胰腺癌射波刀治疗计划中不同Auto—Shells及优化步骤的应用

The application of different Auto-shells and optimization steps of CyberKnife treatment plans for pancreatic cancer

目的在胰腺癌射波刀治疗计划中采用7 shells的1步优化的剂量分布方法（Cao法），并与4 shells的3步优化方法（Blanck法）进行对比。方法回顾性分析20例经射波刀治疗的胰腺癌患者，行CT模拟定位并勾画靶区和危及器官。分别使用Blanck法和Cao法进行剂量优化和评估。比较两种优化方法计划靶区（PTV）的适形指数（CI）、新适形指数（nCI）、均匀指数（HI）、梯度指数（GI）、覆盖率、剂量体积和危及器官受量。结果与Blanck法比较，Cao法PTV的CI值、nCI值减小（1.11±0.05比1.15±0.05，1.20±0.06比1.23±0.06），GI值增大（3.22±0.19比3.11±0.19），靶区覆盖率减少[（92.48±1.85）%比（93.53±2.15）%]，100%及30%处方剂量包绕体积减小（36.46±16.64比38.19±17.68，286.19±126.52比320.93±154.82），机器跳数减小（56 369±20 019比57 814±20 531），差异均有统计学意义（P值均〈0.05）；危及器官受量空回肠全局最大剂量（Dmax）增加（21.17±2.90比20.63±3.13），胃10 cm3体积剂量（D10cc）、十二指肠D5cc和D10cc、脊髓D0.35cc均降低（12.78±2.57比13.11±2.43，11.01±3.45比11.50±3.25，9.30±3.31比9.78±3.07，6.09±0.98比6.59±0.92），差异均有统计学意义（P值均〈0.05）；其余观测指标差异均无统计学意义。结论胰腺癌射波刀治疗计划中使用7 shells的1步优化方法可以获得更优的剂量分布。

ObjectiveTo propose the method of dose distribution calculated by one-step optimization with 7 shells （Cao method） and compare with that by three-step optimization with 4 shells （Blanck method） and CyberKnife treatment plans for pancreatic cancer.Methods20 cases of pancreatic cancer who underwent CyberKnife treatment were retrospectively analyzed, and CT was performed to localize and delineate the target area and endangering organs. Dosage was optimized and evaluated with Blanck method and Cao method. The planning target volume （PTV） conformity index （CI）, new conformity index （nCI）, homogeneity index （HI）, gradient index （GI）, coverage, dose-volume and doses to organs at risk were compared.ResultsCompared with Blanck method, CI （1.11±0.05 vs 1.15±0.05）, nCI （1.20±0.06 vs 1.23±0.06）, coverage [（92.48±1.85）% vs （93.53±2.15）%], volumes encompassed by 100% and 30% prescription dose line （36.46±16.64 vs 38.19±17.68; 286.19±126.52 vs 320.93±154.82） and monitor unit （56 369±20 019 vs 57 814±20 531） were significantly decreased, while GI was increased （3.22±0.19 vs 3.11±0.19）, and all the differences were statistically significant （P〈0.05）. Additionally, Dmax of the intestine （21.17±2.90 vs 20.63±3.13）, D10cc of the stomach （12.78±2.57 vs 13.11±2.43）, D5cc of the duodenum （11.01±3.45 vs 11.50±3.25）, D10cc of the duodenum （9.30±3.31 vs 9.78±3.07） and D0.35cc of the spinal cord （6.09±0.98 vs 6.59±0.92） were all significantly decreased （P〈0.05）. No significant differences were found on other parameters.ConclusionsBetter dose distributions are accessible by one-step optimization with 7 shells in CyberKnife treatment plans for pancreatic cancer.