Basic imaging performance characteristics of a variable field of view PET camera using quadrant sharing detector design

A prototype PET camera has been developed to test the engineering feasibility and application utility of two concepts: (a) a low cost, high resolution detector where each PMT decodes the detection positions for four crystal blocks, and (b) a cheaper variable detector ring which forms a densely-packed ring with a small field of view (FOV) for high sensitivity study of the breast/brain/animals, or a less-packed ring with a large FOV for the whole-body. Design parameters are: (a) BGO detector pitch=2.65-mm transaxial and 2.75 mm axial, (b) PMT diameter=19 mm, (c) 27 image slices 1.4 mm apart, (d) transaxial FOV=32 to 55 cm, (e) axial FOV=3.85 cm, and (f) maximum detector rotation 45°. The basic imaging performance has been measured for the 32 and 55 cm FOV. For the 32 cm FOV, the transaxial average resolution at 0, 5, 10 cm were found to be 2.8, 3.1, 4.0 mm, respectively, while for the 55 cm FOV, the average resolutions were 2.9, 3.1, 3.6 mm. For a 22.2-cm phantom, the detection sensitivity was 82.3 kcps/μCi/cc at the smallest FOV and 16.3 kcps/μCi/cc for the whole body configuration