应用适形放疗技术减少鼻咽癌患者腮腺功能损伤的物理剂量学研究

目的从物理剂量学角度探讨使用三维适形放疗技术(3D-CRT)治疗N0期鼻咽癌病人,保护腮腺功能的可行性。方法选择1例N0鼻咽癌病例作为研究对象。经CT模拟定位,分别设计传统放疗方案和3D-CRT方案。使用剂量-体积直方图(DVH)评价3D-CRT方案靶区剂量均匀性,并比较不同方案腮腺累积剂量。结果3D-CRT放疗计划大野阶段90%等剂量曲线覆盖97.4%计划治疗靶区(PTV),最大剂量为102.2%;缩野阶段90%等剂量曲线覆盖96.2%计划治疗靶区(PTV1)。最大剂量为102.2%。3D-CRT方案腮腺平均剂量为19.6Gy。67%、45%、24%的腮腺体积分别受到大于13.7Gy、18.6Gy、23.1Gy剂量的照射。该剂量低于腮腺耐受量。3D-CRT方案重要器官累计剂量均在耐受量之内,放疗计划在肿瘤覆盖,剂量分布,保护重要器官上被认为可以接受。结论3D-CRT方案治疗N0期鼻咽癌可在保证肿瘤足够的覆盖和剂量的前提下,有效地降低腮腺的放疗剂量。在物理剂量学上是可行的。

A PHYSICAL STUDY OF DOSIOLOGY NO PAROTID SPARING WITH 3-DIMENSIONAL CONFORMAL RADIATION THERAPY FOR NO STAGE NASOPHARYNGEAL CANCER

Objective:To evaluate the feasibility of parotids sparing with 3-dimensional conformal radiotherapy (3D-CRT) in the treatment of N0 stage of nasopharyngeal carcinoma while maintaining adequate coverage of the tumor target. Methods: A patient with T2N0M0 stage of nasopharyngeal carcinoma was selected for this study. A conventional treatment plan and a 3D-CRT plan were designed respectively by CT imitated position . Detailed analysis of the dose distribution of the treatment volume and accumulative dosage of the parotid as well as other important organs was presented using dose-volume histograms (DVH). Results: In the big field step of the 3D-CRT plan,94.7 % of the PTV received more than 90 % of the mean dose of GTV,the maximum dose in the treatment volume was 102.2 %. In the boost step,96.2 % of the PTV received more than 90 % of the mean dose of GTV,the maximum dose in the treatment volume was 102.2 %.The plan was considered clinically to be acceptable. On the other hand,the 3D-CRT plan significantly reduced the dose of the parotid. The mean doses delivered to the parotid were 19.6Gy. No more than 67 %?45 %?24 % of the parotid volume were received more than 13.7 Gy?18.6 Gy?23.1 Gy doses radiation respectively. According to data published on other literatures,such doses would certainly not damage the parotid. Conclusion: 3D-CRT plan has the potential to significantly reduced the parotids dose while maintaining the adequate coverage of the tumor target.