食管癌前后对穿野定位在肿瘤长度的上下界各放() ["A、1.0C、m ","B、1.5C、m ","C、2.0C、m ","D、2.5C、m ","E、3.0C、m "] 食管癌一前两后野定位，机架应为() ["A、-10°、-140°、+120° ","B、0°、-130°、130° ","C、10°、-120°、+140° ","D、0°、-120°、+120° ","E、10°、-130°、+130°"] 直肠癌等中心定位机架为±90°时应() ["A、左右移床 ","B、升降床 ","C、不可升降床 ","D、射野的后界不包括骶尾部 ","E、射野的前界在腹壁"] 乳腺癌切线野定位时，患者背后垫板角度通常选() ["A、20℃~25℃ ","B、25℃~30℃ ","C、30℃~40℃ ","D、5℃~20℃ ","E、≥40℃"] 代表“数字重建影像”的符号是() ["A、BEV ","B、REV ","C、DRR ","D、XR ","E、MLC"] 直肠癌三野等中心定位，两侧野的前界在股骨头的()