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chapter 33 radiobiol

chapter 33 radiobiology

Interphase death Radiation effect that kills a cell before its next division
Linear energy transfer Measure of the rate at which energy is transferred from a particular type of radiation to soft tissue. Approximately 3 keV/m for diagnostic x-rays.
Standard Radiation Orthovoltage x-radiation in the 200 to 250 kVp range
Oxygen enhancement ratio measure of the increased radiosensitivity of tissue in the presence of oxygen
Repopulation One mode of cellular recovery from radiation damage
Extrapopulation Continuing a straight-line relationship into an unmeasured area
Threshold dose Dose below which no effect occurs
Dose protraction Extending exposure of a total dose by delivering continuously but at a reduced rate
Radiation weighting factor Value assigned to different types of radiation based on their LET
Tribondeau An early radiobiologist
The formula for relative biologic effectiveness RBE = dose of standard radiation to produce an effect, divided by dose of test radiation to produce the same effect
An example of fractionated radiation Patients receive the radiation dose at the same dose rate but broken into equal values and given over time (a little today, a little next month, and perhaps a little next year). Radiation oncology patients receive prescribed doses fractionated daily.
Why is high pressure (hyperbaric) oxygen used in radiation oncology To force oxygen into tumors and make them more radiosensitive
Formula for the oxygen enhancement ratio OER = dose necessary under anoxic conditions to produce a given effect divided by the dose necessary under aerobic oxygenated conditions to produce the same effect
How does age affect the radiosensitivity of tissue The younger the tissue, the more radiosensitive it is.
When a radiobiologic experiment is conducted in vitro, what does this mean Outside of the human body. At the cellular or molecular level.
Name three agents that enhance the effects of radiation Methotrexate, actinomycin D, hydroxyurea, vitamin K, halogenated pyrimidines
Name three radioprotective agents Cysteine, cysteamine, and other sulfhydryl groups
Are radioprotective agents used for human application No. To be effective, they must be administered in toxic levels.
Explain the meaning of a radiation dose response relationship Graphical representation of radiation dose and effect
Explain why the linear, non-threshold dose-response is used as a model for diagnostic imaging radiation management An equal amount of radiation dose will not necessarily produce an equal response. Non-threshold implies that no dose of radiation is so small that there is no degree of risk.
Two of the corollaries to the law of bergonie and tribondeau Stem cells are most sensitive. Young tissue and organs are more radiosensitive than old tissues and organs. Tissue in a high state of metabolic activity also has high radiosensitivity. As cellular proliferation increases, so does cellular
What are the units of OER keV/m radiosensitivity.
how are RBE and LET related With increasing LET, RBE increases to a maximum value of approximately 3
Is occupational radiation exposure fractionated, protracted, or continuous Fractionated
How OER and LET are related OER is LET-dependent. OER is highest for low LET radiation, and decreases for high LET radiation (see Figure 33-2).
Created by: hseratt