医用直线加速器是一种比较复杂的大型医用设备 ,在治疗肿瘤过程中取得了相当可观的疗效 ,是肿瘤医院和放疗科不可或缺的一种治疗机器。在放疗过程中 ,为使射野形状与靶区形状的投影一致 ,将规则射野变成不规则射野 ,须在加速器上加挡块 ,这挡块一般放在滤过板上。由于Ｘ线的挡 Medical linear accelerator is a relatively large-scale medical equipment, has achieved considerable results in the treatment of cancer, tumor hospital and radiotherapy is an indispensable treatment machine. In the course of radiotherapy, in order to make the projection of the field shape consistent with the shape of the target, the regular field should be changed into an irregular field, and a stopper must be added to the accelerator. The stopper is generally placed on the filter plate. Because of the X-ray block