1
Q
Energy transferred per unit track length (keV/µm)
A
Linear Energy Transfer (LET)
2
Q
Refers to irradiation of macromolecules outside the body or cell which requires a considerable radiation dose to produce significant effect.
A
In vitro irradiation
3
Q
Standard Radiation, by convention
A
Orthovoltage x-radiation (200 - 250 kVp)
4
Q
Each cell has a nucleus that contains DNA complexed with other molecules in the form of
A
chromosomes
5
Q
Fast Neurons
A
LET: 50 keV/µm
RBE: 10
6
Q
Usually follow high-dose radiation exposure and appear as an early response
A
Deterministic Response
7
Q
How does main-chain scission affect the viscosity and function of large molecules
A
Main-chain scission breaks long-chain macromolecules into smaller segments, leading to reduced molecular weight that allows molecules to move more freely; thus, the viscosity of solutions is decreased
8
Q
Is deterministic effect threshold or nonthreshold?
A
threshold
9
Q
The irradiation of macromolecules inside the cell in its natural state, where it is more radiosensitive
A
In vivo irradiation
10
Q
Single-Hit Chromosome Aberration
A
Linear, nonthreshold type
11
Q
The principal effect of radiation on humans is _
A
indirect
12
Q
Heavy nuclei
A
LET: 1000 keV/µm
RBE: 30
13
Q
Which tissues and organs are radiosensitive?
A
Younger tissues and organs
14
Q
Used for establishing radiation protection guidelines for diagnostic imaging
A
Linear, nonthreshold type
15
Q
the most important molecule in the human body because it contains the genetic information for each cell
A
DNA
16
Q
High-LET radiation with oxygen
A
High Probability of HIT
17
Q
This type of dose-response relationship is characteristic of a deterministic response
A
Nonlinear, threshold type
18
Q
1 MeV electrons
A
LET: 0.3 keV/µm
RBE: 0.9
19
Q
theorized and observed that radiosensitivity was a function of the metabolic state of the tissue being irradiated
A
Bergonie and Tribondeau (1906)
20
Q
3 Physical Factors
A
Linear Energy Transfer
Relative Biological Effectiveness
Protraction and Fractionation
21
Q
synthesis of molecules
A
anabolism
22
Q
example of Radiosensitizers
A
halogenated pyrimidines, methotrexate, actinomycin D, hydroxyurea, and vitamin K
23
Q
Diagnostic x-rays have an RBE of
A
1
24
Q
Occurs during indirect effect where radiation hits other organs (water) first
A
Radiolysis of Water
25
As probability of target interaction and damage ↑
LET ↑
26
“A little bit of radiation is good for you.”
Hormesis
27
High-LET radiation without oxygen
High Probability of HIT
28
Results to Stochastic effects
Linear, nonthreshold type
29
administration of multiple doses of a single drug until a desired effect is reached, but not to exceed the maximum recommended dose.
Incremental Dose
30
above the threshold dose, any increment of dose produces a larger response if that response follows relationship D rather than C.
Linear, threshold type
31
T or F
proteins are less radiosensitive than nucleic acids
T
32
End Result of Hydroperoxyl radical when broken down
Hydrogen Peroxide (H2O2) + Oxygen (O2)
33
dose-response relationship of Linear, threshold type
response is directly proportional to the dose received
34
T or F
the change or loss of a base, also destroys the triplet code and may be reversible
F
35
No change or no mass
ex: x-ray , Gamma, electron
Low LET
36
any dose is expected to produce a response
Nonthreshold
37
Radiosensitivity After birth to maturity
Radioresistant
38
T or F
Twice as much DNA is present in G1 as in G2.
F
39
control the growth and devel- opment of the cell; these in turn determine the charac- teristics of the individual
chromosomes
40
T or F
Diagnostic x-ray imaging is performed under conditions of full oxygenation.
T
41
Multi-Hit Chromosome Aberration
Nonlinear, nonthreshold type
42
As the dose is increased to above DT, it becomes increasingly effective per increment of dose until the dose that corresponds to the inflection point of the curve is reached
Nonlinear, threshold type
43
Give one example of how cross-linking can interfere with normal cell function
during DNA separation in S phase
44
HO*2
hydroperoxyl radical
45
Deterministic effects of radiation
1. Radiation-induced cataracts
2. Acute Radiation Syndrome (ARS)
3. Radiation-induced death
4. Skin effects from high-dose fluoroscopy
46
shrinking caused by sufficient radiation dose
Atrophy
47
End result of Hydrogen Peroxide when broken down
Hydrogen Radical (OH*) + Hydroxyl ion (OH+) or Hydroperoxyl radical (HO2*) + Hydroperoxyl radical (HO2*)
48
how many daughter molecules is replicated by the parent DNA?
2
49
Why are macromolecules, like DNA, more sensitive to ionizing radiation than smaller molecules?
1. larger structures making them easier to be irradiated
2. less abundant
3. crucial roles
50
Measure of the rate at which energy is transferred from ionizing radiation to soft tissue
Linear Energy Transfer (LET)
51
damage that can lead to mutations, loss of heterozygosity, and chromosome rearrangements that cannot be easily repaired, eventually resulting in cell death or cancer.
Double strand break
52
example of Radioprotectors
cysteine & cysteamine
53
level below which there is no response
Threshold
54
“Dose protraction and fractionation cause less effect because time is allowed for intracellular ___ and tissue ___.”
repair; recovery
55
Formula of OER
OER = anoxic (higher number) /
aerobic (lower number)
56
Enhances effect of radiation; used in radiation therapy
Radiosensitizers
57
In stochastic effect: as Radiation Dose increase
Frequency of response in a population increases
58
In deterministic effect: as Radiation Dose increase
Severity of response inrceases
59
This recovery from radiation damage is assisted through repopulation by surviving cells
Intracellular Recovery
60
a DNA damage which commonly happens, but can be easily restored using a repair mechanism
Single-strand break
61
the ability to produce biologic damage increases ↑
LET of radiation increases ↑,
62
2 effects that lead to cell death
Indirect and Direct effect
63
dose-response relationship of Linear, nonthreshold type
response is directly proportional to the dose received
64
Stochastic effects of radiation
1. Radiation-induced leukemia
2. Radiation-induced genetic effect/damage
3. Radiation-induced malignant disease
4. Radiation-induced thyroid cancer
5. Radiation-induced life-span shortening
6. Chronic lymphotic leukemia
65
Most Effects on Cells Results in No Response Because of:
Recovery
Repair Metabolic Processes
66
Radiosensitivity of Fetus
Highly radiosensitive
67
In the Law of Bergonie and Tribondeau, stem cells are __ while mature cells are ___.
Stem cells are radiosensitive; mature cells are radioresistant.
68
Usually follow low radiation exposure and appear as late radiation response years later
Stochastic Response
69
60Co gamma rays
LET: 0.3 keV/µm
RBE: 0.9
70
Is stochastic effect threshold or nonthreshold?
No dose threshold
71
a result of the irradiation of macromolecules wherein a long, single molecule is broken into smaller molecules. This effect causes solutions to become more viscous or thick.
Main-chain scission
72
How effective a type of radiation is at causing biological damage
Relative Biological Effectiveness (RBE)
73
5 MeV alpha particles
LET: 100 keV/µm
RBE: 20
74
Why is radiation damage more severe when exposure occurs in vivo?
In vivo irradiation produces more severe damage since it occurs inside the body, where sensitive cells and molecules reside.
75
Has mass
ex: Alpha particle and neutron
High LET
76
Reduce effect of radiation; cannot be ingested
Radioprotectors
77
unstable atoms that have unpaired electrons in their outermost shell
Free Radicals
78
Tissues with high metabolic activity are
radiosensitive
79
“Radiosensitivity of living tissue varies with maturation and metabolism.”
Law of Bergonie and Tribondeau
80
LET of diagnostic x-rays
3 keV/µm
81
If the two free radicals combine, what is the result?
Hydrogen Peroxide (H2O2) and Hydroperoxyl Radical (HO2*)
82
10 MeV protons
LET: 4.0 keV/µm
RBE: 5.0
83
Example of in vivo reactions
radiolysis of water
84
BIOLOGIC FACTORS AFFECTING RADIOSENSITIVITY
Oxygen effect
Age
Recovery
Chemical Agents
85
T or F
DNA is the most radiosensitive molecule.
T
86
Diagnostic x-rays
LET: 3.0 keV/µm
RBE: 1.0
87
This effect of macromolecule irradiation causes the formation of sticky side structures that causes the linking or attachment to another molecule or to itself.
Cross-linking of macromolecules
88
indicates that even without radiation exposure, that type of response, such as cancer, occurs
Natural Response
89
Radiosensitivity of Old Age
Somewhat radiosensitive
90
dose-response relationship of nonlinear, nonthreshold type
response is not directly proportional to the dose received
91
If the two ions in Radiolysis of water combine what is the end result?
Water (H2O)
92
occurs when the curve stops bending up and begins bending down.
Inflection point
93
A third effect of macromolecule irradiation that leads to disruption of chemical bonds within the molecule, creating point lesions. They result in stochastic radiation effects.
Point lesions (molecular lesions)
94
Low-LET radiation without oxygen
Low Probability of HIT
95
Tissue is more sensitive to radiation when irradiated in the oxygenated state (aerobic) than when irradiated under anoxic (without oxygen) or hypoxic (low-oxygen) conditions.
Oxygen Enhancement Ratio (OER)
96
Duration for full recovery to occur
24 hours
97
Low LET radiation with oxygen
High Probability of HIT
98
“For a cell to die after radiation exposure, its target molecule must be inactivated.”
Target Theory
99
End Result of Radiolysis of Water
Hyrdogen ion (-H+) + Hydroxyl Radical (HOH*) and Hydroxyl ion (OH-)+ Hydrogen Radical (H*)
100
occurs when the cell dies before replicating
Interphase death
101
Radioprotectors include molecules that contain
sulfhydryl group (sulfur and hydrogen bound together)
102
breaking down of molecules
catabolism
103
Total dose is divided into smaller doses; Used in radiation therapy
Fractionation
104
H2O2
Hydrogen Peroxide
105
25 MV x-rays
LET: 0.2 keV/µm
RBE: 0.8
106
Basis for current dose limits
Linear, nonthreshold type
107
Dose is delivered continuously but at a lower dose rate
Protraction
108
A mathematical relationship between various radiation dose levels and magnitude of the observed response.
Radiation Dose-Response Relationship
2B 1ST SEM
flashcards
Decks in class (15)
# Cards
-
FILM SCREEN LEC PRELIMS135
-
RADBIO PRELIMS119
-
RIZAL PRELIMS148
-
PT CARE PRELIMS106
-
IMAGING EQ. PRELIMS181
-
TEM 10045
-
RADBIO MIDTERMS108
-
FILM SCREEN MIDTERMS73
-
PT CARE MIDTERMS88
-
IMG EQ. MIDTERMS229
-
RIZAL MIDTERMS (ACTIVITIES)86
-
LIT MIDTERMS34
-
ENTREP MIDTERMS57
-
RADBIO FINALS111
-
PT CARE FINALS32
