PET prostate imaging with small planar detectors

PET imaging in the pelvis with dual planar detectors has been investigated. The scanner consisted of two 20 cm (transaxial) x 15 cm (axial) planar detectors with 3x3x10 mm3 LGSO elements mounted on a rotating gantry with adjustable detector radii. A 36 cm x 21 cm oval phantom, 40 cm long, with a centered 2.2 cm sphere and 1.3 cm neighboring spheres was used for tests with the spheres at 20:1, 10:1, and 5:1 concentrations relative to the background. Data were acquired with the detectors in a fixed anterior-posterior orientation as well as orbiting the body in limited and full arcs. Images were reconstructed with a fully 3D ML-EM algorithm (in most cases with limited angles.) For the fixed detector position, coronal views showed the larger sphere and the lateral small sphere for the 20:1 and 10:1 concentrations. Transaxial images showed many artifacts in the limited-angle cases. For the orbiting detector data, transaxial image quality improved as the number of angles increased. Significant artifacts were still present, however. The system works satisfactorily, even with limited views, for detection of high-uptake lesions. Further characterization of uptake requires fuller angular sampling.