中心型肺癌快速旋转调强与固定射野动态调强放疗的剂量学比较

Dosimetric comparison between RapidArc and fixed gantry dynamic IMRT for central-type lung cancer radiotherapy

目的 比较快速旋转调强（RapidArc）与固定射野动态调强（dIMRT）两种调强放疗技术在中心型肺癌治疗计划中的剂量学差异.方法 利用瓦里安（Varian）计划系统（Eclipse 8.6）随机选取10例已行dIMRT治疗的中心型肺癌患者,采用容积调强（volumetric modulated are therapy,VMAT）治疗技术设计RapidArc调强放疗计划.在满足靶区处方剂量要求（95%体积的PTV达到66 Gy）的情况下,通过剂量体积直方图DVH评价和比较两种类型治疗计划的PTV最大剂量Dmax、最小剂量Dmin和平均剂量Dmean以及适形指数CI,危及器官的脊髓最大剂量Dmax,双肺的V5、V10、V20、V30,心脏V30,食管V50、V60和平均剂量Dmean,并比较两种治疗计划的总机器跳数（MU）和治疗时间.结果 在中心型肺癌治疗计划中,与dIMRT相比较,RapidArc靶区的Dmax、Dmin和Dmean略有升高,但统计学差异无意义（P＞0.05）,适形指数CI优于dIMRT,且差异具有统计学意义（t=-4.968,P=0.001）.双肺的V5、V10有所上升,V20、V30有所下降;心脏V30受照射体积也有不同程度降低,差异均具有统计学意义.RapidArc总MU减少32%,治疗时间为dIMRT的1/3.结论 两种治疗技术所设计的治疗计划剂量分布均能满足临床治疗需要.RapidArc靶区适形度更高,实际治疗时间明显缩短,同时MU的降低减少了治疗区域正常组织的不必要照射.

Objective To compare the dosimetric difference between RapidArc and fixed gantry angle dynamic IMRT （dIMRT） for central-type lung cancer radiotherapy. Methods Therapy for 10 patients previously treated with dIMRT was replanned with RapidArc. Dose prescription was 66 Gy/33 fraction. Comparative endpoints were planning target volume （PTV） dose, doses to surrounding structures,number of monitor units, and treatment delivery time. Results There was no significant dosimetric difference between RapidArc and dIMRT. Compared with dIMRT, RapidArc slightly elevated target volume dose, lung V5, V10. The average values of lung V20, V30 and heart V30 were larger in dIMRT than those in RapidArc. The number of monitor units was reduced by 32% and the treatment time by 66% in RapidArc.Conclusions Both RapidArc and dIMRT plans could meet the clinical therapy needs. RapidArc could achieve similar target coverage and sparing of organs at risk, with fewer monitor units and shorter delivery time than dIMRT.