肺部小肿瘤γ刀、静态 IMRT 及 VMAT 放疗剂量学比较

摘要

Objective To explore dose distribution difference in body gamma knife,static intensity modulated radiotherapy and volu-metric modulated arc radiotherapy for small mass in lung.Methods Sixteen patients with small mass in lung were enrolled in the study,gamma knife radiotherapy plan,sIMRT plan and VMAT plan made respectively for each mass.All plans were optimized to meet the requirement of 95% target volume (PTV)covered by prescribed dose.We compared multiple parameters such as dosimetric pa-rameters of PTV,organ at risk(OAR),homogeneity index(HI)and comfomity index(CI)of three radiotherapy plans.Results Six-teen cases with three plans of PTV dose distribution and dose parameters could meet the requirements of clinical treatment,and pre-scription dose to cover 95% of the PTV,OAR dose limit could also meet the requirements.The Homogeneity index (CI)and conform-ity index (HI)of Gamma knife plan were 1.67 ±0.13 and 0.70 ±0.06,respectively,which had the worst performance among three plans(P <0.05);the homogeneity index(HI)and conformity index(CI)of PTV in sIMRT and VMAT plan were similar,without obvi-ous difference (t =0.96 and 1.37,P =0.36 and 0.19,respectively).The whole lung V5 ,V10 ,V15 ,V20 ,V25 ,V30 and spinal cord Dmax were the lowest in gamma knife plan withsignificant difference (P =0.00).Although the esophagus Dmax was lower,it had no statistical significance.Compared with VMAT,lung V10,V30 of sIMRT were slightly lower with statistical significance.All the pa-rameters of VMAT plan were higher than those of sIMRT although the Dmax of esophagus and spinal cord,lung V5 ,V15 ,V20 ,V25 were not significantly different (P >0.05).Conclusions Compared with sIMRT and VMAT,gamma knife radiotherapy for the treatment of small mass in lung can obviously increase the target dose and better protect OAR,but is poor in homogeneity and conformity.%目的：比较体部γ刀、静态调强（sIMRT）与容积旋转调强（VMAT）的肺部小肿瘤中放疗计划的剂量学差异。方法选择16例肺部小肿瘤患者，分别设计γ刀、sIMRT（计划2）和 VMAT 计划，使得95％靶体积（PTV）达到处方剂量要求，比较三种计划的靶区剂量、危及器官剂量、均匀指数（HI）及适形指数（CI）的差异。结果16例患者三种计划的 PTV 剂量分布及剂量参数都能达到临床治疗要求，处方剂量覆盖95％的 PTV，危及器官的剂量限值也能满足要求。γ刀计划的适形性（CI）及均匀性（HI）分别为（1．67±0．13）和（0．70±0．06），在三种计划中表现为最差（P ＜0．05）；而 sIMRT 和 VMAT 计划的 PTV 靶区适形性和均匀性相似，差别不明显（t ＝0．96和1．37，P ＝0．36和0．19）。在三种计划中，γ刀计划的全肺 V5、V10、V15、V20、V25、V30和脊髓 Dmax 最低，差异显著（P ＝0．00），而食管 Dmax虽然较低，但并无统计学意义。sIMRT 和 VMAT 相比，肺 V10、V30略低，且有统计学意义，而食管及脊髓最大受照剂量、肺 V5、V15、V20、V25虽然差异不大（P ＞0．05），但 VMAT 计划均高于 sIMRT 计划相应参数值。结论与 sIMRT 和 VMAT 相比，在肺部小肿瘤的放疗中，γ刀能明显提高靶区剂量且较好保护危及器官，但均匀性及适形性较差。