Department of Radiation Safety and Security, Paul Scherrer Institute, Villigen PSI, Switzerland.
Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland.
Sci Rep. 2022 May 18;12(1):8262. doi: 10.1038/s41598-022-10575-4.
The objective of this study was to improve the precision of linear energy transfer (LET) measurements using [Formula: see text] optically stimulated luminescence detectors (OSLDs) in proton beams, and, with that, improve OSL dosimetry by correcting the readout for the LET-dependent ionization quenching. The OSLDs were irradiated in spot-scanning proton beams at different doses for fluence-averaged LET values in the (0.4-6.5) [Formula: see text] range (in water). A commercial automated OSL reader with a built-in beta source was used for the readouts, which enabled a reference irradiation and readout of each OSLD to establish individual corrections. Pulsed OSL was used to separately measure the blue (F-center) and UV ([Formula: see text]-center) emission bands of [Formula: see text] and the ratio between them (UV/blue signal) was used for the LET measurements. The average deviation between the simulated and measured LET values along the central beam axis amounts to 5.5% if both the dose and LET are varied, but the average deviation is reduced to 3.5% if the OSLDs are irradiated with the same doses. With the measurement procedure and automated equipment used here, the variation in the signals used for LET estimates and quenching-corrections is reduced from 0.9 to 0.6%. The quenching-corrected OSLD doses are in agreement with ionization chamber measurements within the uncertainties. The automated OSLD corrections are demonstrated to improve the LET estimates and the ionization quenching-corrections in proton dosimetry for a clinically relevant energy range up to 230 MeV. It is also for the first time demonstrated how the LET can be estimated for different doses.
本研究旨在提高使用[公式：见正文]光激励发光探测器（OSLD）在质子束中测量线性能量传递（LET）的精度，并通过校正读出以纠正与 LET 相关的离子猝灭来改善 OSL 剂量测定。OSLD 在不同剂量下的点扫描质子束中受到照射，用于测量（0.4-6.5）[公式：见正文]范围内的平均通量 LET 值（水中）。使用带有内置β源的商业自动化 OSL 阅读器进行读出，这使得可以对每个 OSLD 进行参考照射和读出，以建立单独的校正。使用脉冲 OSL 分别测量[公式：见正文]的蓝色（F 中心）和紫外（[公式：见正文]-中心）发射带，并将它们之间的比值（UV/蓝色信号）用于 LET 测量。如果同时改变剂量和 LET，则模拟和测量的 LET 值沿中心束轴的平均偏差为 5.5％，但如果以相同的剂量照射 OSLD，则平均偏差减小到 3.5％。使用此处使用的测量程序和自动化设备，用于 LET 估计和猝灭校正的信号变化从 0.9 减少到 0.6％。在不确定度范围内，经猝灭校正的 OSLD 剂量与电离室测量值一致。自动 OSLD 校正被证明可以改善临床相关能量范围内高达 230 MeV 的质子剂量测量中的 LET 估计和离子猝灭校正。这也是首次证明如何为不同剂量估计 LET。
