Effect of detector geometry and surface finish on Cerenkov based time estimation in monolithic BGO detectors
Effect of detector geometry and surface finish on Cerenkov based time estimation in monolithic BGO detectors
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探测器几何形状和表面光洁度对单片 BGO 探测器中基于切伦科夫的时间估计的影响
DOI：
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发表时间：
2022
影响因子：
3.5
通讯作者：
S. Vandenberghe
中科院分区：
文献类型：
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作者：
J. Maebe;S. Vandenberghe
目标。由于切伦科夫光的快速发射，基于锗酸铋(BGO)探测器的飞行时间正电子发射层析成像成为可能。每个511keV光电事件只产生约17个切伦科夫光子，因此高光子收集效率对于获得良好的飞行时间能力至关重要。在这项研究中，我们研究了不同的侧面和背面抛光对单片BGO的光子收集效率和基于切伦科夫的定时性能的影响。接近。研究使用GATE进行伽马和光学光子建模，光子的表面反射由LUT Davis模型模拟。我们比较了不同探测器配置(关于尺寸和表面光洁度)的光子收集效率、前几个光学光子的探测延迟和通过对SiPM信号建模和前沿判别获得的符合时间分辨率估计。对LYSO闪烁体和像素化探测器进行了额外的比较。主要结果。虽然切伦科夫光子发射是定向的，但由于电子在晶体中的散射，许多大入射角的切伦科夫光子被发射出来。用抛光的背面(光电探测器侧)代替粗糙的表面，提高了这些大角度入射光子的收集效率。结果表明，对于单片式50×50×12 mm~3的侧面反射型BGO探测器，光子收集效率总体上提高了34%。切伦科夫光子收集效率也得到了提高，从而减少了最初几个光学光子的光子检测延迟(及其变化)。这导致了更好的重合时间分辨率，主要是通过缩短飞行时间内核中的尾部实现的，在十分之一的最大值时，全宽减少了18%。意义重大。这项研究表明了光子收集效率对切伦科夫基单片探测器定时性能的重要性，以及如何通过不同的表面光洁度来提高光子收集效率。
Objective. Time-of-flight positron emission tomography based on bismuth germanate (BGO) detectors is made possible due to fast emission of Cerenkov light. Only around 17 Cerenkov photons are produced per 511 keV photoelectric event, making high photon collection efficiency crucial for obtaining good time-of-flight capabilities. In this study, we investigate how different lateral and back surface finishes affect the photon collection efficiency and Cerenkov based timing performance in monolithic BGO. Approach. The study is performed using GATE for gamma and optical photon modeling, with surface reflections of photons simulated by the LUT Davis model. We compare for different detector configurations (regarding size and surface finishes) the photon collection efficiency, detection delays of the first few optical photons and coincidence time resolution estimations obtained by modeling the SiPM signals and performing leading edge discrimination. An additional comparison is made to LYSO scintillators and pixelated detectors. Main results. Although Cerenkov photon emission is directional, many high incidence angle Cerenkov photons are emitted due to electron scattering in the crystal. Substituting a polished back (photodetector side) surface for a rough surface increases the collection efficiency of these high angle of incidence photons. Results show that for a monolithic 50 × 50 × 12 mm3 BGO detector with reflective side surfaces, this leads to an overall increase in photon collection efficiency of 34%. Cerenkov photon collection efficiency is also improved, resulting in a reduction of the photon detection delays (and the variation therein) of the first few optical photons. This leads to a better coincidence time resolution, primarily achieved by a shortening of the tails in the time-of-flight kernel, with an 18% reduction in full width at tenth maximum. Significance. This study shows the importance of the photon collection efficiency for timing performance in Cerenkov based monolithic detectors, and how it can be improved with different surface finishes.