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Board Revie > Radiobiology > Flashcards

Radiobiology Flashcards

1
Q

LET

A

Linear Energy Transfer

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2
Q

RBE

A

Relative Biological Effectiveness

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3
Q

OER

A

Oxygen Enhancement Ratio

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4
Q

What is LET defined as?

A

Rate at which energy is deposit as charge particles travel through matter

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5
Q

What is High LET and characteristic of the particles that provide this effect?

A

Particulate Radiation and Mass, Charged particles, short distance and densely ionizing (Straight Path)

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6
Q

What is Low LET and characteristic of the particles that provide this effect?

A

Electromagnetic Radiation and No Mass/Charge, Travel at the speed of light and Sparsely Ionizing (Spiratic Path)

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7
Q

What is the the difference in biological effects compared to physic effects?

A

Biological effects take time as their process of reaction is significantly slower when compared to physics processes

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8
Q

What are compounds that undergo particulate interactions (High LET)?

A

Alpha, Beta, Electron and protons (Neutrons also undergo this process despite no charge or mass)

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9
Q

What are compounds that undergo electromagnetic interactions (Low LET)?

A

Xrays and Gamma rays

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10
Q

Alpha Particles

A

High Ionizing Density (Highest LET), +2 Charge, He nuclei

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11
Q

Neutron Particles

A

High Ionizing Density (2nd Highest LET), No Charge

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12
Q

Beta Particles

A

E- or Positrons (- or +), Low ionization density

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13
Q

X ray and Gamma Rays

A

Photons, Low ionization Density, High penetrating Power

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14
Q

Direct Action

A

Direct interaction of the radiation with the DNA, Pre-dom with High LET,

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15
Q

Indirect Action

A

Indirect interaction of the Radiation that interacts through a medium such as water, Pre-dom with Low LET

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16
Q

What happens to the survival curve as LET increases from X-rays to Alpha particles?

A

As the LET increases the curves begins to become steeper and the shoulder decreases in size

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17
Q

Indirectly Ionizing

A

High Energy, Small Wavelength, Large Frequency (Xrays and Gammas)

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18
Q

Relative Biological Effectiveness

A

Dose in Gy from a 250 Kv Xray divided by the dose in Gy of another radiation that has the same effect

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19
Q

How does RBE change with LET?

A

As LET increases, the RBE becomes more likely to increase the Damage and create cell overkill

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20
Q

What LET causes Cell kill?

A

100 KeV/um

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21
Q

Hypoxic

A

Oxygen depleted

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22
Q

Aerobic

A

Oxygen Rich

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23
Q

How do you find the OER?

A

Hypoxic/Aerobic

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24
Q

What occurs with more oxygen within the cell?

A

More oxygen within the cell will create an environment in which free radicals are more frequently occurring increase the damage to the cell

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25
Q

What the relationship with OER and survival curves?

A

Those radiations that have lower OER exhibit survival rates that are more steeper compared to the those that have high OER (More Densely ionizing= Lower OER= Steeper survival curve)

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26
Q

What is the relationship with OER and RBE, when looking at LET?

A

Inverse relationship, High LET do not have a desire for High OER, which then creates a high RBE, Low LET desire do not desire a LOW OER which creates a Low RBE

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27
Q

What are the effects of radiation on DNA?

A

Hydrogen Bond, Loss of Base, Single strand break, Double strand break, Cross-links

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28
Q

What is the most deadly Radiation induced effect on DNA?

A

Double strand break

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29
Q

What is the Radiation induced effect on DNA is two independent events?

A

Cross-link

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30
Q

What are the 4 chromosomal Abberrations?

A

Deletion, Duplication, Inversion and Translocation

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31
Q

Explain Translocation chromosomal aberration?

A

The strands exchange information and create a new sequence of information

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32
Q

What are 3 lethal chromosome configurations?

A

Ring, Dicentric and Anaphase Bridge

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33
Q

Explain the ring chromosome configuration

A

Chromosomes have broken segments of deleted genetic material and then fusion between the two original chromosomes occurs, creating a ring

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34
Q

Dicentric vs Acentric Fragmentation

A

Chromosomes that are irradiated break, to which fusion between the broken arms occurs and you create a Dicentric fragment (Large fragment with double centromeres) or Acentric fragment (Small fragment with no centromere)

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35
Q

What is the cellular response to being irradiated?

A

Division Delay, Interphase Death or Productive Failure

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36
Q

What occurs during division delay in the response to radiation?

A

Delay in mitosis or recovery, Mitotic overshoot

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37
Q

What occurs during interphase death in the response to radiation?

A

Apoptosis, Cell line dependent, radiosensitive cells die at lower doses

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38
Q

What occurs during reproductive failure in the response to radiation?

A

cell fail to undergo repeated division, (Dose increase creates reproductive failure)

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39
Q

In vivo

A

In living organism

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40
Q

In vitro

A

In glassware or artificial environment

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41
Q

What two factors are considered in cell survival curves?

A

Survival vs. Dose

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42
Q

How do you find plating efficiency?

A

Colonies counted/ # cells seeded

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43
Q

How do you find Survival Fraction?

A

of colonies counted/ # of cells seeded x Plating efficiency

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44
Q

Who are Puck and Marcus?

A

Created the first studies done on cell survival curves for radiation

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45
Q

What are the 3 cell parameters measured on survival curves?

A

n, Dq and Do

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46
Q

What is n?

A

Extrapolation # (Width of shoulder)

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47
Q

What is Dq?

A

Quasi-threshold (Width of shoulder region)

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48
Q

What is Do?

A

Radio-sensitivity (Measure of cell survival

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49
Q

What is the extrapolation number?

A

Extrapolate exponential portion back to Y-axis and number of targets to be hit to cause cell death (2-10 mammalian)

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50
Q

What is the quasi-threshold dose?

A

Terminal portion of curve intercepts dose axis at 100%, represents SF= 1 so a 100% survival

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51
Q

What is the Radiosensitivity variable, Do?

A

Reciprocal of Slope, dose that inactive all but 37% of population (1-2 Gy for mammalian)

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52
Q

What does a higher Do mean?

A

More resistant

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53
Q

What would a survival curve for a low Do look like?

A

Steeper, with a Lower Do, the radiosensitive is higher for lower dose creating a survival curve with a more drastic result

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54
Q

Higher LET= _______ in survival?

A

Decrease, more damaging, less likely chance of survival

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55
Q

What occurs to the survival curve as the LET gets higher?

A

Steeper and Lower Do as the dose to immobilize the majority of the population lowers

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56
Q

If given the option to choice between G2 and M, in regards to which is most radiosensitive, which would be the better answer?

A

M

57
Q

What are the three types of damage that can occur to cells?

A

Lethal, Sublethal and Potentially Lethal Damage

58
Q

What are the three SSSs of sublethal damage?

A

Sublethal, Split Fx, and Shoulder

59
Q

How was potentially lethal damage originally studied?

A

Irradiated cells were placed in suboptimal cell division conditions

60
Q

What was the result of studying potentially lethal damage?

A

Survival increased for the irradiated cells in suboptimal conditions as they were not forced to undergo cell division compared to those that are forced to in optimum conditions, requires 6-12 hours

61
Q

Radio-sensitivity is directly proportional to? Indirectly proportional to?

A

Directly proportional to reproductive activity and indirectly proportional to degree of differentiation

62
Q

More Reproductive cells = _________ radio-sensitive ?

A

More

63
Q

Least Differentiation= _______ Radiosensitive?

A

More

64
Q

What are the classification of cells based on radiosensitive?

A

VIM, DIM, Multi-potential, RPM and FPM

65
Q

VIM

A

Vegetative inter-mitotic, rapidly dividing, undifferentiated

66
Q

DIM

A

Differentiation Inter-mitotic, Actively dividing

67
Q

RPM

A

Reverse Post-mitotic, not normal dividing, variably differentiated

68
Q

FPM

A

Fixed Post-mitotic, do not divide highly differentiated

69
Q

What is the most sensitive cell classification?

A

VIM

70
Q

What is the least sensitive cell classification?

A

FPM

71
Q

Multipotential Connective Tissue

A

Irregularly dividing

72
Q

Example of VIM

A

Erythoblast

73
Q

Example of Multipotential Connective Tissue

A

Spermatocyte

74
Q

Example of FPM

A

Nerve Cell

75
Q

Radiosensitizers

A

Increase response to radiation, (Ex: Oxygen)

76
Q

Radioprotectors

A

Decrease response to radiation, protection of Dose limiting structures

77
Q

What is the best radiosensitizer?

A

Oxygen

78
Q

When is oxygen give to patients for their treatment?

A

Administered during treatment

79
Q

What is acute responding tissue?

A

Tissue rxn within few months after XRT, Rapidly dividing organs (Intestine, Bone Marrow, Testes)

80
Q

What is late responding tissue?

A

Tissue rxn greater than 3 months post xrt, slow dividing organs (Lung and Kidney)

81
Q

What is the LD 50/30?

A

Dose to produce lethality to 50% of the population in 3o days (LD 50/60 for humans)

82
Q

What is the LD 50/30 for humans?

A

3.5-4.5 Gy

83
Q

Acute radiation Syndrome 3 area affected

A

Hematopoietic, Gastrointestinal, CNS/CV

84
Q

Hematopoietic (Bone Marrow)

A

2-10 Gy, infection and hemorrhaging, 6 weeks to 6 days survival avg , dose dependent (Lowers chances of survival)

85
Q

Gastrointestinal (ARS)

A

10-100 Gy, Small intestine damaged, No survival, 3-10 days survival avg, no dose dependent

86
Q

CNS/CV (ARS)

A

> 100 Gy, Cerebral Edema, no Survival, 2-3 day survival avg, Dose Dependent (Lowers chances of survival)

87
Q

What is the LD 50/60 for ARS?

A

400 cGy

88
Q

What are the specific conditions to induce ARS?

A

Acute exposure (within minutes), Area exposed is total body, Exposure to external penetrating sources

89
Q

Whats different about internal deposition and inducing full ARS syndrome?

A

internal Radioactive materials do not induce full syndrome

90
Q

What are some ARS scenarios that have occurred “Naturally”

A

Hiroshima/Nagasacki and Chernobyl

91
Q

What are the 4 stages of ARS?

A

Prodromal, Latent, Manifest Illness, Recovery/death

92
Q

What happens to the stages of ARS as severity increases?

A

The stages decrease in time

93
Q

Prodromal

A

Initial stage, N/V and Diarrhea,Minutes to Days

94
Q

Latent

A

no symptoms, healthy looking, weeks down to hours

95
Q

Manifest Illness

A

Symptoms return, obvious illness, Exhibit specific symptoms, min to weeks

96
Q

What are the two types of radiation effects?

A

Stochastic and Deterministic

97
Q

Stochastic Effects

A

no threshold, no dose dependent, higher dose creates higher chance of expecting results (Cancer, Herediatary effects)

98
Q

Deterministic Effects

A

Threshold, Severity is dose dependent, Higher dose creates higher change of expecting results (Cataracts, Skin injuries)

99
Q

What is another name for late effects?

A

Somatic

100
Q

Somatic Effects

A

Non-specific Life shortening, Carcinogenesis, Cataractogenesis, Embryo/fetus effects

101
Q

Non-specific life shortening

A

Radiation-inducing aging, shortened life span, those chronically exposed will die before those that weren’t

102
Q

Carcinogenesis

A

SINGLE MOST IMPORTANT LATE SOMATIC EFFECT, Marie Curie died due to working with radiation unsafely

103
Q

What is the latency period for leukemia?

A

5-7 years, absolute risk

104
Q

What is the latency period for solid cancers?

A

20-60 years, relative risk

105
Q

six solid radiation inducing cancers?

A

Skin, Bone, Breast, Lung, and Thyroid

106
Q

Cataractogenesis

A

Deterministic effect, Threshold of 2 Gy (Stationary 2-6 Gy, Progressive 6-12 Gy)

107
Q

Embryonic and Fetal

A

Dose and age of gestation dependent,

108
Q

3 stages of embryonic and fetal impact?

A

Prenatal, Major organogenesis, Fetal

109
Q

Prenatal

A

0-9 days, prenatal death

110
Q

Major organogenesis

A

10-42 days, Congenital abnormalities and neonatal death

111
Q

Fetal

A

> 6 weeks - term, Functional abnormalities

112
Q

Hereditary Effects

A

Genetics based, Double dose- 1 Gy,

113
Q

What is the genetic counseling recommendation for conceptions post xrt?

A

6 months

114
Q

True or False. Radiation produced new mutations and also increases an already existing number.

A

False, Radiation does not create any new mutations, only increase the already existing ones

115
Q

Fractionation

A

Multifraction regime that produces better tumor control for given level of normal tissue toxicity than a single large dose

116
Q

What are the 4 R’s of Radiobiology?

A

Repair, Repopulation, Reassortment and Reoxygenation

117
Q

1st R, Repair

A

repair of sublethal damage between dose fraction

118
Q

2nd R, Repopulation

A

cell repopulate if given appropriate amount of time

119
Q

3rd R, Reassortment

A

Cycling cells into sensitive phases of the cell cycle

120
Q

4th R, Reoxygenation

A

enhance cell kill

121
Q

Acute tumor hypoxia

A

Low oxygen concentration, temporary closing or blocking of blood vessels

122
Q

Chronic tumor hypoxia

A

Peristent low oxygen concentration, exist in viable tumor cells close to necrosis

123
Q

Normoxic

A

Normal oxygen concentration

124
Q

Dose-Response Relationships

A

Radiation Biology applied to Clinical radiotherapy is concerned with the relationship b/w a given absorbed dose of radiation and the consequent biologic response

125
Q

With increasing radiation dose, effects may increase in ______ in ____ or both?

A

Severity (grade) and Frequency (Incidence)

126
Q

Therapeutic ratio

A

percent of tumor control achieved for given level of normal tissue damage

127
Q

Therapeutic ratio factors (____/_____)

A

Tumor control probability/Normal Tissue Complication Probability

128
Q

In regards to therapeutic window, the further apart the curves creates what?

A

A larger therapeutic window

129
Q

Law of Bergonie and Tribondeau

A

Mitotic Activity and Differentiation

130
Q

Rubin and Casarett

A

Radiosensitivity

131
Q

Tolerance Dose

A

dose the produced an acceptably probability of treatment complications (TD 5/5 and TD 50/5)

132
Q

Emami provides?

A

TD for 1/3, 2/3, and whole organ with clinical endpoint

133
Q

QUANTEC provides?

A

Dmax, Mean dose, Dose/volume parameters

134
Q

TD 5/5

A

Dose which when given to population will result in a minimum 5% several complication rate within 5 years

135
Q

TD 50/5

A

Dose which when given to population will result in a maximum 50% several complication rate within 5 years

136
Q

Early Responding Tissue (VIM, DIM)

A

Rapidly dividing cells, (Skin, Bone Marrow, Intestinal lining and testes)

137
Q

Late responding Tissue (RPM FPM)

A

Slowly dividing cells (Lung,CNS, Kidney, Liver)

138
Q

What dose QUANTEC stand for?

A

Quantitative analyses of normal tissue effects in the clinic

Board Revie (5 decks)

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