三维CT与四维CT确定胸段食管癌计划靶体积比较研究

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PTV 3D ,常规外扩获取PTV conv ,PTV 4D 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<03cm,PTV4D/PTV3D分别为0.80、0.88、0.71,PTV4D/PTVconv分别为0.67、0.73、0.76(χ2=－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(χ2=－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。

Comparative study of planning target volumes based on three-dimensional computed tomography and four-dimensional computed tomography in treatment of upper-thoracic, middle-thoracic, and lower-thoracic esophageal cancers

Objective 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, middle-thoracic, 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. PTV 3D was obtained on 3DCT according to GTV motions in 3D directions measured on 4DCT;PTV conv was obtained on 3DCT using a 1.0 cm margin to CTV;PTV 4D was obtained by fusion of 10 time phases of 4DCT images.
Results Among the patients with upper-thoracic, middle-thoracic, and lower-thoracic ECs, the median centroid shifts between PTV 3D and PTV 4D and between PTV conv and PTV 4D in the 3D directions were all less than 0.3 cm;the median ratios of PTV 4D to PTV 3D were 0.80, 0.88, and 0.71, respectively, compared with 0.67, 0.73, and 0.76 for median PTV 4D /PTV conv ratios (χ²=－3.18, P= 0.001;χ²=－2.98, P= 0.003;χ²=－3.06, P= 0.002);the median dice similarity coefficient (DSC) between PTV 3D and PTV 4D were 0.87, 0.90, and 0.81, respectively, compared with 0.80, 0.84, and 0.83 for DSC between PTV conv and PTV 4D (χ²=－3.18,P=0.001;χ²=－2.98,P=0.003;χ²=－3.06,P=0.002);the differences between the degree of inclusion (DI) of PTV 4D in PTV 3D and DI of PTV 4D in PTV conv were all less than 2%. The patients withupper-thoracic and middle-thoracic ECs had the irradiated normaltissue volumes due to PTV 3D decreased by11.81% and 11.86%, as compared with those due to PTV conv ,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 PTV 4D ;for the patients with lower-thoracic EC, 3DCT-based PTV using conventional margins provides an ideal conformity with PTV 4D .