Particle therapy can largely benefit from the detailed and wide-range spectrometric and directional characterization of energetic charged particles provided by compact Timepix detectors. Among several physical quantities that can be derived, the assessment of the linear energy transfer (LET) which is based on the deposited energy and particle's track length remains challenging. Due to the detector's pixel pitch, sensor thickness and charge sharing effect, an accurate estimation of the particle's incident angle and hence the track length, has been limited to particles with incident angles greater than 20⁰ with respect to the normal of the sensor layer. This is critical for clinical beams which are highly directional, and measurements with radiation detectors are generally performed with sensitive volumes orthogonally placed with respect to the beam direction. In this work, we present a novel method in which we exploit the morphological cluster parameters to derive the proton's incident angle, thus enabling a precise directional reconstruction over the full field-of-view 2π (solid angle), and within 2° from the reference angles for Timepix detectors with 300 and 500 μm thick Si sensors. As a consequence, the calculation of the track length was also improved, resulting in a more precise LET estimation. The experimental LET spectra and the frequency-averaged LET (LET_F) were compared against Monte Carlo simulations using TOPAS for a wide range of proton energies (12 MeV–200 MeV) and incident angles (0–85⁰). An agreement within 12% was found between measured and simulated LET_F. A comparison with LET values based on the PSTAR database also showed an agreement within 10%. We demonstrated the feasibility of a precise LET calculation and directional response with an improved angular resolution down to normal incidence using a single-layer Timepix detector, while avoiding the use of a stacked telescope array.

粒子疗法可以在很大程度上受益于紧凑型 Timepix 探测器提供的高能带电粒子的详细和广泛的光谱和定向表征。在可以导出的几个物理量中，基于沉积能量和粒子轨迹长度的线性能量转移 (LET) 评估仍然具有挑战性。由于探测器的像素间距、传感器厚度和电荷共享效应，对粒子入射角以及轨迹长度的准确估计仅限于相对于传感器层法线入射角大于 20⁰ 的粒子。这对于高度定向的临床光束至关重要，使用辐射探测器进行的测量通常使用相对于光束方向正交放置的敏感体积进行。在这项工作中，我们提出了一种新的方法，我们利用形态簇参数来推导质子的入射角，从而能够在整个视场 2π（立体角）上进行精确的定向重建，并且在距离 2° 范围内。具有 300 和 500 μm 厚 Si 传感器的 Timepix 探测器的参考角。因此，轨道长度的计算也得到了改进，从而产生了更精确的 LET 估计。实验 LET 光谱和频率平均 LET (LET 因此，可以在全视场 2π（立体角）上进行精确的定向重建，并且与具有 300 和 500 μm 厚 Si 传感器的 Timepix 探测器的参考角相差 2° 以内。因此，轨道长度的计算也得到了改进，从而产生了更精确的 LET 估计。实验 LET 光谱和频率平均 LET (LET 因此，可以在全视场 2π（立体角）上进行精确的定向重建，并且与具有 300 和 500 μm 厚 Si 传感器的 Timepix 探测器的参考角相差 2° 以内。因此，轨道长度的计算也得到了改进，从而产生了更精确的 LET 估计。实验 LET 光谱和频率平均 LET (LET_F ) 与使用 TOPAS 的蒙特卡罗模拟进行了比较，用于各种质子能量 (12 MeV–200 MeV) 和入射角 (0–85⁰)。在测量和模拟的 LET _F之间发现了 12% 以内的一致性。与基于 PSTAR 数据库的 LET 值的比较也表明一致性在 10% 以内。我们展示了使用单层 Timepix 探测器进行精确 LET 计算和方向响应的可行性，并将角分辨率提高到垂直入射，同时避免使用堆叠的望远镜阵列。