Department of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany.
Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Phys Med Biol. 2024 Jun 21;69(13). doi: 10.1088/1361-6560/ad4e8e.
This work investigates the use of passive luminescence detectors to determine different types of averaged linear energy transfer (LET-) for the energies relevant to proton therapy. The experimental results are compared to reference values obtained from Monte Carlo simulations.Optically stimulated luminescence detectors (OSLDs), fluorescent nuclear track detectors (FNTDs), and two different groups of thermoluminescence detectors (TLDs) were irradiated at four different radiation qualities. For each irradiation, the fluence- (LET-f) and dose-averaged LET (LET-d) were determined. For both quantities, two sub-types of averages were calculated, either considering the contributions from primary and secondary protons or from all protons and heavier, charged particles. Both simulated and experimental data were used in combination with a phenomenological model to estimate the relative biological effectiveness (RBE).All types ofLET-could be assessed with the luminescence detectors. The experimental determination ofLET-fis in agreement with reference data obtained from simulations across all measurement techniques and types of averaging. On the other hand,LET-dcan present challenges as a radiation quality metric to describe the detector response in mixed particle fields. However, excluding secondaries heavier than protons from theLET-dcalculation, as their contribution to the luminescence is suppressed by ionization quenching, leads to equal accuracy betweenLET-fandLET-d. Assessment of RBE through the experimentally determinedLET-dvalues agrees with independently acquired reference values, indicating that the investigated detectors can determineLET-with sufficient accuracy for proton therapy.OSLDs, TLDs, and FNTDs can be used to determineLET-and RBE in proton therapy. With the capability to determine dose through ionization quenching corrections derived fromLET-, OSLDs and TLDs can simultaneously ascertain dose,LET-, and RBE. This makes passive detectors appealing for measurements in phantoms to facilitate validation of clinical treatment plans or experiments related to proton therapy.
本工作研究了使用被动发光探测器来确定与质子治疗相关能量的不同平均线性能量传递（LET-）类型。将实验结果与蒙特卡罗模拟获得的参考值进行了比较。在四种不同辐射质量下，对光激励发光探测器（OSLD）、荧光核径迹探测器（FNTD）和两组不同的热释光探测器（TLD）进行了辐照。对于每种辐照，确定了剂量（LET-d）和剂量平均 LET（LET-d）的剂量-（LET-f）和平均LET。对于这两个量，计算了两种平均值的子类型，要么考虑初级和次级质子的贡献，要么考虑所有质子和较重的带电粒子的贡献。结合唯象模型，使用模拟和实验数据来估计相对生物效应（RBE）。所有类型的 LET-都可以用发光探测器来评估。实验测定的 LET-f 在所有测量技术和平均类型上都与模拟获得的参考数据一致。另一方面，作为描述探测器在混合粒子场中响应的辐射质量度量，LET-d 可能具有挑战性。然而，从 LET-d 计算中排除比质子重的次级，因为它们对发光的贡献被电离猝灭抑制，导致 LET-f 和 LET-d 之间的精度相等。通过实验确定的 LET-d 值评估 RBE 与独立获得的参考值一致，表明所研究的探测器可以为质子治疗提供足够准确的 LET-。OSLD、TLD 和 FNTD 可用于确定质子治疗中的 LET-和 RBE。通过从 LET-中得出的离子化猝灭校正来确定剂量的能力，OSLD 和 TLD 可以同时确定剂量、LET-和 RBE。这使得被动探测器在幻影中的测量具有吸引力，有助于验证临床治疗计划或与质子治疗相关的实验。
