Purdy J A, Prasad S C, Walz B J, Cotter G W
Int J Radiat Oncol Biol Phys. 1985 Dec;11(12):2177-81. doi: 10.1016/0360-3016(85)90101-4.
Application of a contact X ray therapy unit for endocavitary irradiation of selected rectal carcinomas is gaining acceptance as a treatment of choice. The patient is placed on a proctoscopic table in the surgical suite and the anus is anesthetized and dilated to allow insertion of a 3 cm diameter proctoscope designed to admit the X ray tube. The measured half-value layer for 50 kVp X rays filtered by 1.0 mm of aluminum was determined to be 0.65 mm of aluminium. The dose rate at the end of the 4.0 cm source-skin-distance (SSD) cone was measured to be on the order of 1000 rad/minute. Radiation surveys performed for several treatment geometries indicate that exposure rate levels in the environs immediately around the patient can be quite high. Radiation measurements were made for the following locations: where the radiotherapist stands holding the X ray tube; at the side of the patient where the technologist or any supporting personnel might stand; and at the patient's posterior surface in the direction where the anesthesiologist might stand. Radiation levels ranged from 0.001 to 1.0 roentgen (R) per hour and depend primarily on the depth and angle of the X ray tube inserted into the rectum.
一种用于选定直肠癌腔内照射的接触式X射线治疗装置作为一种首选治疗方法正逐渐被接受。患者被安置在外科手术套房的直肠镜检查台上，肛门进行麻醉和扩张，以便插入一个设计用于容纳X射线管的直径3厘米的直肠镜。经测量，由1.0毫米铝过滤的50千伏峰值X射线的半价层为0.65毫米铝。在4.0厘米源皮距（SSD）锥体末端的剂量率经测量约为1000拉德/分钟。对几种治疗几何结构进行的辐射测量表明，患者周围环境中的照射率水平可能相当高。在以下位置进行了辐射测量：放射治疗师手持X射线管站立的地方；技术人员或任何辅助人员可能站立的患者一侧；以及麻醉师可能站立方向的患者后表面。辐射水平范围为每小时0.001至1.0伦琴（R），主要取决于插入直肠的X射线管的深度和角度。
