Romanchek Gregory, Abbaszadeh Shiva
Dept. of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61891, USA.
Dept. of Electrical and Computer Engineering, University of California Santa Cruz, Santa Cruz, CA 95064, USA.
Proc SPIE Int Soc Opt Eng. 2023 Feb;12463. doi: 10.1117/12.2654423. Epub 2023 Apr 7.
Coincidence timing calibration is fundamental to PET imaging. The electronics, cable lengths, and detector physics such as charge drift and depth dependence add to the measured time differences in coincidence sorting - increasing random rate, decreasing true rate, and degrading system performance. This work investigates the parameter selection for convex optimization (Ordinary Least Squares) for timing calibration. We test the correlation between commonly selected parameters and the experimentally measured coincidence time difference. Additionally, we test 127 nested models of a parameterized regression equation to identify the those which optimize MSE, BIC, and FWHM, respectively. In each of these models, the FWHM performance improved ~53%, though the value shifted from ~ 304 to 160 ns - far from ~ 10 ns FWHM CZT can achieve. The results point to the lack of a necessary parameter, such as trigger threshold level or temperature, or data which is too variable for the OLS optimization.
符合时间校准是正电子发射断层扫描（PET）成像的基础。电子设备、电缆长度以及诸如电荷漂移和深度依赖性等探测器物理特性会增加符合排序中测量到的时间差异，从而增加随机率、降低真率并降低系统性能。这项工作研究了用于时间校准的凸优化（普通最小二乘法）的参数选择。我们测试了常用参数与实验测量的符合时间差之间的相关性。此外，我们测试了一个参数化回归方程的127个嵌套模型，以分别识别那些优化均方误差（MSE）、贝叶斯信息准则（BIC）和半高宽（FWHM）的模型。在这些模型中的每一个中，FWHM性能提高了约53%，尽管该值从约304纳秒变为160纳秒——远未达到碲锌镉（CZT）探测器可实现的约10纳秒FWHM。结果表明缺少必要的参数，如触发阈值水平或温度，或者数据对于普通最小二乘法优化来说变化太大。
