螺旋断层加速器与常规加速器在肺癌调强放疗中的剂量学评估初探

目的:分析、比较用于治疗非小细胞肺癌(NSCLC)的基于Helical TomoTherapy(HT)和常规加速器的调强放疗(IMRT)计划靶区剂量均匀性、适形度以及危及器官受照体积和剂量分布方面的差异,为HT技术进一步深入运用于临床工作提供了参考数据。方法:回顾性随机选择10例NSCLC患者,分别采用HT加速器和常规加速器对每例NSCLC患者行IMRT计划设计,然后比较靶区及危及器官(OARs)的剂量体积参数的差异。结果:在靶区方面,HT IMRT计划的靶区剂量均匀性指数(HI)和适形度指数(CI)均优于常规加速器IMRT(P=0.035、P=0.000)。在OARs方面,对于正常肺组织、V50、V30、V10、V5、平均剂量Dmean的差异有显著性意义(P=0.019、P=0.001、P=0.000、P=0.004、P=0.010)。就V5、V10、Dmean而言,HT计划高于常规加速器计划,就V20、V30、V50而言,HT计划低于后者。食管V35、Dmean的差异有显著性意义(P=0.006、P=0.015),而食管V55、心脏、脊髓等危及器官的受量基本相同。结论:对于NSCLC,基于HT的调强放疗能够提高更好的靶区适形度和均匀性,正常肺组织低剂量区受照体积增大,在临床应用中应予以注意。

Dosimetric Comparison of Helical Tomotherapy and Conventional Linac-based Intensity Modulated Radiotherapy for Lung Cancer

To compare HT and conventional linac-based intensity modulated radiotherapy （IMRT） for non-small cell lung cancer （NSCLC） in terms of homogeneity index, conformity index, dose and volumepammeters of OARs. Methods： For a cohort of 10 patients,HT and Elekta precise linac-based 6MV IMRT planning Was performed using identical planning objectives and dose constraints. Doses were computed with commercially available .TPS using convolution/superposition （CS） algorithm. Plans were compared according to dose-volume histogram （DVH） analysis in terms of PTV homogeneity.and conformity indices （HI and CI） as well as OARs dose and volume parameters, Results： Significant differences between HT and conventional linac-based plans were observed for Hland CI （P=0.035,P=0.000）. For D_mean, V5, V10, V30, V50 of lung, significant difference existed between HT and Elekta precise-based IMRT （P=019,P=0.001 ,P=0.000,P=0.004,P=0.010）. D_mean, V5 and V10 of HT were higher than those of the conventional linac while V20, V30 and V50 of HT were lower than those of the latter. Foresophagus, V35, D_mean were significantly different （P=0.006,P=0.015）. The difference in high dose area for esophagus as well as heart and cord was not significant. Conclusions： For NSCLC, HT-based IMRT achieved better HI and CI. However, the irradiated volume of lung in low dose area increased which should arouse attentin in clinial work.