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Oral Radiology > Radiation Biology Part 2 > Flashcards

Radiation Biology Part 2 Flashcards

1
Q

what is acute radiation syndrome

A
  • a collection of signs and symptoms following acute whole body radiation exposure
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2
Q

how is acute radiation syndrome recorded

A
  • animal experiments
  • patient therapeutic radiation exposures
  • atomic bombings
  • radiation accidents
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3
Q

what is sub lethal exposure considered

A

less than 2 Gy - 200 rads

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4
Q

what is lethal exposure considered

A

~2-8 Gys - 200-800 rads

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5
Q

what is supralethal exposure considered

A

more than 8 Gys- 800 rads

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6
Q

higher dose, ____ latent period and _____ onset of severe symptoms

A

shorter; rapid

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7
Q

what are the stages of acute radiation syndrome

A
  • prodromal period
  • hematopoietic syndrome
  • gastrointestinal syndrome
  • central nervous system and cardiovascular syndrome
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8
Q

describe the prodromal syndrome

A
  • less than 2 Gy or less than 200 rads
  • sub lethal exposure
  • shortly after exposure to whole body radiation individual might develop nausea, vomiting, diarrhea, anorexia, malaise, fatigue, drowsiness and listlessness
  • symptoms resolve after several weeks
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9
Q

describe hemopoietic syndrome

A
  • 2-10 Gy or 200-1,000 rads
  • irreversible injury to the proliferative capacity of the spleen and bone marrow with loss of circulating peripheral blood cells
  • infection from the lymphopenia and granulocytopenia
  • hemorrhage from thrombocytopenia
  • anemia from the erythrocytopenia
  • death within 10-30 days
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10
Q

describe gastrointestinal syndrome

A
  • 100-100 Gy or 1,000-10,000 rads
  • extensive damage to the GI system and hemopoietic system
  • extensive injury to the rapidly proliferating basal epithelial cells of the intestinal villi which leads to atrophy and ulceration
  • loss of plasma and electrolytes
  • hemorrhage and ulceration
  • diarrhea, dehydration and weight loss
  • infection
  • death in 3-5 days
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11
Q

describe cardiovascular and central nervous system syndrome

A

more than 100 Gy or 10,000 rads
- radiation induced damage to neurons and fine vasculature of brain
- intermittent stupor, incoordination, disorientation and convulsions from extensive CNS damage
- irreversible damage with death in a few minutes to 48 hours

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12
Q

when are radiation treatments to the oral cavity done

A

surgical, radiation and chemotherapy

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13
Q

oral tissues are subjected to high doses of radiation during treatment of malignant tumors of:

A

the soft palate, tonsils, floor of mouth, nasopharynx, and hypopharynx

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14
Q

what are the total radiation doses to treat malignant tumors

A

6,000- 8,000 rads

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15
Q

what is the dose for solid tumors, lymphomas and intraoral cancer

A
  • solid tumor: 60-80 Gy
  • lymphomas 20-40 Gy
  • intraoral cancer: 50 Gy
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16
Q

1 Gy = ______ micro Sv

A

1 million

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17
Q

what is the dose for FMX

A

3.5 microSv

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18
Q

what is the dose for single intraoral radiograph

A

1.3 micro SV

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19
Q

what is the dose for panoramic radiograph

A

9 micro Sv

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20
Q

describe fractionation

A
  • fractionation of the total dose into multiple small doses provides greater tumor destruction than a single large dose
  • also increases cellular repair of the normal tissues
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21
Q

what are the effects of radiation on the. mucosa

A
  • mucositis
  • secondary infections
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22
Q

what are the effects of radiation on the taste buds

A

loss of taste
- epithelial atrophy by 2nd-3rd week of treatment
- recovery of taste will occur 2-4 months following treatment

23
Q

what are the effects of radiation on the salivary glands

A

xerostomia
- if a portion of the salivary gland has been spared, dryness subsides in 6 months to 1 year

24
Q

what are the effects of radiation on bone

A

osteoradionecrosis

25
Q

what are the effects of radiation on muscle

A

fibrosis

26
Q

what are the effects of radiation on the teeth

A
  • adult teeth are resistant to direct effects of radiation exposure
  • susceptible to effects of xerostomia
  • no effect on crystalline structure of enamel, dentin or cementum
  • radiaiton does not increase the solubility of teeth
27
Q

what are the effects of radiation on growing teeth

A
  • their growth may be altered
  • if the radiation precedes calcification the tooth bud may be destroyed
  • if radiation occurs after initiation of calcification teeth may demonstrate malformation and arrest general growth
  • defects in permanent dentition such as retarded root development, dwarfed teeth, or failure to form one or more teeth
  • teeth will still erupt
28
Q

major salivary glands are often exposed to radiation during treatment of carcinoma of:

A

oral cavity or oropharynx

29
Q

what is the mechanism of action of damage to salivary glands during exposure to radiation

A
  • parenchymal cells are very sensitive to X rays and are replaced by fibrosis and adiposis with parenchymal degeneration and loss of fine vasculature
  • especially true in parotid glands
30
Q

the residual saliva after radiation exposure:

A

has a lowered pH from 6.5 to 5.5 which is acidic enough to initiate decalcification of enamel
- the buffering capacity of saliva is reduced 40-45%

31
Q

what dose of radiation in childrens teeth shows hypoplasia

A

200 R at the age of 5 months

32
Q

what are radiaiton caries

A
  • a rampant form of decay that may affect individuals who recieved a course of radiation therapy that include exposure of the salivary glands
33
Q

the primary damage to bone in osteoradionecrosis is form irradiation to:

A

fine vascualture and marrow- affecting vascular and hemopoietic elements

34
Q

what is the maximum permissible dose for occuptaional limits

A

5.0 rem/year (5,000 mrem or 50mSv

35
Q

what is the maximum permissible dose for non occupational limits

A

0.5 rem/year (500mrem) or 5 mSv

36
Q

what are the pregnancy occupational limits? 9 months pregnant? 1month pregnant?

A

0.5 rem/year (500 mrem), 5mSv at 9 months and 0.5mSv at 1 month

37
Q

what is the average annual effective dose of ionizing radiation in the US

A

3.6

38
Q

what is the average annual x ray diagnosis dose for US

A

0.39

39
Q

what is the average nuclear medicine dose for the US

A

0.14

40
Q

what fraction of medical practice accounts for radiation exposure

A

1/6

41
Q

what fraction of radiation exposure comes from medical imaging

A

1/2

42
Q

what is the dose is mrem of the average dental exposure

A

1.5

43
Q

what is the amount of 1 day of background radiation

A

8.5mSv

44
Q

why does cancer risk decrease with increasing age

A

because children have more years of life during which a potential cancer can be expressed and children are more radiosensitive since they have larger portion of dividing cells

45
Q

what cancers have the highest risk from dental radiographic exposure

A

leukemia and thyroid

46
Q

what percentage of radiation comes from artificial/manmade radiation sources

A

2%

47
Q

what do artificial/manmade radiation sources come from

A
  • consumer products: televisions, wristwatches, computers
  • airport scanners
  • nuclear fuel cycle
  • weapons production
  • fall out from atomic weapons
48
Q

what is 250 rads radiation erythema

A

threshold radiation erythema dose

49
Q

what is 500 rads radiation erythema

A

average radiation erythema dose

50
Q

what is 750 rads radiation erythema

A

maximum radiation erythema dose

51
Q

in 1959 at an 8 inch focal distance what amount of exposures deliver TED

A

62 exposures

52
Q

in 2023 at an 8 inch distance what amount of exposures deliver TED

A

298

53
Q

is radiation stochastic or deterministic

A

deterministic

Oral Radiology (26 decks)

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