在无模拟机及等中心旋转治疗机的放疗科食管癌患者放疗时只能取前野仰卧位、背野及背夹角野俯卧位。皮瘤距的确定,一般通过摄一张俯卧位吞钡的水平侧位片,分别测算其背瘤距及胸瘤距。但胸背前后径及各皮瘤距(胸瘤距、背瘤距)随体位不同而有变化,作者利用XIMATRON Ⅲ型模拟定位 In radiotherapy patients with esophageal cancer who did not have a simulator and an isocentric rotation machine, they could only take prone positions in the supine position, back field and back angle. The determination of the distance between the tumors is generally measured by taking a prone position horizontally and laterally. However, the anteroposterior diameter of the thoracodorsal dorsal sulcus and the distance between the epithelial tumors (thoracic distance and back tumor distance) varied with different postures. The authors used the XIMATRON III model to simulate positioning.