5.2 Biologic Effects of Radiation Flashcards
are the most
radiosensitive cells in the body
lymphocytes and the spermatogonia
RBCs that transport oxygen
Erythrocytes
involved inclotting of blood to prevent
hemorrhage
Thrombocytes
scavenger type of cells used to fight bacteria
Granulocytes
involved in the immune response
Lymphocytes
All cells of the hemopoietic system develop from stem cells called _____
pluripotential
This immediate response of radiation sickness is
prodromal period.
is the time after exposure during which there is no sign of radiation sickness
latent period
is characterized by a
reduction in white blood cells, red blood cells, and
platelets
hematologic syndrome
GI death occurs principally because of
severe
damage to the cells lining the intestines
The ultimate cause of death in CNS syndrome is
elevated fluid content of the brain
follows a nonlinear,
threshold dose-response relationship
Acute radiation lethality
The cause of death in Hematologic syndrome is
generalized infection, electrolyte
imbalance, and dehydration
Damage to _____ cells results in the earliest
manifestation of radiation injury to the skin
basal
Dose-response curves differ in two ways:
- They are either linear or nonlinear
2. They are either threshold or nonthreshold
Diagnostic radiology is primarily concerned with ______ dose-response relationships
linear, non-threshold
is termed the ambient or natural response.
RA
Even at zero dose, nonthreshold relationships exhibit a measurable
response
RA
exhibit a response,
regardless of the dose
nonthreshold dose-response relationships
In 1980, the Committee on the Biological Effects of Ionizing Radiation (BEIR Committee) concluded that the effects of low doses of
low LET radiation follow a ______
linear quadratic dose-response relationship
At low doses, the curve is linear. At higher
doses, the curve becomes curvilinear. The curve is nonthreshold
linear quadratic dose-response relationship
The portion of the curve where increases in dose show no or little
increase in effect is named the ____
toe
is considered the
area of the curve in which a leveling off occurs, again demonstrating
no or little increase in effect
shoulder
In 1990, with 10 additional years of human data, the BEIR committee revised its radiation risk estimates and adopted the ______ dose-response relationship as most relevant
linear, nonthreshold
Current radiation protection guidelines are established using the
______ dose-response relationship model
linear nonthreshold
means s-shaped
Sigmoid
is applied predominately to the high dose effects
observed in radiotherapy
Sigmoid dose-response curve
There is normally a threshold below which no observable effects
occur
radiotherapy
With a sigmoid dose-response curve, there is a _____ relationship between dose and effect, meaning that the effect is not
directly proportional to the dose
nonlinear
The dose-response curve for deterministic effects
threshold, nonlinear
occur randomly
in nature
Stochastic effects
Stochastic effects also referred as
statistical response
isthe most devastating human response
to radiation exposure
Death
is one in which the probability of occurrence of effects, rather
than their severity, increases with dose
Stochastic effects
Nonstochastic
Deterministic
are thought to be nonthreshold, as damage to
a few cells or even a single cell could theoretically produce the disease
Stochastic effects
2 Gyt (200 rad), Whole Body
Death
250 mGyt (25 rad), Whole Body
Hematologic
depression
2 Gyt (200 rad), Small field
Skin erythema
3 Gyt (300 rad), Small field
Epilation
50 mGyt (5 rad), Whole body
Chromosome aberration
100 mGyt (10 rad), Local tissue
Gonadal
dysfunction
Diagnostic x-ray beams always result in ______, which is less harmful than
whole-body exposure.
partial-body exposure
is a self-renewing system
Male gametogenesis
From the ____ pluripotential stem cell, a number of cell types are produced
single
Response of Ovaries and Testes to Radiation
100 mGyt
Minimal detectable response
Response of Ovaries and Testes to Radiation
2000 mGyt
Temporary infertility
Response of Ovaries and Testes to Radiation
5000 mGyt
Sterility
The male stem cell is the ____, which matures into the _____
spermatogonia,
spermatocyte
The spermatocyte in
turn multiplies and develops into a _____, which finally differentiates into the functionally mature germ
cell, the _____
spermatid,
spermatozoa or sperm
Irradiation of the _____ early in life reduces their
size (atrophy) through germ cell death
ovaries
is the normal incidence or response with no radiation exposure
RN
10–20 kVp
Grenz rays
Germ cells are produced by both ovaries and testes, but they develop from the stem cell phase to the mature cell phase at different rates and at different times. This process of development is called ______
gametogenesis
The stem cells of the ovaries are the _____, and
they multiply in number only before birth during fetal
life
oogonia
The most radiosensitive cell during female germ cell development is the oocyte in the ____ follicle
mature
are the lymph nodes, spleen, and thymus
Lymphoid Tissue
Products of bone marrow stem cells
- Lymphocytes
- Granulocytes
- Thrombocytes
- Erythrocytes
Developing granulocytes and erythrocytes spend about ______ in the bone marrow
8 to 10 days
Thrombocytes have a lifetime of approximately ____ in the bone marrow
5 days
Thrombocytes have a lifetime of approximately ____ and erythrocytes a lifetime of nearly _____
1 week ,
4 months
After exposure, the first cells to become affected are the _____
lymphocytes
Reduced number of lymphocytes
Lymphopenia
Rapid increase followed first by a rapid decrease in number of granulocytes
Granulocytosis
Slower decrease of number of granulocytes
Granulocytopenia
depletion of platelets
thrombocytopenia
