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ORAL RADIOLOGY EXAM 2 > radiation biology > Flashcards

radiation biology Flashcards

1
Q

interactions of x radiation with matter

A

ionization

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2
Q

radiation injury

A

a. direct vs indirect
b. dose response curves
c. deterministic vs stochastic risk
d. somatic vs genetic effects
e. sequence of radiation injury

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3
Q

dose units for radiation measurement:
1. exposure dose
2. absorbed dose
3. equivalent dose
4. effective dose

A
  1. exposure dose: R vs. coulombs/kg
  2. absorbed dose: RAD vs. Gray (G)
  3. equivalent dose: REM vs. Sievert (Sv)
  4. effective dose: REM vs. Sievert (Sv)
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4
Q

ionize air

A

exposure
traditional unit: R
SI unit: air kerma

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5
Q

energy absorbed by tissue

A

absorbed dose
traditional unit: rad
SI unit: Gy

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6
Q

modified by radiation weighting factor

A

equivalent dose
traditional unit: rem
SI unit: Sv

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7
Q

modified by tissue weight factor

A

traditional unit: rem
SI unit: Sv

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8
Q

measure of the capacity of radiation to ionize air

A

exposure

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9
Q

exposure traditional unit

A

R roentgen

and air kerma in metric (kinetic energy released in matter)

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10
Q

absorbed dose:

A

rad
radiation absorbed dose

100 radiation energy in 1 gram of absorbed material

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11
Q

use to compare the biological effects of different types of radiation

A

equivalent dose (I)

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12
Q

radiation weighing factor (Wr) depends on the type and energy:

A

of the radiation involved

Ht (equivalent dose)= Dt (absorbed dose) x Wr (radiation weighing factor)

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13
Q

measure of the biological effectiveness of a radiation to ionize matter

A

equivalent dose

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14
Q

the quality factor for x-radiation is

A

1

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15
Q

equivalent dose unit is REM that stands for

A

roentgen equivalent in man

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16
Q

equivalent dose is equivalent to

A

RAD x QF

(absorbed dose x Wr)

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17
Q

since QF for x-radiation is 1, the RAD units for x-radiation are ____to REM units

A

equal

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18
Q

effective dose calculation

A

E= SUM(Z) Wt x Ht
E= Z (tissue weight factor) x (dose equivalence to tissue)

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19
Q

this measure is used to specifically calculate risks of radiation to human tissues on a common scale

A

effective dose

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20
Q

product of the sum of dose equivalence to the specific tissues or organs exposed and the biological tissue weighting factor

A

effective dose

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21
Q

**used to assess risk of non-uniform radiation to localized part of body and degree to which this would increase a person’s whole body risk of:

A

effective dose

  1. cancer induction and or
  2. induction of genetic mutations
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22
Q

area exposed is related to the

A

maximum size of the beam

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23
Q

1 of 4 things can happen when you expose an object to x-radiation

A
  1. no interaction (pass right thru) 9%
  2. coherent scattering (heat and no ionize) 7%
  3. photoelectric absorption 27%
  4. compton scattering 57%
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24
Q

two ionizing effects are

A
  1. compton (incoherent) scatter
  2. photoelectric effect
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25
Q

mechanism of injury from xray interaction with matter (ionization)

A

radiation injury

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26
Q

ionization from ionizing radiation exposure sets off multiple direct and indirect molecular reactions in ____secs

enzymatic repair or further deleterious molecular changes occur in

deterministic and stochastic effects take place over time from

A

< 1 second

in mins to hours

months to decades to generations

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27
Q

x-ray photon enters object (patient or other tissues) and exits with no change in its energy

A

no interaction 9%

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28
Q

x-ray photon collides with an orbital electron and loses its energy.

-ejected photoelectron loses its energy and results in an atom with an altered electric state ( example: + charge)

A

photoelectric interaction
30% of all interactions

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29
Q

in this interaction, the ionized matter is unstable and seeks a more stable configuration.

the new configuration may include new ionic bonds, different covalent bonds, etc.

if the degree of photoelectric effect is significant, this may affect:________

these effects are often deleterious biologic changes, like altered metabolic function or malignancy

A

photoelectric interaction AND compton interaction/scatter

affect biologic structure, function or both

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30
Q
  1. xray photon collides with an outer orbital electron losing some energy
  2. xray photon continues in different direction with less energy creating more scatter until all the energy is lost
  3. results in an atom with an altered eletric state (ex: + charge)
A

compton interaction/scatter
62% of interactions

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31
Q
  1. xray photon of low energy interacts with an outer orbital electron and changes direction
  2. no photoelectron produced
  3. no ionization occurs
A

coherent interaction
8% of interactions

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32
Q

with direct and indirect radiation injury, both:

A
  1. effects occur quickly
  2. take hours to decades to become evident
  3. result of ionization
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33
Q

this ionizes biologic maromolecules
contributes to ~1/3 of biologic effects

A

direct effect

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34
Q

xray photons absorbed by H2O-> free radicals-> biologic damage
contributes to ~2/3 of biologic effects

A

indirect effect

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35
Q

radiation strikes biologically active molecule= biologically active

A

direct effect

36
Q

damaged molecule no longer capable of proper function= molecular death

A

radiation damage theory (bioloically active equals this)

37
Q

3 outcomes of direct effect of UV light on skin DNA

A
  1. repair (healed)
  2. inaccurate repair (mutation)
  3. no repair (death)
38
Q

method of cell damage from radiolysis of water caused by x-radiation

A

primary

indirect effect

39
Q

indirect effect.

photon + ____-> H2O-> OH+H

A

H2O

40
Q

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

A

free radical

41
Q

free radical formation

A

xray photons interact with water in cells

ionization occurs

resulting in free radical formation

42
Q

highly reactive and unstable
lifetime=10^-10 seconds

A

free radical formation

43
Q

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

A

toxic substances

44
Q

(dose) amount of radiation is correlated with response or damage

A

dose-response curves

45
Q

curves are ______for diagnositic xradiation

A

theoretical

46
Q

threshold non-linear curve,

small exposures to a substance (does/does not) produce measurable change

A

doesn’t

47
Q

what must be reached for exposure to produce measurable change

A

must meet threshold before changes are observed

48
Q

most biologic effects are (linear/non-linear)

A

non-linear

49
Q

dose is proportional to the response
-no matter how small dose, there is some damage or risk

A

linear non-threshold curve

50
Q

no threshold
-minimal damage at first with increased rate of damage with increased dose

A

nonlinear nonthreshold curve

51
Q

determinisitic risk/effect

A
  1. have threshold
  2. severity is proportional to the dose
    examples:
    erythema
    xerostomia’cataract
    fertility
    alopecia
    *fetal development
52
Q

fetal effective dose

A

OMR imaging, 0.01mGy

53
Q

threshold radiation erythema dose (TED)

A

250 rads

54
Q

average radiation erythema dose

A

500 rads

55
Q

maximum radiation erythema dose

A

750 rads

56
Q
  1. have no dose threshold
  2. probability of occurrence is proportional to dose
  3. severity of effects does not depend on dose
A

stochastic effect

57
Q

genetic mutations cause malignancy (stochastic effect)

A

to somatic cells

58
Q

genetic mutations cause heritable effects
(stochastic effect)

A

to germ cells

59
Q

radiation-induced cancer is not seen in doses _____10 mGy

throughout pregnancy

A

<

60
Q

no affect on parent, affects future generation

A

genetic injury

61
Q

affects parent and no effect on future generatiion

A

somatic injury

62
Q

all those except reproductive cells

A

somatic cells

63
Q

seen in the person irradiate
and NOT transmitted to future generations
(induction of cancer, leukemia, cataracts)

A

somatic effects/mutations

64
Q

not seen in person irradiated
passed on to future generations

A

genetic effects/mutations

65
Q

sequence of radiation injury

A
  1. latent period
  2. period of injury
  3. recovery period
66
Q

time that elapses between exposure and appearance of clinical signs

A

latent period

67
Q

latent period can be short or long depending on

A

total dose and dose rate

68
Q

shorter latent period if

A
  1. increased amount of radiation
  2. faster dose rate
69
Q

genetic effects of latent period

A

may be generations before clinical effects are seen

70
Q
  • Cell death
  • Changes in cell function
  • Breaking or clumping of chromosomes
  • Giant cell formation
  • Cessation of mitotic activity
  • Abnormal mitotic activity
A

period of injury

71
Q
  • full recovery for a large percentage of
    individuals from a few weeks up to two years
    after exposure
A

recovery period

72
Q

No recovery period i.e, death likey at higher does of
>1.2 Gy (120 Rads).

A

> 1.2 Gy (120 Rads).

73
Q

factors modifying effects of x-radiation

A
  1. Total dose
  2. Dose rate
  3. Oxygen
  4. Area exposed
  5. Cell type and function
  6. Age
74
Q

increase total dose:

A

increase damage

75
Q

increase dose rate

A

decrease cellular repair which increases damages

76
Q

increase oxygen content

A

increase radiosensitivity
increase tissue damage

77
Q

young, immature, rapidly growing and dividing, least specialized

(what cell type)

A

radiosensitive

78
Q

mature, specialized cells

(what cell type)

A

radioresistant

79
Q

____ more sensitive than reptiles, insects, bacteria

A

Mammals (species)

80
Q

Mitotic activity
increase frequency of cell division = ___sensitivity

A

increase sens

81
Q

Mitotic activity
Immature cells/not highly specialized = ___sensitivity

A

increase sens

82
Q

Cell metabolism
increase metabolism = ___sensitivity

A

increase sens

83
Q

tissues/organs
1. high sens to radiation
2. least radioresistant

A

Blood cells
Small lymphocyte – most sensitive
Bone marrow
Reproductive cells
Intestinal mucosa
Mucous membrane

84
Q

tissues/organs
Intermediate sensitivity to radiation

A

Connective tissue
Breast (women)
Small blood vessels
Growing bone and cartilage
Salivary gland

85
Q

tissues and organs
Fairly low sensitivity to radiation

A

Thyroid gland
Skin

86
Q

tissues/organs
Low sensitivity to radiation
Most radioresistant

A

Muscle
Nerve
Mature bone

ORAL RADIOLOGY EXAM 2 (5 decks)

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