鼻咽癌螺旋断层放疗与常规调强放疗的剂量学分析

A Dosimetric Analysis between Helical Tomotherapy and Conventional IMRT for Nasopharyngeal Carcinoma

目的比较鼻咽癌在螺旋断层放疗(Helical Tomotherapy)和常规调强放疗(IMRT)两种不同治疗系统中治疗计划的剂量学分布,并对靶区和危及器官的剂量进行分析。材料与方法选择18例鼻咽癌病例,将其定位数据信息及靶区器官轮廓分别传输至Tomotherapy TPS工作站及Varian Eclipse TPS工作站并设计调强放疗计划,18例患者的处方剂量相同,其中鼻咽部原发灶GTVnx为73.92Gy/33F;可见的转移淋巴结GTVnd为69.96 Gy/33F;高危临床靶区CTV1为60.06Gy/33F;预防照射区CTV2为50.96Gy/28F,通过对靶区的适形度指数(CN)、均匀性指数(H1)和危及器官(OARs)的最大剂量及平均剂量等各项指标比较2组治疗计划,对两组数据进行配对t检验。结果螺旋断层放疗组中PGTVnx、PT1、PTV2的CN值分别为0.910±0.010、0.855±0.020、0.871±0.021,常规调强组中PGTVnx、PTV1、PTV2的CN值分别为0.867±0.025、0.822±0.020、0.811±0.012,螺旋断层放疗组中PGTVnx、PTV1、PTV2的HI值分别为1.049±0.009、1.1 35±0.030、1.034±0.011,常规调强组中PGTVnx、PTV1、PTV2的HI值分别为1.060±0.011、1.222±0.023、1.094±0.015,各组P值均<0.005。螺旋断层放疗组相比常规调强放疗组各靶区的的均匀性指数和适形度指数均有不同程度的改善;危及器官的最大剂量和平均剂量也有所下降,腮腺平均剂量较常规调强放疗组低4 Gy左右,V30、V35也显著低于常规调强放疗,P值<0.005。结论对于鼻咽癌,螺旋断层放疗技术相对于常规调强技术改善了剂量学分布,使得靶区在获得更好的剂量分布同时显著降低了正常组织的受照剂量。

Objective To compare the treatment planning in Helical Tomotherapy （HT） and conventional intensity modulated radiation treatment（IMRT） system in 2 different dosimetry distribution of nasopharyngeal carcinoma （NPC）, and analyze the target area and the dose to organ at risk. Materials and Methods Chose 18 cases of NPC and transfer their positioning data information and the outline of target organs to Tomotherapy workstation and TPS Varian Eclipse TPS workstation for the design of [MRT, and the prescription dose which used on these 18 patients are the same, with 73.92Gy/33 for the gross tumor volume（GTVnx）; 69.96 Gy/33F for the positive lymph nodes（GTVnd）; 60.06Gy/33F for the high risk clinical target volume （CTV1）; 50.96Gy/28F for the lower risk clinical target volume （CTV2）. Compared the treatment planning of the 2 groups through conformation number （CN）, homogeneity index （HI） of the target area, and maximum and average dose of the organs at risk （OARs） , and performed a paired t test on the datas of the two groups. Results The CN of PGTVnx, PTV1, PTV2 in HT groups were 0.910 ± 0.010, 0.855±0.020, 0.871±0.021, and in conventional IMRTgroups were 0.867±0.025, 0.822±0.020, 0.811±0.012. The HI of PGTVnx, PTV1, PTV2 in HT groups were 1.049±0.009, 1.135±0.030, 1.034±0.011, and in cOnventional IMRT groups were 1.060±0.011, 1.222±0.023, 1.094±0.015. P〈 0.005. Compared with the conventional intensity-modulated groups, in HT groups the CN and HI of target areas had improved with different degrees, the maximum and average dose to organs at risk were also decreased, average dose in parofid glands is about 4 Gy lower, V30, V35 were significantly lower than that in conventional IMRT, P〈 0.005. Conclusion For NPC, compared with conventional IMRT technology, HT technique improves the dosimetry distribution, and helps target area to get better dose distribution and reduces the exposure dose to normal tissues at the same time.