Repair of Radiation Damage and the Dose-Rate Effect Chapter 5

1. 1 Repair of Radiation Damage and the Dose-Rate Effect Chapter 5

2. 2 Overview Classification of radiation damage �Lethal�, �potentially lethal� and �sublethal� radiation damage Repair and radiation quality Dose-rate effect & inverse dose-rate effect Brachytherapy or endocurietherapy Intracavity and interstitial therapy Radiolabeled immunoglobulin therapy

3. 3 Classification of Radiation Damage (Mammalian Cells) Lethal damage (LD) leads to cell death irreversible irreparable Sublethal damage (SLD) can be repaired in hours unless additional damage added second dose interacts evident by increased survival with fractionated doses

4. 4 Classification of Radiation Damage Potentially lethal damage (PLD) damage which can be modified by post-irradiation environment evident by increased survival w/ delayed assay All terms are simply �operational� mechanisms of cell repair & radio-resistance not completely understood at molecular level and in mammals

5. 5 Potentially Lethal Damage Examples of survival influence varying environmental conditions: in vitro incubated in balanced salt solution (not growth medium) post exposure increased survival (PLD repair) not a good model of physiologic system however better in vitro model (mimic tumor cells in vivo) density-inhibited, stationary-phase cell cultures cells remained density-inhibited for 6 - 12 hours results in enhanced cell survival

6. 6 X-ray Survival Curve for Density-Inhibited, Stationary-Phase Cells