IMRT或3DCRT计划评估——适形指数（CI）

A new set of conformity indices for evaluating intensity-modulated radiotherapy or three-dimensional conformal radiotherapy plans

目的 推荐一组适形指数用于判断IMRT或3DCRT计划中靶区和OAR受量是否满足临床剂量处方的要求。方法 从已治NSCLC的IMRT或3DCRT计划中随机抽取30例计划,按文中定义的新适形指数进行评估分析,根据评估结果选出其中待改进的计划并对其制定2个改进方案,评估改进前后计划组参数值以及靶区和OAR剂量学参数的差异并配对t检验差异。结果 30例计划中处方剂量线（面）包裹的体积比PTV体积大25%,即处方剂量线（面）包裹的体积中只有75%体积是靶区,而大约有25%PTV的正常肺组织会受到和靶区一样的剂量,30例计划中95%靶区都受到了处方剂量,虽然有5%靶区受量低于处方剂量,但仍然能保证几乎100%靶区受到了90%处方剂量;两改进组与原计划组相比,方案（1）与原临床计划组在CI2、CI4、CI5、CI6和HI中都相近（P=0.240-0.780）,CI1和CI3不同（P=0.002、0）;PTV的Dmax、Dmin、Dmean和正常肺组织V5、V20,心脏V30、V40及脊髓Dmax都近似（P=0.211-0.964）;方案（2）与原临床组在CI2、CI4和CI5中都相近（P=0.308、0.308、0.106）,在CI1、CI3、CI6和HI不同（P=0.001-0.014）;PTV的Dmax、Dmin、Dmean和正常肺组织V5、V20及脊髓Dmax都不同（P=0.008-0.036）,心脏V30、V40近似（P=0.083、0.080）。结论 文中推荐的适形指数方法定量评估了计划中靶区适形度及OAR中接受处方剂量情况,有利于设计出更高水平的个性化计划。

Objective To propose a new set of conformity indices （CIs） that may be useful for evaluating whether the prescribed doses to target volume and organs at risk （OAR） in intensity-modulated radiotherapy （IMRT） or three-dimensional conformal radiotherapy （3DCRT） plans meet clinical requirements. Methods A total of 30 patients＇ plans were randomly selected from the IMRT or 3DCRT plans for non-small cell lung cancer and analyzed with the newly defined CIs described in this article. The plans to be improved were selected according to the evaluating results, and two schemes were developed to improve these plans. Then, the differences in CI, Dmax, Dmin, and Dmeanof the planning target volume （PTV）, V5 and V20 of the normal lung, V30 and V40 of the heart, and Dmax of the spinal cord were investigated with the paired t-test.Results Among the 30 plans, the average volume covered by the prescribed isodose line （VRI） was 25% larger than the PTV, so the normal lung tissue with a volume approximately 25% of PTVwas given the same dose as the target volume, and the volume covered by the prescribed isodose line in the target V （C） R was only 75% of the volume VR. Ninety-five percent of the target volume received a full prescribed dose;only 5% of the target volume received less than the prescribed dose, but which was still within 90% of the prescribed dose. In the comparison between the original plans and the plans improved using the first scheme, CI2, CI4, CI5, CI6, and homogeneity index （HI） were not significantly different （P=0.240-0.780）, and CI1 and CI3 showed significant differences （P=0.002 and 0）;Dmax, Dmin, and Dmean of the PTV, V5 and V20 of the normal lung, V30 and V40 of the heart, and Dmax of the spinal cord were not significantly different （P=0.211-0.964）. In the comparison between the original plans and the plans improved using the second scheme, CI2, CI4, and CI5 were not significantly different （P=0.308, 0.308, and 0.106）, CI1, CI3, CI6, and HI showed significant differences （P=0.001-0.014）;Dmax, Dmin, and Dmean of the PTV, V5 and V20 of the normal lung, and Dmax of the spinal cord showed significant differences （P=0.008-0.036）, and V30 and V40 of the heart were not significantly different （P=0.083 and 0.080）. Conclusions The new set of CIs proposed in this paper may be a good tool for evaluating the conformity of the target and the prescribed dose to OAR and thus developing better individualized treatment plans.