Kollaard Robert P, Dries Wim J F, van Kleffens Herman J, Aalbers Tony H L, van der Marel Hans, Marijnissen Hans P A, Piessens Marleen, Schaart Dennis R, de Vroome Henk
Department of Radiotherapy, Catharina Hospital, Eindhoven, The Netherlands.
Radiother Oncol. 2006 Feb;78(2):223-9. doi: 10.1016/j.radonc.2005.12.006. Epub 2006 Feb 2.
It is estimated that one third of the institutes applying clinical beta sources does not perform independent dosimetry. The Netherlands commission on radiation dosimetry (NCS) recently published recommended quality control procedures and detectors for the dosimetry of beta sources. The main issues of NCS Report 14 are summarized here.
A dosimetry survey was performed among 23 institutes in The Netherlands and Belgium. Well ionization chambers, a plastic scintillator, plane-parallel ionization chamber, diode and radiochromic film were used for determination of source strength (dose rate at reference distance) and uniformity of intravascular and ophthalmic sources. The source strength of multiple sources of each type was measured and compared with the source strength specified by the manufacturer.
The standard deviation of the difference between measured and specified source strength was mostly about 3%, but varied between 0.8 and 15.8% depending on factors such as source type, detector, phantom and manufacturers calibration. The average non-uniformity was about 7% for intravascular sources and 20% for ophthalmic sources. It is estimated that the total relative standard uncertainty can be kept below +/-4% (1 sigma) with all detectors tested. Maximum deviations in source strength of 10% and a non-uniformity below 10% (intravascular) and 30% (ophthalmic) are recommended.
Dosimetric and non-dosimetric quality control procedures on beta sources are recommended. They enable standardized measurements, including the determination of relative source strength and non-uniformity. Absolute calibrations depend on the future introduction of primary standards for clinical beta sources.
据估计，应用临床β源的机构中有三分之一未进行独立剂量测定。荷兰辐射剂量测定委员会（NCS）最近发布了β源剂量测定的推荐质量控制程序和探测器。本文总结了NCS报告14的主要问题。
在荷兰和比利时的23家机构中进行了剂量测定调查。使用井型电离室、塑料闪烁体、平行板电离室、二极管和放射变色胶片来测定源强（参考距离处的剂量率）以及血管内和眼科源的均匀性。测量了每种类型多个源的源强，并与制造商规定的源强进行比较。
测量的源强与规定的源强之间差异的标准偏差大多约为3%，但根据源类型、探测器、模体和制造商校准等因素，其在0.8%至15.8%之间变化。血管内源的平均不均匀性约为7%，眼科源为20%。据估计，使用所有测试的探测器，总相对标准不确定度可保持在±4%（1σ）以下。建议源强的最大偏差为10%，血管内源的不均匀性低于10%，眼科源低于30%。
建议对β源进行剂量测定和非剂量测定质量控制程序。它们能够实现标准化测量，包括相对源强和不均匀性的测定。绝对校准取决于未来临床β源一级标准的引入。
