Multiple point sources collimated with transaxial septa for high energy gamma camera transmission scanning

The axial imaging properties of the transmission scanning system for attenu ation correction of gamma camera coincidence imaging are evaluated. This sy stem uses multiple Cs-137 point sources collimated by transaxial septa alre ady in place for emission imaging. Both the spacing and the degree of colli mation of the sources can be controlled. Axial image quality was evaluated with three levels of collimation (4 mm, 7 mm, and 10 mm slot, all 6 cm deep ) and two source spacing distances (1.3 cm and 2.6 cm). A multiple disk pha ntom with adjustable spacing was imaged, as well as a thorax phantom. The 4 mm collimation and 1.3 cm source spacing provided well-resolved images of the disks with 2.9 cm center-to-center spacing. The best collimation/spacin g combinations come with substantial overlap of flux from difference source s in the detector. Axial resolution can be adequately controlled with extra lead collimation of the sources.