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Imaging > Lecture 10 > Flashcards

Lecture 10 Flashcards

1
Q

radiation biology

A

study of the biological effect of ionizing radiation on tissue

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2
Q

biological effects of radiation

A

stochastic effects and deterministic which is acute

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3
Q

stochastic effects

A

late effects: cancer and hereditary

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4
Q

what does the probability and severity do with stochastic dose effects

A

probability increases with dose, but severity is independent of dose

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5
Q

deteministic effects

A

acute effects: erythema, cataracts, blood cell defects, acute radiation syndrome

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6
Q

what does the probability and severity do with deterministic dose effects

A

severity increases with dose, but probability is independent of dose

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7
Q

what is the most common way to get deterministic and what is the most common way to get stochaistic

A

deterministic-is from occupational, but there is not very often. Diagnostic X-rays are the most common for stochastic. There is a threshold for the deterministic effects

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8
Q

how does ionizing radiation deposit energy

A

excitation, ionization, thermal heating- largest but very small component

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9
Q

what produces chemical changes in the tissue

A

excitation and ionization, which produce biological effects

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10
Q

what are biological effects of radiation

A

delayed after a period of time

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11
Q

can you tell the difference between chemical or physical agents

A

no

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12
Q

what is the direct effect of radiation on the tissue

A

photon directly ionizes or excites a DNA molecule, which then DN< RNA< protein or enzyme is then ionized or excited

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13
Q

what is the indirect effect of radiation on the tissue

A

a reactive chemical is produced, which interacts with water and the majority of tissue is water. This produces free radiacals, which have an unpaired electron, so they are very reactive.

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14
Q

what can ROS form

A

water, which does nothing or it can form a hydrogen peroxide which is damaging to interact with macromolecules

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15
Q

what enhances ROS damage

A

O2

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16
Q

what predicts the severity of biological response

A

the cell function that is affected especially the cell division

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17
Q

what happens to cells with the most damage

A

they apoptosis, and eliminate future biological response

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18
Q

what is target theory

A

model of cell damage. a cell may be inactivated by a certain number of hits. A hit may be direct or indirect interaction. Cells have certain DNA that is not redundant. A hit to redundant molecules will not result in cell death

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19
Q

is dingle strange or double stranded breaks more common and what are they

A

single are more common and they are more easily repaired. The double stranded happen less frequently but are harder to repair

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20
Q

what two things can cause a mutation

A

base deletion or substitution

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21
Q

what happens to chromosomes when hit with radation

A

broken ends are sticky and and can rejoin with other broken ends, and this repair can lead to a whole mess
can lead to eccentric or miscombined with different translocations.

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22
Q

what are the aberrations present with the chromosomes

A

dicentric, acentric, ring

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23
Q

what can be used to estimate the amount of radiation received

A

the number of aberrations in human lymphocytes can be used to estimate the amount of radiation exposure received. Total body doses>.25gy can be detected many years later

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24
Q

cell radiosensitivity

A

used to evaluate the effect of radiation on cell proliferation under various conditions including different types of ration, environmental factors, different types of cells. Cells are grown in tissue culture the exposed to radiation then surviving colonies are counted. Cell survival curve shows fraction surviving versus dose

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25
Q

what is n

A

it is the extrapolation number between n2-10 and the number of hits required to inactivate cell or the number or critical targets in a cell

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26
Q

what is D0

A

1/slope indicates the general radio sensitivity of cells

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27
Q

what is a large D0 mean

A

it means there is a radioresistance

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28
Q

low D0 means what

A

radiosensistive

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29
Q

D0 is usually between

A

1-2 gy

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30
Q

Dq

A

threshold dose- width of the shoulder region. Measures ability of cells to recover from sublethal damage.

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31
Q

what is large Dq

A

cells can easily recover or low energy radiation

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32
Q

what factors effect the radio sensitivity of cells

A

dose rate, dose fractionation, radiation quality, oxygen, chemical protectiors, type of cell, stage of the cell cycle

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33
Q

dose rate and fractionantion

A

high dose rates cause greater amage. Fractionation of dose reduces the biological damage. Low dose rates and fractionation gives the cells time to reapiar

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34
Q

LET

A

linear energy transfer. high LET is alpha protons and high energy photons. Low LET means there is beta stuff and gamma rays

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35
Q

dose low or high LET cause more damage

A

high

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36
Q

does free O2 increase or decrease damage

A

increased cell damaged because there can be formation of products.

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37
Q

what do chemical protectors do

A

decrease cell damage and these chemicals scavenge free radiacls and add an H to help DNA repair like sulhydrl amifostine, but almost need it to be toxic

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38
Q

which cells have the greatest sensitivity

A

rpid devision, large number or future divisions, low differentiation, lymphocytes are radio resistant, but still kinda radiosensitive

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39
Q

what cell cycle is most sensitivie

A

during M and late G2 phase

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40
Q

what cell cycle phase is most resistant

A

late S phase

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41
Q

what happens if the parenchyma is radioresistant

A

damages first occurs in the vasculartue so later effects of blood flow

42
Q

if the parenchyma is radiosensative

A

quick damage

43
Q

what are some radiosensitive organs

A

skin, reproductive organs, eye, hematopoietic cells, GI, CNS

44
Q

radiation effect on the skin what is the threshold

A

1-2. Early effects are erythema, inflammation, dry desquamation, most desquamation. late atrophy, fibrosis, changes in pigmentation, necrosis, ulcers, cancer.there are some changes like loss of chair, sweat and sebum. Eraly hits the epidermis while late is the dermis

45
Q

2-6gy to skin

A

erythema and temproary hair loss

46
Q

6-10 to skin

A

more erythema

47
Q

15 to skin

A

severe erythema and dry desquamation

48
Q

20-50 to skin

A

intense erythema, acute radiation dermatitis, moist desquamation, edema, dermal hypoplasia, vascular damage, permanent epilation, permanent pigment changes

49
Q

above 50 to skin

A

ulceration and necrosis

50
Q

radiation effects to gonads

A

2.5 is sterility for temporary and 5gy is permanent- spermatogenesis is most sensitive

51
Q

female gonad effects

A

intermediate follicles, 1.5 gy temporary and 6 is permanent. exams are rare over 50

52
Q

radiation effects to eye

A

lens because cannot remove damages- shorter for high doses but usually over a uear

53
Q

what is there threshold dose for the eye

A

2-7 old new .5. protracted 4 gy over 2 months or 5.5 gy over 4months.

54
Q

how much dose a head CT give

A

50mGy to eye

55
Q

acute radiation syndrome

A

large acute radiation exposure to the whole body. Combination of 3 syndromes, hematopeotic, GI, neuro, and chernobyl causes 30 cases or it

56
Q

prodome ARS

A

anorexia, nausea, vomiting, diarrhea- up to 6 hours

57
Q

latent ARS

A

no symptoms for up to 4 weeks

58
Q

manifest ARS

A

4-6 weeks prodrome plus organ damage

59
Q

recover or death

A

after 6 weeks

60
Q

hematopeotic sundrome

A

stem cells in bone marrow-

61
Q

.5-1 in heme

A

decrease CBC

62
Q

<2 in heme

A

generally recoverable

63
Q

2 in heme

A

die in six weeks with no treatment

64
Q

> 8gy heme

A

wil die without treatment in 1-2 weeks without BMT

65
Q

GI sundrome

A

crypt cells are hit and no longer reproduce. damage to intestinal lining

66
Q

what is the GI dose range

A

10 is the threshold and above 12 is fatal within 5-12 dyas

67
Q

what is the neuromuscular effect and threhold

A

50 and it is rate and will occur within 2-5 days from cardiovascular shock

68
Q

what is the range of developing leukemia

A

2-3 years

69
Q

what is the latency for solid tumors

A

more than 40 years

70
Q

why is it difficult to study radiation induced cancer

A

cancer incidence is high in the population

71
Q

what was the mean dose from the atomic bomb

A

200 mSv

72
Q

what is the dose for an abdomen CT affecting BMT

A

5mgy

73
Q

in AK treatment

A

see increased leukemia incidence

74
Q

what happened with the mastitis patients

A

increased doses lead to increased breast cancers

75
Q

what happened with the radium girls

A

osteogenic sarcoma- threshold of 5gy of radium. high LET from Ra226 and 228 and this is 100 times the population

76
Q

how does the dose data stack up for cancer

A

more data for high dose exposures but it is insufficient for lower doses. Use dose response to predict the lower ones

77
Q

what is the formula for the dose response curve

A

it is R=aD+BD2 and it is not linear because linear overestimates the indicence

78
Q

what are the pitfalls of the non threshold model for dose response

A

it estimates a higher cancer incidence at lowe doses compared to threshold model

79
Q

what are the pitfalls of the non threshold linear model for dose response

A

more likely to overestimate at low doses ,but it is the best for conservative model, but it cannot predict excess cancers from this model

80
Q

relative risk method

A

ratio of cancer indcidence in the exposed group relative to general population. excess RR is 1-RR

81
Q

absolute risk

A

number of excess ration induced cancers that occur in an exposed population for specific dose per year

82
Q

Beir V report

A

exposure to low levels of ionizing radiation. contains the cancer incidence estimates from a panel of experts

83
Q

cancer mortality risks from BEIR

A

8% per Sv adult workers and high dose/dose rates. Dose and dose rate effectiveness

84
Q

what is the best model for leukemia and bone cancer

A

linear quadratic model

85
Q

what is the most frequent radiation induced cancer

A

leukemia and it has low incidence otherwise. children have 2-3 year latency, >45 8-10 hear latency. linear quadrative

86
Q

what is the absolute lifetime risk for leukemia

A

1% per Sv exposure

87
Q

what is the second most common radiation cancer

A

thryid females are at higher risk. Latent for 5-35 years. Mortality is low though

88
Q

what is the latent period of breast cancer

A

10-40 years and long period of expression. Risk increases with age

89
Q

what were the hereditary results from radiation in flies and mice

A

radiation cuases mutations, and not different from spontaneous mutations

90
Q

what happened with human sutdies

A

no increase in genetic effect above spontaneous

91
Q

what is the genetically significant dose

A

does expected to produce the same genetic effect to the entire population as the actual dose received by a specific group. GSD is used to evaluate the magintude of the effect of certain exposure. Depends on gondola dose and expected offspring

92
Q

what are the effects of radiation to the conceptus

A

congential abnormaltities, growth retardation, reduced IQ, increased cancer risk, but dependent on the stage

93
Q

what is the effect at the preimplantation stage

A

all of nothing. prenatal death or repair and replacement of damaged cells will occur.

94
Q

what is the threshold dose at primimplantation

A

50-100 or 250 after implantation

95
Q

when is organogenedid 2-8 weeks

A

it is the most critical because of the changes to organs. this is at 100-200

96
Q

fetal growth stage

A

8 to birth- nervous and sensory organs can be affected, but reduced IQ or behavioral, but there are less major malformations.

97
Q

micorcephaly

A

small heads

98
Q

mental retardation

A

seen in ecvess

99
Q

what is the most common time that in utero radiation would cause cancer

A

doses as low as 10mgy can cause it with the 3rd trimester being the most sensitive, but it is controversial

100
Q

what test has the highest in utero dose

A

CT

101
Q

most exams for diagnosis

A

do not get above 100 so there is usually not much effect

Imaging (19 decks)

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