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14 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Compare lethal damage, sub-lethal damage and potentially lethal damage
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lethal is irreversible, sub-lethal does not kill the cell unless further damage takes place and potentially lethal damage can be altered by post irradiation conditions
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What are the 4 R's of radiobiology?
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1. Repair
2. Reoxygenation 3. Reassortment 4. Repopulaton |
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What causes mitotic death?
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When there are 2 DNA strand breaks
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What is the dose rate effect
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Simply put the lower the dose rate the greater the survival fraction
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What is the oxygen effect?
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The presence of oxygen, which is a radiosensitizer, during or immediately following irradiation increases radiosensitivity
why is this? |
O2 makes radiation damage "fixed"
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What is OER?
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The ratio of doses of hypoxic vs aerated dells.
OER = D0 hyposxic cells/D0 oxygenated cells |
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define:
hypoxic anoxic necrotic |
hypoxic - low oxygen
anoxic - no oxygen necrotic - dead |
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True or False: O2 levels above 2% greatly increase the oxygen effect
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False cell killing from normal aeration to 2% is the same, above that there is no significant increase
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What is the OER for exposure to x and gamma rays?
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2.5 to 3.0
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What is reassortment in the 4 r's of radiobiology?
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redistribution of a cell population as to their place in the cell cycle
what effect does this have on a cell population? |
synchronization
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What is Repopulation in the 4 r's of radiobiology?
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When the dose is split, or given a low dose rate, cellular survival increases due to cellular division
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When using external beam therapy what is the general protocol for tumor treatment?
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well collimated high energy x-rays consisting of 5 days of therapy, 2 days off and continuing for about 5 weeks
What R's of the 4 r's of radiotherapy apply to this treatment? |
all 4
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why is brachytherapy done for prostrate cancer treatment
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prostrate cancer is slow growing so an isotope with a longer half life is implanted in proximity to tumor to treat it. shorter treatments would allow it to repair
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What are the 2 goals in radiotherapy?
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1. pain reduction
2. stop cancer cells |
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