旋转调强与静态调强在俯卧位宫颈癌放疗中的剂量学比较

Dosimetric comparison between volume-modulated arc therapy and intensity modulated radiation therapy for cervical carcinoma in prone position

目的:对容积旋转调强放射治疗(VMAT)和静态调强放射治疗(IMRT)在宫颈癌术后俯卧位放疗中的应用进行剂量学比较。方法:选取30例宫颈癌术后患者,使用Varian Eclipse10.0计划系统,对每例患者分别设计VMAT计划和IMRT计划,处方量为5000cGy(200cGy/次×25次)。比较俯卧位时2种治疗技术的靶区剂量分布和危及器官受照剂量。结果:2组计划平均均匀性指数均为0.08,平均适形性指数VMAT为0.80,IMRT为0.76,无统计学差异;与IMRT计划相比,VMAT计划的股骨头D5%、小肠D10%、膀胱D50%、脊髓Dmax平均受照剂量分别下降了730cGy、720cGy、530cGy和500cGy,均有统计学差异;直肠D50%及结肠的D10%、Dmax无显著性差异。VMAT计划的MU均值(638)显著低于IMRT计划(932,P<0.05);VMAT计划的治疗时间均值(143s)显著低于IMRT计划(223s,P<0.01)。结论:VMAT技术用于宫颈癌术后的俯卧位放射治疗安全高效,在小肠D10%、脊髓、股骨头、膀胱等正常组织的保护上更好,而且省时、保证了治疗精度。

Objective:To compare dosimetry of postoperative radiotherapy for cervical carcinoma using volumemodulated arc therapy(VMAT)and intensity modulated radiation therapy(IMRT).Methods:Thirty postoperative cervical carcinoma patients were selected for this study,who were treated with a dose of 50 Gy dividing into25 fractions at planning target volume(PTV)by Eclipse10.0.Each case was planned with VMAT and IMRT techniques comparing with target conformability index,homogeneity index,dose-volume histogram data,monitor units and treatment time.Results:The mean conformability indexes of the two groups were 0.80 and 0.76 respectively,and the mean homogeneity index was 0.08.The average dose of VMAT in the D10% of intestine,Dmax of spinal cord,D5% of femoral head,and D50% of bladder were7.2 Gy,5.0 Gy,7.3 Gy and 5.3 Gy respectively,all were less than those of IMRT.While D50% of rectum and D10%,Dmax of colon were with no difference.There were significant differences in the mean MU and therapy time between VMAT and IMRT(P<0.05,P<0.01).Conclusion:The VMAT technique achieves similar target dose distribution as that of the IMRT for cervical carcinoma in prone position,and with better protection of organs at risk such as D10% of intestine,spinal cord,femoral head and bladder.Compared with IMRT,VMAT as a highly effective treatment technique can significantly reduce uncertain factors in the treatment process with less MU and time duration.