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