Characterization of the Vereos Digital Photon Counting PET System

Objectives To characterize the first fully integrated digital detector PET/CT system.

Methods We previously reported basic performance of a prototype digital PET detector [1]. Here we present original data from a next generation time-of-flight (TOF) digital PET system (Vereos PET/CT, Philips Healthcare). Performance was evaluated with NEMA NU 2-2012. Timing and energy resolution were monitored with built-in QC procedures. Sensitivity measurements were performed over the clinically-relevant count rate range. Timing, energy and spatial resolution were characterized across the full clinical count rate range using point and line source methods [2-3].

Results 316 ps timing resolution and 11.1 % energy resolution were achieved. The TOF sensitivity gain for a 20 cm object was 4.2. NEMA results on the system follow. Spatial resolution [mm FWHM] ranged from 4.11 and 3.96 at 1 cm to 5.79 and 6.20 at 20 cm, transverse and axial, respectively. Sensitivity was 5.7 kcps/MBq with TOF effective sensitivity of 24.1 kcps/MBq. 171 kcps peak NECR and > 680 kcps peak true rate were obtained at 50 kBq/mL, with 30 % scatter fraction. NEMA image quality tests demonstrated hot sphere contrast ranging from 62 % (10 mm) to 88 % (22 mm), cold sphere contrasts of 86 % (28 mm) and 89 % (37 mm) and excellent image uniformity. Measurements of timing, energy, and spatial resolution stability a wide count rate range, performed on factory systems, demonstrated timing resolution stable within 5% up to singles rates observed at peak NECR. Energy and spatial resolutions were stable within 1 %. Clinical sensitivity measurements performed on factory systems showed maximum dead time effects of 13 % at singles rates seen at 30 MBq/mL in count loss measurements.

Conclusions The Vereos PET/CT with digital photon counting technology represents the first fully-digital PET scanner. System characteristics include high resolution, stable performance over count rate and time, and excellent image quality.

Research Support This study was sponsored by Philips Healthcare. The authors are employees of, or have a scientific cooperation contract with, Philips Healthcare.