Laboratório de Ciências Radiólogicas, Universidade do Estado do Rio de Janeiro, RJ, Brazil. Brazilian Nuclear Energy Comission, CNEN, Rio de Janeiro, RJ, Brazil.
Phys Med Biol. 2018 Apr 5;63(8):085004. doi: 10.1088/1361-6560/aab2b8.
Two Fricke-based absorbed dose to water standards for HDR Ir-192 dosimetry, developed independently by the LCR in Brazil and the NRC in Canada have been compared. The agreement in the determination of the dose rate from a HDR Ir-192 source at 1 cm in a water phantom was found to be within the k = 1 combined measurement uncertainties of the two standards: D /D = 1.011, standard uncertainty = 2.2%. The dose-based standards also agreed within the uncertainties with the manufacturer's stated dose rate value, which is traceable to a national standard of air kerma. A number of possible influence quantities were investigated, including the specific method for producing the ferrous-sulphate Fricke solution, the geometry of the holder, and the Monte Carlo code used to determine correction factors. The comparison highlighted the lack of data on the determination of G(Fe) in this energy range and the possibilities for further development of the holders used to contain the Fricke solution. The comparison also confirmed the suitability of Fricke dosimetry for Ir-192 primary standard dose rate determinations at therapy dose levels.
巴西 LCR 和加拿大 NRC 独立开发的两种基于 Fricke 的 HDR Ir-192 剂量水吸收标准进行了比较。在水模体中 1cm 处，从 HDR Ir-192 源确定剂量率时，两个标准的测量不确定度 k=1 时，结果一致：D/D=1.011，标准不确定度=2.2%。剂量基准标准与制造商规定的剂量率值在不确定度范围内也一致，该值可追溯到空气比释动能的国家标准。研究了许多可能的影响因素，包括生产硫酸亚铁 Fricke 溶液的具体方法、支架的几何形状以及用于确定校正因子的蒙特卡罗代码。该比较突出表明，在该能量范围内缺乏关于 G(Fe) 测定的数据，以及进一步开发用于容纳 Fricke 溶液的支架的可能性。该比较还证实了 Fricke 剂量测定在治疗剂量水平下用于 Ir-192 初级标准剂量率测定的适用性。
