Diverging collimators are used to obtain reduced images of an object or detect a wide field-of-view (FOV) by using a small gamma camera. In gamma cameras equipped with diverging collimators, a monolithic scintillator, and a pixel scintillator array, gamma rays are obliquely incident on the scintillator surface when considering a source that is located near the periphery of the FOV. In such a situation, the spatial resolution is reduced due to oblique detection along the depth direction. In this study, we designed a novel system that improves the spatial resolution of the periphery of the FOV. A tapered crystal array is used to configure the scintillation pixels so that they coincide with the angle relative to the collator hole. This allows imaging of individual scintillation pixel locations, even if the events to be detected occur at different distances. That is, even if an event is detected at various points along the diagonal direction, the gamma rays interact with only a single crystal pixel, thus, the resolution is not degraded. The resolutions of the monolithic scintillator and the tapered crystal array were compared and evaluated using Geant4 Application for Tomographic Emission (GATE) simulations. The dimensions of the monolithic scintillator are 69.4 mm × 69.4 mm × 10.0 mm while those of the tapered crystal array are 49.4 mm × 49.4 mm at the small end and 69.4 mm × 69.4 mm at the large end, with a length of 20 mm. The tapered array contains 45 × 45 elements, and the pixel size is 1 mm × 1 mm at the small end and 1.4 mm × 1.4 mm at the large end. The diverging collimator has dimensions of 69.4 mm × 69.4 mm at the small end and 109.4 mm × 109.4 mm at the large end, with a length of 20 mm. The spatial resolutions of the obtained images were 3.22, 3.77, and 4.63 mm in the monolithic scintillator and 3.25, 3.29, and 3.12 mm in the tapered crystal array. A 16.8% spatial resolution improvement was seen with the tapered crystal array as compared to the monolithic scintillation crystal for all gamma source positions.

中文翻译：

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使用锥形晶体阵列提高具有发散准直器的伽马相机的空间分辨率

发散准直器用于获取物体的缩小图像或通过使用小型伽马相机检测宽视场 (FOV)。在配备发散准直器、单片闪烁器和像素闪烁器阵列的伽马相机中，当考虑位于 FOV 外围附近的源时，伽马射线倾斜入射到闪烁器表面。在这种情况下，由于沿深度方向的倾斜检测，空间分辨率会降低。在这项研究中，我们设计了一种新颖的系统，可以提高 FOV 外围的空间分辨率。锥形晶体阵列用于配置闪烁像素，使其与相对于校准器孔的角度一致。这允许对单个闪烁像素位置进行成像，即使要检测的事件发生在不同的距离。即，即使在沿对角线方向的各个点检测到事件，伽马射线也仅与单晶像素相互作用，因此分辨率不会降低。使用 Geant4 Application for Tomographic Emission (GATE) 模拟比较和评估单片闪烁体和锥形晶体阵列的分辨率。单片闪烁体的尺寸为 69.4 mm × 69.4 mm × 10.0 mm，而锥形晶体阵列的尺寸为小端 49.4 mm × 49.4 mm 和大端 69.4 mm × 69.4 mm，长度为 20 mm。锥形阵列包含 45 × 45 个元素，小端像素尺寸为 1 mm × 1 mm，大端像素尺寸为 1.4 mm × 1.4 mm。发散准直器的尺寸为 69.4 mm × 69。小端4mm，大端109.4mm×109.4mm，长度20mm。获得的图像的空间分辨率在单片闪烁体中为 3.22、3.77 和 4.63 毫米，在锥形晶体阵列中为 3.25、3.29 和 3.12 毫米。对于所有伽马源位置，与单片闪烁晶体相比，锥形晶体阵列的空间分辨率提高了 16.8%。