鼻咽癌后程三维适形放疗与常规放疗方案3D-TPS剂量分布的研究

COMPARISON OF THE PLANNED DOSE DISTRIBUTIONS BETWEEN LATE COURSE 3-D CONFORMAL RADIOTHERAPY PLAN AND CONVENTIONAL PLANS IN USING 3D-TPS FOR NASOPHARYNGEAL CARCINOMA

目的 :用 3D- TPS计算其等剂量分布的方法比较鼻咽癌后程 3D- CRT方案和两种常规放疗方案的优劣。方法 :选择鼻咽癌原发灶 T2 ～ T4 8例 ,第一阶段按常规放疗 ,在放疗后程 ,全组对治疗部位作 CT模拟定位 ,同时分别设计 3D- CRT方案与两种常用治疗方案即双耳前野、鼻前野加双耳前野作比较 ,通过 DVH和剂量分布截面图 ,评估这 3种方案中靶区内最小剂量、靶区内平均剂量、治疗区与靶区的适合度、危及器官的最大剂量及其 5 0 %体积受量 D50 、重要器官腮腺、颞颌关节、咬肌的平均剂量及其 D50 ,全组病例以上述每项指标的均数和标准差的百分率进行比较。结果 :3D- CRT方案与常规二野方案比较 ,靶区适合度和危及器官最大剂量差异有统计学意义 (均 P <0 .0 5 ) ,危及器官 5 0 %体积受量差异无统计学意义 (P >0 .0 5 ) ,其余指标差异均有统计学意义 (均 P <0 .0 1)。 3D- CRT方案与三野方案比较 ,靶区适合度和腮腺 5 0 %体积受量均 P <0 .0 5 ,其余指标均 P <0 .0 1。结论 :在鼻咽癌放疗后程 ,采用 3D- CRT方案比两种常规放疗方案能更好地保护脑干、颈髓 ,更好地提高靶区适合度和靶区内最小剂量以及靶区内平均剂量 ,并同时能减少腮腺、颞颌关节和咬肌的平均剂量和 5 0 %体积受量 ,使它们得到尽可能的保护。

Objective:To compare the merit and inferiority of calculating isodose distributions between late course three-dimensional conformal radiotherapy (LC 3D-CRT)plan and conventional radiotherapy(CRT) plans in using 3D-TPS for nasopharyngeal carcinoma(NPC).Methods:Eight selected patients with NPC,the stage of whose primary lesions were T 2-T 4 during the the initial course of radiotherapy,CRT were used,during late course of radiotherapy, irradiatet locations of all observed patients were located by CT simulation .At the same time,the LC 3D-CRT and two CRT plans i. e bilateral pre-auricular fields,pre-nasalfields plus bilateral pre-auricular fields were compared,respectively,by using dose -volume histogram (DVH)and dose profile to evaluate some indexes of three plans including minimum target dose (Dmin),mean target dose (MTD),the compatibilities of treatment volume and target volume (TVR), maximal dose in organ at risk (OAR Dmax) and 50% volume dose (D 50), MTD and D 50 of some critical sensitive organs,such as parotids,temporomandibular joints,masseteric muscles, comparison of the percentage in median value (MV) and standard deviation (SD) of above relevant items between LC 3D-CRT plan and two CRT 3D-TPS plans.Result:In comparing 3D-CRT plan with conventional plans, both the compatibilities of TV and OAR Dmax were P<0.05, 50%volume dose in organ at risk was P>0.05, indexes of all others were P<0.01. In comparing 3D-CRT plan with three fields plans,both the compatibities of TV and 50% volume dose inpaeotids were P<0.05;indexes of all others were P<0.05.Conclusion:During late course of radiotherapy,in using 3D TPS for NPC LC 3D-CRT plan was better than two CRT plans.LC 3D-CRT plan can effectively protect brain stem,cervical spinal cord,and it can significantly enhance the compatibilities of TV, Dmin and MTD,in the meantime, LC 3D-CRT plan can reduce MTD and D 50 of parotids temporomandibular joints and masseteric muscles,therefore these organs were protected to a great extent.