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Radiation protection > chapter 7 EXAM 3 > Flashcards

chapter 7 EXAM 3 Flashcards

1
Q

what is the goal of radiobiologic research

A

the accurate description of the effects of radiation on humans so that radiation can be used more safely in diagnosis and more effectively in therapy

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2
Q 
generalizations about radiation effects on living organisms 
#1
A

the interaction of radiation in cells is a probability function or a matter of chance
ionizing radiation does not seek out certain cells.

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3
Q

generalizations about radiation effects on living organisms #2

A

the initial deposition of energy occurs very rapidly

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4
Q

generalizations about radiation effects on living oragnisms #3

A

radiation interaction in a cell is nonselective

energy is deposited randomly

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5
Q

generalizations about radiation effects on living organisms #4

A

the visible changes in the cells, tissues and organs due to ionizing radiation are not unique. They can’t be distinguished from damage produced by other types of trauma
cancer is cancer

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6
Q

generalizations about radiation effects on living organisms #5

A

the biologic changes in cells and tissues resulting from radiation occur only after a period of time. The length of time depends on the initial dose and varies from weeks or even years

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7
Q

3 radiation energy transfer determinants

A
  1. Linear energy transfer (LET)
  2. relative biologic effectiveness (RBE)
  3. oxygen enhancement ratio (REO)
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8
Q

characteristics of ionizing radiation

A

charge
mass
energy

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9
Q

Linear Energy Transfer (LET)

A

the measure of the rate at which energy is transferred from ionizing radiation to soft tissue

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10
Q

LET is expressed in

A

kiloelectronvolts per micrometer

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11
Q

the LET of diagnostic xrays is

A

3 KeV/micrometer

considered Low LET

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12
Q

LET is a factor in

A

assessing potential tissue and organ damage from exposure to ionizing radiation

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13
Q

when LET increases,

A

the likelihood of biologic response increases

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14
Q

T or F

LET helps determine radiation weighting factors

A

true

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15
Q

radiation is divided into 2 categories according to LET

A
  1. low LET

2. high LET

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16
Q

Low LET

A

xrays and gamma rays

electromagnetic radiation is sparsely ionizing therefore it is Low LET

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17
Q

when interacting with biologic tissue Low LET causes damage primarily

A

through indirect action which involves the production of free radicals

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18
Q

free radicals

A

a solitary atom or a combo of atoms that behave as extremely reactive single entities as a result of the presence of an unpaired electron

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19
Q

Low LET radiation generally causes what kind of damage to the DNA

A

sublethal damage

repair enzymes revers the damage

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20
Q

direct action means

A

it will hit the nucleus of a cell

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21
Q

indirect action means

A

it will hit water

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22
Q

high LET includes

A

particles that possess large mass and charge

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23
Q

high LET causes

A

dense ionization along its length of track and more likely to interact with biologic tissue
way more destruction

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24
Q

examples of high LET radiation

A

alpha particles
ions of heavy nuclei
low energy neutrons
charged particles released from interactions between neutrons and atoms

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25
Q

T or F

high LET loses energy more rapidly than low LET

A

True

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26
Q

why does high LET lose energy more rapidly than low LET

A

high LET produces more ionization per unit of distance traveled
they exhaust their energy in a shorter length of track and cannot travel as far

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27
Q

the higher the LET the greater

A

the biologic response

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28
Q

relative biologic effectiveness definition

A

RBE

a term relating the ability of radiations with different LETs to produce a specific biologic response

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29
Q

RBE describes

A

the ratio of the dose of a reference radiation to a dose of radiation of the type in question that is necessary to produce the same biologic reaction in a given experiment

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30
Q

RBE =

A

dose in Gy from 250 kvp xrays / dose in Gy of test radiation

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31
Q

RBE is used to refer to

A

experiments with specific cells or animal tissues

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32
Q

RBE is not practical for

A

specifying radiation protection dose levels in humans

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33
Q

as LET increas so does

A

RBE

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34
Q

high LET radiations such as alpha partices has a high

A

RBE

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35
Q

low LET radiations such as xrays and gamma rays have a low

A

RBE

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36
Q

xrays have an RBE of

A

1

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37
Q

oxygen effect

A

biologic tissue is more sensitive to radiation when irradiated in an oxygenated (aerobic) state than when it is exposed to radiation under anoxic or hypoxic conditions

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38
Q

t or f

The oxygen enhancement ratio (OER) describes the oxygen effect numerically

A

true

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39
Q

Oxygen enhancement ratio (OER) definition

A

the ratio of dose required to produce a given biologic response in the absence of oxygen to the dose required to produce the same response in the presence of oxygen

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40
Q

OER =

A

dose necessary under anoxic conditions to produce a given effect / dose necessary under aerobic condtions to produce the same effect

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41
Q

xrays and gamma rays have an OER of what when radiation dose is high

A

3

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42
Q

when radiation doses are lower than 2 Gy the OER may be

A

less (about 2)

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43
Q

OER values for high let radiations are what and why

A

1

because the high LET radiations are so effective in producing damage, the presence or absence of oxygen doesn’t matter

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44
Q

radiation induced damage is observed on 3 levels

A
  1. molecular
  2. cellular
  3. organic
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45
Q

T or F

any visible radiation induced injuries to cells or the organism always begin with damage at the molecular level

A

true

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46
Q

molecular damage results in

A

the formation of structurally changed molecules that may impair cellular functioning

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47
Q

organic level:

when a sufficient number of somatic cells are affected,

A

the entire body processes could be adversely affected

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48
Q

organic level:

if germ cells are damaged,

A

the damage may be passed onto future generations in the form of genetic mutations

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49
Q

when ionizing radiation interacts with a cell,

A

ionizations and excitations are produced in vital macromolecules (such as DNA) or in the nedium in which the cellular organisms are suspended (water)

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50
Q

direct action (effect)

A

biologic damage occurs when any type of radiation ionizes master or key molecules such as DNA causing them to become inactive or functionally altered

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51
Q

what could the damages of direct action lead to

A

inappropriate chemical reactions

essential biochemical processes may not occur in the cell

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52
Q

indirect action (effect)

A

occurs when the radiation interacts with water in the cell causing the formation of free radicals

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53
Q

when the water molecule is irradiated through indirect action

A

a free radical is formed and can migrate tot eh master or key molecule (DNA) and can result in cell death

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54
Q

direct effect may result after exposure to…..

but is much more likely to happen after exposure to …

A

any type of radiation

high LET radiation than Low LET radiation

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55
Q

since the human body is 80% water and less than 1% DNA it’s assumed that

A

most of the effects of radiation in you result from the indirect effect

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56
Q

the primary mechanism for indirect action is

A

the radiolysis of water

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57
Q

radiolysis of water definition

A

when water is irradiated, it dissociates into other molecular products

58
Q

for every molecule of DNA in the cell there are how many molecules or water

A

1.2 x 10^7

59
Q

when a water molecule is irradiated it absorbs energy and dissociates into

A

a positive water ion and an electron

60
Q

t or f

after the initial ionization of a water molecule, many reactions can happen

A

true

61
Q

type of reaction that can happen from ionization of a water molecule

A

the ion pair AKA positive water molecule and electron may rejoin into a stable water molecule
no damage occurs

62
Q

type of reaction that can happen from ionization of a water molecule

A

if the ions do not rejoin the electron can attach to another water molecule and produce another type of reaction (a negative water ion)

63
Q

t or f
the HOH+ (positive water molecule) and the HOH- (negative water molecule) are unstable and can break apart into smaller molecules

A

true

64
Q

HOH+ becomes

A

a hydrogen ion (H+) and a hydroxyl radical (OH+)

65
Q

HOH- becomes

A

a hydroxyl ion (OH-) and a hydrogen radical (H*)

66
Q

the ultimate result of the interaction of radiation with water is

A

the formation of an ion pair and 2 free radicals (H* and OH+)

67
Q

the free radicals can also produce

A

other products that are poisonous to the cell and act as toxic agents

68
Q

the OH+ (hydroxyl radical) can join with a similar molecule and form

A

hydrogen peroxide
toxic to the cell
can kill

69
Q

the H* (hydrogen radical) can interact with molecular oxygen to form

A

hydroperoxyl radical

can kill the cell

70
Q

free radicals are believed to be a major factor in

A

the production of damage via indirect action in the cell

71
Q

2 points that are considered about the effects of radiation on DNA

A
  1. much of the damage in DNA can be, and is repaired by the cell
  2. all types of DNA damage are not equal in terms of their biologic significance
72
Q

5 effects of ionizing radiation on DNA

A
  1. single strand break
  2. double strand break
  3. double strand break in the same rung of DNA
  4. mutation
  5. covalent cross links
73
Q

single strand breaks (SSB)

A

the ionizaiton of a DNA macromolecule resulting in a break of one of its chemical bonds.
it severs one of the sugar phosphate chain side rails.

74
Q

single strand break type of injury is also called a

A

point mutation

75
Q

point mutations commonly occur with what kind of radiation

A

low LET radiation

76
Q

can single strand breaks be repaired?

A

yes
repair enzymes can reverse the damage
no long term consequences to the cell

77
Q

double strand breaks

A

ionization of a DNA macromolecule resulting in the rupture of one or more of its chemical bonds
creates one or more breaks in each of the 2 sugar phosphate chains

78
Q

double strand breaks occur most commonly with what type of radiation

A

high LET radiation

79
Q

can double strand breaks be repaired?

A

yes, but not as easily as SSB

80
Q

double strand break in the same rung of DNA

A

if both strands of DNA are broken at the same nitrogenous base or rung resulting in complete breakage of DNA

81
Q

can double strand breaks in the same rung of DNA be repaired ?

A

no it results in death or impaired functions of the new daughter cells

82
Q

mutation

A

changes in genes caused by the loss or change of base in the DNA chain

83
Q

mutation may not be

A

reversible and cause acute consequences for the cell

84
Q

covalent cross links can occur in

A

many different patterns

all are potentially fatal to the cell if not properly repaired

85
Q

intrastrand cross link

A

cross link formed between 2 places on the same DNA strand

86
Q

interstrand cross link

A

cross link formed between complementary DNA strands or between entirely different DNA molecules

87
Q

3 effects of ionizing radiation on chromosomes

A
  1. radiation induced chromosome breaks
  2. chromosomal fragments
  3. chromosome anomalies
88
Q

radiation induced chromosome breaks may be viewed microscopically during

A

metaphase and anaphase of cell division

89
Q

the effects of radiation induced chromosome breaks is

A

the visible difference in the structure of the chromosome

90
Q

chromosome fragments

A

2 or more fragments are produced after chromosomal breakage

each has a fractured extremity and broken ends appear sticky and can adhere to another sticky end

91
Q

2 types of chromosome anomalies observed at metaphase

A
  1. chromosome aberrations

2. chromatid aberrations

92
Q
  1. chromosome aberrations
A

lesions that result when irradiation occurs early in interphase before DNA synthesis takes place

93
Q
  1. chromatid aberrations
A

lesions that result when irradiation of an individual chromatid occurs later in interphase after DNA synthesis has taken place

94
Q

4 consequences to the cell from structural changes in biologic tissue

A
  1. restitution
  2. deletion
  3. broken end rearrangement
  4. broken end rearrangement without visible damage to the chromatids
95
Q
  1. restitution
A

a process in which chromosome breaks rejoin in their original configuration with no visible damage

96
Q
  1. deletion
A

part of the chromosome or chromatid is lost at the next cell division creating an aberation known as an acentric fragment

97
Q
  1. broken end rearrangement
A

where a grossly misshapen chromosome may be produced

98
Q
  1. broken end rearrangement without visible damage to teh chromatids
A

where the chromatids genetic material has been rearranged even though the chromatid appears normal

99
Q

target theory

A

a concept that the cell dies if inactivation of the master or key molecule occurs as a result of exposure to ionizing radiation

100
Q

damage to cell’s nucleus can result in various types of ways (7 types)

A
  1. instant death
  2. reproductive death
  3. apoptosis or programmed cell death
  4. mitotic or genetic death
  5. mitotic delay
  6. interference with function
  7. chromosome breakage
101
Q

instant death can occur when

A

the cells are irradiated with a high 1000 gray dose of xrays or gamma rays over a period of a few secs or mins
well above diagnostic range

102
Q

instant death affects

A

vital functions of cytoplasmic organelles , the cell membrane, the nucleus and DNA

103
Q

reproductive death

A

permanent loss of cells ability to reproduce because of exposure to doses of 1-10 gray
cell will function normally just won’t reproduce

104
Q

apoptosis

A

cell that dies from radiation exposure before it attempts division

105
Q

t or f

radiosensitivity of the cell governs the dose required to induce apoptosis

A

true

106
Q

mitotic or genetic death

A

ionizing radiation affect cell division by retarding or by permanently inhibiting the mitotic process
can happen at small doses

107
Q

mitotic delay

A

failure of a cell to divide on time
can occur when exposed to as little as 0.01 gray
after the delay the cell functions normal

108
Q

interference of function

A

permanent or temporary interference of cell function independent of the cell’s ability to divide

109
Q

chromosomal breakage

A

breaking of one or both sugar phosphate chains of DNA

110
Q

cell survival curves

A

method of displaying the radiation sensitivity of a particular type of cell

111
Q

vertical axis on cell survival curve

A

surviving fraction

112
Q

horizontal axis on cell survival curve

A

radiation dose

113
Q

immature cells

A

nonspecialized
more radiosensitive
undergo rapid cell division

114
Q

mature cells

A

specialized
more radioresistant
divide at a slower rate or don’t divide at all

115
Q

t or f LET affects cell radiosensitivity

A

true

116
Q

hyperbaric oxygen

A

sometimes used in conjunction with radiation to treat certain types of cancers

117
Q

law of bergonie and tribondeau formed when? and why?

A

1906

theorized and observed that radiosensitivity was a function of the metabolic state of the tissue being irradiated

118
Q

law of bergonie and tribondeau states

A

the radiosensitivity of cells is directly proportional to their reproductive activity and inversely proportional to their degree of differentiation

119
Q

hematologic depression is caused by how much dose delivered within a few days

A

0.25 Gyt

120
Q

time necessary for bone marrow cells to recover depends on amount of radiation received
below 1 Gy =

A

repopulation occurs within weeks of irradiation

121
Q

time necessary for bone marrow cells to recover depends on amount of radiation received
1-10 Gy or more =

A

severely depletes the # of bone marrow cells and require a longer recovery period

122
Q

time necessary for bone marrow cells to recover depends on amount of radiation received
very high doses =

A

permanent decrease in number of stem cells

123
Q

t or f

erythrocytes are among the most radiosensitive of human tissues

A

true

124
Q

whole body doses in excess of 5 Gy

A

may die within 30-60 days

125
Q

lethal dose of radiation for humans is specified as

A

LD 50/60

126
Q

lethal dose of radiation for animals is specified as

A

LD 50/30

127
Q

the lethal dose for humans in grays is

A

3-4 grays

128
Q

what are the most radiosensitive blood cells in the human body

A

lymphocytes manufactured in bone marrow

129
Q

a dose of what does what to neutrophils

A

a dose of 0.5 gray can cause a reduction in # of neutrophils present in blood

130
Q

a dose of waht can do what to lymphocytes

A

a dose of .25 gray decreases the number of lymphocytes, but they can recover quickly

131
Q

epithelial tissue is highly radiosensitive or radioinsensitive

A

radiosensitive

132
Q

muscle tissue is highly radiosensitive or radioinsensitive

A

radioinsensitive

133
Q

nerve tissue is highly radiosensitive or radioinsensitive

A

radioinsensitive

134
Q

spermatogenia (germ cells) are highly radiosensitive or radioinsensitive

A

radiosensitive
mature = insensitive
immature = sensitive

135
Q

radiation dose of 2 Gy to reproductive cells can cause

A

temporary sterility for as long as 12 months

136
Q

radiation dose of 5 or 6 Gy to reproductive cells can cause

A

permanent sterility

137
Q

radiation dose of 0.1 Gy to reproductive cells may

A

depress male sperm population

138
Q

male reproductive cells exposed to dose of 0.1 Gy or more

A

may cause genetic mutations in future generations

139
Q

radiation dose of 2 Gy to the ovaries may cause

A

temporary sterility

140
Q

radiation dose of 5 Gy to the ovaries may cause

A

permanent sterility

141
Q

small doses as low as 0.1 Gy to the ovaries may cause

A

menstrual irregularities

Radiation protection (12 decks)

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