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000 Radiation Safety > Biological effects of Ionizing Radiation - MT1 - 5Qs > Flashcards

Biological effects of Ionizing Radiation - MT1 - 5Qs Flashcards

1
Q

What is radiosensitivity?

A

The differences in sensitivity by various tissues according to amount and type of radiation

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2
Q

How does fluoroscopy compare to x-ray radiation?

A

Fluoroscopy is dynamic (moving) imaging, while x-ray imaging is static

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3
Q

What percent of x-ray units in the united states are dental

A

~50%

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4
Q

Dental radiographic examination hold what position in terms of greatest number and cost?

A

2nd (chest radiographs are first)

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5
Q

What are the 2 broad categories of biological effects from radiation?

A
  1. Deterministic

2. Stoichastic

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6
Q

Describe the characteristics associated with Stoichastic effects

A
  1. No does threshold
  2. All or non – probability of occurrence of effects is does dependent
  3. Long-term effects
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7
Q

What are 2 illnesses associated with deterministic effects of radiation?

A
  1. Oral mucosal changes

2. Radiation sickness

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8
Q

Describe the characteristics of dose with deterministic effects of radiation

A
  1. There is a DOSE THRESHOLD
  2. Severity of response is proportional to dose
  3. Acute effects
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9
Q

Are stoichastic effects considered acute or chronic?

A

Chronic

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10
Q

Are deterministic effects considered acute or chronic?

A

Acute

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11
Q

What are 2 illnesses commonly associated with stoichastic effects of radiation?

A
  1. Radiation-induced cancer

2. Radiation-induced mutations

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12
Q

What is the DIRECT biological effect of radiation with water in the body?

A

Free Radical Production – leading to dissociation and cross-linking

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13
Q

About what fraction of biological effects are created by direct action of x-ray photons with water in the body?

A

~1/3 due to direct effects

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14
Q

What is the INDIRECT biological effect of radiation with water in the body?

A

Radiolysis of Water – produces hydrogen peroxide, hydrogen radical, hydroxyl radical, and hydroperoxyl radicals

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15
Q

About what fraction of biological effects are created by indirect action of x-ray photon with water in the body?

A

~2/3

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16
Q

Name the 4 biological structures/mechanisms affected by radiation

A
  1. Biological molecules
  2. Cell structures
  3. Cell cycle
  4. Tissues and organs
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17
Q

What are the products resulting from radiolysis of water?

A

Produces free radicals and hydrogen peroxide which is terrible for biological molecules

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18
Q

Describe the consequences of free radical production

A

Free radicals cause unstable products to be produced and these unstable biological molecules will try to divide further (dissociation), and then these further divided molecules will pick up other biological molecules thus creating highly abnormal molecules within the body (cross-linking)

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19
Q

What are the 6 possible detrimental effects that radiation my have on a cell and the structures within the cell?

A
  1. Chromosomal break
  2. Vacuolization
  3. Mitotic Changes
  4. Impaired function
  5. Recovery
  6. Cell Death
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20
Q

Is a chromosomal bread worse for single strands or double strands?

A

Double strands

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21
Q

What is the purpose of vacuolization?

A

To clear out a cell of debris following severe damage

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22
Q

What are the 2 effects that radiation can have on the cell cycle?

A
  1. Mitotic delay

2. Cell Death

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23
Q

What phase of the cell cycle is most sensitive to radiation?

A

M phase

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24
Q

What 2 phases of the cell cycle are most impacted by mitotic delay?

A
  1. G1 (arrest)

2. G2 (block)

25
Q

What 2 phases of the cell cycle are impacted by cell death following radiation?

A

G2 and M phases

26
Q

What are is the correct sequence of cell cycle phase sensitivity from most sensitive to least sensitive?

A

M > G1 > G2 > S

27
Q

What are the short-term effects of radiation of tissues and organs dependent upon?

A

Short-term effects depend on sensitivity of parenchymal cells

28
Q

What are the long-term effects of radiation of tissues and organs dependent upon?

A

Long-term effects depend primarily on the extent of damage to the fine vasculature

29
Q

In terms of radiosensitivity, what are the 5 types/categories of cells?

A
  1. Vegetative intermitotic
  2. Differentiating intermitotic
  3. Multipotent connective tissue
  4. Reverting post-mitotic
  5. Fixed postmitotic
30
Q

Give an example of vegetative intermitotic cell type and its level of radiosensitivity

A

These are the most radiosensitive type of cells and include cells from the basal layer of the oral mucosal membrane

31
Q

Give an example of a reverting postmitotic cell type and its level of sensitivity

A

Reverting postmitotic cells are fairly radioresistant and include cells of the salivary glands

32
Q

Do all cell types respond the same to radiation?

A

NO

33
Q

List the 5 types of cells according to their relative radiosensitivity

A

Vegetative > Differentiating > Multipotent > Reverting > Fixed

34
Q

What type of cells (and give 2 examples) are most radioresistant?

A

Fixed postmitotic are most resistant and include neurons and muscle cells

35
Q

What is the “Law of Bergonie and Tribondeau” state?

A

Cells tend to be radiosensitive based on 3 specific properties:

  1. High division rate
  2. Long dividing future
  3. Are of unspecialized type
36
Q

Name 5 highly radiosensitive tissues/organs

A
  1. Lymphocytes
  2. Bone marrow
  3. Testes
  4. Intestines
  5. Mucous membranes
37
Q

What are the acute effects resulting from 100Gy exposure?

A

Death occurs within hours due to cerebrovascular syndrome (neurological and cardiovascular breakdown)

38
Q

What are the acute effects of 0.5-3.5 Gy exposure?

A

Varying degrees of nausea, vomiting, diarrhea, redness of the skin, loss of hair, blisters, and depression of immune system

39
Q

What are the acute effects of 2-5 Gy exposure?

A

Death occurs within several weeks after exposure due to hematopoietic syndrome (damage to bone marrow)

40
Q

What are the acute effects of 1 Gy exposure?

A

Mild radiation sickness, depressed white blood cell count (prodromal syndrome)

41
Q

What are the acute effects of 5-12 Gy exposure?

A

Death occurs within days after exposure due to Gastrointestinal Syndrome (bloody diarrhea, and destruction of intestinal mucosa)

42
Q

What are the acute effects of 0.25 Gy exposure?

A

Erythema, blistering and residual smooth, soft, depressed scar

43
Q

In what units are dental diagnostic images measured in?

A

uSv (note, 1 Gy = 1 Sv)

44
Q

How are radiation effects dependent on time?

A

Effect of radiation is dependent on time because for an equal dose of radiation, those exposed with said amount over a longer period of time will have worse effects

45
Q

What is the most important somatic effect from x-radiation?

A

Radiation-induced cancer

46
Q

Is there a proven link between x-radiation from diagnostic radiology to genetic mutation?

A

No

47
Q

What 4 tissues are most highly susceptible to radiation-induced cancer?

A
  1. Colon
  2. Stomach
  3. Lung
  4. Bone marrow
48
Q

Are salivary and thyroid glands highly susceptible to radiation-induced cancer?

A

No, they have low susceptibility

49
Q

What are the 3 key points of ALARA?

A
  1. No practice shall be adopted unless its introduction produces a positive net benefit
  2. All exposures shall be kept as low as reasonable achievable (every patient Tx plan is customized)
  3. The dose equivalent to individuals shall not exceed the limits recommended
50
Q

What kind of film should be used in practice and why?

A

If using film, the highest speed of film should be used because it allows for substantial reduction in the radiation required to expose the film

51
Q

What is the effective dose occupational limit according to NCRP and ICRP?

A

50mSv

52
Q

What is the effective dose non-occupational limit according to NCRP vs ICRP?

A 
NCRP = 5 mSv
ICRP = 1 mSv
53
Q

Where does most of the world’s radiation come from?

A

Radon isotope in the soil

54
Q

In the last 10 years, what has been the fastest growing contribution the the world’s radiation levels?

A

CT scans

55
Q

Is radiation induced carcinogenesis an additive or non-additive effect?

A

Additive effect

56
Q

Is there any form of radiation that is 100% safe?

A

No. All radiation is potentially harmful

57
Q

What is the correlation between occurrence and dose regarding radiation-induced cancer?

A

The probability of occurrence of radiation-induced cancer increases with increasing dose

58
Q

Are children more or less susceptible to radiation vs adults?

A

Children are more radiosensitive

59
Q

Approximately how many extra fatal cancers occur per million dental radiographs?

A

2.5

000 Radiation Safety (71 decks)

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