胸中段食管癌容积调强放射治疗计划孔径形状控制器参数的优化研究

Aperture shape controller parameters optimization of volume intensity modulated radiotherapy plan for middle thoracic esophageal cancer

目的比较Eclipse15.6治疗计划系统光子优化算法中孔径形状控制器(ASC)各参数对胸中段食管癌容积旋转调强放射治疗(VMAT)计划的剂量学评价指标和治疗计划传递精度的影响,为胸中段食管癌患者的临床治疗提供剂量学保障。方法选取10例在扬州大学附属医院放疗科进行VMAT治疗的胸中段食管癌患者为研究对象,仅更改6个ASC可选调制强度参数Off(Off组)、Very Low(VL组)、Low(L组)、Moderate(M组)、High(H组)、Very High(VH组)后自动优化计算并生成6组VMAT计划。以Off组为参考,比较各组剂量-体积直方图(DVH)、靶区适形性指数(CI)、靶区均匀性指数(HI)、机器跳数(MU)、孔径形状复杂性指数(ACM)以及危及器官(肺、脊髓)的剂量学指标等,确定适合胸中段食管癌的ASC参数设置。结果ASC设置的6种VMAT计划的靶区剂量均可满足临床需求。VL组、L组、M组、H组、VH组的计划靶区(PTV)平均剂量(D_(mean))均高于Off组,差异有统计学意义(P<0.05)。L组的靶区CI、HI与Off组比较,差异有统计学意义(P=0.016、0.001)。H组(t=3.833,P=0.004)、L组(t=2.605,P=0.029)、VL组(t=4.671,P=0.001)的肺D_(mean)和VH组(t=3.108,P=0.013)、M组(t=2.828,P=0.020)的脊髓D_(mean)以及H组(t=2.700,P=0.024)、VL组(t=2.819,P=0.020)的脊髓最大剂量(D_(max))与Off组比较,差异均有统计学意义。VL组、L组、M组、H组、VH组的肺D_(max)、V_(20)、V_(30)与Off组比较,差异无统计学意义(P>0.05)。VL组、L组、M组、H组、VH组的ACM、MU均低于Off组,差异有统计学意义(P<0.05)。结论胸中段食管癌VMAT计划方案中,在相同条件自动优化的前提下,6个ASC设置参数均可满足临床要求。综合考虑计划质量和交付精度的影响,本研究推荐的ASC调制参数为Low参数。

Objective To compare the effects of aperture shape controller(ASC)parameters in Eclipse 15.6 photon optimization algorithm on dosimetry evaluation indexes and treatment plan delivery accuracy of volume intensity modulated radiotherapy(VMAT)plan for middle thoracic esophageal cancer,and to provide dosimetric guarantee for clinical treatment patients with middle thoracic esophageal cancer.Methods Ten patients with middle thoracic esophageal cancer who were treated with VMAT in the department of radiotherapy of the Affiliated Hospital of Yangzhou University were selected as study objects.Only six ASC optional modulation intensity parameters Off(Off group),Very Low(VL group),Low(L group),Moderate(M group),High(H group),Very High(VH group)were automatically optimized and six groups of VMAT treatment plans were generated.Taking Off group as reference,dose volume histogram(DVH),conformity index(CI),homogeneity index(HI),monitor units(MU),aperture complexity metric(ACM)and dosimetry indexes of organs at risk(lung and spinal cord)were compared to determine the ASC parameters suitable for middle thoracic esophageal cancer.Results The target dose of 6 kinds of VMAT treatment plansset by ASC could meet the clinical requirements.In terms of target area mean dosage(D_(mean)),the setting of ASC in the VL group,L group,M group and H group were higher than that in the Off group(P<0.05).There were significant differences in CI and HI between the Low group and the Off group(P=0.016,0.001).Compared with the Off group,there were significant differences in D_(mean) of lung in the H group(t=3.833,P=0.004),the L group(t=2.605,P=0.029),VL group(t=4.671,P=0.001),D_(mean) of spinal cord in the VH group(t=3.108,P=0.013)and M group(t=2.828,P=0.020),maximum dosage(D_(max))of spinal cord in the H group(t=2.700,P=0.024)and VL group(t=2.819,P=0.020).D_(max),V_(20),V_(30) of the lung in the VL group,L group,M group,H group and VH group showed no significant differences compared with the Off group(P>0.05).The ACM and MU of the VL group,L group,M group,H group and VH group were lower than those of the Off group(P<0.05).Conclusion For the VMAT plan of middle thoracic esophageal cancer,the six ASC setting parameters can meet the clinical planning requirements under the premise of automatic optimization under the same conditions.Thus,it should be set to low ASC modulation parameter considering the impact of plan quality and delivery accuracy.