Eich H T, Haverkamp U, Micke O, Prott F J, Müller R P
Department of Radiotherapy, University of Cologne, Germany.
Rontgenpraxis. 2000;53(2):62-6.
In vivo dosimetry in bladder and rectum as well as determining doses on suggested reference points following the ICRU report 38 contribute to quality assurance in HDR-brachytherapy of cervical carcinoma, especially to minimize side effects. In order to gain information regarding the radiation exposure at ICRU reference points in rectum, bladder, ureter and regional lymph nodes those were calculated (digitalisation) by means of orthogonal radiographs of 11 applications in patients with cervical carcinoma, who received primary radiotherapy. In addition, the doses at the ICRU rectum reference point was compared to the results of in vivo measurements in the rectum. The in vivo measurements were by factor 1.5 below the doses determined for the ICRU rectum reference point (4.05 +/- 0.68 Gy versus 6.11 +/- 1.63 Gy). Reasons for this were: calibration errors, non-orthogonal radiographs, movement of applicator and probe in the time span between X-ray and application, missing connection of probe and anterior rectal wall. The standard deviation of calculations at ICRU reference points was on average +/- 30%. Possible reasons for the relatively large standard deviation were difficulties in defining the points, identifying them on radiographs and the different locations of the applicators. Although 3 D CT, US or MR based treatment planning using dose volume histogram analysis is more and more established, this simple procedure of marking and digitising the ICRU reference points lengthened treatment planning only by 5 to 10 minutes. The advantages of in vivo dosimetry are easy practicability and the possibility to determine rectum doses during radiation. The advantages of computer-aided planning at ICRU reference points are that calculations are available before radiation and that they can still be taken into account for treatment planning. Both methods should be applied in HDR-brachytherapy of cervical carcinoma.
膀胱和直肠的体内剂量测定以及按照国际辐射单位与测量委员会（ICRU）第38号报告在建议的参考点上确定剂量，有助于宫颈癌高剂量率近距离放射治疗的质量保证，尤其是可将副作用降至最低。为了获取有关直肠癌、膀胱、输尿管及区域淋巴结ICRU参考点处辐射暴露的信息，对接受原发性放射治疗的宫颈癌患者的11次治疗应用进行了正交X线片计算（数字化）。此外，将ICRU直肠参考点处的剂量与直肠内的体内测量结果进行了比较。体内测量结果比为ICRU直肠参考点确定的剂量低1.5倍（4.05±0.68 Gy对6.11±1.63 Gy）。原因如下：校准误差、非正交X线片、在X线检查与治疗应用之间的时间段内施源器和探头的移动、探头与直肠前壁连接缺失。ICRU参考点处计算的标准差平均为±30%。标准差相对较大的可能原因是定义这些点、在X线片上识别它们以及施源器位置不同存在困难。尽管基于三维CT、超声或磁共振的使用剂量体积直方图分析的治疗计划越来越成熟，但这种标记和数字化ICRU参考点的简单程序仅使治疗计划延长了5至10分钟。体内剂量测定的优点是易于实施且能够在放疗期间确定直肠剂量。在ICRU参考点进行计算机辅助计划的优点是在放疗前即可获得计算结果，并且这些结果仍可用于治疗计划。这两种方法都应应用于宫颈癌的高剂量率近距离放射治疗。
