基于放疗中重复四维CT的食管癌大体肿瘤体积位移变化的比较研究

目的 基于重复四维CT (4DCT)模拟定位增强扫描探讨放疗中胸段食管癌原发肿瘤分次放疗内靶区位移变化。方法 29例胸段食管癌患者分别于放疗前及放疗10、20、30次时行4DCT模拟定位增强扫描,获得各时相原发肿瘤大体肿瘤体积(GTV)及内大体肿瘤体积(IGTV)。比较同次4DCT扫描所得胸上、中、下段食管癌GTV三维方向位移差异,各时段4DCT扫描所得同段食管癌GTV间同一方向位移差异及疗程中IGTV空间位置和体积变化。结果 胸中段患者初次及放疗20次时GTV位移在左右、前后、上下方向均不同(P=0.000~0.016),放疗10次时GTV位移上下与左右、前后方向均不同(P=0.000~0.006);胸下段患者初次及放疗10、20次时GTV位移上下与前后方向也不同(P=0.004~0.013);放疗疗程中不同治疗时段间GTV同一方向位移均相似(P=0.102~0.823)。疗程中IGTV空间位置变化不明显(P=0.689~0.999),而其体积在放疗20次时缩小最明显(P=0.012~0.029)。结论 放疗疗程中不同时段同一部位食管癌同一方向位移变化并不明显,尽管放疗20次时IGTV明显缩小但疗程中其空间位置变化不大。

A comparative study of GTV displacements of primary thoracic esophageal carcinoma based on repeated 4DCT scans during radiotherapy

Objective To investigate the target volume displacements of primary thoracic esophageal carcinoma (TEC) based on repeated enhanced four-dimensional computed tomography (4DCT) scans during fractionated radiotherapy. Methods Twenty-nine patients with TEC underwent enhanced 4DCT before and in the 10^th, 20^th, and 30^th fractions of radiotherapy to delineate the gross tumor volumes (GTVs) and internal gross tumor volumes (IGTVs) in all phases. The GTV displacements of upper, middle, or lower TEC in three-dimensional directions in each time of 4DCT were compared, and the GTV displacements of upper, middle, or lower TEC in the same direction in all 4DCT scans were also compared.The changes in the centroid positions and volumes of IGTV during radiotherapy were determined. ResultsFor the patients with middle TEC, significant differences were found between the GTV displacements in left-right (LR) direction, anterior-posterior (AP) direction, and superior-inferior (SI) direction when 4DCT was performed before or in the 20^th fraction of radiotherapy (P=0.000—0.016), and significant differences were found between the GTV displacements in SI direction and LR and AP directions when 4DCT was performed in the 10^th fraction of radiotherapy (P=0.000—0.006). For the patients with lower TEC, there were significant differences between the GTV displacements in SI direction and AP direction when 4DCT was performed before or in the 10^th or 20^th fraction of radiotherapy (P=0.004—0.013). There were no significant differences between the GTV displacements in the same direction in all 4DCT scans (P=0.102—0.823). There were no significant changes in the centroid positions of IGTV during radiotherapy (P=0.689—0.999), and the most significant decreases in IGTV volumes were seen in the 20^th fraction of radiotherapy (P=0.012—0.029). Conclusions Under free breathing, the GTV displacement of upper,middle, or lower TEC in the same direction shows no significant changes in different 4DCT scans during radiotherapy;the IGTV volumes decrease significantly in the 20^th fraction of radiotherapy, but there are no significant changes in the centroid positions of IGTV during radiotherapy.