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Oral Radiology > Radiation Biology Part I > Flashcards

Radiation Biology Part I Flashcards

1
Q

what is the exposure dose

A

the amount of radiaiton coming out of the XR tube head
- a measure of the capacity of radiation to ionize air

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1
Q

what are the dose units for radiation measurement

A
  • exposure dose
  • absorbed dose
  • equivalent dose
  • effective dose
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2
Q

what is the absorbed dose

A

the amount of radiation coming out of the XR tube that is absorbed by the patient

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3
Q

what is the equivalent dose

A

a way to measure different types of radiation equaly, absorbed dose times damaging effect

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4
Q

what is the effective dose

A

calculated dose

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5
Q

what is the traditional unit and SI unit of exposure dose

A

-R
-air kerma

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6
Q

what is the traditional unit and SI unit of absorbed dose

A

-rad
- Gy

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7
Q

what is the traditional unit and SI unit of equivalent dose

A
  • rem
    -Sv
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8
Q

what is the traditional unit and SI unit of equivalent dose

A
  • rem
    -Sv
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9
Q

what is the formula for the equivalent dose

A

Ht = DT (absorbed dose) x Wr (radiation weighing factor)
or RAD x QF

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10
Q

what is the QF for x radiation

A

1

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11
Q

what can the effective dose be used to calculate

A

risk of non uniform radiation to the localized part of body and degree to which this would icnrease a persons whole body risk of cancer and/or induction of genetic mutations

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12
Q

what is the formula for an effective dose

A
  • the sum of dose equivalence to the specific tissues or organs exposed and the biological tissue weighting factor
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13
Q

produces for more exposure: round or rectangular

A

round

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14
Q

ionization from exposure sets of a multiple direct and indirect molecular reactions in _____

A

less than 1 second

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15
Q

how long do enzymatic repair or further deleterious molecular changes occur

A

minutes to hours

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16
Q

how long to determinstic and stochastic effects take place

A

months to decades to generations

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17
Q

what are determinisitc effects and examples

A
  • lethal DNA damage, cell death, decreased tissue and organ function
  • EX: xerostomia, osteoradionecrosis, cataracts, decreased fetal development
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18
Q

what are the stochastic effects and examples

A
  • sub lethal DNA damage, gene mutation, replication of mutated cells
  • EX: leukemia, thyroid cancer, salivary gland tumors, heritable disorders
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19
Q

what are the interactions of X Radiation with matter and their prevalence

A
  • no interaction ~9%
  • photoelectric effect ~27-30%
  • compton scatter ~57-62%
  • coherent (thomson) scatter ~7%
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20
Q

which types of interaction of X radiation with matter are ionizing

A

photoelectric effect and compton scatter

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21
Q

describe the no interaction x radiation

A

X ray photon enters object and exits with no change in its energy

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22
Q

decsribe photoelectric interaction

A
  • x ray photon collides with an inner orbital electron and loses its energy and results in an atom with an altered electric state
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23
Q

describe the ionized matter after photoelectric interaction

A
  • unstable and seeks a more stable configuration
  • new configuration may be new ionic bonds, different covalent bonding
  • may effect biologic structure function or both
  • effects are often deleterious biologic changes
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24
Q

describe compton scatter

A
  • x ray photon collides with an outer orbital electron losing some energy
  • x ray photon continues in different direction with less energy creating more scatter until al the energy is lost
  • results in an atom with an altered electric state
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25
Q

describe coherent interaction

A
  • x ray photon of low energy interacts with an outer orbital electron and changes direction
  • no photoelectron produced
  • no ionization occurs
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26
Q

what are the types of injury with x ray interation with matter

A
  • direct
  • indirect
  • both occur quickly
  • both take hours to decades to become evident
  • both are a result of ionization
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27
Q

describe direct effects

A
  • directly ionizes biologic macromolecules
  • contributes to 1/3 of biologic effects
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28
Q

describe indirect effects

A
  • x ray photons absorbed by H2O-> free radicals -> biologic damages
  • contributes to 2/3 of biologic effects
  • primary method of cell damage from radiolysis of water cause by xradiation
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29
Q

what are the fates of DNA damage

A
  • repair
  • misrepair/mutation
  • unrepaired
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30
Q

what is a free radical

A

a free atom or molecule carrying an unpaired orbital electron in the outer shell

31
Q

describe free radical formation

A

-x ray photons interact with water in cells-> ionization -> free radical formation
- highly reactive and unstable
- lifetime 10^-10 seoncds

32
Q

free radicals seek a more stable configuration which results in the formation of:

A

toxic substances

33
Q

dose of radiation is correlated with:

A

the response or damage

34
Q

curves are ____ for diagnosit x radiation

A

theoretical

35
Q

describe a threshold non linear curve

A

-small exposures to a substance do not produced measurable changes
- a thershold must be reached before changes are observed
- most biologic effects are non linear

36
Q

describe linear non threshold curve

A
  • dose is proportional to the response
  • no matter how small the dose, there is some damage or risk
  • stochastic effect
37
Q

describe non linear non threshold curve

A
  • no threshold
  • minimal damage at first with increased rate of damage with increased dose
38
Q

describe deterministic risk/effect

A
  • has a threshold
  • severity is proportional to the dose
39
Q

what are examples of deterministic risk/effect

A
  • erythema
  • xerostomia
  • cataract
  • fertility
  • fertility
  • alopecia
  • osteoradionecrosis
  • fetal development
40
Q

what is the fetal dose for OMR imaging

A

0.01 mGy

41
Q

describe stochastic effects

A
  • have no dose threshold
  • probability of occurence is propportional to dose
  • severity of effects does not depend on dose
42
Q

what do genetic mutations to somatic cells cause

A

malignancy
- affects parent
- no affect on future generation

43
Q

what do genetic mutations to germ cells cause

A

-heritable effects
- no affect on parent but affects future generations

44
Q

radiation induced cancer not seen in doses:

A

less than 10 mGy

45
Q

what are somatic cells

A

all those except reproductive cells

46
Q

what types of injuries are seen in somatic effects/mutations

A

cancer, leukemia, cataracts

47
Q

what is the sequence of radiation injury

A
  • latent period
  • period of injury
  • recovery period
48
Q

what is the latent period

A

time that elapses between exposure and appearance of clinical signs

49
Q

what does the length of the latent period depend on

A

total dose
dose rate

50
Q

a shorter latent period if:

A

increased amount of radiation
- faster dose rate

51
Q

what happens in the period of injury

A
  • cell death
  • changes in cell functino
  • breaking or clumping of chromosomes
  • giant cell formation
  • cessation of mitotic activity
  • abnormal mitotic activity
52
Q

what are the factors modifying effects of x radiation

A
  • total dose
  • dose rate
  • oxygen
  • area exposed
  • cell type and function
  • age
53
Q

increased total dose =

A

increased damage

54
Q

what does the dose rate describe

A

the frequency of dose delivery

55
Q

increased dose rate ->

A

decreased cellular repairs and increased damages

56
Q

increased oxygen content =

A

increased radiosensitivity and increased tissue damage

57
Q

what is radiosensitivity

A

young, immature, rapidly growing and dividing, least specialized

58
Q

what is radioresistant

A

mature, specialized cells

59
Q

increase in cell division =

A

increased sensitivity

60
Q

immature cells/not highly specialized =

A

increased sensitivity

61
Q

increased metabolism =

A

increased sensitvity

62
Q

what cells are highly sensitive/least radioresistant

A
  • blood cells
  • small lymphocyte- most sensitive
  • bone marrow
  • reproductive cells
  • intestinal mucosa
  • mucous membrane
63
Q

what tissues have an intermediate sensitivity to radiation

A
  • connective tissue
  • breast -women
  • small blood vessels
  • growing bone and cartilage
  • salivary gland
64
Q

what tissues have a fairly low sensitvity to radiation

A

thyroid gland
- skin

65
Q

what tissues have low sensitivity to radiation

A
  • muscle
  • nerve
  • mature bone
66
Q

what aged individuals are more at risk and why

A

pediatric patients because rate of cellular and organ growth puts tissues at greatest level of radiosensitivity
- greater life expectancy puts children 2-10 greater risk of being afflicted with a radiation induced cancer

67
Q

females less than 10 years old are______ to develop fatal cancer than a 50 year old

A

~5 to 6X more likely

68
Q

what does RAD stand for

A

Radiation Absorbed Dose

69
Q

what does radiation weighing factor depend on

A

type and energy of the radiation involved

70
Q

what is the radiation weighing factor for high energy radiations

A

greater than 1

71
Q

what is the radiation weighing factor for high energy protons

A

5

72
Q

whatis the radiation weighing factor for alpha particles

A

20

73
Q

what does REM stand for

A

roentgen equivalent in man

74
Q

what is REM =?

A

RAD x Q.F.

75
Q

does effective dose measure deterministic or stochastic effects

A

stochastic effects

76
Q
A

Oral Radiology (26 decks)

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