口咽癌自动固定野调强放疗计划的可行性研究

Feasibility of the Automatically Planned Fixed-Field Intensity Modulated Radiation Therapy for Oropharyngeal Cancer Patients

目的:比较口咽癌自动固定野调强放射治疗(intensity modulated radiation therapy,IMRT)计划和人工容积旋转弧形调强治疗(volumetric modulated arc therapy,VMAT)计划的剂量学参数等差异,评估自动IMRT计划在口咽癌中的应用可行性。方法:选取25例口咽癌患者,采用Pinnacle^(3)计划系统分别为25例患者设计自动IMRT计划(IM-RT_(auto))和人工VMAT计划(VMAT_(manu)),两组计划采用相同的靶区处方剂量、危及器官剂量体积限制和迭代次数。比较2组计划靶区的D_(95)、D_(mean)、D_(2)、适形度指数和均匀性指数(homogeneity index,HI)、危及器官的受照剂量、优化时间、机器跳数以及优化次数。结果:两组计划均满足临床处方剂量要求。VMAT_(manu)组的靶区略优于IMRT_(auto)组,其中原发肿瘤、高危亚临床病灶和阳性淋巴结等靶区的D_(2)和HI优于IMRT_(auto)组(P<0.05)。IMRT_(auto)组的危及器官剂量学参数优于VMAT_(manu)组,其中IMRT_(auto)组的脑干D_(max)和下颌骨V50优于VMAT_(manu)组(P<0.05),其余危及器官差异无统计学意义(P>0.05)。IMRT_(auto)组机器跳数增加了16.5%(P<0.05)、优化次数差异无统计学意义(P>0.05),但是计划优化时间明显少于VMAT_(manu)组,优化时间减少了55.8%(P<0.05)。结论:对于口咽癌,IMRT_(auto)组可以获得与VMAT_(manu)组类似的计划质量,同时显著提高了计划优化效率,具有临床可行性。

Objective:To compare the differences in dosimetric parameters between the automatically planned intensity modulated radiation therapy(IMRT_(auto))and the manually planned volumetric modulated arc therapy(VMAT_(manu))for oropharyngeal cancer patients,and evaluate the feasibility of IMRT_(auto) for oropharyngeal cancer.Methods:IMRT_(auto) and VMAT_(manu) with the same prescription dose,optimization con straints and iterations were designed by Pinnacle^(3) Auto-Planning for 25 oropharyngeal cancer patients.Differences in D_(95),D_(mean),D_(2),conformity index(CI),homogeneity index(HI),close to organs at risk(OARs),optimization time,monitor unit and optimization frequency were compared between the two plans.Results:Both groups met the requirements of clinical prescription dose.VMAT_(manu) was superior to IMRT_(auto) in D_(2) and HI for planning clinical tumor volume for the high-risk foci(PCTV1),planning gross tumor volume(PGTV)and planning gross tumor volume with positive lymph nodes(PGTVln)(P<0.05).IMRT_(auto) was better than VMAT_(smanu) in D_(max) to the brainstem and V_(50) to the mandible(P<0.05);and the advantage was not significant in dosimetric parameters for other OARs(P>0.05).The monitor unit of IMRT_(auto) was 16.5% greater than that of VMAT_(manu)(P<0.05).There was no statistically significant difference in the optimization frequency between the two groups(P>0.05).The optimization time of IMRT_(auto) was less than that of VMAT_(manu) by 55.8%(P<0.05).Conclusion:IMRTaul„is clinically as applicable as VMAT_(manu) for orophanngeal cancer,and is more efficient in the optimization than the latter.