radbio finals Flashcards
(166 cards)
1
Q
What is the study of effects of ionizing radiation on biologic effects?
A
radiobiology
2
Q
two types of effects
A
*deterministic effect
*stochastic effect
3
Q
type of effects that if the radiation response increases in severity with increasing radiation dose
- occurs within days after the radiation exposure.
an EARLY EFFECT
A
deterministic effect
4
Q
type of effects that if the incidence of the radiation response increases with increasing radiation dose
- not observed for months or years
a LATE EFFECT
A
stochastic effect
5
Q
what is the unit of radiation exposure or intensity?
A
Exposure (R)
6
Q
what is the SI unit of roentgen?
A
air kerma (Gya)
7
Q
What is the unit of radiation absorbed dose; quantity of radiation received by the patient?
A
Dose (rad)
8
Q
What is the SI unit of rad/dose?
A
gray (Gyt)
9
Q
What is the unit of occupational radiation exposure; used to expressed the quantity of radiation received by radiation workers & populations?
A
Equivalent dose (rem)
10
Q
What is the unit of radioactivity?
A
curie (Ci)
11
Q
What is the SI unit of Curie?
A
Becquerel (Bq)
12
Q
what are the DETERMINISTIC EFFECTS of radiation on humans?
A
*Acute Radiation Syndrome (ARS): hematologic syndrome, gastrointestinal syndrome, CNS syndrome
*Local tissue damage: skin, gonads, extremities
*Hematologic depression
*Cytogenetic damage
13
Q
what are the STOCHASTIC EFFECTS of radiation on humans?
A
*Leukemia
*malignant disease: bone cancer, lung cancer, thyroid cancer, breast cancer
*Local tissue damage: skin, gonads, eyes
*shortening of life span
*Genetic damage: cytogenetic damage, doubling dose, genetically significant dose
14
Q
effects of fetal irradiation:
A
*prenatal death
*neonatal death
*congenital malformation
*childhood malignancy
*diminished growth and development
15
Q
Radiation response occurs within minutes or days after radiation exposure
A
early effect of radiation
16
Q
Radiation response that is not observe for 6 months or longer after radiation exposure
A
late effect of radiation
17
Q
85% of the body consists of?
A
hydrogen and oxygen
18
Q
What determines the character & degree of the radiation interaction that occurs?
A
atomic composition
19
Q
Atomic composition of the body:
A
60.0 % hydrogen
25.7 % oxygen
10.7 % carbon
2.4 % nitrogen
0.2 % calcium
0.1 % phosphorus
0.1 % sulfur
0.8 % trace elements
20
Q
Who first named the cell as the biologic building block?
A
Robert Hooke (1665)
21
Q
Who accurately described a living cell on the basis of his microscopic observations?
A
Anton van leeuwenhoek (1673)
22
Q
They showed that cells are the basic functional units in all plants & animals
A
Schneider & Schwann (1838)
23
Q
They described the molecular structure of deoxyribonucleic acid (DNA) as genetic substance of the cell
A
Watson & Crick (1953)
24
Q
What project results in precise mapping of 40,000 human genes?
A
Human Genome Project (2000)
25
What defines the nature of radiation response?
molecular & tissue composition of body
26
molecular & tissue composition of body:
80.0 % water
15 % protein
2 % lipids
1 % carbohydrates
1 % nucleic acid
1 % other
27
What is the very large molecules that sometimes consist of hundreds of thousands of atoms?
macromolecule
28
What are the four macromolecules?
proteins
lipids
carbohydrates
nucleic acids
29
What is the molecule that is life-supporting & contains carbon?
organic molecule
30
principal organic molecules:
protein
lipids
carbohydrates
31
What is the rarest molecule in the body concentrated in the nucleus of a cell (DNA): most critical & radiosensitive target molecule?
nucleic acid
32
Two principal type of nucleic acid:
*DNA
*RNA
33
What is the function of nucleic acid?
growth and development of the cell
34
What is the simplest & the most abundant molecular constituent in the body: approximately 80% of human substance?
water
35
what is the important role of water?
delivering energy to the target molecules
36
composition of water:
2 atoms of hydrogen
1 atom of oxygen
37
Functions of water:
- Provide some form & shape
- Assist in maintaining body temperature
- Enter into some biochemical reactions
38
What are the end products in the catabolism?
water and carbon dioxide
39
What is the breaking down into smaller pieces of macromolecules?
catabolism
40
What is the production of large molecules from small?
anabolism
41
What is the long chain macromolecules that consist of a linear sequence of amino acids connected by peptide bonds?
proteins
42
How many amino acids need in protein synthesis?
22
43
Functions of protein:
- Provide structure & support (muscles)
- Enzymes, hormones & antibodies
44
What is the metabolic production of proteins?
protein synthesis
45
linear sequence/arrangement of protein:
AA—AA—AA—AA ...
- AA is the amino acid, and — is the peptide bond
46
what is the generalized formula for a protein?
CnHnOnNnTn
47
Molecules that are necessary in small quantities to allow a biochemical reaction to continue, even though they do not directly enter into the reaction
enzymes
48
Molecules that exercise regulatory control over some body functions
hormones
49
A primary defense mechanism of the body against infection & disease
antibodies
50
Invasive & infectious agent
antigen
51
Organic macromolecules composed solely of carbon, hydrogen, & oxygen
lipids
52
Similar to lipids but their structure is different: also called SACCHARIDES
carbohydrates
53
3 sugars:
*polysaccharides - largest
*monosaccharides - singe chain
*disaccharides - double
54
simple sugar
glucose
55
- control center for life
- contains all the hereditary information that represents a cell or whole individual
deoxyribonucleic acid (DNA)
56
Attached to each deoxyribose molecule
Nitrogenous Organic Bases
57
Nitrogenous Organic Bases:
purines: adenine & guanine
pyrimidines: thymine & cytosine
58
- A human polysaccharide
- It stored in tissues of the body
- It used only when quantities of the simple sugar (glucose) are inadequate
glycogen
59
The base sugar-phosphate combination
nucleotide
60
two types of RNA
*messenger RNA
*transfer RNA
61
RNA 3 major varieties:
1. Ribosomal – It has a specific role to play in carrying out DNA’s instruction for building proteins
2. Messenger – carries the information for building the protein from the DNA gens to the ribosomes, the protein –synthesizing sites
3. Transfer – ferries amino acids to the ribosomes. Translation of the message and the binding together of amino acids to form the protein
62
tissue composition of the body:
Muscle - 43%
Fat - 14 %
Organs - 12 %
Blood - 8 %
Subcutaneous tissue - 6%
Bone marrow - 4 %
Skin - 3 %
63
RESPONSE TO RADIATION IS RELATED TO CELL TYPE
*high sensitivity: Lymphocytes, Spermatogonia, Erythroblasts, Intestinal Crypt Cells
*intermediate sensitivity: Endothelia cells, Osteoblasts, Spermatids, Fibroblasts
*low sensitivity: muscle cells and nerve cells
64
- The covering tissue
- It lines all the exposed surfaces of the body, both exterior & interior
- It covers the skin, the blood vessels, the abdominal, chest cavities & GI tract
epithelium
65
It binds tissue & organs together
connective & supporting tissue
66
A special type of tissue that can contract
muscle tissue
67
The avenue by which electrical impulses are transmitted throughout the body for control & response
nerve tissue
68
Part of an organ that contains tissues representative of that particular organ
parenchymal
69
Part of an organ that is composed of connective tissue & vasculature
stromal
70
- Determined by the function of the organ in the body
- The rate at which cells mature within the organ
- The inherent radiosensitivity of the cell type
radiosensitivity of tissues & organs
71
Principal Aim of the Study of Radiobiology
To understand radiation dose-response relationships
72
A mathematical & graphic function that relates radiation dose to observed response
Dose-Response Relationship
73
they theorized & observed that radiosensitivity was a function of metabolic state of tissue being irradiated
Jean Bergonie & Louis Tribondeau (1906)
74
Law of Bergonie & Tribondeau
1. Stem cells are radiosensitive; Mature cells are radioresistant
2. Younger tissues and organs are radiosensitive
3. Tissues with high metabolic activity are radiosensitive
4. A high proliferation rate for cells & a high growth rate for tissues result in increased radiosensitivity
75
PHYSICAL FACTORS THAT AFFECT RADIOSENSITIVITY
- Linear Energy Transfer (LET)
- Relative Biologic Effectiveness (RBE)
- Protaction
- Fractionation
76
- measure of the rate at which energy is transferred from ionizing radiation to soft tissue
- Expressed in: keV/μm
- Diagnostic X-rays: 3 keV/μm
LET
77
Factor used in radiation protection that accounts for differences in biologic effectiveness between different radiations
radiation weighting factor (Wr)
78
ratio of the dose of standard radiation necessary to produce a given effect to the dose of test radiation needed for the same effect
RBE
79
80
standard radiation by convention
- Range: 200-250 kVp
- used in radiation oncology and early radiobiologic research.
orthovoltage x-rays
81
The dose is delivered continuously but at a lower dose rate
protraction
82
The dose is delivered at the same dose in equal portions at regular intervals
fractionation
83
biologic factors that affect radio sensitivity
- Oxygen Effect
- Age
- Recovery
- Chemical Agents
- Hormesis
84
Ratio of the dose necessary to produce a given effect under anoxic conditions to the dose necessary to produce the same effect under aerobic conditions
oxygen enhancement ratio (OER)
85
Two Important Applications in Radiology
* It is used to design therapeutic treatment routines for patient with cancer
* It revealed provide the basis for radiation control activities
86
Two Characteristics of Dose-Response Relationship
* Threshold Dose - The level below which there is no response
* Linear Dose-Response Relationship - The response is directly proportionate to the dose
87
linear dose-response relationship
o Linear Nonthreshold type: intersects at zero or below
o Linear Threshold Type: intercept the dose axis at some value greater than zero
88
It is used in establishing radiation protection guidelines for diagnostic imaging
nonlinear dose-response relationship
89
nonlinear dose-response relationship
o Nonlinear nonthreshold: large response results from a very small radiation dose
o Nonlinear Threshold Type: below the threshold, no response is measured
90
The inflection point occurs when the curve stops bending up and begins bending down. Above this level, incremental doses become less effective
s-type/sigmoid type
91
Estimation of value beyond the range of known values
extrapolation
92
the principal radiation interaction in the body
WATER
93
Irradiation outside of the cell or body
- considerable radiation dose is produce a measurable
In vitro
94
Irradiation with the cell or body required to effect.
- demonstrates that macromolecules are considerably more radiosensitive in their natural state.
in vivo
95
Three Major Effects When Macromolecules Are Irradiation In A Solution In Vitro
*Main-chain Scission - breakage of the backbone of the long-chain macromolecules
*Cross-linking - Process of side spurs created by irradiation & attached to a neighboring macromolecules or to another segment of the same molecule
*Point Lesion - Any change that results in the impairment or loss of function at the point of a single chemical bond
96
Radiation Effects on DNA
* Chromosome aberration or cytogenetic damage
* Abnormal metabolic activity
* Structural change
97
Type of Chromosome Aberrations
* Terminal deletion
* Dicentric formation
* Ring formation
98
Unobservable Radiation Response of DNA
* Main-chain scission with only one side rail severed
* Main-chain scission with both side rail severed
* Main-chain scission & subsequent cross-linking
* Rung breakage causing separation of bases
* Change in or loss of a base
99
Poisonous to the cell & therefore acts as a toxic agent
- Chemical Formula: H2O2
hydrogen peroxide
100
direct and indirect effect
* Direct Effect - If the initial ionizing event occurs on the target molecule
* Indirect Effect - If the initial ionizing event occurs on a distant, noncritical molecule
101
The principal effect of radiation on humans is INDIRECT
wala
102
target molecule
DNA
103
target theory:
cell death will occur only if the target molecule is inactivated. DNA, the target molecule, is located within the cell nucleus.
104
An area on the cell occupied by the target molecule or by a sensitive site on the target molecule
target
105
Radiation interaction with the target or molecules
hit
106
Low-LET Radiation & ABSENCE of Oxygen:
- Low probability of hit on the target molecules
107
Low-LET Radiation & PRESENCE of Oxygen:
High probability of hit on the target molecules
108
High-LET Radiation & ABSENCE of Oxygen:
High probability of a hit by direct effect
109
High-LET Radiation & Presence of Oxygen:
Does not result in additional hits
110
Process by which normal cells produce a visible colony in a short time
cell cloning
111
2 models of cell survival
*Single-Target, Single-Hit Model = applies to biologic targets such as enzymes, viruses & bacteria
*Multi-Target, Single-Hit Model = applies to more complicated biologic system such as human cells
112
When the radiation dose reaches a level sufficient to kill 63% of the cells (37% survival)
- measure of the radiosensitivity of the cell
D37
113
D37
- Low D37: highly radiosensitive
- High D37: highly radioresistant
114
The mean lethal dose
- A constant related to the radiosensitivity of the cell
- It is equal to D37 in the linear portion of the graph
D0
115
D0
- Large D0: radioresistant cells
- Small D0: radiosensitive cells
116
The threshold dose
- A measure of the width of the shoulder of the multitarget single-hit model
- It is related to the capacity of the cell to recover from sublethal damage
Dq
117
A damage that must be accumulated before the cell dies
sublethal damage
118
Designed to describe the capacity of a cell to recover from sublethal damage
split-dose irradiation
119
- The dose of radiation to the whole body that causes 50% of irradiated subjects to die within 60 days
- It quantitatively measured the acute radiation lethality
LD 50/60
120
The most devastating human response to radiation exposure
death
121
It is of only academic interest in diagnostic radiology
acute radiation-induced lethality
121
Radiation sickness that occurs in human after the whole-body dose s of 1 Gy (100 rad) or more of ionizing radiation delivered over a short time
acute radiation syndrome
122
The dose necessary to produce a given syndrome and the mean survival time are the principal quantitative measures of human radiation lethality
manifest illness
122
3 syndromes
*Hematologic Death,
*Gastrointestinal (GI) Death
*Central Nervous System (CNS) Death
123
The time after exposure during which there is no sign of radiation sickness
latent period
124
The immediate response of radiation sickness
prodromal period
125
- It occurs principally because of severe damage to the cells lining the intestines
gastrointestinal syndrome
125
- It is characterized by a reduction in white cells, red cells and platelets
- appear in a matter of a few hours and may persist for several days.
hematologic syndrome
126
Average time between exposure & death
mean survival time
127
- Its ultimate cause is elevated fluid content of the brain
central nervous system syndrome
128
The shrinkage of an organ or tissue due to cell death
atrophy
128
As the radiation dose increases from 2 to 10 Gyt (200– 1000 rad), the mean survival time decreases from approximately 60 to 4 days
wala
129
Cells Replacement Rate:
2 % per day (50 % for GI)
129
3 layers of skin
* Epidermis: outer layer
* Dermis: intermediate layer of connective tissue
* Subcutaneous: layer of fat & connective tissue
130
The stem cells that mature as they migrate to the surface of the epidermis
basal cells
130
- 2nd wave
- The clinical tolerance for radiation therapy
moist desquamation
131
- 3rd wave
- Ulceration & denudation of the skin
- required interruption of treatment.
desquamation
131
- 1st wave
- A sunburn-like reddening of the skin
- The first observed biologic response to radiation exposure
erythema
132
- One of the hazards to the patient the early of radiology
x-ray induced erythema
132
loss of hair
epilation/alopecia/fox mange
133
- Dose of radiation, usually about 200 rad, that causes redness of the skin
skin-erythema dose (SED)
134
The male gonads
- It produces spermatogonia & matures into sperm
testes
134
The female gonads
- It produces oogonia & matures into ovum
ovaries
134
They grow to encapsulate the oogonia
primordial follicles
135
progression of germ cell
Male: Spermatogonia (most radiosensitive) → Spermatocyte → Spermatid → Sperm
Female: Primordial Follicle → Mature Follicle (most radiosensitive) → Corpus Leteum → Ovum
135
Produced by both ovaries & testes
germ cells
135
process of development of germ cells
gametogenesis
135
The stem cells of the ovaries
- They multiply in number only before birth & during fetal life
oogonia
135
a matures oogonia
oocyte
136
A mature female germ cell
- Fertilization: 400-500 ova
- Number of years of menstruation times 13 per year
ovum
136
The stem cells of the testes
- Continually being produced from stem cells progressively through a number of stage to maturity
spermatogonia
137
A matured spermatogonia
spermatocyte
137
A matured spermatocyte
spermatid
138
A mature male germ cell
- Maturation Process: 3-5 weeks
spermatozoa/sperm
139
The most sensitive phase in the gametogenesis of the spermatozoa
spermatogonial stem cells
140
A self-renewing system
male gametogenesis
141
The only monitoring performed on x-ray & radium workers before
periodic blood examination
142
- Stem cell that has the ability to develop into several different types of mature cells
pluripotential stem cell
143
4 principal types of blood cell
- Lymphocytes (WBC) = involved in the immune response
- Granulocytes = Scavenger type of cells used to fight bacteria
- Erythrocytes (RBC) = Blood cells that are transportation agents for oxygen
- thrombocytes (platelets) = clotting of blood to prevent hemorrhage
143
- It manufactures most circulating blood cells including lymphocytes
bone marrow
144
Probability of frequency of the biologic response to radiation as a function of radiation dose
stochastic radiation response
145
Developed on early radiologists who performed fluoroscopic examination
radiodermatitis
145
- Studies of large numbers of people exposed to a toxic substance require considerable statistical analyses
epidemiologic studies
146
It occurs on the posterior pole of the lens
radiation-induced cataract
146
humans can expect a reduced life span of approximately 10 days for every rad.
wala
147
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