Nadig Vanessa, Herweg Katrin, Chou Mitch M C, Lin Jack W C, Chin Edmund, Li Chu-An, Schulz Volkmar, Gundacker Stefan
Department of Physics of Molecular Imaging Systems (PMI), Institute for Experimental Molecular Imaging (ExMI), RWTH Aachen University, D-52074 Aachen, Germany.
National Sun Yatsen University, Kaohsiung 80424, Taiwan.
Phys Med Biol. 2023 Mar 20;68(7). doi: 10.1088/1361-6560/acbde4.
Together with novel photodetector technologies and emerging electronic front-end designs, scintillator material research is one of the key aspects to obtain ultra-fast timing in time-of-flight positron emission tomography (TOF-PET). In the late 1990s, Cerium-doped lutetium-yttrium oxyorthosilicate (LYSO:Ce) has been established as the state-of-the-art PET scintillator due to its fast decay time, high light yield and high stopping power. It has been shown that co-doping with divalent ions, such as Caand Mg, is beneficial for its scintillation characteristics and timing performance. Therefore, this work aims to identify a fast scintillation material to combine it with novel photosensor technologies to push the state of the art in TOF-PET.This study evaluates commercially available LYSO:Ce,Ca and LYSO:Ce,Mg samples manufactured by Taiwan Applied Crystal Co., LTD regarding their rise and decay times as well as their coincidence time resolution (CTR) with both ultra-fast high-frequency (HF) readout and commercially available readout electronics, i.e. the TOFPET2 ASIC.The co-doped samples exhibit state-of-the-art rise times of on average 60 ps and effective decay times of on average 35 ns. Using the latest technological improvements made on NUV-MT SiPMs by Fondazione Bruno Kessler and Broadcom Inc., a 3 × 3 × 19 mmLYSO:Ce,Ca crystal achieves a CTR of 95 ps (FWHM) with ultra-fast HF readout and 157 ps (FWHM) with the system-applicable TOFPET2 ASIC. Evaluating the timing limits of the scintillation material, we even show a CTR of 56 ps (FWHM) for small 2 × 2 × 3 mmpixels. A complete overview of the timing performance obtained with different coatings (Teflon, BaSO) and different crystal sizes coupled to standard Broadcom AFBR-S4N33C013 SiPMs will be presented and discussed.This work thoroughly evaluates commercially available co-doped LYSO:Ce crystals and, in combination with novel NUV-MT SiPMs, shows a TOF performance that significantly exceeds the current state of the art.
与新型光电探测器技术和新兴的电子前端设计一起，闪烁体材料研究是在飞行时间正电子发射断层扫描（TOF-PET）中实现超快速计时的关键方面之一。在20世纪90年代后期，掺铈的硅酸镥钇（LYSO:Ce）因其快速的衰减时间、高光输出和高阻止本领而成为最先进的PET闪烁体。研究表明，与二价离子（如Ca和Mg）共掺杂有利于其闪烁特性和计时性能。因此，这项工作旨在确定一种快速闪烁体材料，并将其与新型光电传感器技术相结合，以推动TOF-PET技术达到新水平。本研究评估了台湾应用晶体有限公司生产的市售LYSO:Ce,Ca和LYSO:Ce,Mg样品的上升和衰减时间，以及它们与超快速高频（HF）读出和市售读出电子设备（即TOFPET2 ASIC）的符合时间分辨率（CTR）。共掺杂样品的上升时间平均为60 ps，处于最先进水平，有效衰减时间平均为35 ns。利用布鲁诺·凯斯勒基金会和博通公司在NUV-MT SiPM上取得的最新技术改进，一块3×3×19 mm的LYSO:Ce,Ca晶体在超快速HF读出时CTR为95 ps（半高宽），在适用系统的TOFPET2 ASIC下CTR为157 ps（半高宽）。通过评估闪烁体材料的计时极限，我们甚至展示了对于2×2×3 mm的小像素，CTR为56 ps（半高宽）。将展示并讨论使用不同涂层（特氟龙（Teflon）、硫酸钡（BaSO））以及与标准博通AFBR-S4N33C013 SiPM耦合的不同晶体尺寸所获得的计时性能的完整概述。这项工作全面评估了市售的共掺杂LYSO:Ce晶体，并与新型NUV-MT SiPM相结合，展示出显著超越当前技术水平的TOF性能。
