility/infertility

female

A

In general younger patient, more dose required to cause sterility

female age 12 - 10 Gy

female age 45 - 2Gy

female no age given - around 6 Gy

47
Q

Sterility

male

A

Male temporary 0.15 Gy - 2.5 Gy

Male permanent - 5 Gy

48
Q

Male/Female shielding

A

Male

Just below symphysis

Female

1 inch medial to each palpable asis

49
Q

Symptom/Dose

nausea (30% of people)

A

0.75 - 1.25 Gy WB

50
Q

Symptom/Dose

Depress lymphocytes

A

0.25 Gy WB

51
Q

Symptom/Dose

LD 50/60 (Marrow)

A

3-4 Gy WB

52
Q

Symptom/Dose

LD 50/4 (GI)

A

8 - 10 Gy WB

53
Q

Symptom/Dose

LD CNS

A

>20 Gy

54
Q

Symptom/Dose

double normal mutation rate

A

1 Gy

55
Q

Effective background USA dose

A

3mSv per year

56
Q

Dose trigger for addnl F/U

A

15 Gy to a single exposure field

sentinel event

57
Q

Exposure limits

Occupational

lens

A

150 mSv/year

58
Q

Exposure limits

Radiation worker

A

50 mSv/year

59
Q

Exposure limits

occupational

extremity

A

500mSv/year

60
Q

Public exposure limits

infrequent

A

5mSv/year

61
Q

Public exposure limits

continuous

A

1mSv/year

62
Q

Public exposure limits

embryo/fetus via mother

A

5mSv/year

(1mSv to fetus directly)

63
Q

Public exposure limits

fetus post declared preg

A

0.5mSv/month

64
Q

Public exposure limits

controlled areas

A

50 mSv/year

65
Q

Public exposure limits

uncontrolled areas

A

5 mSv/year

66
Q

Public exposure limits

Genetically Significant dose

A

0.25 mSv

67
Q

High yield blitz

majority of energy received by biologic material from x-rays is transferred by?

A

electrons

68
Q

High yield blitz

60% of damage to biologic tissue is mediated by?

A

free radicals

69
Q

High yield blitz

A

final number of DS DNA breaks more important than initial, some will be repaired

70
Q

High yield blitz

Risk of radiation induced Ca

adult

kid

old person

A

4-5% per Sv adult

15% per Sv kid

1/10th that older than 50

71
Q

High yield blitz

Transient erythema timing

A

can be seen in hours, main wave after 10 days

72
Q

High yield blitz

radiation sterility in females

A

mimics menopause

in males no effect on libido or hormone levels, latent period

73
Q

High yield blitz

A

Radon workers get more lung cancer

74
Q

High yield blitz

highest contributor to USA effective dose

A

inhaled Radon, an alpha emitter, 55% of effective dose

75
Q

High yield blitz

gen pop man made greatest exposure?

A

medical imaging

76
Q
A

physics factoids (8 decks)

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