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

This paper describes the novel geometry and initial results of a singles tr ansmission system for PETRRA, a whole-body PET camera with rotating planar detectors. Special frames mounted on to the front face of each detector sup port a collimated Cs-137 source in various positions. Cone-beam transmissio n data are acquired during 360 degrees gantry rotation and images are recon structed using the Feldkamp algorithm. The radial transaxial 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 posit ion are combined to form a complete dataset. The axial FOV depends on the a mount of collimation in the axial direction and could be increased by horiz ontal couch motion. Preliminary singles transmission images of both real an d 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 plan ar detectors.