Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
Phys Med Biol. 2018 Feb 26;63(5):05NT02. doi: 10.1088/1361-6560/aaa815.
Optical coupling is an important factor in detector design as it improves optical photon transmission by mitigating internal reflections at light-sharing boundaries. In this work we compare optical coupling materials, namely double-sided acrylic polymer tapes and silicone optical grease (SiG), in the context of positron emission tomography. Four double-sided tapes from 3 M of varying thicknesses (0.229 mm-1.016 mm) and adhesive materials ('100MP', 'A100', and 'GPA') were characterized with spectrophotometer measurements as well as photopeak amplitude and energy resolution measurements using lutetium-yttrium oxy-orthosilicate (LYSO) coupled to photomultiplier tubes (PMT) or silicon photomultipliers (SiPMs). Transmission spectra from the spectrophotometer showed over 80% transmission for all tapes at 420 nm and above, with 89.6% and 88.8% transmission for the 0.508 mm and 1.016 mm thick GPA tapes, respectively, at 420 nm. Measurements with single-pixel LYSO-PMT and 4 × 4 array (one-to-one coupled) LYSO-SiPM setups determined that SiG had the greatest photopeak amplitude, with tapes showing 2.1%-14.8% reduction in photopeak amplitude with respect to SiG. Energy resolution changed by less than 4% on a relative basis between tapes and SiG with PMT measurements, however for the SiPM array measurements the energy resolution improved from 15.6% ± 2.7% full-width at half-maximum to 11.4% ± 1.2% for SiG and 1 mm GPA respectively. Data acquired with dual-layer offset LYSO arrays (light sharing detector designs) demonstrated that a detector coupled with 1 mm thick GPA tape produced equivalent detector flood histograms to those from a design coupled with SiG and a 1 mm thick glass lightguide. No significant degradation in photopeak amplitude and energy resolution was observed over five months of measurements, indicating the tapes maintain their coupling integrity over several months. Though minimal photopeak amplitude degradation compared to SiG occurs, double-sided tapes are convenient alternatives for optical coupling materials since they diffuse light intrinsically, acting as a light guide, offer mechanical support and durability, are easily applied and removed from scintillators/photodetectors, and are relatively inexpensive and readily available.
光学耦合是探测器设计中的一个重要因素，因为它通过减轻光共享边界处的内部反射来提高光光子的传输效率。在这项工作中，我们比较了光学耦合材料，即双面丙烯酸聚合物胶带和硅脂光学油脂（SiG），在正电子发射断层扫描（PET）的背景下。我们对来自 3M 的四种不同厚度（0.229 毫米-1.016 毫米）和不同胶黏材料（'100MP'、'A100'和'GPA'）的双面胶带进行了特征描述，包括分光光度计测量以及使用掺镥硅酸钇（LYSO）耦合光电倍增管（PMT）或硅光电倍增管（SiPM）的光电峰幅度和能量分辨率测量。分光光度计的传输光谱显示，在 420nm 及以上波长下，所有胶带的传输率均超过 80%，0.508mm 和 1.016mm 厚的 GPA 胶带的传输率分别为 89.6%和 88.8%。使用单像素 LYSO-PMT 和 4x4 阵列（一对一耦合）LYSO-SiPM 进行的测量确定，SiG 具有最大的光电峰幅度，与 SiG 相比，胶带的光电峰幅度降低了 2.1%-14.8%。PMT 测量的相对基础上，胶带与 SiG 的能量分辨率变化小于 4%，然而，对于 SiPM 阵列的测量，能量分辨率从 SiG 的 15.6%±2.7%半峰全宽（FWHM）提高到 1mm GPA 分别为 11.4%±1.2%和 SiG。使用双层偏移 LYSO 阵列（光共享探测器设计）获得的数据表明，与使用 SiG 和 1mm 厚玻璃光导耦合的设计相比，使用 1mm 厚 GPA 胶带耦合的探测器产生了等效的探测器洪水直方图。在五个月的测量中，没有观察到光电峰幅度和能量分辨率的显著下降，这表明胶带在几个月内保持其耦合完整性。尽管与 SiG 相比，光电峰幅度有最小的降解，但双面胶带是光学耦合材料的方便替代品，因为它们内在地扩散光，充当光导，提供机械支撑和耐用性，易于施加和从闪烁体/光电探测器上移除，并且相对便宜且易于获得。
