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23 Radiology > 4.1 - Radiation Biology > Flashcards

4.1 - Radiation Biology Flashcards

1
Q

biologic effects of radiation

A
  • radiographs made with ionizing radiation
  • interaction with xrays with biologic macromolecules
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2
Q

risk for cell damage is ___ but never ___

A

SMALL but never ZERO

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3
Q

what does ALARA stand for

A

as low as reasonably achievable

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4
Q

[low OR high] energy xrays are completely absorbed by the body (photoelectric absorption)

A

LOW

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5
Q

when do low energy xrays interact with biologic macromolecules? what does it look like on xray?

A

completely absorbed by body (photoelectric absorption) and appears radio-opaque

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6
Q

what is the release of fast-moving secondary electrons that can cause further biologic interaction when interacting with biologic macromolecules

A

compton scattering

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7
Q

[low or high] energy xrays are a major interaction

A

HIGH

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8
Q

high energy xrays are a major site of biologic damage to what

A

DNA

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9
Q

___: the photon directly interacts with and ionizes a biologic macromolecule,
the free electrons produced by the ionization interaction (secondary electrons) may also
interact DIRECTLY with biologic macromolecules

A

Direct Action

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10
Q

1/3 [direct/indirect]
2/3 [direct/indirect]

A

direct = 1/3
indirect = 2/3

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11
Q

what do direct actions produce

A

unstable free radicals

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12
Q

what do indirect actions produce

A

unstable free radicals

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13
Q

___: the secondary electron interacts with, for example, a water molecule to
produce a hydroxyl RADICAL (OH-) which in turn produces the damage to the DNA

A

Indirect Action

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14
Q

indirect actions mostly involve what

A

electrons interacting with water

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15
Q

what refers to how water dissociates into H and OH when irradiated

A

radiolysis of water (type of indirect action)

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16
Q

what is the time between when energy is absorbed and the damage is done to when signs and symptoms are visible

A

latent period

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17
Q

what does latent period depend on

A

amount of radiation and the particular type of damage

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18
Q

cancer from radiation has a long or short latent period

A

long

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19
Q

cells are MOST sensitive to radiation during what phase

A

G2 and M

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20
Q

cells are LESS sensitive to radiation in what phase

A

G1 phase

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21
Q

cells are least sensitive to radiation in what phase

A

S phase

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22
Q

what happens if DNA strand break occurs before chromosomal duplication (late G1, early S) the break is replicated and both sister chromatids will carry the damage

A

chromosome abberations

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23
Q

what happens if DNA strand break occurs AFTER chromosomal duplication (late S, G2) only one of the sister chromatids will carry the break)

A

chromatid aberrations

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24
Q

what is damage to DNA in reproductive cells (sperm or ova) and damage can be passed onto future offspring

A

genetic mutation

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25
Q

what is damage to body cell (somatic cell, non-sperm/ova) and damage passed onto other cells of same time in that person, not to future offspring

A

somatic mutation

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26
Q

what is the most likely effect of stochastic effects

A

carcinogenesis

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27
Q

what is radiation that modifies DNA

A

gene mutation

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28
Q

what can be an initiator, promotor, or may convert premalignant cells into malignant ones

A

gene mutation (radiation modified DNA)

29
Q

do radiation effects increase with dose

A

yes

30
Q

is there a safe level of exposure?

A

no! dental doses are low but not zero

31
Q

what are deterministic effects of cells

A
  1. nucleus more sensitive than cytoplasm
  2. causes of cell death from radiation
32
Q

what is the most sensitive site of cell

A

DNA in chromosomes (nucleus is more sensitive than cytoplasm)

33
Q

what happens when damaged cells released molecules that kill adjacent cells

A

bystander effect

34
Q

what can induce programmed cell death

A

apoptosis

35
Q

most sensitive cells are cells that:

A
  1. divide rapidly over many generations
  2. primitive or immature
  3. undifferentiated
36
Q

what are the most sensitive cells (ranked)

A

1 . Small lymphocytes
2. Bone marrow
3. Reproductive cells
4. Intestine
5. Mucous membranes

37
Q

least sensitive cells are those that

A
  1. divide rarely
  2. are mature
  3. are specialized
38
Q

least sensitive cells ranked

A
  1. muscle and nerve cells
  2. lungs
  3. kidneys
  4. liver
  5. salivary glands
    MartiN LUthe KIng LIkes Salivary glands
39
Q

what are the types of acute radiation syndrome with Gy level

A

prodromal (1-2 Gy)
hematopoietic (2-7 Gy)
GI (7-15 Gy)
Cardiovascular and CNS (>50 Gy)

40
Q

can you cause acute radiation syndrome with dental diseae

A

no

41
Q

symptom and Gy of:

prodromal

A

1-2 Gy
nausea, vomiting, diarrhea

42
Q

symptom and Gy of:

hematopoietic

A

2-7 Gy
damage to bone marrow, infection, bleeding, anemia

43
Q

symptom and Gy of:

GI

A

7-15 Gy
damage to lining of GI tract, ulceration, septicemia, death

44
Q

symptom and Gy of:

cardiovascular and CNS

A

> 50 Gy
die

45
Q

what are late effects of low dose

A

cataract formation

46
Q

dental dose is ___ lower than threshold

A

1250 times

47
Q

effects of low doses on fetal w/ day

A
  1. preimplantation (0-9 days)
  2. organogenesis (10 days to 8 weeks)
  3. early fetal period or later organogenesis (8-25 weeks)
  4. late fetal period
48
Q

describe stage and days:

preimplantation

A
  1. Preimplantation (0-9 days): most sensitive stage for lethal effect; threshold for effect is
    100 mGy
49
Q

describe day and stage:

organogenesis

A
  1. Organogenesis (10 days to 8 weeks): mental retardation, microcephaly, growth
    retardation
50
Q

describe day and stage:

early fetal period or late organogenesis

A
  1. Early fetal period or late organogenesis (8-25 weeks): mental retardation
51
Q

describe stage:

late fetal period

A
  1. Late fetal period: excess absolute risk is about 6%/Gy for early child cancer
52
Q

what does it mean if small volume of tissue exposed

A

fewer cells damaged

53
Q

how does oxygen affect radiation

A

hypoxia decreases the effect

54
Q

how does LET affect radiation

A

higher LET causes more double-strand breaks

55
Q

what radiation treatment is administered as many daily small doses

A

fractionation

56
Q

benefits of fractionation

A
  • Increased cellular repair of surrounding normal tissues that are unavoidably exposed
  • Repopulation of surrounding normal cells
  • Increases the mean oxygen tension (reoxygenation) in an irradiated tumor, rendering the tumor radiosensitive
  • Reassortment of the tumor cells to be in the most sensitive part of the cell cycle
57
Q

process of radiotherapy involving the oral cavity

A
  • 2 Gy is delivered daily for a weekly exposure of 10 Gy
  • Radiotherapy course continues for 6-7 weeks until a total of 60 to 70 Gy is delivered
58
Q

what is the golden window

A

lowest risk of ORN (4 months after radiotherapy)
highest risk (4-12 months post therapy)

59
Q

xerostomia can be radiation induced by what

A

apoptosis of salivary acinar cells

60
Q

what can cause rampant cares from radiotherapy

A

decreased salivary flow

61
Q

3 types of radiation caries

A

1) Lesions that affect the cervical aspect of the teeth extending along the CEJ
2) Demineralized and worn occlusal surfaces
3) Color changes in the dentin along with occlusal wear

patients may present with any combination of the above lesions

62
Q

does radiotherapy affect mature and developed teeth

A

no

63
Q

how can radiotherapy affect developing teeth

A
  • May completely destroy tooth bud
  • Arrest the growth potential that a bud may have
  • Result in malformations of the tooth
  • Eruptive mechanisms of the teeth ARE NOT affected
64
Q

ORN Gy levels

A
  • 1-4 Gy
  • 10 Gy
  • 20 Gy
  • 60-70 Gy
65
Q

what happens at 1-4 Gy

A

sitmulatory effects on osteoblasts - new bone formation

66
Q

what happens at 10 Gy

A

death of chondroblasts and osteoblasts

67
Q

what happens at 20 Gy

A

single dose in a young child = irreversible growth retardation and short stature

68
Q

what happens at 60-70 Gy

A

radiation damage to mature, intact bone (a more radioresistant tissue)

69
Q

what happens to musculature from radiotherapy

A
  • Fibrosis and scarring (limiting function)
  • If muscles of mastication (usually masseter and temporalis) are affected it may result in TRISMUS (reduced opening of the jaw)

23 Radiology (15 decks)

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