Performance evaluation of a new high-sensitivity time-of-flight clinical PET/CT system

Li Huo,Haiqun Xing,Hui Zhang,Tong Wang,Jiantao Ba,Wenjia Zhu,Fang Li,Nan Li,Heyu Wu

doi:10.1186/s40658-018-0229-4

Abstract

BackgroundPoleStar m660 is a newly developed clinical PET/CT system with time-of-flight (TOF) capability. The aim of this study is to characterize the performance of the new system. Spatial resolution, sensitivity, scatter fraction, and noise equivalent count rate (NECR) were measured on the scanner according to the NEMA NU 2-2012 protocol. The timing resolution was measured using a rotating line source that orbited around the center of field of view (CFOV) at a radius of 20 cm. The image quality phantom was also imaged to quantify the percent contrast, percent background variability, and residual error. The impacts of data acquisition time and bed overlap on the PET image quality were also evaluated using phantom and patient studies.ResultsThe transverse (axial) spatial resolutions were 3.59 mm (3.67), 4.08 mm (4.65), and 5.32 mm (6.48) full width at half maximum (FWHM) at 1 cm, 10 cm, and 20 cm, respectively, off the CFOV. The measured sensitivity was 10.7 cps/kBq at the CFOV and 10.4 cps/kBq at 10 cm off the CFOV. The peak NECR was 216.7 kcps at an activity concentration of 29.1 kBq/ml, and the scatter fraction was 38.2%. An average of 435 ps FWHM timing resolution was measured. For the image quality phantom, the contrast recovery ratios ranged from 33.9 to 76.4%, while the background variability ranged from 4.7 to 2.0%. In the preliminary clinical study, no noticeable difference in the image quality was observed when the scan time for the whole body and brain was reduced to 1 min/bed and 3 min, respectively. The tested 21% bed overlap showed no significant difference in the image quality compared with the default 38% bed overlap setting.ConclusionsThe physical performances of the PoleStar m660 PET/CT system showed good sensitivity, count rate performance, and timing resolution. The improved performance could help to reduce the acquisition time and bed overlap in the clinical application without detectable compromise in the image quality.

Highlights

PoleStar m660 is a newly developed clinical positron emission tomography (PET)/Computed tomography (CT) system with timeof-flight (TOF) capability
Silicon photomultiplier (SiPM) are promising for improved timing resolution, high-performance Photomultiplier tube (PMT)-based PET detectors with optimized design can achieve a significant improvement in timing resolution compared with the existing commercial systems [12, 17]
Scanner A PoleStar m660 PET/CT scanner was recently installed at Peking Union Medical College Hospital (PUMCH) that consisted of a high-speed 64-slice helical CT subsystem and a PMT-based whole-body TOF-PET subsystem

Summary

Introduction

PoleStar m660 is a newly developed clinical PET/CT system with timeof-flight (TOF) capability. The impacts of data acquisition time and bed overlap on the PET image quality were evaluated using phantom and patient studies. PoleStar m660 (SinoUnion Healthcare Inc., Beijing, China) is a newly introduced PMT-based high-performance PET/CT scanner, and an initial evaluation of a prototype system has been reported by Huo et al [18] showing a system timing resolution of 434 ps FWHM. A reduction in the overlap will inevitably cause non-uniformity in the axial system sensitivity; in practice, the impacts on the image quality are subject to evaluation In both phantom and patient scans in this study, we found no significant degradation in image quality with smaller bed overlaps down to 21% (25 overlapped planes of a total of 117 planes). The reduction of bed overlaps from 45 planes to 25 planes could lead to one bed position reduction for the same scan range in a typical whole-body scan, and lead to improved throughput in routine clinical practices

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