摘要目的 比较基于PET-CT与4DCT所构建非小细胞肺癌(NSCLC)原发肿瘤内生物靶区(IBTV)与生物靶区(BTV)、内靶区(ITV)体积差异,并分析IBTV应用于放疗计划的可行性.方法 15例NSCLC患者序贯完成3DCT、4DCT、18氟代脱氧葡萄糖(18F-FDG) PET-CT胸部定位扫描.基于4DCT 10个呼吸时相图像勾画原发肿瘤大体肿瘤体积(GTV)并融合获得ITV.基于PET图像标准摄取值(SUV)≥2.0阈值勾画原发肿瘤靶区并定义为BTV.以ITV和BTV融合构建内生物靶区(IBTV),比较IBTV与ITV、BTV体积差异及空间匹配.比较基于IBTV与ITV、BTV放疗计划的剂量学参数差异.结果 以中位数(四分位间距)表示.结果 ITV、BTV比较差异无统计学意义(P＞0.05),而IBTV与ITV、BTV三者间差异有统计学意义(F=22.533,P＜0.05).要包括＞95％体积的IBTV,基于BTV需要外扩9.0(6.0,12.0) mm,基于ITV需要外扩10.00(7.0,12.0)mm,两者差异无统计学意义(P＞0.05).BTV与ITV的戴斯相似性系数(DSC)为0.72(0.54,0.79).基于计划生物靶区(PBTV)或者计划内靶区(PITV)制定的调强放疗计划,仅能保证85.6％(80.5％,91.2％)的PITV或者80.2％(74.4％,87.6％)的PBTV体积达到处方剂量,而且均匀性指数(HI)和适形度指数(CI)均不理想.结论 基于PET-CT或者4DCT的放疗计划,难以保证依据ITV或者BTV外扩得到的PTV的合理剂量分布,建议参考IBTV定义PTV和制定放疗计划.

abstractsObjective To compare the size of the internal target volume (ITV),biological target volume (BTV) and internal biological target volume (IBTV) based on PET-CT and 4DCT for primary nonsmall cell lung cancer (NSCLC),as well as try to apply IBTV in radiotherapy planning.Methods A total of 15 patients with NSCLC were sequentially scanned by an axial enhanced 3DCT,4DCT and 18F-FDG PET-CT in the thoracic region.The gross target volumes (GTVs) of ten phases of 4DCT images were contoured,and ITV was obtained by fusion of ten GTVs.BTV based on PET-CT images was determined by the SUV 2.0.The IBTV was defined by fusion of ITV and BTV.Planning target volumes (PTVs) based on ITV,BTV,and IBTV (PITV,PBTV,PIBTV) were obtained by ITV,BTV and IBTV with a 10-mm expansion respectively.The metrics of PIBTV,PITV and PBTV were compared,and the planning parameters of target volumes and risk organs were evaluated.Results There was no significant difference between ITV and BTV,but there was significant difference between IBTV and ITV and BTV (F=22.533,P ＜ 0.05).To include more than 95％ volume of IBTV,it is necessary to expand the margin of 9.0(6.0,12.0)mm based on BTV or 10.00(7.0,12.0)mm based on ITV.There was no significant difference between the two groups (P ＞ 0.05).Dice's similarity coefficient of BTV and ITV was 0.72(0.54,0.79).The intensity modulated radiotherapy plan based on PBTV can guarantee 85.6％ (80.5％,91.2％) of PITV to reach the prescription dose,compared with 80.2％ (74.4％,87.6％) of PBTV by the plan from PITV.Additionally,the conformity index and homogeneity index were not ideal.The dosimetric parameters of PITV and PBTV in the PIBTV plan were much better than those in PBTV-and PITV plan.Conclusions The radiotherapy plan based on PET-CT or 4DCT could not guarantee a reasonable dose distribution of PTV expanded from ITV or BTV.Thus,using IBTV for radiotherapy is advised.