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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
ARS Bone Marrow Dose latent period outcome
\>2Gy 1-6 weeks possible to survive
26
ARS GI Dose latent period outcome
\>8Gy 5-7 days death within 2 weeks
27
ARS CNS Dose latent period outcome
20-50 Gy 4-6 hours Death within 3 days
28
lethal dose 50/30
Dose that will kill 50% of people within 30 days ## Footnote **3-4 Gy without treatment**
29
Fetus and radiation First 2 weeks
50-100 mGy may cause fetal loss (all or nothing).
30
Fetus and radiation 8 - 15 weeks
8-15 weeks = MOST VULNERABLE over 1**00-200 mGy a/w** **reduced head diameter and retardation**
31
Fetus and radiation childhood leukemia
increased risk with just a few radiographs
32
Fetal thyroid
BEFORE week 8 does NOT take up iodine after that = hosed
33
General risk of cancer
4-5% per Sv
34
Skin stuff Early transient erythema Dose onset
2Gy Hours
35
Skin stuff Robust erythema Dose onset
6 Gy 1 week
36
Skin stuff Telangiectasia Dose onset
10Gy 52 weeks
37
Skin stuff Dry desquamation Dose onset
13 Gy 4 weeks
38
Skin stuff Moist desquam/ulceration Dose onset
18Gy 4 weeks
39
Skin stuff Secondary ulceration Dose onset
24 Gy skin dose \>6 weeks
40
Hair temporary epilation
3Gy 21 days onset
41
Hair Permanent epilation
7 Gy 21 days
42
Cataracts anterior vs posterior
senile cataracts = anterior ## Footnote **radiation cataracts = posterior lens**
43
Cataracts latent period
20 years after exposure
44
Cataracts acute exposure
2.5 Gy
45
cataracts annual dose rate limit
0.15 Gy/year
46
Sterility/infertility female
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
Sterility male
Male temporary 0.15 Gy - 2.5 Gy Male permanent - 5 Gy
48
Male/Female shielding
Male Just below symphysis Female 1 inch medial to each palpable asis
49
Symptom/Dose nausea (30% of people)
0.75 - 1.25 Gy WB
50
Symptom/Dose Depress lymphocytes
0.25 Gy WB
51
Symptom/Dose LD 50/60 (Marrow)
3-4 Gy WB
52
Symptom/Dose LD 50/4 (GI)
8 - 10 Gy WB
53
Symptom/Dose LD CNS
\>20 Gy
54
Symptom/Dose double normal mutation rate
1 Gy
55
Effective background USA dose
**3mSv per year**
56
Dose trigger for addnl F/U
15 Gy to a *single exposure field* ## Footnote *sentinel event*
57
Exposure limits Occupational lens
150 mSv/year
58
Exposure limits Radiation worker
50 mSv/year
59
Exposure limits occupational extremity
500mSv/year
60
Public exposure limits infrequent
5mSv/year
61
Public exposure limits continuous
1mSv/year
62
Public exposure limits embryo/fetus via mother
5mSv/year | (1mSv to fetus directly)
63
Public exposure limits fetus post declared preg
0.5mSv/month
64
Public exposure limits controlled areas
50 mSv/year
65
Public exposure limits uncontrolled areas
5 mSv/year
66
Public exposure limits Genetically Significant dose
0.25 mSv
67
High yield blitz majority of energy received by biologic material from x-rays is transferred by?
electrons
68
High yield blitz 60% of damage to biologic tissue is mediated by?
free radicals
69
High yield blitz
final number of DS DNA breaks more important than initial, some will be repaired
70
High yield blitz Risk of radiation induced Ca adult kid old person
4-5% per Sv adult 15% per Sv kid 1/10th that older than 50
71
High yield blitz Transient erythema timing
can be seen in hours, main wave after 10 days
72
High yield blitz radiation sterility in females
mimics menopause in males no effect on libido or hormone levels, latent period
73
High yield blitz
Radon workers get more lung cancer
74
High yield blitz highest contributor to USA effective dose
inhaled Radon, an alpha emitter, 55% of effective dose
75
High yield blitz gen pop man made greatest exposure?
medical imaging
76

physics factoids (8 decks)

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