Development and evaluation of a new high-TOF-resolution all-digital brain PET system
Lei Fang, Bo Zhang, Bingxuan Li, Xiangsong Zhang, Xiaoyun Zhou, Jigang Yang, Ang Li, Xinchong Shi, Yuqing Liu, Michael C. Kreißl, N. d’Ascenzo, Peng Xiao, Qingguo Xie
Abstract
Abstract Objective. Time-of-flight (TOF) capability and high sensitivity are essential for brain-dedicated positron emission tomography (PET) imaging, as they improve the contrast and the signal-to-noise ratio (SNR) enabling a precise localization of functional mechanisms in the different brain regions. Approach. We present a new brain PET system with transverse and axial field-of-view (FOV) of 320 mm and 255 mm, respectively. The system head is an array of 6 × 6 detection elements, each consisting of a 3.9 × 3.9 × 20 mm 3 lutetium–yttrium oxyorthosilicate crystal coupled with a 3.93 × 3.93 mm 2 SiPM. The SiPMs analog signals are individually digitized using the multi-voltage threshold (MVT) technology, employing a 1:1:1 coupling configuration. Main results. The brain PET system exhibits a TOF resolution of 249 ps at 5.3 kBq ml −1 , an average sensitivity of 22.1 cps kBq −1 , and a noise equivalent count rate (NECR) peak of 150.9 kcps at 8.36 kBq ml −1 . Furthermore, the mini-Derenzo phantom study demonstrated the system’s ability to distinguish rods with a diameter of 2.0 mm. Moreover, incorporating the TOF reconstruction algorithm in an image quality phantom study optimizes the background variability, resulting in reductions ranging from 44% (37 mm) to 75% (10 mm) with comparable contrast. In the human brain imaging study, the SNR improved by a factor of 1.7 with the inclusion of TOF, increasing from 27.07 to 46.05. Time-dynamic human brain imaging was performed, showing the distinctive traits of cortex and thalamus uptake, as well as of the arterial and venous flow with 2 s per time frame. Significance. The system exhibited a good TOF capability, which is coupled with the high sensitivity and count rate performance based on the MVT digital sampling technique. The developed TOF-enabled brain PET system opens the possibility of precise kinetic brain PET imaging, towards new quantitative predictive brain diagnostics.