Jen Y M, Hendry J H
Cancer Research Campaign Department of Experimental Radiation Oncology, Paterson Institute for Cancer Research, Christie Hospital (NHS), Trust, Manchester, UK.
Radiother Oncol. 1993 Feb;26(2):117-24. doi: 10.1016/0167-8140(93)90092-m.
The fractionation sensitivity of kidney clonogenic epithelial cells (X-irradiation in vivo, assay in vitro) was quantified using the linear-quadratic model. The cells were assayed either immediately after the fractionation schedule or after a time delay in order to compare the relative amounts of dose sparing due to fractionation (conventionally sublethal damage repair) and to post-irradiation delay intervals before assay (conventionally potentially-lethal damage repair). As the delay before assay was increased, there was a tendency for both alpha and beta to decrease, and as a consequence the alpha/beta ratio stayed virtually unchanged (3.3-4.4 Gy) regardless of delay time before assay. No change in survival was observed from 12 h to 6 weeks after neutron irradiation (62 MeVp-->Be), suggesting that the change observed after X-rays was due to repair rather than repopulation. As the interfraction intervals in an 8-fraction X-irradiation schedule were increased in steps from 6 h to 5 days, there was improved survival, consistent with the presence of long-term repair. These studies provide further evidence for the potential importance of long-term repair in late reacting tissues not only during but also after multifraction irradiation schedules.
使用线性二次模型对肾克隆形成上皮细胞的分次照射敏感性（体内X射线照射，体外测定）进行了量化。细胞在分次照射方案结束后立即进行测定，或者在经过一段时间延迟后进行测定，以便比较由于分次照射（传统上为亚致死损伤修复）和测定前的照射后延迟间隔（传统上为潜在致死损伤修复）所导致的剂量节省的相对量。随着测定前延迟时间的增加，α和β均有下降趋势，因此，无论测定前的延迟时间如何，α/β比值实际上保持不变（3.3 - 4.4 Gy）。中子照射（62 MeVp→铍）后12小时至6周未观察到存活率变化，这表明X射线照射后观察到的变化是由于修复而非再增殖。在8分次X射线照射方案中，分次间隔从6小时逐步增加到5天，存活率提高，这与长期修复的存在一致。这些研究进一步证明了长期修复在晚期反应组织中不仅在多次照射方案期间而且在照射后潜在的重要性。
