Design study of a brain-dedicated time-of-flight PET system with a hemispherical detector arrangement
Design study of a brain-dedicated time-of-flight PET system with a hemispherical detector arrangement
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DOI：
10.1088/1361-6560/ab63ee
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发表时间：
2020-02-01
影响因子：
3.5
通讯作者：
Yamaya, Taiga
中科院分区：
文献类型：
--
作者：
Takyu, Sodai;Ahmed, Abdella M.;Yamaya, Taiga
飞行时间（TOF）是目前正电子发射层析成像（PET）的标准技术，但其在小直径PET系统中的有效应用还没有得到很好的研究。在本文中，我们模拟了一个具有半球形探测器的脑专用TOF-PET系统。我们模拟了一个具有280 ps重合解析时间（CRT）的Hamamatsu TOF-PET模块（C13500-4075LC-12），其中一个12 x 12的多像素光子计数器（MPPCs）阵列连接到一个4.1 x 4.1 mm(2)横截面的LFS晶体阵列，基于一对一耦合。另一方面，对于小直径PET系统，由于视差误差导致的空间分辨率下降需要仔细解决。理想的PET检测器应该同时具有相互作用深度（DOI）和TOF功能，但是基于光共享的典型DOI检测器往往会降低TOF性能。因此，在这项工作中，我们研究了具有适当晶体长度的非doi探测器，这是抑制视差误差和降低灵敏度之间的折衷。使用GEANT4，我们比较了两个TOF探测器，一个20 mm长的非DOI和一个10 mm长的非DOI，以及一个总长度为20 mm（即5 x 4 mm）的非TOF 4层DOI探测器。我们模拟了一个对比度幻象，并评估了重建图像的对比度恢复系数（CRC）和噪声水平（变异系数，COV）之间的关系。10 mm长的非doi以降低视差误差为代价，成像质量优于20 mm长的非doi。例如，在COV = 20%时，10mm长的非doi的10mm热球CRC值为72%，是20mm长的非doi的1.2倍。10 mm长的非DOI的收敛CRC值与非tof 4层DOI的收敛CRC值几乎相等，并且10 mm长的非DOI的收敛速度比非tof 4层DOI的收敛速度快。基于仿真结果，我们对晶体长度为10 mm的单对TOF-PET探测器原型系统进行了评估，该系统产生了250 +/- 8 ps的CRT。总之，我们证明了半球形探测器配置的脑专用TOF-PET系统的可行性。
Time-of-flight (TOF) is now a standard technology for positron emission tomography (PET), but its effective use for small diameter PET systems has not been studied well. In this paper, we simulated a brain-dedicated TOF-PET system with a hemispherical detector arrangement. We modeled a Hamamatsu TOF-PET module (C13500-4075LC-12) with 280 ps coincidence resolving time (CRT), in which a 12 x 12 array of multi pixel photon counters (MPPCs) is connected to a lutetium fine silicate (LFS) crystal array of 4.1 x 4.1 mm(2) cross section each, based on one-to-one coupling. On the other hand, spatial resolution degradation due to the parallax error should be carefully addressed for the small diameter PET systems. The ideal PET detector would have both depth-of-interaction (DOI) and TOF capabilities, but typical DOI detectors that are based on light sharing tend to degrade TOF performance. Therefore, in this work, we investigated non-DOI detectors with an appropriate crystal length, which was a compromise between suppressed parallax error and decreased sensitivity. Using GEANT4, we compared two TOF detectors, a 20 mm long non-DOI and a 10 mm long non-DOI, with a non-TOF, 4-layer DOI detector with a total length of 20 mm (i.e. 5 x 4 mm). We simulated a contrast phantom and evaluated the relationship between the contrast recovery coefficient (CRC) and the noise level (the coefficient of variation, COV) for reconstructed images. The 10 mm long non-DOI, which reduces the parallax error at the cost of sensitivity loss, showed better imaging quality than the 20 mm long non-DOI. For example, the CRC value of a 10 mm hot sphere at COV = 20% was 72% for the 10 mm long non-DOI, which was 1.2 times higher than that of the 20 mm long non-DOI. The converged CRC values for the 10 mm long non-DOI were almost equivalent to those of the non-TOF 4-layer DOI, and the 10 mm long non-DOI converged faster than the non-TOF 4-layer DOI did. Based on the simulation results, we evaluated a one-pair prototype system of the TOF-PET detectors with 10 mm crystal length, which yielded the CRT of 250 +/- 8 ps. In summary, we demonstrated support for feasibility of the brain-dedicated TOF-PET system with the hemispherical detector arrangement.