宫颈癌术后静态调强放疗与单个和2个全弧容积调强弧形治疗的剂量学比较

Dosimetric comparison between IMRT and a single full arc,two full arc VMAT for postoperative cervical cancer patients

目的:比较宫颈癌术后静态调强放疗(IMRT)与单个全弧容积调强弧形治疗(VMAT)(Arc1)、2个全弧VMAT(Arc2)的计划质量、治疗效率和执行精度,为临床上宫颈癌术后VMAT治疗的弧数选择提供参考依据。方法:选取20例宫颈癌术后患者,给以相同的处方剂量和优化参数,分别设计7个野IMRT(7F-IMRT)、Arc1和Arc2计划,比较7F-IMRT与Arc1计划和Arc2计划的计划靶体积(PTV)和危及器官(OAR)的剂量学差异、治疗计划机器跳数(MU)和执行时间,采用γ分析法评价通过率,验证治疗计划的剂量准确性。结果:Arc2计划靶区适形度(CI)和靶区剂量均匀性(HI)均优于7F-IMRT计划(P<0.05),7F-IMRT优于Arc1计划(P<0.05);Arc2计划直肠V50、小肠V40和V10均低于7F-IMRT计划(P<0.05),而Arc1计划的直肠、膀胱和小肠的近似最大剂量(D2cc)、平均剂量(Dmean)和V50均高于7F-IMRT计划(P<0.05或P<0.01);与7F-IMRT计划比较,Arc2计划的MU和治疗时间分别减少24%和54%(P<0.05),剂量验证的3mm/3%的γ通过率三者比较差异均无统计学意义(P>0.05)。结论:宫颈癌术后患者VMAT治疗,采用单个全弧难以满足临床要求,宜至少采用2个全弧,能缩短治疗时间,减少治疗中分次内误差和患者的不适感。

Objective： To compare the planning quality, treatment efficiency and delivery accuracy for treating the postoperative cervical cancer patients with intensity modulated radiotherapy （IMRT） and two kinds of volumetric modulated arc therapy （VMAT）, and to provide the reference basis for selecting the number of arcs in the VMAT treatment of postoperative cervical cancer in clinic. Methods： Twenty patients with cervical cancer after operation were planned with the same dose prescription and optimization parameters by means of 7-field IMRT （7F-IMRT）, a single full arc （Arcl） and two full arc （Arc2） VMAT, respectively. The dosimetric differences of planning target volumes （PTV） and organs at risk （OAR）, the number of monitor units （MU） and treatment delivery time and the accuracy of treatment plan dose verification were compared among the three treatment plans. Results： The conformity index （CI） and the dose distribution homogeneity index （HI） of PTV for Arc2 plan were best （P〈0.05）, and 7F-IMRT was superior to Arc1 plan （P〈0. 05）. The value of Vs0 in the the rectum, V40 and V10 in small bowel for Arc2 plan were lowest （P〈0.05）, while the near-maximum absorbed dose （D2cc） , the mean dose （D ） and the values of Vso in rectum, bladder, and small bowel for Arel plan were higher than 7F-IMRT （P（ 0.05 or P〈0.01）. Compared with 7F-IMRT plan, the number of MU and treatment delivery time for Are2 plan were decreased by 24% and 54%, respectively （P（0.01）. There were no significant differences in the pass ratios of 3mm/3 % y analysis of dose verification among three plans （P〉0.05）. Conclusion： A single full arc of VMAT is difficult to meet the clinical requirements for the postoperative cervical cancer patients. At least two full arcs should be chosen, and the treatment time can be shortened as a result, there will reduce the fractional error and patient discomfort.