Performance Study of the Whole-Body, Multilayer Positron Computed Tomograph. - PCTW-II -

A whole body Positron CT has been developed. The system has a gantry consisting of 4 detector-rings and provides 7 slice-images simultaneously. The continuously rotating scan method is employed in this system. Each detector-ring consists of 192 gamma-ray detectors using BGO scintillation crystals (12×24×24 mm). A dual rectangular photomultiplier tube has been developed to increase the detector packing factor and to improve detector performance. Spatial resolution for reconstructed image is equal to 7.6 mm FWHM at the center of FOV. In a 20 cm-dia. cylindrical phantom, sensitivities are 33.9 kcps/(μCi/cc) and 52.0 kcps/(μCi/cc) in the in-plane and cross-plane, respectively. These include scattered coincidence events. By using the "projection background cutting method", scatter coincidence counts are estimated as 21.6 % and 23.3 % of the total coincidence counts in the in-plane and cross-plane, respectively.