鼻腔NK/T细胞淋巴瘤RapidArc容积旋转调强与动态适形调强的剂量学比较

D osimetric comparison of volumetric modulated arc therapy(Rapid Arc) with dynamic intensity-modulated radiotherapy for nasal natural killer/T-cell lymphoma

目的比较Rapid Arc容积旋转调强(volumetric modulated arc therapy,VMAT)与动态适形调强(dynamic intensity modulated radiotherapy,d IMRT)在鼻腔NK/T细胞淋巴瘤放疗计划中的剂量学差异。方法用Varian Eclipse 8.6治疗计划系统对10例鼻腔NK/T细胞淋巴瘤患者分别制订二弧Rapid Arc和固定角度9野d IMRT放疗计划,靶区照射剂量均为50 Gy/25次,使用剂量体积直方图比较两种计划中靶区、危及器官的剂量学差异。结果与Rapid Arc计划相比,d IMRT计划靶区(PTV)的最小剂量(Dmin)增大3.48 Gy(t=-3.810,P=0.004),PTV的最大剂量(Dmax)减小2.12 Gy(t=3.979,P=0.003),PTV的平均剂量(Dmean)减小1.65 Gy(t=4.933,P=0.001),适形指数(CI)无显著差异(t=-1.516,P=0.164),均匀指数(HI)更好(t=5.068,P=0.001);右侧视神经Dmax减小0.75 Gy(t=3.266,P=0.010),右侧眼球Dmean减小2.24 Gy(t=2.351,P=0.043),脊髓Dmax减小1.92 Gy(t=2.828,P=0.020),脊髓Dmean减小0.46 Gy(t=3.497,P=0.007),左侧腮腺Dmean减小1.45 Gy(t=3.483,P=0.007),其余正常组织Rapid Arc和d IMRT计划剂量相当。结论二弧Rapid Arc计划和9野d IMRT计划的靶区剂量分布均能达到临床要求;d IMRT计划的HI更好,对部分正常器官的保护优于Rapid Arc计划,Rapid Arc计划的机器跳数(MU)较低,约为d IMRT计划的1/3,有利于提高治疗效率。

Objective To compare dosimetry between volumetric modulated arc therapy（RapidArc）and nine-field fixed-gantry dynamic intensity-modulated radiotherapy （dIMRT）for nasal natural killer/T-cell lymphoma. Methods RapidArc and dIMRT plans were generated for 10 patients with natural killer/T-cell lymphoma based on the Varian Eclipse 8.6 radiation treatment planning system. Planning target volume（PTV）and organs at risk（OAR）were evaluated using dose-volume histograms（DVHs）. Results Compared to RapidArc,the dIMRT approach showed higher Dmin for PTV （3.48 Gy,t=-3.810,P=0.004）,lower Dmax for PTV（2.12 Gy,t=3.979,P=0.003）,lower Dmean for PTV（1.65 Gy,t=4.933,P=0.001）,superior homogeneity index（t=5.068, P=0.001）,and similar conformity index. In addition,the dIMRT approach was associated with lower values of Dmax for the right optic nerve （0.75 Gy,t=3.266,P=0.010）,Dmean for the right eyeball （2.24 Gy,t=2.351,P=0.043）,Dmax for the spinal cord （1.92 Gy,t=2.828,P=0.020）,Dmean for spinal cord（0.46 Gy,t=3.497,P=0.007）and Dmean for the left parotid（1.45 Gy,t=3.483,P=0.007）. Conclusions Both RapidArc and dIMRT plans satisfied clinical requirements,but dIMRT plans were associated with superior homogeneity index,better protection of some OARs as well as greater monitor unit.