Andreo P
Department of Radiation Physics, Karolinska Institute, Stockholm, Sweden.
Int J Radiat Oncol Biol Phys. 1990 Nov;19(5):1233-47. doi: 10.1016/0360-3016(90)90237-e.
Recent studies indicate that the calibration of therapeutic beams is one of the main sources of uncertainty in the mean absorbed dose to the target volume in radiotherapy. Interaction coefficients and data used through the different steps in the calibration are pointed out as the main contribution to this uncertainty. Procedures used to select dosimetric data, that is, input parameters used in the specification of the quality of the beam, cause another contribution. In this paper the actual status of the data used for the dosimetry of photon and electron beams is introduced first. Uncertainties along the dosimetric chain are analyzed according to the procedure and data used in recent publications. Uncertainties in stopping-power ratios, considered the main contribution, are discussed in detail starting from the basic electron stopping-power data. Overall uncertainties in the presently available set of stopping-power ratios are analyzed. Recent developments in the dosimetry of electron beams, related to the effect of energy and angular spread and electron and photon contamination, are discussed in connection with the procedure to select stopping-power ratios for clinical dosimetry. Uncertainties along the dosimetric chain are evaluated in terms of the present knowledge of error sources.
近期研究表明，治疗束的校准是放射治疗中靶体积平均吸收剂量不确定性的主要来源之一。校准过程中不同步骤所使用的相互作用系数和数据被指出是造成这种不确定性的主要因素。用于选择剂量学数据（即用于指定束流质量的输入参数）的程序也会导致不确定性。本文首先介绍了用于光子束和电子束剂量测定的数据的实际状况。根据近期出版物中使用的程序和数据，分析了剂量测定链中的不确定性。从基本电子阻止本领数据出发，详细讨论了阻止本领比的不确定性，其被认为是主要影响因素。分析了当前可用的阻止本领比数据集的总体不确定性。结合临床剂量测定中选择阻止本领比的程序，讨论了电子束剂量测定的最新进展，这些进展与能量和角展宽以及电子和光子污染的影响有关。根据目前对误差来源的认识，评估了剂量测定链中的不确定性。
