Abstract：
Objective. This work introduces a novel approach to performing active and passive dosimetry for beta-emitting radionuclides in solution using common dosimeters. The measurements are compared to absorbed dose to water (Dw) estimates from Monte Carlo (MC) simulations. We present a method for obtaining absorbed dose to water, measured with dosimeters, from beta-emitting radiopharmaceutical agents using a custom SPECT/CT compatible phantom for validation of Monte Carlo based absorbed dose to water estimates.Approach. A cylindrical, acrylic SPECT/CT compatible phantom capable of housing an IBA EFD diode, Exradin A20-375 parallel plate ion chamber, unlaminated EBT3 film, and thin TLD100 microcubes was constructed for the purpose of measuring absorbed dose to water from solutions of common beta-emitting radiopharmaceutical therapy agents. The phantom is equipped with removable detector inserts that allow for multiple configurations and is designed to be used for validation of image-based absorbed dose estimates with detector measurements. Two experiments with131I and one experiment with177Lu were conducted over extended measurement intervals with starting activities of approximately 150-350 MBq. Measurement data was compared to Monte Carlo simulations using the egs_chamber user code in EGSnrc 2019.Main results. Agreement withink= 1 uncertainty between measured and MC predictedDwwas observed for all dosimeters, except the A20-375 ion chamber during the second131I experiment. Despite the agreement, the measured values were generally lower than predicted values by 5%-15%. The uncertainties atk = 1 remain large (5%-30% depending on the dosimeter) relative to other forms of radiation therapy.Significance. Despite high uncertainties, the overall agreement between measured and simulated absorbed doses is promising for the use of dosimeter-based RPT measurements in the validation of MC predictedDw.
摘要：
目的：这项工作介绍了一种使用普通剂量计对溶液中的β发射放射性核素进行主动和被动剂量测定的新颖方法。将测量结果与来自蒙特卡洛(MC)模拟的吸收剂量对水(Dw)的估计进行比较。我们提出了一种获得水吸收剂量的方法，用剂量计测量，使用定制的SPECT/CT兼容体模验证基于蒙特卡罗的吸收剂量对水的估计值。
方法:圆柱形,丙烯酸SPECT/CT兼容的体模能够容纳IBAEFD二极管，IBARAZOR二极管，ExradinA20-375平行板离子室，未层压的EBT3薄膜，和薄的TLD100微立方体的目的是测量从常见的β-发射放射性药物治疗剂的溶液中对水的吸收剂量。体模配备了可移动的探测器插件，允许多种配置，并设计用于验证基于图像的吸收剂量估计与探测器测量。在延长的测量间隔内进行两个131I实验和一个177Lu实验,起始活性约为150-350MBq。使用EGSnrc2019中的egs_chorter用户代码将测量数据与蒙特卡罗模拟进行了比较。
主要结果:所有剂量计观测到的测量值和MC预测值在k=1不确定度内一致,在第二个131I实验期间，除了IBARAZOR二极管和A20-375离子室。尽管达成了协议,测量值通常比预测值低5-15%。相对于其他形式的放射治疗,k=1处的不确定性仍然很大(5-30%,取决于剂量计)。
重要意义：尽管不确定性很大，对于在MC预测的Dw的验证中使用基于剂量计的RPT测量,测量和模拟吸收剂量之间的总体一致性是有希望的.
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