肿瘤椎体骨转移立体定向放疗计划在3种设备的剂量分布比较

Comparison of dose distribution of stereotactic radiotherapy plan for vertebral bone metastases of tumors on three devices

目的比较射波刀(CK)、断层治疗(TOMO)、加速器容积调强弧形治疗(VMAT)设备在恶性肿瘤椎体骨转移立体定向放疗(SBRT)中剂量学优劣。方法分析30例恶性肿瘤椎体骨转移患者临床资料,用上述3种设备实施SBRT计划设计,统一导入MIM软件评估。处方剂量:大体肿瘤体积24 Gy分2次。优化目标:脊髓Dmax限制17 Gy,马尾最大剂量限制20 Gy。D98%>95%的计划靶体积处方剂量。主要参数包括PTV适形指数(CI)、均匀性指数(HI)、梯度指数(GI)、脊髓(或马尾)的Dmax和治疗时间。结果VMAT的PTV最大覆盖剂量(D2)显著高于Tomo(P<0.01)和CK(P<0.01)。CK的CI和HI均低于VMAT(均P<0.01)和Tomo(均P<0.01)。VMAT的GI明显高于Tomo(P<0.01),Tomo的GI明显高于CK(P<0.01)。CK治疗时间最长,VMAT治疗时间小于Tomo(all P<0.01)。结论3种放疗设备均能很好地完成满足临床要求的恶性肿瘤椎体骨转移SBRT计划。CK拥有更优的剂量跌落梯度,VMAT取得了更优的靶区适形性;Tomo组各参数较为居中。VMAT与Tomo所需时间比CK短。临床可根据病例及靶区特点选择适合的放疗系统。

Objective To compare dosimetric data of stereotactic body radiation therapy(SBRT)plans with CyberKnife(CK),Tomotherapy(Tomo)and volumetric-modulated arc therapy(VMAT)for spine bone metastasisof tumor.Methods Clinical data of 30 spine bone metastasismalignant tumor patients were retrospectively analyzed.The treatment plans were designed by three apparatuses and transferred to MIM system.Prescription dose:the gross tumor volume was 24 Gy points in 2 times,with the primary goals of Maintaining the max tolerance of the cord(17 Gy)or cauda equine(20 Gy)and the plan target volume(PTV)to receive at least 95%of the prescribed dose.The extraction of parameters mainly included conformity index(CI),homogeneity index(HI),gradient index(GI),target volume coverage,maximum cord(or cauda)dose,and treatment time per fraction.Results PTV mean D2%coverage in VMAT was significantly lager with Tomo(P<0.01)and CK(P<0.01).The CI and HI in CK were significantly lower with Tomo and VMAT(all P<0.01).The best GI was found in CK,followed by Tomo,and VMAT showed the worst(all P<0.01).VMAT had the least treatment time vs Tomo(P<0.01)and CK(P<0.01).Conclusions All three radiotherapy apparatuses can meet the requirement of SBRT for spine bone metastasis of malignant tumor.More rapid dose fall-off could be obtained in CK.VMAT provide better target conformity.The parameters of Tomo are in the middle.The treatment time of VMAT and Tomo are much shorter than CK.The suitable radiotherapy system can be selected according to the characteristics of cases and target areas.