胸上段食管癌断层定野与断层螺旋放疗和容积旋转调强放疗的剂量学比较

Dosimetric comparison among TomoDirect, Helical Tomotherapy and VMAT in the treatment of upper thoracic esophageal carcinoma

目的 比较胸上段食管癌断层定野放疗（TD）、断层螺旋放疗（HT）和容积旋转调强放疗（VMAT）的剂量学差异，为临床上食管癌放疗方式的选择提供依据。方法 选取15例临床分期为cT2～4N0～1M0的胸上段食管癌患者，分别设计TD、HT和VMAT 3种计划。比较靶区的剂量体积直方图（DVH）、均匀指数（HI）、适形指数（CI）、危及器官（OAR）受量、治疗时间和机器跳数（MU）的差异。结果 HT和TD计划的D2和Dmean均明显低于VMAT计划；TD计划的D98和HT相似，但均高于VMAT计划。对于HI，HT 〈 TD 〈 VMAT，3组之间差异有统计学意义（F=81.603，P 〈 0.05）。3组计划的CI差异无统计学意义（P〉0.05）。双肺的V15，HT明显高于VMAT和TD （t=3.547、-2.626，P 〈 0.05）。TD计划的V20与HT计划的相似，但高于VMAT计划（t=2.824、3.052， P 〈 0.05）。3组计划中的脊髓Dmax无明显差异。HT和TD的执行时间、MU均高于VMAT，差异具有统计学意义（t=21.617、15.693、10.018、7.802，P 〈 0.05）。结论 与VMAT相比，HT和TD计划可明显改善胸上段食管癌靶区的剂量分布，可获得更好的适形度。但VMAT比HT或TD明显降低双肺V20、MU及治疗时间。TD与HT相比，HT的靶区剂量分布更好，但TD降低了双肺的V15，且缩短治疗时间。

Objective To compare the dosimetric difference among TomoDirect （TD） radiotherapy, Helical Tomotherapy（HT）and volumetric modulated arc therapy（VMAT）in the treatment of upper thoracic esophageal carcinoma. Methods A total of 15 patients with cT2-4N0-1M0 upper thoracic esophageal squamous cell carcinoma were enrolled. Three plans were generated using the same dose objective for each patient：TD, HT and VMAT. Dose-volume histogram（DVH）, homogeneity index （HI）, conformal index （CI）, dose at organ at risk （OAR）, delivery time and monitor unit （MU） were compared among different plans. Results The D2 and Dmean values in the HT and TD plans were significantly lower than those in the VMAT plans. The D98 value in the TD was similar to that in the HT, but lower than that in the VMAT. The HI of HT was significantly better than those of TD and VMAT （F=81.603, P 〈 0.05）. For the CI, there was no significant difference among the three techniques （P〉0.05）. For the V15 of lung, HT was significantly higher than TD （t=-2.626, P 〈 0.05） and VMAT（t=3.547, P 〈 0.05）. The V20 of lung in TD was similar to that in HT, but higher than that in VMAT（t=2.824, 3.052, P 〈 0.05）. The Dmax of spinal cord showed no significant difference among the three techniques. VMAT had a significantly shorter delivery time and lower MU compared with HT and TD （t=21.617, 15.693, 10.018, 7.802,P 〈 0.05）. Conclusions HT and TD could gain a better planning target volume （PTV） coverage and HI than VMAT in the treatment of upper thoracic esophageal carcinoma. However, VMAT achieved the lowest lung V20, the least MUs and the shortest delivery time. HT achieved a better PTV coverage compared with TD, but TD had a lower lung V15 MUs and shorter delivery time compared with HT.