Essers M, Mijnheer B J
Department of Radiation Oncology, University Hospital Rotterdam - Daniel den Hoed Cancer Center/Dijkzigt Hospital, The Netherlands.
Int J Radiat Oncol Biol Phys. 1999 Jan 15;43(2):245-59. doi: 10.1016/s0360-3016(98)00341-1.
In this critical review of the current practice of patient dose verification, we first demonstrate that a high accuracy (about 1-2%, 1 SD) can be obtained. Accurate in vivo dosimetry is possible if diodes and thermoluminescence dosimeters (TLDs), the main detector types in use for in vivo dosimetry, are carefully calibrated and the factors influencing their sensitivity are taken into account. Various methods and philosophies for applying patient dose verification are then evaluated: the measurement of each field for each fraction of each patient, a limited number of checks for all patients, or measurements of specific patient groups, for example, during total body irradiation (TBI) or conformal radiotherapy. The experience of a number of centers is then presented, providing information on the various types of errors detected by in vivo dosimetry, including their frequency and magnitude. From the results of recent studies it can be concluded that in centers having modern equipment with verification systems as well as comprehensive quality assurance (QA) programs, a systematic error larger than 5% in dose delivery is still present for 0.5-1% of the patient treatments. In other studies, a frequency of 3-10% of errors was observed for specific patient groups or when no verification system was present at the accelerator. These results were balanced against the additional manpower and other resources required for such a QA program. It could be concluded that patient dose verification should be an essential part of a QA program in a radiotherapy department, and plays a complementary role to treatment-sheet double checking. As the radiotherapy community makes the transition from the conventional two-dimensional (2D) to three-dimensional (3D) conformal and intensity modulated dose delivery, it is recommended that new treatment techniques be checked systematically for a few patients, and to perform in vivo dosimetry a few times for each patient for situations where errors in dose delivery should be minimized.
在本次对当前患者剂量验证实践的批判性综述中，我们首先证明可以获得高精度（约1 - 2%，1个标准差）。如果仔细校准用于体内剂量测定的主要探测器类型——二极管和热释光剂量计（TLD），并考虑影响其灵敏度的因素，进行准确的体内剂量测定是可行的。然后评估了应用患者剂量验证的各种方法和理念：对每位患者每个分次的每个射野进行测量、对所有患者进行有限次数的检查，或对特定患者群体进行测量，例如在全身照射（TBI）或适形放疗期间。接着介绍了一些中心的经验，提供了关于通过体内剂量测定检测到的各种类型误差的信息，包括其频率和大小。从近期研究结果可以得出结论，在拥有配备验证系统的现代设备以及全面质量保证（QA）计划的中心，仍有0.5 - 1%的患者治疗存在剂量输送方面大于5%的系统误差。在其他研究中，对于特定患者群体或加速器没有验证系统时，观察到误差频率为3 - 10%。这些结果与这样一个QA计划所需的额外人力和其他资源进行了权衡。可以得出结论，患者剂量验证应成为放疗科QA计划的重要组成部分，并对治疗单复查起到补充作用。随着放疗界从传统二维（2D）向三维（3D）适形和调强剂量输送转变，建议对少数患者系统地检查新的治疗技术，并在应将剂量输送误差最小化的情况下，对每位患者进行多次体内剂量测定。
