PET Performance of the GEMINI TF: A Time-of-flight PET/CT Scanner

We present a summary of the performance of a new-generation of commercial PET/CT scanners with time-of-flight (TOF) capability. The Philips GEMINI TF uses 28,336 lutetium-yttrium oxyorthosilicate detector elements, 4 times 4 times 22 mm³, arranged in 28 modules that define a 90 cm diameter "cylinder". Our evaluation was done in terms of NEMA NU 2-2001 methodology supplemented by additional phantom scans designed to assess the capability of a fast, TOF scanner. Transverse resolution was 4.8 and 5.2 mm FWHM and axial resolution was 4.4 and 5.3 mm at 1 and 10 cm, respectively. The sensitivity was 7.25 and 7.56 cps/kBq at center and at 10 cm. Peak noise-equivalent count rate was 110 kcps obtained at 17.4 kBq/mL. Hot-sphere contrast recovery was 31.4, 49.7, 60.3, and 68.9% for 10, 13, 17 and 22 mm spheres at a 4 to 1 concentration ratio. Cold-sphere contrast recovery was 68.1 and 72.3% for 28 and 37 mm spheres. These contrast recoveries were independent of incremental translations in the axial direction. Overall, the scanner demonstrated high spatial resolution, sensitivity, and count rate performance. This translates into good visual quality for brain imaging as demonstrated using clinical and phantom images.