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chapter 33 radiobiol
chapter 33 radiobiology
| Question | Answer |
|---|---|
| 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
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