Singles transmission scanning for rotating positron cameras with large-area detectors

This paper describes the novel geometry and initial results of a singles transmission system for PETRRA, a whole-body PET camera with 400×600 mm BaF₂-TMAE detectors. Special frames mounted on to the front face of each detector support a collimated Cs-137 source in various positions. Cone-beam transmission data are acquired during 360° gantry rotation and images are reconstructed using the Feldkamp algorithm. The radial field of view (FOV) can be increased by using two source positions displaced either side of the central position. The truncated data acquired from each source position are combined to form a complete dataset. The axial FOV depends on the amount of collimation in the axial direction and could be increased by horizontal couch motion. Preliminary singles transmission images of both real and simulated thorax phantoms have been obtained. The effects of varying the linear sampling interval, the number of projections and the axial FOV have been studied. The singles transmission scanning system, described here and developed for PETRRA, could be applied to other PET cameras with large planar detectors