Monaco计划系统中不同优化模式在固定野调强和容积旋转调强下宫颈癌剂量学比较

Dosimetric Comparison of 9-Field dMLC IMRT and VMAT for Cervical Carcinoma Using Different Optimization Modes in Monaco Treatment Planning System

目的∶对比Monaco计划系统中固定野调强中动态多叶准直器(dynamic mli-eaf colimator,dMIC)和容积旋转调强(volumetric modulated arc therapy,VMAT)方式在靶区优先(Pareo)和正常组织优先(Canstraind)模式下宫颈癌放疗计划的剂量学差异。方法∶选取22例官宫颈癌患者,分别采用dMLC和VMAT调强方式、Parao和Costmindl模式设计放疗计划,其中dMLC为9野均分,VMAT为1野2全弧,并保持优化条件和参数设置不变。对4个计划分别比较靶区剂量分布、危及器官(organs a isk,OAR)受量和机器参数。结果∶Pareto和Constmined优化模式对靶区剂量和OAR受量均没有明显影响。VMAT调强的靶区最大值(Dmax)、平均值(Dmean)和均匀性指数(homogeneity in-dex,H)均高于dMLC。Pareto和Contrind优化模式对膀胱V40、直肠V40、小肠V30、盆骨V30和左右股骨头Dmean均无显著性影响。但膀胱、直肠和小肠的1cm^3体积受照剂量(D1cc)在dMIC明显低于VMAT方式。机器跳数在Pareto模式下,VMAT明显高于dMLC,但VMAT的出束时间却明显低于dMLC。结论∶VMAT技术可以明显缩短治疗时间,提高治疗效率,且靶区均匀性更好,但对膀胱、直肠和小肠的高剂量控制不如dMLC。另一方面,Comnstrineld模式对膀胱、直肠和小肠的高剂量控制也略优于Pret模式。因此,在一般条件下,我们推荐在宫颈癌计划设计中采用VMAT调强方式和Constrained优化模式。

Objective:To compare the difference between the Pareto optimization mode and the Constrained optimization mode designed by Monaco treatment planning system in the dosimetry of dynamic multi-lea£collimator(dMLC)intensity-modulated radiotherapy(IMRT)and volumetric modulated arc therapy(VMAT)for cervical carcinoma.Methods:22 patients with cervical carcinoma were recruited.Dose distribution was optimized and evaluated by using 9-field dMLC IMRT and 1-field 2-arc VMAT using Pareto and Constrained optimization modes with the same parameters and optimization conditions.Target doses,doses of organs at risk(OAR)and machine parameters of four optimization plans were compared.Results:There were no significant differences in target doses and OAR between the two optimization modes no matter what modulated radiotherapy was used.The maximal dose(Dmax),mean dose(Dmean)and homogeneity index(HI)of VMAT for targets were significantly higher in those of dMLC.However,neither the Pareto mode nor the Constrained mode had effects on bladder V40,rectum V40,small bowel V30,pelvic V30 or left and right femoral DmeaT1.Dlcc in bladder,rectum and small intestine in dMLC were significantly lower than those in VMAT.In the Pareto mode,the monitor unit was significantly higher for VMAT than that for dMLC;but the deliver time was significantly lower for VMAT than that for dMLC.Conclusion:VMAT could significantly reduce treatment time,improve treatment efficiency,and provide better target homogeneity.But the high dose area of bladder,rectum and small bowel is controlled more effectively in dMLC.The Constrained mode also provides slightly better high-dose control of bladder,rectum and small bowel than the Parbto mode.Therefore,VMAT and the Constrained optimization model is generally recommended for cervical cancer.