容积旋转调强与固定野调强在宫颈癌根治性放疗中的剂量学比较

目的 比较容积旋转调强(VMAT)与7野固定野调强(dIMRT)两种放射治疗技术在中晚期宫颈癌放射治疗中的剂量学差异。方法 选取10例不适合行腔内照射的中晚期宫颈癌患者,分别制定7野调强放疗计划和容积旋转调强放疗计划。利用剂量体积直方图来统计GTV和PTV的相关参数、适行指数(CI)、均匀性指数(HI),小肠、直肠、膀胱、股骨头正常组织的剂量体积参数,以及机器跳数(MU)及治疗时间。结果 VMAT技术GTV的平均剂量略高于7IMRT且具有统计学意义,GTV的D₂、D₉₈、CI、HI差异无统计学意义,PTV中的D₂、D₉₈、D_mean、CI、HI差异均无统计学意义,VMAT技术直肠的V₄₀、V₄₆、D_mean优于7IMRT且差异有统计学意义,V₁₀、V₂₀、V₃₀差异无统计学意义,两种计划在小肠、膀胱、股骨头的剂量分布差异无统计学差异。VMAT技术机器跳数较7IMRT减少35.68%,平均治疗时间减少61.5%。结论 VMAT技术在剂量分布上与7IMRT相当或略优,但机器跳数和治疗时间明显减少。

Dosimetric Comparison of Volumetric Modulated Arc Therapy with Fixed Field Intensity modulated Radiotherapy for Cervical Carcinoma

Objective To compare the dosimetric difference between volumetric modulated arc therapy (VMAT) and seven fixed field intensity modulated radiotherapy (7IMRT) in middle and advanced cervical carcimona. Methods Ten patients of middle and advanced cervical carcinoma who are unsuitable for brachytherapy for technical or medical reasons were enrolled in this study. Seven field IMRT and VMAT plans were generated for these patients. Dose volume histograms were adopted for the statistics of D₂,D₉₈,D_mean,conformal index(CI),homogeneity index(HI) of GTV and PTV,dose volumetric parameters of normal tissues,the small intestine,rectum,bladder and femoral heads,total accelerator output monitor units and total treatment time. Results The mean dose of the GTV for the VMAT plan is higher than that of the 7IMRT plan, which has statistical significant differences. The D₂,D₉₈,CI,HI of the GTV for both plans have no significant differences, and still the D₂,D₉₈,D_mean, CI,HI of the PTV for the two plans have no significant differences. VMAT has a better sparing effect on the V₄₀,V₄₆, D_mean of the rectum and the two plans have no significant differences on the V₁₀,V₂₀,V₃₀, of the rectum. And the effect of other sparing on the small intestine,bladder and femoral heads is weak between VMAT and IMRT. The mean monitor units by VMAT is fewer by 35.68% in comparison with those of 7IMRT,the treatment time by VMAT is shorer by 61.5% in comparison with that of 7IMRT. Conclusion VMAT achieves equal or better target coverage and organs at risk sparing while using fewer monitor units and less time. Key words Cervical Carcinoma; Volumetric Modulated Arc Therapy; Fixed Field Intensity Modulated Radiotherapy; Dosimetrics