Radiobiology Flashcards
(138 cards)
1
Q
LET
A
Linear Energy Transfer
2
Q
RBE
A
Relative Biological Effectiveness
3
Q
OER
A
Oxygen Enhancement Ratio
4
Q
What is LET defined as?
A
Rate at which energy is deposit as charge particles travel through matter
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)
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)
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
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)
9
Q
What are compounds that undergo electromagnetic interactions (Low LET)?
A
Xrays and Gamma rays
10
Q
Alpha Particles
A
High Ionizing Density (Highest LET), +2 Charge, He nuclei
11
Q
Neutron Particles
A
High Ionizing Density (2nd Highest LET), No Charge
12
Q
Beta Particles
A
E- or Positrons (- or +), Low ionization density
13
Q
X ray and Gamma Rays
A
Photons, Low ionization Density, High penetrating Power
14
Q
Direct Action
A
Direct interaction of the radiation with the DNA, Pre-dom with High LET,
15
Q
Indirect Action
A
Indirect interaction of the Radiation that interacts through a medium such as water, Pre-dom with Low LET
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
17
Q
Indirectly Ionizing
A
High Energy, Small Wavelength, Large Frequency (Xrays and Gammas)
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
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
20
Q
What LET causes Cell kill?
A
100 KeV/um
21
Q
Hypoxic
A
Oxygen depleted
22
Q
Aerobic
A
Oxygen Rich
23
Q
How do you find the OER?
A
Hypoxic/Aerobic
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
25
What the relationship with OER and survival curves?
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)
26
What is the relationship with OER and RBE, when looking at LET?
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
27
What are the effects of radiation on DNA?
Hydrogen Bond, Loss of Base, Single strand break, Double strand break, Cross-links
28
What is the most deadly Radiation induced effect on DNA?
Double strand break
29
What is the Radiation induced effect on DNA is two independent events?
Cross-link
30
What are the 4 chromosomal Abberrations?
Deletion, Duplication, Inversion and Translocation
31
Explain Translocation chromosomal aberration?
The strands exchange information and create a new sequence of information
32
What are 3 lethal chromosome configurations?
Ring, Dicentric and Anaphase Bridge
33
Explain the ring chromosome configuration
Chromosomes have broken segments of deleted genetic material and then fusion between the two original chromosomes occurs, creating a ring
34
Dicentric vs Acentric Fragmentation
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)
35
What is the cellular response to being irradiated?
Division Delay, Interphase Death or Productive Failure
36
What occurs during division delay in the response to radiation?
Delay in mitosis or recovery, Mitotic overshoot
37
What occurs during interphase death in the response to radiation?
Apoptosis, Cell line dependent, radiosensitive cells die at lower doses
38
What occurs during reproductive failure in the response to radiation?
cell fail to undergo repeated division, (Dose increase creates reproductive failure)
39
In vivo
In living organism
40
In vitro
In glassware or artificial environment
41
What two factors are considered in cell survival curves?
Survival vs. Dose
42
How do you find plating efficiency?
Colonies counted/ # cells seeded
43
How do you find Survival Fraction?
of colonies counted/ # of cells seeded x Plating efficiency
44
Who are Puck and Marcus?
Created the first studies done on cell survival curves for radiation
45
What are the 3 cell parameters measured on survival curves?
n, Dq and Do
46
What is n?
Extrapolation # (Width of shoulder)
47
What is Dq?
Quasi-threshold (Width of shoulder region)
48
What is Do?
Radio-sensitivity (Measure of cell survival
49
What is the extrapolation number?
Extrapolate exponential portion back to Y-axis and number of targets to be hit to cause cell death (2-10 mammalian)
50
What is the quasi-threshold dose?
Terminal portion of curve intercepts dose axis at 100%, represents SF= 1 so a 100% survival
51
What is the Radiosensitivity variable, Do?
Reciprocal of Slope, dose that inactive all but 37% of population (1-2 Gy for mammalian)
52
What does a higher Do mean?
More resistant
53
What would a survival curve for a low Do look like?
Steeper, with a Lower Do, the radiosensitive is higher for lower dose creating a survival curve with a more drastic result
54
Higher LET= _______ in survival?
Decrease, more damaging, less likely chance of survival
55
What occurs to the survival curve as the LET gets higher?
Steeper and Lower Do as the dose to immobilize the majority of the population lowers
56
If given the option to choice between G2 and M, in regards to which is most radiosensitive, which would be the better answer?
M
57
What are the three types of damage that can occur to cells?
Lethal, Sublethal and Potentially Lethal Damage
58
What are the three SSSs of sublethal damage?
Sublethal, Split Fx, and Shoulder
59
How was potentially lethal damage originally studied?
Irradiated cells were placed in suboptimal cell division conditions
60
What was the result of studying potentially lethal damage?
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
Radio-sensitivity is directly proportional to? Indirectly proportional to?
Directly proportional to reproductive activity and indirectly proportional to degree of differentiation
62
More Reproductive cells = _________ radio-sensitive ?
More
63
Least Differentiation= _______ Radiosensitive?
More
64
What are the classification of cells based on radiosensitive?
VIM, DIM, Multi-potential, RPM and FPM
65
VIM
Vegetative inter-mitotic, rapidly dividing, undifferentiated
66
DIM
Differentiation Inter-mitotic, Actively dividing
67
RPM
Reverse Post-mitotic, not normal dividing, variably differentiated
68
FPM
Fixed Post-mitotic, do not divide highly differentiated
69
What is the most sensitive cell classification?
VIM
70
What is the least sensitive cell classification?
FPM
71
Multipotential Connective Tissue
Irregularly dividing
72
Example of VIM
Erythoblast
73
Example of Multipotential Connective Tissue
Spermatocyte
74
Example of FPM
Nerve Cell
75
Radiosensitizers
Increase response to radiation, (Ex: Oxygen)
76
Radioprotectors
Decrease response to radiation, protection of Dose limiting structures
77
What is the best radiosensitizer?
Oxygen
78
When is oxygen give to patients for their treatment?
Administered during treatment
79
What is acute responding tissue?
Tissue rxn within few months after XRT, Rapidly dividing organs (Intestine, Bone Marrow, Testes)
80
What is late responding tissue?
Tissue rxn greater than 3 months post xrt, slow dividing organs (Lung and Kidney)
81
What is the LD 50/30?
Dose to produce lethality to 50% of the population in 3o days (LD 50/60 for humans)
82
What is the LD 50/30 for humans?
3.5-4.5 Gy
83
Acute radiation Syndrome 3 area affected
Hematopoietic, Gastrointestinal, CNS/CV
84
Hematopoietic (Bone Marrow)
2-10 Gy, infection and hemorrhaging, 6 weeks to 6 days survival avg , dose dependent (Lowers chances of survival)
85
Gastrointestinal (ARS)
10-100 Gy, Small intestine damaged, No survival, 3-10 days survival avg, no dose dependent
86
CNS/CV (ARS)
>100 Gy, Cerebral Edema, no Survival, 2-3 day survival avg, Dose Dependent (Lowers chances of survival)
87
What is the LD 50/60 for ARS?
400 cGy
88
What are the specific conditions to induce ARS?
Acute exposure (within minutes), Area exposed is total body, Exposure to external penetrating sources
89
Whats different about internal deposition and inducing full ARS syndrome?
internal Radioactive materials do not induce full syndrome
90
What are some ARS scenarios that have occurred "Naturally"
Hiroshima/Nagasacki and Chernobyl
91
What are the 4 stages of ARS?
Prodromal, Latent, Manifest Illness, Recovery/death
92
What happens to the stages of ARS as severity increases?
The stages decrease in time
93
Prodromal
Initial stage, N/V and Diarrhea,Minutes to Days
94
Latent
no symptoms, healthy looking, weeks down to hours
95
Manifest Illness
Symptoms return, obvious illness, Exhibit specific symptoms, min to weeks
96
What are the two types of radiation effects?
Stochastic and Deterministic
97
Stochastic Effects
no threshold, no dose dependent, higher dose creates higher chance of expecting results (Cancer, Herediatary effects)
98
Deterministic Effects
Threshold, Severity is dose dependent, Higher dose creates higher change of expecting results (Cataracts, Skin injuries)
99
What is another name for late effects?
Somatic
100
Somatic Effects
Non-specific Life shortening, Carcinogenesis, Cataractogenesis, Embryo/fetus effects
101
Non-specific life shortening
Radiation-inducing aging, shortened life span, those chronically exposed will die before those that weren't
102
Carcinogenesis
SINGLE MOST IMPORTANT LATE SOMATIC EFFECT, Marie Curie died due to working with radiation unsafely
103
What is the latency period for leukemia?
5-7 years, absolute risk
104
What is the latency period for solid cancers?
20-60 years, relative risk
105
six solid radiation inducing cancers?
Skin, Bone, Breast, Lung, and Thyroid
106
Cataractogenesis
Deterministic effect, Threshold of 2 Gy (Stationary 2-6 Gy, Progressive 6-12 Gy)
107
Embryonic and Fetal
Dose and age of gestation dependent,
108
3 stages of embryonic and fetal impact?
Prenatal, Major organogenesis, Fetal
109
Prenatal
0-9 days, prenatal death
110
Major organogenesis
10-42 days, Congenital abnormalities and neonatal death
111
Fetal
> 6 weeks - term, Functional abnormalities
112
Hereditary Effects
Genetics based, Double dose- 1 Gy,
113
What is the genetic counseling recommendation for conceptions post xrt?
6 months
114
True or False. Radiation produced new mutations and also increases an already existing number.
False, Radiation does not create any new mutations, only increase the already existing ones
115
Fractionation
Multifraction regime that produces better tumor control for given level of normal tissue toxicity than a single large dose
116
What are the 4 R's of Radiobiology?
Repair, Repopulation, Reassortment and Reoxygenation
117
1st R, Repair
repair of sublethal damage between dose fraction
118
2nd R, Repopulation
cell repopulate if given appropriate amount of time
119
3rd R, Reassortment
Cycling cells into sensitive phases of the cell cycle
120
4th R, Reoxygenation
enhance cell kill
121
Acute tumor hypoxia
Low oxygen concentration, temporary closing or blocking of blood vessels
122
Chronic tumor hypoxia
Peristent low oxygen concentration, exist in viable tumor cells close to necrosis
123
Normoxic
Normal oxygen concentration
124
Dose-Response Relationships
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
With increasing radiation dose, effects may increase in ______ in ____ or both?
Severity (grade) and Frequency (Incidence)
126
Therapeutic ratio
percent of tumor control achieved for given level of normal tissue damage
127
Therapeutic ratio factors (____/_____)
Tumor control probability/Normal Tissue Complication Probability
128
In regards to therapeutic window, the further apart the curves creates what?
A larger therapeutic window
129
Law of Bergonie and Tribondeau
Mitotic Activity and Differentiation
130
Rubin and Casarett
Radiosensitivity
131
Tolerance Dose
dose the produced an acceptably probability of treatment complications (TD 5/5 and TD 50/5)
132
Emami provides?
TD for 1/3, 2/3, and whole organ with clinical endpoint
133
QUANTEC provides?
Dmax, Mean dose, Dose/volume parameters
134
TD 5/5
Dose which when given to population will result in a minimum 5% several complication rate within 5 years
135
TD 50/5
Dose which when given to population will result in a maximum 50% several complication rate within 5 years
136
Early Responding Tissue (VIM, DIM)
Rapidly dividing cells, (Skin, Bone Marrow, Intestinal lining and testes)
137
Late responding Tissue (RPM FPM)
Slowly dividing cells (Lung,CNS, Kidney, Liver)
138
What dose QUANTEC stand for?
Quantitative analyses of normal tissue effects in the clinic
