基于4DCT的食管癌靶区运动的初步研究

目的 探讨4DCT下的平静呼吸状态食管癌靶区运动特征。方法 20例食管癌患者在平静呼吸状态下采用4DCT采集食管肿瘤运动信息,勾画GTV,测量并记录每个GTV等中心点坐标、体积,并计算中心点在不同呼吸时相的移动距离及体积变化情况。结果 同段食管癌靶区中心在头脚方向位移(0.521±0.319) cm,较左右方向的(0.169±0.083) cm、前后方向的(0.167±0.095) cm均大(P均<0.05)(颈段P=0.009;胸上段P=0.016;胸中段P=0.000)。不同段食管癌靶区中心在同一方向最大位移不同(左右P=0.023;前后P=0.212;头脚P=0.007)。各呼吸时相中食管癌运动规律并不完全一致,以T0时相为基准时相,食管癌GTV等中心点在T50时相时各三维方向上的位移最大。呼气末与吸气末食管靶区体积无变化(P=0.313)。结论 同段食管癌靶区在不同方向运动幅度不同,不同段病灶同一方向的运动幅度也不同,行精确放疗时应综合考虑。对于颈段及胸中上段食管癌,依据吸气末和呼气末融合图像获得ITV可行。颈段及胸中上段食管靶区在呼吸周期中形变不明显。

A preliminary study on target motion in esophageal cancer during normal breathing with four-dimensional computed tomography

Objective To investigate the characteristics of target motion in esophageal cancer during normal breathing with four-dimensional computed tomography (4DCT). Methods Twenty patients with primary esophageal cancer received respiratory gated 4DCT to obtain the target motion during normal breathing and delineate the gross tumor volume (GTV). The center coordinate and volume of each GTV were measured and recorded to calculate the displacement of the GTV center and the change in volume in different respiratory phases. Results The displacement of the GTV center in each esophageal segment in superior-inferior direction (0.521±0.319 cm) was significantly greater than that in right-left direction (0.169±0.083 cm) and that in anterior-posterior direction (0.167±0.095 cm)(all P<0.05). The maximum displacement of the GTV center in each direction was significantly different in different esophageal segments (all P<0.05). The displacement of the GTV center in each direction was not entirely consistent in different respiratory phases. The displacement of the GTV center in each direction in T50 phase was greatest when T0 phase was the reference phase. The volume of GTV had no significant changes at the end of the expiratory phase and the inspiratory phase (P=0.313). Conclusions The displacement of GTV center in each esophageal segment in superior-inferior direction is significantly greater than that in right-left direction and that in anterior-posterior direction and the displacement of GTV center in each direction is significantly different in different esophageal segments. Therefore, all the factors should be considered to develop a reasonable target for precise radiotherapy. For esophageal cancer in cervical and upper chest esophageal segment, it is reasonable to delineate ITV based on the fusion image of the images at the end of inspiratory phase and expiratory phase. The deformation of target volume of the esophageal cancer in the cervical and upper chest esophageal segment is not significant in the respiratory cycle.