宫颈癌容积调强与固定野动态调强放疗技术的剂量学比较

目的比较旋转容积调强技术(VMAT)、固定7野(7-IMRT)及9野动态调强技术(9-IMRT)在宫颈癌根治性放疗中的剂量学参数。方法选取12例接受根治性放疗的宫颈癌患者,对同一CT图像分别进行二弧VMAT、7野IMRT及9野IMRT计划设计,比较3种放疗计划的靶区剂量和危及器官的剂量学差异、靶区剂量适形度、均匀性以及加速器跳数。结果 VMAT、7-IMRT和9-IMRT计划的靶区剂量均能够满足剂量学要求,在靶区均匀性和适形度上,VMAT计划更优,7野计划最差。危及器官保护方面,VMAT计划中膀胱V30、直肠V30、V50和股骨头V20的体积均低于7野和9野计划(P<0.05)。相较于9野计划,7野计划的膀胱V30和股骨头V20均略低(P<0.05)。VMAT计划的加速器跳数MU(757.69±137.04)低于7野计划(802.65±183.85)和9野计划(1 102.31±190.07)。结论宫颈癌根治性放疗患者,采用VMAT、7-IMRT及9-IMRT技术均可达到临床靶区剂量要求和危及器官的保护。VMAT计划在靶区的均匀性和适形度上优于7-IMRT和9-IMRT,9-IMRT优于7-IMRT计划;同时VMAT具有降低危及器官剂量的优势,机器跳数明显降低,提高了宫颈癌放射治疗的效率。

Dosimetric study of volumetric-modulated arc radiotherapy and fixed field-intensity modulated radiation therapy for cervix neoplasms

Objective To compare the dosimetric and organ at risk dose differences of volumetric modulated arc therapy(VMAT), seven-fixed field intensity-modulated radiation therapy(7-IMRT) and nine-fixed field intensity-modulated radiation therapy(9-IMRT) for cervix cancer treated with the definitive whole pelvic radiotherapy.Methods CT images of twelve patients treated with three plans of VMAT, 7-IMRT and 9-IMRT techniques were compared in terms of parameters of target, organ at risk(OAR), conformity index(HI) and conformity index(CI) . The MUs were scored to measure the expected treatment efficiency.Results All the three plans could achieve the clinically acceptable target coverage. The VMAT plans were the best, while 7-IMRT was the worst in HI and CI of targets. VMAT imposed least doses to the bladder at dose level of 30 Gy, the rectum at the dose level of 30 and 50 Gy. VMAT was the same least on femoral head the volume received 20 Gy(P<0.05). Compared with 9-IMRT, 7-IMRT showed compared volume of bladder at dose level of 30 Gy, and reduced the volume of femoral head at 20 Gy. The MUs of VMAT plans(757.69±137.04) were significantly less than those of 7-IMRT plans(802.65±183.85) and 9-IMRT plans(1 102.31±190.07).Conclusion Three types of plans can achieve the clinical dosimetric demands and protect the OARs. VMAT has the best performance on CI and HI, and decrease the volume of the high-dose area in OARs.VMAT plans have fewer MUs and significantly improve the treatment efficiency regarding total MUs.