Radiation Biology Flashcards
Tissue is m ore sensitive to radiation when exposed to:
Oxygen
The dissociation of molecules by ionizing radiation
Radiolysis
Displays sensitivity of a particular cell type; used in radiation therapy
Cell survival curve
Oxygenated cells have [more/less] indirect damage potential
More
Most radiosensitive blood cells
Lymphocytes
Whole body dose of ___ will cause hematologic depression
0.25 Gy
Whole body dose of _____ may cause death within 30-60 days
greater than 5 Gy
Temporary sterilization can occur at:
2 Gy
Permanent sterilization can occur at:
5-6 Gy
The characteristics of ionizing radiation vary among different types of radiation. Characteristics include:
Charge, mass, energy
3 essential concepts of how ionizing radiation effects can vary in biologic tissue:
-Linear energy transfer
-Relative biologic effectiveness
-Oxygen enhancement ratio
Average energy deposited per unit length of track
Linear energy transfer (LET)
The ___ value of the radiation involved is an essential factor in assessing potential tissue and organ damage from exposure to that type of radiation.
LET
When LET increases, the chance of a significant biologic response in the radiosensitive DNA macromolecule:
Increases
Gamma rays, x-rays, and electrons are examples of [low/high] LET radiation
Low
Alpha particles, ions of heavy nuclei, low-energy neutrons, and charged particles released from interactions between neutrons and atoms are examples of [low/high] LET
High
When low-LET radiation interacts with biologic tissue, it causes damage to a cell primarily through an indirect action that involves the production of molecules called:
Free radicals
High-LET radiation includes particles that possess substantial:
Mass and charge
With a double-strand break in the same rung of the DNA ladder-like structure, complete ______ occurs
Chromosomal breakage
Describes the comparative capabilities of radiation with differing LETs to produce a particular biologic reaction.
Relative biologic effectiveness (RBE)
Ratio for RBE
dose of a reference radiation to the dose of radiation of the type in question that is necessary to produce the same biologic reaction
Used to calculate the equivalent dose (EqD) to determine the ability of a dose of any kind of ionizing radiation to cause biologic damage.
Radiation weighting factor
Refers to the enhancement of the therapeutic or detrimental effect of ionizing radiation due to the presence of oxygen.
Oxygen enhancement ratio (OER)
radiation dose required to cause a particular biologic response of cells in an oxygen-deprived environment to the radiation dose required to generate an identical response under normal oxygenated conditions.
OER Ratio
In living systems, biologic damage stemming from exposure to ionizing radiation is examined on three levels:
Molecular, cellular, organic systems
A free radical is a molecular unit that has no net electrical charge but, because of having ______, it is an extremely reactive entity.
an unpaired valence electron
The concept of radiation damage to specific sensitive locations resulting from discrete and random events is known as:
Target theory
States that the radiosensitivity of cells is directly proportional to their reproductive activity and inversely proportional to their degree of differentiation.
Law of Bergonie and Tribondeau
What would be considered a safe radiation dose for the gonads of both males and females?
0 Gyt
Because the genetic information to be passed on to future generations is contained in the strict sequence of nitrogenous bases, the loss or change of a base in the DNA chain represents a (an):
Mutation
Direct action may occur after exposure to any type of radiation, but it is much more likely to occur after exposure to:
high-LET radiation
The radiation dose required to produce mitotic death is:
less than the dose needed to produce apoptosis in slowly dividing cells or nondividing cells.
When free radicals previously produced by the interaction of radiation with water molecules act on a molecule such as DNA, the damaging action of ionizing radiation is indirect in the sense that the radiation is not the immediate cause of injury to the macromolecule. What is the immediate cause of this damage?
The free radicals produced by the interaction of radiation with water molecules
Which of the following humans is most radiosensitive?
An embryo-fetus during the first trimester of pregnancy
T/F: Patients are not expected to sustain appreciable damage to either the blood or the blood-forming organs as a consequence of the examination.
True
