Onishi Yuya, Ota Ryosuke
Central Research Laboratory, Hamamatsu Photonics K. K., 5000 Hirakuchi, Hamana-ku, Hamamatsu 434-8601, Japan.
Phys Med Biol. 2025 Mar 3;70(6). doi: 10.1088/1361-6560/adb936.
. Coincidence time resolution (CTR) in time-of-flight positron emission tomography (TOF-PET) has significantly improved with advancements in scintillators, photodetectors, and readout electronics. Achieving a CTR of 100 ps remains challenging due to the need for sufficiently thick scintillators-typically 20 mm-to ensure adequate sensitivity because the photon transit time spread within these thick scintillators impedes achieving 100 ps CTR. Therefore thinner scintillators are preferable for CTR better than 100 ps. To address the trade-off between TOF capability and sensitivity, we propose a readout scheme of PET detectors.. The proposed scheme utilizes two orthogonally stacked one-dimensional PET detectors, enabling the thickness of the scintillators to be reduced to approximately 13 mm without compromising sensitivity. This is achieved by stacking the detectors along the depth-of-interaction (DOI) axis of a PET scanner. We refer to this design as the cross-stacked detector, or xDetector. Furthermore, the xDetector inherently provides DOI information using the same readout scheme.. Experimental evaluations demonstrated that the xDetector achieved the best CTR of 175 ps full width at half maximum (FWHM) and an energy resolution of 11% FWHM at 511 keV with 3 × 3 × 12.8 mmlutetium oxyorthosilicate crystals, each coupled one-to-one with silicon photomultipliers. The CTRs are between the xDetector and reference detector with a single timing resolution of 111.2 ± 0.8 ps FWHM. In terms of-spatial resolution, the xDetector exhibited an asymmetric resolution due to its readout scheme: one resolution was defined by the 3.2 mm readout pitch, while the other was calculated using the center-of-gravity method.. The xDetector effectively resolves the trade-off between TOF capability and sensitivity while offering scalability and DOI capability. By integrating state-of-the-art scintillators, photodetectors, and readout electronics with the xDetector scheme, achieving a CTR of 100 ps FWHM alongside high DOI resolution becomes a practical possibility.
随着闪烁体、光电探测器和读出电子学的进步，飞行时间正电子发射断层扫描（TOF-PET）中的符合时间分辨率（CTR）有了显著提高。由于需要足够厚的闪烁体（通常为20毫米）以确保足够的灵敏度，实现100皮秒的CTR仍然具有挑战性，因为这些厚闪烁体内的光子传输时间展宽阻碍了实现100皮秒的CTR。因此，对于优于100皮秒的CTR，更薄的闪烁体是优选的。为了解决TOF能力和灵敏度之间的权衡问题，我们提出了一种PET探测器的读出方案。所提出的方案利用两个正交堆叠的一维PET探测器，能够将闪烁体的厚度减小到约13毫米而不影响灵敏度。这是通过沿PET扫描仪的相互作用深度（DOI）轴堆叠探测器来实现的。我们将这种设计称为交叉堆叠探测器或x探测器。此外，x探测器使用相同的读出方案固有地提供DOI信息。实验评估表明，使用3×3×12.8毫米的正硅酸镥晶体，每个晶体与硅光电倍增管一对一耦合，x探测器在511keV时实现了175皮秒半高宽（FWHM）的最佳CTR和11%FWHM的能量分辨率。x探测器与具有111.2±0.8皮秒FWHM单定时分辨率的参考探测器之间的CTR。在空间分辨率方面，x探测器由于其读出方案而表现出不对称分辨率：一种分辨率由3.2毫米的读出间距定义，而另一种分辨率是使用重心法计算的。x探测器有效地解决了TOF能力和灵敏度之间的权衡问题，同时提供了可扩展性和DOI能力。通过将先进的闪烁体、光电探测器和读出电子学与x探测器方案相结合，实现100皮秒FWHM的CTR以及高DOI分辨率成为一种实际可能。
