Performance measurements for the GSO-based brain PET camera (G-PET)

Performance measurements on the high sensitivity, high resolution G-PET scanner have been completed. This scanner with a diameter of 42.0 cm and axial field-of-view of 25.6 cm was designed for brain receptor imaging, as well as regular clinical and blood perfusion studies in the brain. The transverse and axial resolution near the center are 4.0 and 5.0 mm (fwtm of 8.0 and 10.0 mm), respectively. At a radial offset of 10 cm these numbers deteriorate by less than 12%. The absolute sensitivity of this scanner measured with a 70 cm long line source is 4.57 cps/kBq. Scatter fraction measured with a line source in a 20 cm diameter by 19 cm long cylinder is 34.5%. For the same cylinder, the peak NEC rate is measured to be 75 kcps at an activity concentration of 12.95 kBq/ml (0.35 μCi/cc), while the peak true coincidence rate is 200 kcps. Image contrast measured with six spheres placed in the cylinder with an activity concentration ratio of 8:1 is 21-24% for the smallest sphere (diameter of 10 mm). However, due to the loss of counts near the sphere edges, the image contrast for this sphere is as high as 36% when using a region half the size of the sphere diameter and a 30 minutes acquisition time. We also show results from the 3D Hoffman brain phantom as well as ¹⁸F-FDG patient scans. These images illustrate the high visual quality of images acquired on the G-PET scanner.