摘要目的 比较基于三维CT (3DCT)和四维CT (4DCT)构建的胸段食管癌原发肿瘤计划靶体积(PTV)的位置及体积差异性.方法 43例胸段食管癌患者于同次CT模拟定位时序贯完成3DCT和4DCT扫描.通过4DCT获取自由呼吸状态下靶区中心点三维方向最大位移,依据靶区位移不均匀外扩获取PTV3D,常规外扩获取PTVconvPTV4D则通过4DCT的10个时相靶区融合获得.结果 胸上、中、下段食管癌患者PTV3D和PTVconv与PTV4D中心点位置差异三维方向上中位数均＜0.3 cm,PTV4D/PTV3D分别为0.80、0.88、0.71,PTV4D/PTVconv分别为0.67、0.73、0.76(x2=-3.18、-2.98、-3.06,P=0.001、0.003、0.002).胸上、中、下段食管癌PTV3D与PTV4D靶区相似度中位数分别为0.87、0.90、0.81,PTVconv与PTV4D的分别为0.80、0.84、0.83(x2=-3.18、-2.98、-3.06,P=0.001、0.003、0.002).三组患者PTV3D及PTVconv对PTV4D的包含度差异均＜2％.胸上、中段食管癌PTV3D造成正常组织受照体积比PTVconv降低了11.81％、11.86％,胸下段食管癌增加了2.93％.结论 对胸中上段食管癌3DCT不均匀外扩构建的PTV与4DCT构建的PTV符合度较好,对胸下段食管癌常规外扩构建的PTV与4DCT构建的PTV符合度相对较为理想.

abstractsObjective To determine the centroid and volumetric differences between the planning target volumes (PTVs) for primary tumor based on four-dimensional computed tomography (3DCT) and four-dimensional computed tomography (4DCT) in the treatment of upper-thoracic,middle-thoracic,and lower-thoracic esophageal cancer (EC).Methods Forty-three patients with upper-thoracic,middlethoracic,and lower-thoracic ECs underwent 3DCT and 4DCT simulation scans in sequence during free breathing.The maximum motions of gross tumor volume (GTV) centroid position in 3D directions were obtained by 4DCT scans.PTV3D was obtained on 3DCT according to GTV motions in 3D directions measured on 4DCT;PTV was obtained on 3DCT using a 1.0 cm margin to CTV;PTV4D was obtained by fusion of 10 time phases of 4DCT images.Results Among the patients with upper-thoracic,middle-thoracic,and lowerthoracic ECs,the median centroid shifts between PTV3D and PTV4D and between PTV and PTV4D in the 3D directions were all less than 0.3 cm; the median ratios of PTV4D to PTV3D were 0.80,0.88,and 0.71,respectively,compared with 0.67,0.73,and 0.76 for median PTV4D/PTV ratios (xx2 ＝-3.18,P =0.001 ; x2 =-2.98,P =0.003 ; x2 =-3.06,P =0.002) ; the median dice similarity coefficient (DSC)between PTV3D and PTV4D were 0.87,0.90,and 0.81,respectively,compared with 0.80,0.84,and 0.83 for DSC between PTV and PTV4D (x2 ＝-3.18,P =0.001 ; x2 =-2.98,P =0.003 ; x2 =-3.06,P =0.002) ;the differences between the degree of inclusion (DI) of PTV4D in PTV3D and DI of PTV4D in PTV were all less than 2％.The patients with upper-thoracic and middle-thoracic ECs had the irradiated normal tissue volumes due to PTV3D decreased by 11.81％ and 11.86％,as compared with those due to PTV but the value was increased by 2.93％ for those with lower-thoracic EC.Conclusions For the patients with upper-thoracic and middle-thoracic EC,3DCT-based PTV using asymmetrical margins provides a good coverage of PTV4D; for the patients with lower-thoracic EC,3DCT-based PTV using conventional margins provides an ideal conformity with PTV4D.