Conti Maurizio, Bendriem Bernard, Casey Mike, Chen Mu, Kehren Frank, Michel Christian, Panin Vladimir
CPS Innovations, 810 Innovation Drive, Knoxville, TN 37919, USA.
Phys Med Biol. 2005 Oct 7;50(19):4507-26. doi: 10.1088/0031-9155/50/19/006. Epub 2005 Sep 13.
Time-of-flight (TOF) positron emission tomography (PET) was studied and preliminarily developed in the 1980s, but the lack of a scintillator able to deliver at the same time proper time resolution and stopping power has prevented this technique from becoming widespread and commercially available. With the introduction of LSO in PET, TOF is now a feasible option. TOF reconstruction has been implemented in the CPS Hi-Rez PET scanner, both with 2D filtered-back-projection (FBP2D) and 3D ordered subset expectation maximization (OSEM3D). A new procedure has been introduced in the time alignment to compensate for the limited digital time resolution of the present electronics. A preliminary version of scatter correction for TOF has been devised and is presented. The measured time resolution of 1.2 ns (FWHM) allowed for a signal-to-noise ratio increase of about 50% in phantoms of about 40 cm transaxial size, or a gain larger than 2 in noise equivalent counts (NEC). TOF reconstruction has shown the expected improvement in SNR, both in simulation and experimental data. First experimental results show two improvements of TOF reconstruction over conventional (non-TOF) reconstruction: a lower noise level and a better capability to resolve structures deep inside large objects.
飞行时间（TOF）正电子发射断层扫描（PET）在20世纪80年代得到了研究并初步发展，但由于缺乏一种能够同时提供合适的时间分辨率和阻止本领的闪烁体，这项技术未能得到广泛应用和商业化。随着LSO引入PET，TOF现在成为了一种可行的选择。TOF重建已在CPS Hi-Rez PET扫描仪中实现，采用了二维滤波反投影（FBP2D）和三维有序子集期望最大化（OSEM3D）方法。在时间校准中引入了一种新程序，以补偿当前电子设备有限的数字时间分辨率。已经设计并展示了一种TOF散射校正的初步版本。在横向尺寸约为40 cm的体模中，测量得到的1.2 ns（半高宽）时间分辨率使信噪比提高了约50%，或噪声等效计数（NEC）增益大于2。TOF重建在模拟和实验数据中均显示出信噪比的预期改善。首次实验结果表明，TOF重建相对于传统（非TOF）重建有两个改进：更低的噪声水平和更好地分辨大物体内部深处结构的能力。
