Li Hongdi, Wang Chao, An Shaohui, Lu Xingyu, Dong Yun, Liu Shitao, Baghaei Hossain, Zhang Yuxuan, Ramirez Rocio, Wong Wai-Hoi
H. Baghaei, Y. Zhang, R. Ramirez and W.-H. Wong are with The University of Texas MD Anderson Cancer Center, Houston, Texas, USA. H. Li, S. An, C. Wang and S. Liu were with The University of Texas MD Anderson Cancer Center, Houston, Texas, USA; they are now with UIH, Shanghai, China. X. Lu and Y. Dong are with UIH, Shanghai, China.
IEEE Trans Nucl Sci. 2015 Jun;62(3):799-804. doi: 10.1109/TNS.2015.2430751. Epub 2015 Jun 3.
Accurate PET system timing alignment minimizes the coincidence time window and therefore reduces random events and improves image quality. It is also critical for time-of-flight (TOF) image reconstruction. Here, we use a thin annular cylinder (shell) phantom filled with a radioactive source and located axially and centrally in a PET camera for the timing alignment of a TOF PET system. This timing alignment method involves measuring the time differences between the selected coincidence detector pairs, calibrating the differential and integral nonlinearity of the time-to-digital converter (TDC) with the same raw data and deriving the intrinsic time biases for each detector using an iterative algorithm. The raw time bias for each detector is downloaded to the front-end electronics and the residual fine time bias can be applied during the TOF list-mode reconstruction. Our results showed that a timing alignment accuracy of better than ±25 ps can be achieved, and a preliminary timing resolution of 473 ps (full width at half maximum) was measured in our prototype TOF PET/CT system.
精确的正电子发射断层扫描（PET）系统时间校准可将符合时间窗最小化，从而减少随机事件并提高图像质量。这对于飞行时间（TOF）图像重建也至关重要。在此，我们使用一个填充有放射性源的薄环形圆柱体（外壳）模体，该模体轴向且位于正电子发射断层扫描相机的中心，用于TOF PET系统的时间校准。这种时间校准方法包括测量所选符合探测器对之间的时间差，使用相同的原始数据校准时间数字转换器（TDC）的微分和积分非线性，并使用迭代算法推导每个探测器的固有时间偏差。每个探测器的原始时间偏差被下载到前端电子设备，并且在TOF列表模式重建期间可以应用残余的精细时间偏差。我们的结果表明，可以实现优于±25皮秒的时间校准精度，并且在我们的原型TOF PET/CT系统中测量到初步的时间分辨率为473皮秒（半高宽）。
