Design and simulation of a novel method for determining depth-of-interaction in a PET scintillation crystal array using a single-ended readout by a multi-anode PMT
Design and simulation of a novel method for determining depth-of-interaction in a PET scintillation crystal array using a single-ended readout by a multi-anode PMT
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DOI：
10.1088/0031-9155/55/13/017
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发表时间：
2010-07-07
影响因子：
3.5
通讯作者：
Hong, Seong Jong
中科院分区：
文献类型：
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作者：
Ito, Mikiko;Lee, Jae Sung;Hong, Seong Jong
具有交互深度 (DOI) 编码功能的 PET 探测器可同时实现高空间分辨率和高灵敏度。为了使用单端读出器从单层闪烁晶体阵列获取 DOI 信息，作者设计了一种基于晶体阵列内光扩散的方法，并通过单个闪烁光子跟踪进行蒙特卡罗模拟来证明这一概念。采用网格法构建了闪烁晶体阵列模型。传统的网格是使用具有矩形齿的梳状反射条来构造的，以光学隔离闪烁晶体。然而，作者建议使用三角形齿，这样闪烁光子仅在晶体上半部分的 x 方向上传播，而在下半部分中则在 y 方向上传播。 DOI 位置可以通过考虑二维光色散的程度来估计，二维光色散的程度可以根据放置在晶体阵列下方的位置敏感 PMT 的多个阳极输出来确定。在主要模拟中，使用了由 1.5 mm x 1.5 mm x 20 mm 晶体的 29 x 29 阵列和具有 16 x 16 像素的多阳极 PMT 组成的晶体块。还通过仿真探讨了晶体尺寸和非均匀 PMT 输出增益的影响。 1.5 x 1.5 x 20 mm(3) 晶体的 DOI 分辨率估计平均为 2.16 mm。尽管洪水图与深度相关，但当晶体阵列的一角受到 511 keV 伽马射线（峰谷比类似于 9:1）照射时，每个晶体在所有深度都得到了很好的识别。当晶体长度为 28 mm、晶体表面积为 1.5 x 1.5 mm(2) 或 2.0 x 2.0 mm(2) 时，DOI 分辨率优于 3 mm。所设计的光共享方法无需使用双端读出或多晶体阵列即可获得出色的 DOI 分辨率。
PET detectors with depth-of-interaction (DOI) encoding capability allow high spatial resolution and high sensitivity to be achieved simultaneously. To obtain DOI information from a mono-layer array of scintillation crystals using a single-ended readout, the authors devised a method based on light spreading within a crystal array and performed Monte Carlo simulations with individual scintillation photon tracking to prove the concept. A scintillation crystal array model was constructed using a grid method. Conventional grids are constructed using comb-shaped reflector strips with rectangular teeth to isolate scintillation crystals optically. However, the authors propose the use of triangularly shaped teeth, such that scintillation photons spread only in the x-direction in the upper halves of crystals and in the y-direction in lower halves. DOI positions can be estimated by considering the extent of two-dimensional light dispersion, which can be determined from the multiple anode outputs of a position-sensitive PMT placed under the crystal array. In the main simulation, a crystal block consisting of a 29 x 29 array of 1.5 mm x 1.5 mm x 20 mm crystals and a multi-anode PMT with 16 x 16 pixels were used. The effects of crystal size and non-uniform PMT output gain were also explored by simulation. The DOI resolution estimated for 1.5 x 1.5 x 20 mm(3) crystals was 2.16 mm on average. Although the flood map was depth dependent, each crystal was well identified at all depths when a corner of the crystal array was irradiated with 511 keV gamma rays (peak-to-valley ratio similar to 9:1). DOI resolution was better than 3 mm up to a crystal length of 28 mm with a 1.5 x 1.5 mm(2) or 2.0 x 2.0 mm(2) crystal surface area. The devised light-sharing method allowed excellent DOI resolutions to be obtained without the use of dual-ended readout or multiple crystal arrays.