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RT 206 > 4.1 Fundamental Principles of Radiobiology > Flashcards

4.1 Fundamental Principles of Radiobiology Flashcards

1
Q

refers to the breakdown of a cell caused by damage to its membrane

A

lysis

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2
Q

process that results in an increase of the number of cells

A

cell proliferation

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3
Q

enlargement of an organ or tissue caused by an increase in the
amount of organic tissue that results from cell proliferation

A

hyperplasia

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4
Q

outside the body or cell

A

in vitro

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5
Q

inside the living cell

A

in vivo

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6
Q

experimented on rodent testicles to observe the effects of radiation

A

Jean Alban Bergonié and Louis Tribondeau (1906)

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7
Q

Law of Bergonie and Tribondeau

A
  1. Stem or immature cells are more radiosensitive than
    mature cells.
  2. Younger tissues and organs are more radiosensitive than
    older tissues and organs.
  3. The higher the metabolic cell activity, the more radiosensitive
    it is.
  4. The greater the proliferation and growth rate for tissues, the
    greater the radiosensitivity.
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8
Q

suggested that the intrinsic susceptibility of
damage to any cell by ionizing radiation is identical but timing of manifestation of radiation-produced damage varies according to cell type

A

Paul Ancel and P. Vitemberger (1925)

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9
Q

The testes were selected because they contain both ____

A

mature and immature cells

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10
Q

mature cells

A

spermatozoa

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11
Q

execute the

organ’s principal function

A

mature cells (spermatozoa)

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12
Q

immature cells

A

spermatogonia and spermatocytes

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13
Q

evolve into mature, functional cells

A

The immature cells (spermatogonia and spermatocytes)

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14
Q

The ______ cells divide frequently, whereas the ______ cells
do not divide

A

spermatogonia,

spermatozoa

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15
Q

After irradiating the testes, _______

noticed the immature cells were injured at lower doses than the mature cells

A

Jean Alban Bergonié and Louis Tribondeau (1906)

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16
Q

Supported by their observations, Bergonie and Tribondeau proposed a law
describing radiation sensitivity for all body cells. Their law maintains
that actively mitotic and undifferentiated cells are most susceptible
to damage from ionizing radiation

A

Law of Bergonie and Tribondeau

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17
Q

This law concludes that compared to a child or mature adult, the
fetus is most radiosensitive

A

Law of Bergonie and Tribondeau

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18
Q

modified the

law of Bergonie and Tribondeau

A

Paul Ancel and P. Vitemberger (1925)

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19
Q

Paul Ancel and P. Vitemberger experiments on mammals demonstrated that there are two factors that affect the manifestation
of radiation damage to the cell:

A
  1. The amount of biologic stress the cell receives
  2. Pre- and post-irradiation conditions to which the cell
    is exposed
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20
Q

Ancel and Vitemberger theorized that the most significant biologic stress on the cell is the need for ______

A

cell division

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21
Q

They determined that a given dose of radiation will cause the same degree of damage to all cells, but only if and when the cell divides will damage be demonstrated

A

Paul Ancel and P. Vitemberger (1925)

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22
Q

Even though Ancel and Vitemberger convey radiosensitivity differently than Bergonie and Tribondeau, they do agree with them by
placing a significant emphasis on the amount of _____ activity
involved

A

mitotic

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23
Q

In the 1920s, researchers learned that the process of ionization in tissues was the cause of biologic results. The two mechanisms recognized were:

A

• Direct ionization along charged particle tracks caused direct
effects
• The formation of free radicals caused indirect effects

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24
Q

original ionization occurs directly on target

molecule

A

direct effects

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25
Q

original ionization occurs with water and transfers ionization to target molecule

A

indirect effects

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26
Q

In the early days of radiation, it was generally held that the biggest
dose (tolerated), given as ____ as possible, was the best treatment

A

fast

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27
Q

During the period, roughly 1920 to 1930, ______ argued
that the differential effect of X-rays on cancer and normal tissues
could be best obtained by giving the treatment slowly.

A

Claude Regaud

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28
Q

For example,
healing was very much better when skin cancer was treated over a
period of a week than in one day

A

Fractionation Theory

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29
Q

experimented on sheep testicles and found that if original dose was
fractionated into smaller doses spread over a period of time, animals would be
sterile but with considerably less damage to their skin

A

Claude Regaud

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30
Q

It was found that if the original dose was fractionated, or broken up into smaller doses spread out over a period of
time, the animals would still become sterile, but with considerably less
damage to their skin. Regaud called this the _____

A

Fractionation Theory

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31
Q

Extension of a total dose over a period of time (in days or weeks), in order to
minimize unwanted radiation effects on normal tissue

A

Fractionation Theory

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32
Q

argued that the differential effect of X-rays on cancer and

normal tissues could be best obtained by giving the treatment slowly

A

Claude Regaud

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33
Q

refers to the ability of normal tissues to

replenish themselves following injury.

A

Repopulation

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34
Q

is defined as the time during which a course of radiation is given

A

Protraction

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35
Q

The logic is that by protracting a course of radiation therapy of _____, one allows for
hyperplastic compensation in some critically affected normal tissues.

A

five to six weeks

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36
Q

Although it is likely that no increase in tolerance will be obtained
unless the protraction is extended to a period longer than _____,
some benefit may be obtained from this.

A

four weeks

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37
Q

The reason for the _____ requirement is that it may take this long for damaged cells to
die, to go through the process of lysis, thereby creating a local depletion of cells; and for the remaining cells to mount a replacement
proliferation. It is also likely that the tumor cells will continue to
proliferate throughout this period

A

four-week

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38
Q

discovered that ionizing radiation produced mutations

through his experiment with fruit flies

A

Herman Muller (1927)

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39
Q

He found that the radiation-induced mutations were the same as those
produced in nature. Irradiating the fruit flies did not create any
unusual effects, but the frequency of mutations was intensified.

A

Herman Muller (1927)

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40
Q

This implies that the effects of ionization were not unique to radiation;
that is, they could have been caused by things other than radiation.
Muller’s finding is termed _______

A

mutagenesis

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41
Q

determined oxygen to be a radiosensitizer because it increases the cell-killing effect of a given dose of radiation

A

Charles Rick

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42
Q

This occurs as a result of the increased production of free radicals when ionizing radiation is delivered in the presence of oxygen. This was named the _____

A

oxygen effect

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43
Q

did extensive research on the hydrolysis

of water with the resulting liberation of free radicals.

A

D. Lea (1946)

44
Q

D. Lea termed his

finds the mechanism of ____

A

indirect action

45
Q

experimented with the root tips of Vicia faba, discovered that the frequency of chromosome aberrations produced by X-rays depends on the amount of oxygen present during irradiation

A

John Read and John Thoday (1947)

46
Q

exposed human uterine
cervix cells to varying doses of radiation.They experimentally determined
reproductive failure by counting the number of colonies formed by these
irradiated cells

A

Theodore Puck and Phillip Marcus (1956)

47
Q

doing cancer research
using irradiated Chinese hamster cells, discovered the ability of cells to
recover from small radiation doses

A

Mortimer Elkind and H. Sutton-Gilbert (1959)

48
Q

Cells are distinguished by their rate of proliferation and their stage of development

A

Radiosensitivity

49
Q

known as undifferentiated, precursor, or stem cells

A

Immature cells

50
Q

Cells that are considered highly radiosensitive include:

A

lymphocytes, spermatogonia, erythroblasts, and intestinal crypt cells

51
Q

Cells that have an intermediate radiosensitivity include:

A

endothelial cells, osteoblasts, spermatids, and fibroblasts

52
Q

Cells that have low radiosensitivity include:

A

muscle and nerve

cells, and chondrocytes

53
Q

depends upon what part of the cell cycle the

cell is in

A

Cell radiosensitivity

54
Q

are judged the most radiosensitive phases of the cell cycle

A

Mitosis, and the passage from late G1 into early S-phase

55
Q

is considered to be the most radioresistant cell cycle

phase

A

Mid- to late S-phase

56
Q

Numerous experiments have determined that the _____ of a cell is considerably more radiosensitive than is the cytoplasm of the cell

A

nucleus

57
Q

is the most radiosensitive part of the cell

A

DNA

58
Q

its radiosensitivity

is intermediate between that of DNA and protein

A

RNA

59
Q

Chromosome-produced radiation damage can be analyzed during the _____
portion of the cell cycle

A

metaphase

60
Q

order of radiosensitivity

A

DNA> RNA> protein

61
Q

When a cell is irradiated,

three events may occur:

A

division delay, interphase

death, and cell death

62
Q

It has been proven in experiments that low doses of radiation delay cell mitosis in humans. The specific cause for this slow-down,
known as ______, is unknown

A

division delay

63
Q

cell death before entering mitosis which depends on which cell is irradiated

A

Interphase death

64
Q

Highly mitotic cells demonstrate interphase death at doses ____ than cells that are not highly mitotic

A

lower

65
Q

It is theorized that when there is a change in the cell membrane,
electrolytes become _____

A

imbalanced

66
Q

The consequence for cells that do not divide repetitively, or that divide numerous times resulting in
dead cells being produced, is failure of ______

A

cell reproduction

67
Q

When noting biologic changes that occur in cells caused by irradiating them, the following should be emphasized:

A

-Radiation interaction with cells has to do with chance and
probability.
-The first deposit of radiation is given very rapidly, approximately
within 10^-17 seconds.
-The interaction of radiation within the cell is random.
-It cannot be determined if visible changes to cells, tissues, and
organs are caused by radiation or other sources.
-Radiation doses to cells cause biologic changes only following a
period of time that is dose dependent, and may vary from minutes to years

68
Q

Factors that affect

Radiosensitivity

A
  • Physical Factors

- Biologic Factors

69
Q

Factors that affect
Radiosensitivity
-Physical Factors

A
  • Linear Energy Transfer
  • Relative Biologic Effectiveness
  • Protraction and Fractionation
70
Q

Factors that affect
Radiosensitivity
-Biologic Factors

A
  • Oxygen Effect
  • Age
  • Recovery
  • Chemical Agents
71
Q

The factors affecting cell response include:

A
  • linear energy transfer (LET)
  • relative biologic effectiveness (RBE)
  • oxygen enhancement ratio (OER).
72
Q

is a measure of the rate at which energy is deposited as a charged particle travels through matter, and is described in
terms of keV/µm

A

Linear Energy Transfer (LET)

73
Q

another method of expressing radiation quality and determining the value of radiation weighing factor (W)

A

Linear Energy Transfer (LET)

74
Q

ability to induce biologic response _____ as LET increases

A

increases

75
Q

electromagnetic radiation produce few and sparse interactions because of their
fast-moving electrons (which have negligible mass and a –1 charge), is regarded as ___ LET radiation

A

low

76
Q

particulate radiation which are highly ionizing
and have substantial mass and/or charge, are more likely to interact with tissue. These radiations lose their energy quickly, and produce numerous ionizations within a very short distance, is considered ___ LET radiation

A

high

77
Q

is a function of the physical characteristics of radiation, that is, mass and charge

A

Linear Energy Transfer (LET)

78
Q

x- and gamma-rays

A

electromagnetic radiation

79
Q

alpha particles and neutrons

A

particulate radiations

80
Q

The higher the LET of radiation, the _____ the chance for a

biologic interaction

A

greater

81
Q

LET of 25 MV x-rays

A

0.2 keV/µm

82
Q

LET of Cobalt-60 gamma rays

A

0.3 keV/µm

83
Q

LET of 1 MeV electrons

A

0.3 keV/µm

84
Q

LET of Diagnostic x-rays

A

3 keV/µm

85
Q

LET of 10 MeV protons

A

4 keV/µm

86
Q

LET of Fast Neutrons

A

50 keV/µm

87
Q

LET of 5 MeV alpha particles

A

100 keV/µm

88
Q

LET of Heavy nuclei

A

1000 keV/µm

89
Q

RBE of 25 MV x-rays

A

0.8

90
Q

RBE of Cobalt-60 gamma rays

A

0.9

91
Q

RBE of 1 MeV electrons

A

0.9

92
Q

RBE of Diagnostic x-rays

A

1

93
Q

RBE of 10 MeV protons

A

5

94
Q

RBE of Fast Neutrons

A

10

95
Q

RBE of 5 MeV alpha particles

A

20

96
Q

RBE of Heavy nuclei

A

30

97
Q

The relative effect of LET is quantitatively described by the

A

relative biologic effectiveness (RBE)

98
Q

is a comparison of a dose of test radiation to a dose of 250 keV X-ray that produces the same biologic response

A

relative biologic effectiveness (RBE)

99
Q

measures the biologic effectiveness of radiations having different LETs

A

relative biologic effectiveness (RBE)

100
Q

The constant is the _____, not the radiation dose.

A

biologic response

101
Q

RBE=

A

RBE= Dose of standard radiation necessary to produce a given effect / Dose of test radiation necessary to
produce the same effect

102
Q

Factors that influence RBE include:

A

radiation type, cell or tissue
type, physiologic condition, biologic result being examined, and the
radiation dose rate

103
Q

In comparing LET and RBE, as LET increases, RBE ______

A

increases

104
Q

The ability of ionizing radiation to produce a biologic response increases as the LET of radiation _____

A

increases

105
Q

When LET is ____, ionizations occur frequently, increasing the probability of interaction with the target
molecule

A

high

106
Q

The standard radiation, by convention, is ____ in the range of ____

A

orthovoltage x-radiation,

200 to 250 kVp

107
Q

This
type of x-ray beam was used for many years in radiation
oncology and in essentially all early radiobiologic
research

A

orthovoltage x-radiation

RT 206 (9 decks)

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