Department of Radiology, The University of Pennsylvania, Philadelphia, PA 19104, United States of America.
Phys Med Biol. 2018 Mar 2;63(5):055008. doi: 10.1088/1361-6560/aaad76.
The advent of silicon photomultipliers (SiPMs) has introduced the possibility of increased detector performance in commercial whole-body PET scanners. The primary advantage of these photodetectors is the ability to couple a single SiPM channel directly to a single pixel of PET scintillator that is typically 4 mm wide (one-to-one coupled detector design). We performed simulation studies to evaluate the impact of three different event positioning algorithms in such detectors: (i) a weighted energy centroid positioning (Anger logic), (ii) identifying the crystal with maximum energy deposition (1st max crystal), and (iii) identifying the crystal with the second highest energy deposition (2nd max crystal). Detector simulations performed with LSO crystals indicate reduced positioning errors when using the 2nd max crystal positioning algorithm. These studies are performed over a range of crystal cross-sections varying from 1 × 1 mm to 4 × 4 mm as well as crystal thickness of 1 cm to 3 cm. System simulations were performed for a whole-body PET scanner (85 cm ring diameter) with a long axial FOV (70 cm long) and show an improvement in reconstructed spatial resolution for a point source when using the 2nd max crystal positioning algorithm. Finally, we observe a 30-40% gain in contrast recovery coefficient values for 1 and 0.5 cm diameter spheres when using the 2nd max crystal positioning algorithm compared to the 1st max crystal positioning algorithm. These results show that there is an advantage to implementing the 2nd max crystal positioning algorithm in a new generation of PET scanners using one-to-one coupled detector design with lutetium based crystals, including LSO, LYSO or scintillators that have similar density and effective atomic number as LSO.
硅光电倍增管 (SiPM) 的出现为商用全身 PET 扫描仪带来了提高探测器性能的可能性。这些光电探测器的主要优势是能够将单个 SiPM 通道直接耦合到单个 PET 闪烁体像素，闪烁体像素通常为 4mm 宽（一对一耦合探测器设计）。我们进行了模拟研究，以评估三种不同事件定位算法在这些探测器中的影响：(i) 加权能量质心定位（Anger 逻辑），(ii) 确定具有最大能量沉积的晶体（1 最大晶体），和 (iii) 确定具有第二高能量沉积的晶体（2 最大晶体）。使用 LSO 晶体进行的探测器模拟表明，使用 2 最大晶体定位算法可减少定位误差。这些研究在晶体横截面从 1mm×1mm 到 4mm×4mm 以及晶体厚度从 1cm 到 3cm 的范围内进行。对具有长轴向视野（70cm 长）的全身 PET 扫描仪（85cm 环直径）进行了系统模拟，并显示当使用 2 最大晶体定位算法时，点源的重建空间分辨率有所提高。最后，当使用 2 最大晶体定位算法时，与使用 1 最大晶体定位算法相比，对于 1cm 和 0.5cm 直径的球体，对比度恢复系数值分别提高了 30%至 40%。这些结果表明，在新一代 PET 扫描仪中使用基于 lutetium 的晶体（包括 LSO、LYSO 或与 LSO 具有相似密度和有效原子数的闪烁体）实现 2 最大晶体定位算法具有优势，这种设计采用一对一耦合探测器。
