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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
describe compton scatter
- 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
25
describe coherent interaction
- x ray photon of low energy interacts with an outer orbital electron and changes direction - no photoelectron produced - no ionization occurs
26
what are the types of injury with x ray interation with matter
- direct - indirect - both occur quickly - both take hours to decades to become evident - both are a result of ionization
27
describe direct effects
- directly ionizes biologic macromolecules - contributes to 1/3 of biologic effects
28
describe indirect effects
- 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
29
what are the fates of DNA damage
- repair - misrepair/mutation - unrepaired
30
what is a free radical
a free atom or molecule carrying an unpaired orbital electron in the outer shell
31
describe free radical formation
-x ray photons interact with water in cells-> ionization -> free radical formation - highly reactive and unstable - lifetime 10^-10 seoncds
32
free radicals seek a more stable configuration which results in the formation of:
toxic substances
33
dose of radiation is correlated with:
the response or damage
34
curves are ____ for diagnosit x radiation
theoretical
35
describe a threshold non linear curve
-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
describe linear non threshold curve
- dose is proportional to the response - no matter how small the dose, there is some damage or risk - stochastic effect
37
describe non linear non threshold curve
- no threshold - minimal damage at first with increased rate of damage with increased dose
38
describe deterministic risk/effect
- has a threshold - severity is proportional to the dose
39
what are examples of deterministic risk/effect
- erythema - xerostomia - cataract - fertility - fertility - alopecia - osteoradionecrosis - fetal development
40
what is the fetal dose for OMR imaging
0.01 mGy
41
describe stochastic effects
- have no dose threshold - probability of occurence is propportional to dose - severity of effects does not depend on dose
42
what do genetic mutations to somatic cells cause
malignancy - affects parent - no affect on future generation
43
what do genetic mutations to germ cells cause
-heritable effects - no affect on parent but affects future generations
44
radiation induced cancer not seen in doses:
less than 10 mGy
45
what are somatic cells
all those except reproductive cells
46
what types of injuries are seen in somatic effects/mutations
cancer, leukemia, cataracts
47
what is the sequence of radiation injury
- latent period - period of injury - recovery period
48
what is the latent period
time that elapses between exposure and appearance of clinical signs
49
what does the length of the latent period depend on
total dose dose rate
50
a shorter latent period if:
increased amount of radiation - faster dose rate
51
what happens in the period of injury
- cell death - changes in cell functino - breaking or clumping of chromosomes - giant cell formation - cessation of mitotic activity - abnormal mitotic activity
52
what are the factors modifying effects of x radiation
- total dose - dose rate - oxygen - area exposed - cell type and function - age
53
increased total dose =
increased damage
54
what does the dose rate describe
the frequency of dose delivery
55
increased dose rate ->
decreased cellular repairs and increased damages
56
increased oxygen content =
increased radiosensitivity and increased tissue damage
57
what is radiosensitivity
young, immature, rapidly growing and dividing, least specialized
58
what is radioresistant
mature, specialized cells
59
increase in cell division =
increased sensitivity
60
immature cells/not highly specialized =
increased sensitivity
61
increased metabolism =
increased sensitvity
62
what cells are highly sensitive/least radioresistant
- blood cells - small lymphocyte- most sensitive - bone marrow - reproductive cells - intestinal mucosa - mucous membrane
63
what tissues have an intermediate sensitivity to radiation
- connective tissue - breast -women - small blood vessels - growing bone and cartilage - salivary gland
64
what tissues have a fairly low sensitvity to radiation
thyroid gland - skin
65
what tissues have low sensitivity to radiation
- muscle - nerve - mature bone
66
what aged individuals are more at risk and why
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
females less than 10 years old are______ to develop fatal cancer than a 50 year old
~5 to 6X more likely
68
what does RAD stand for
Radiation Absorbed Dose
69
what does radiation weighing factor depend on
type and energy of the radiation involved
70
what is the radiation weighing factor for high energy radiations
greater than 1
71
what is the radiation weighing factor for high energy protons
5
72
whatis the radiation weighing factor for alpha particles
20
73
what does REM stand for
roentgen equivalent in man
74
what is REM =?
RAD x Q.F.
75
does effective dose measure deterministic or stochastic effects
stochastic effects
76

Oral Radiology (26 decks)

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