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From Flashcardlet > Definitions Rad Bio > Flashcards

Definitions Rad Bio Flashcards

0
Q

Mitotic delay

A

Delay of entry into mitosis, resulting in cell accumulation in G2. Result of treatment.

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1
Q

Mitotic Catastrophe

A

(MC)
Improper completion of cell division b.c of unrepaired or misrepared DNA damage. MC occurs after irradiation & is the major cause of cell death.

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2
Q

alpha/beta ratio

A

The ratio of the parameters alpha and beta in the LQ model

Often used to quantify the fractionation sensitivity of tissues

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3
Q

Accelerated fractionation

A

intensification of RT by increasing dose per fraction (distinct from hyperfractionation)

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4
Q

Hyperfractionation

A

Decrease in dose per fraction with more doses per day.

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5
Q

Acute hypoxia

A

low oxygen concentrations associated with changes in blood flow through vessels.
Also called transient or perfusion limited hypoxia

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6
Q

Anoxia

A

the absence of oxygen

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7
Q

Asymmetrical divisions

A

Divisions of stem cells into one stem cell and one differentiating cell

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8
Q

Autophagy

A

Process in which cellular components are self-digested through the lysosome pathway

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9
Q

BER

A

Base Excision Repair

DNA repair pathway for repairing damage to DNA bases.

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10
Q

BED

A

Biologically Effective Dose

the total dose that would be required in small doses to give an equivalent effect.

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11
Q

BNCT

A

Boron neutron capture therapy

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12
Q

Cell Cycle time

A

time between mitoses

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13
Q

Bragg Peak

A

Region of maximum dose deposition near the end of the tracks of protons, alpha particles, and heavier ions

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14
Q

CDK

A

Cyclin Dependent kinase

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15
Q

Chronic hypoxia

A

persisent low oxygen concentration
Also called diffusion limited hypoxia
Occurs at distances 150 micrometers or greater from blood vessels

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16
Q

Cell Death

A

the permanent loss of clonogenic capacity

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17
Q

Cell loss factor

A

rate of cell loss from a tumor
Cell loss = 1- Tpot - Td
Where Tpot is the potential doubling time
Td = cell population doubling time

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18
Q

CHART

A

Continuous Hyperfractionated Accelerated Radiation Therapy

a schedule delivering 54 Gy in 36 fractions, with 3 fractions per day on 12 consecutive days (including weekends)

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19
Q

Clonogenic cells / Clonogenic survival

A

Cells that have the capacity to produce descendants

Fraction of cells that survive after exposure to or treatment with an agent that causes cell death.

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20
Q

DDR

A

DNA Damage Response

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21
Q

Do

A

in the multi-target theory, Do = the radiation dose that reduces survival to e^-1 (0.37) of its previous value (on exponential part of cell survival curve).

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22
Q

DMF

A

Dose Modifying Factor
an agent that acts to change the dose of radiation
ratio of dose w/o to dose with the agent for the same effect

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23
Q

Dose-rate effect

A

Increase in isoeffective radiation dose with decreaing radiaiton dose rate

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24
Q

DRF

A

Dose-reduction factor

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25
Q

Doubling time

A

time for tumor to double in size

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26
Q

Double trouble

A

a hot-spot within a treated volume that is also receiving a higher dose per fraction (greater BED)

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27
Q

Early normal-tissue responses

A

Radiation-induced normal tissue damage that is expressed weeks to a few months after exposure (w/in 90 days)
Alpha/Beta ratio usu. high (>6 Gy)

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28
Q

ED50

A

effect dose 50%

Radiation dose estimated to produce a normal tissue effect in 50% of subjects irradiated

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29
Q

Elkind repair

A

recovery of the ‘shoulder’ on a radiation dose cell survival curve when irradiation follows a ‘priming’ dose

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30
Q

EQD2

A

Equivalent total dose in 2-Gy fractions

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31
Q

EQD2,t

A

Equivalent dose in 2-Gy fractions bu adjusted for a possible difference in overall treatment time by using a reference overall time, t

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32
Q

EUD

A

Equivalent uniform dose

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33
Q

Extrapolated total dose (ETD)

A

Calculated isoeffective dose, at an infinitely low dose rate or fraction size

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34
Q

Extrapolation number

A

a parameter in the multitarget equation for cell survival

The point on the surviving fraction axis to which the straight part of the curve back-extapolates

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35
Q

Functional subunits (FSUs)

A

concept of a minimal functional tissue structure

Also called ‘tisue recruiting units (TRU)”

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36
Q

1 Gy

A

absorbed dose, in SI units
= 1 J/ 1 kg
=100 rad

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37
Q

Grey equivalents (GyE)
or
Cobalt fray equivalent

A

GyE or CGE for densely ionizing radiation is equal to the measured physical dose in gray multiplied by the RBE factor

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38
Q

Growth delay

A

Extra time required for an irradiated tumorl vs an unirradiated tumor to reach a given size

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39
Q

Growth fraction

A

the proportion of cells in a population that are cycling

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40
Q

Hierarchical tissues

A

tissues comprising a lineage of stem cells, transit cells, and post mitotic (differentiatin or mature) cells

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41
Q

HR

A

homologous recombination

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42
Q

Hyperbaric oxygen (HBO)

A

jhigh oxygen pressures) 2-3 atm to enhance oxygen availability in radiotherapy

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43
Q

Hyperthermia

A

heating tumors above normal phyiological temperatures to help with cancer therapy

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44
Q

Hypofractionation

A

the use of higer dose fractions than normal

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45
Q

Hypoplasia

A

reduction in cell numbers in a tissue

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46
Q

Hypoxia

A

low oxygen tension

very low levels required to make cells maximally radioresistant

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47
Q

Hypoxic cell cytotoxins

A

agents that kill hypoxic cells preferentially

48
Q

Hypoxic fraction

A

Fraction of hypoxic cells within a tumor

49
Q

Incomplete repair

A

Increased damage from fractionated RT when the time interval between doses is too short to allow complete recovery

50
Q

Indirect action

A

Damage to DNA by free radicals formed through the ionization of nearby water molecules

51
Q

Initial slope

A

steepness of the initial part of the cell survival curve, usually indicated by the value of ALPHA in the LQ model

52
Q

Interphase death

A

also known as apoptosis

the death of irradiated cells before they reach mitosis

53
Q

Ionization

A

The process of removing electrons from (or adding electrons to) atoms or molecules, thereby creating ions

54
Q

IRIF

A

Ionizing radiation-induced foci

Used to describe the accumulation of DNA damage-response proteins that localize to sites of DNA damage after irradiaiton

55
Q

Isoeffect plots

A

Graphs for the total dose for a given effect

example: ED50 plotted against dose per fraction or dose rate

56
Q

Labellig Index (LI)

A

% cells positive for a certain signal

57
Q

Late normal tissue response

A

RT induced normal tissue damage that is expressed months to years after exposure
The alpha/beta ratio tends to be small (<5 Gy)

58
Q

Latent time or

latency interval

A

Time between onset of irradiation and clinical manifestation of radiation effects

59
Q

LD50/30

A

Radiation dose to produce lethality in 50% of a population of individuals within 30 days

60
Q

Linear Energy Transfer (LET)

A

The rate of energy loss along the track of an ionizing particle. Usually expressed in keV/um

61
Q

Linear-quadratic (LQ) Model

A

Model in which the effect (E) is a linear quadratic function of dose (d)
E = ad + bd^2
cell survival:
S = exp(-ad - bd^2)

62
Q

Local tumor control

A

The complete regression of a tumor without later regrowth during followup
Requires that all cancer stem cells have been permanently inactivated

63
Q

Log-phase culture

A

a cell culture growing exponentially

64
Q

Mean inactivation dose (D_bar)

A

An estimate of the average radiation doseto inactivate a cell
Calculated as the area under the survival curve, plotted on linear coordinates

65
Q

Mitotic catastrophe

A

Improper completion of cell division because of unrepaired or misrepaired DNA damage
MC occurs frequently after irradiation and is a major cause of cell death

66
Q

Mitotic delay

A

Delay of entry into mitosis, resulting in an accumulation of cells in G2, as a result of treatment

67
Q

Mitotic index

A

% of cells in mitosis at any given time

68
Q

MMR

A

Mismatch repair

69
Q

Multitarget equation

A

Model that assumes the presence of a number of critical targets in a cell, all of which require to kill the cell
Surviving fraction = 1 - [1 - exp (D/Do)]^n

70
Q

Necrosis

A

Cell death associated with loss of cellular membrane integrity.
Occurs in anoxic areas of tumors and is also a cause of cell death after irradiation

71
Q

NER

A

Nucleotide excision repair

72
Q

NHEJ

A

Non-homologous end-joining

73
Q

Non-stochastic effect

A

An effect where the severity increases with increasing dose
has threshold effect
AKA deterministic effect

74
Q

NTCP

A

Normal tissue complication probability

75
Q

Oxygen Enhancement Ratio (OER)

A

Ratio of dose given under anoxic conditions to the dose resulting in the same effect when given under some defined level of oxygen tension.

76
Q

PET

A

Positron emission tomography

77
Q

Plating Efficiency (PE)

A

% of in vitro plated cells that form colonies

78
Q

Potential Doubling Time (Tpot)

A

Theoretical cell population doubling time in the absence of cell loss

79
Q

Plateau phase cultures

A

AKA stationary phase

Cell cultures grown so that proliferation is markedly reduced.

80
Q

Potentially Lethal Damage (PLD) repair

A

increase in cell survival that may occur during an interval between treatment and assay, caused by post-irradiation modification

81
Q

Prodromal Phase

A

Signs and symptoms within 48 hours post TBI (or partial)

“radiation sickness”

82
Q

Programmed Cell Death

A

Cell death that occurs as the result of an active process carried out by molecules in the cell.
Examples: apoptosis, autophagy, senescence and necrosis

83
Q

Quasi-threshold Dose (Dq)

A

Dose pint of extrapolation of the exponential portion of a multitarget survival curve back to the level of unity.
Surviving fraction: Dq = Do*ln(n)

84
Q

Reassortment or Redistribution

A

Return towards a more even cell age distribution, following the selective killing of cells in certain phases of the cell cycle

85
Q

Relative Biological Effectiveness (RBE)

A

Ratio of dose of a reference radiation quality (usually Co-60 gamma rays or 250keV X-rays) and dose of a test radiation that produce equal effect

86
Q

Reoxygenation

A

Process by which surviving hypoxic clonogenic cells become better oxygenated during the period after irradiation of a tumor.

87
Q

Repair

A

Restoration of the integrity of damaged macromolecules

88
Q

Repopulation

A

Proliferation of surviving clonogenic tumor cells

89
Q

Reproductive integrity

A

Ability of cells to divide many times and thus be ‘clonogenic’

90
Q

Senscence

A

Permanent arrest of cell division associated with differentiation, aging, or cellular damage

91
Q

Sensitizer Enhancement Ratio (SER)

A

Same as dose-modifying factor (DMF), but typically used to describe radiosensitizing agents so that SER > 1

92
Q

Sievert (Sv)

A

Dose equivalent in radiation protection.

Dose in grays multiplied by a radiation quality factor

93
Q

SF2

A

Surviving fraction of cells following a dose of 2 Gy

94
Q

SNP

A

Single nucleotide polymorphism

95
Q

Split dose recovery

A

Decrease in radiation effect when a single radiation dose is split into two fractions separated by times up to a few hours, or recovery from sublethal damage

96
Q

SSBR

A

Single strand break repair

97
Q

Stochastic (non-deterministic) effect

A

An effect where the incidence, but not the severity, increases with increasing dose
Examples:Mutagenesis, carcinogenesis, teratogenesis

98
Q

Sublethal Damage (SLD)

A

Non-lethal cellular injury that can be repaired.

Described in the LQ model as the beta term

99
Q

Symmetrical Division

A

Division of each stem cell into two stem cell daughters, occurring during radiation-induced repopulation in normal tissues

100
Q

Target theory

A

The idea tht the shoulder on cell survival curves results from the number of unrepaired lesions per cell

101
Q

TBI

A

Total body irradiation

102
Q

TCD50

A

The radiation dose that gives a 50% tumor control probability

103
Q

TCP

A

Tumor control probability

104
Q

Telangiectasia

A

Pathologically dilated capillaries observed in all irradiated tissues and organs in association with late radiation effects

105
Q

Theragnostics

A

Use of molecular imaginv to assisst in perscribing the distribution on radiation dose in 4 dimensions (3 spatial + time)

106
Q

Therapeutic Index (or Ratio)

A

Relationship between tumor cure and normal tissue damage

TI > 1 implies a more favorable ratio of efficacy to toxicity

107
Q

Time-dose Relationships

A

The dependence of isoeffective radiation dose on the overall treatment time and number of fractions/fraction size in RT

108
Q

Time Factor

A

the change in isoeffective total dose for local tumor control or normal tissue complications that follows a change in the overall treatment duration

109
Q

Tolerance Dose

A

Maximum radiation dose or that is associated with an acceptable complication probability (usually ~1-5%)

110
Q

Transient hypoxia

A

low oxygen concentrations associated with the transient closing of blood vessels
AKA acute or perfusion limited hypoxia

111
Q

Tumor bed effect (TBE)

A

Slower rate of tumor growth after irradiation due to stromal injury (vascular injury)

112
Q

Tumor cord

A

Sleeve of viable tumor growing around vessels

113
Q

Volume Doubling Time

A

Time for tumor to double in volume

114
Q

Volume Effect

A

Dependence of radiation damage on the volume of tissue and the anatomical distribution of radiation dose to the organ

115
Q

Xenografts

A

transplants between species (ie, human tumor into rat or mouse)

116
Q

“Deterministic effect:

A

severity increases with dose; practical threshold; probability of occurrence increases with dose (e.g., cataract).”

117
Q

“Stochastic effect:

A

severity independent of dose; no threshold; probability of occurrence increases with dose (e.g., cancer).”

From Flashcardlet (43 decks)

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