ABSTRACT
The performance of the PENN-PET 240H scanner from UGM Medical Systems is tested and compared to the prototype PENN-PET scanner built at the University of Pennsylvania. The UGM PENN-PET scanner consists of six continuous position-sensitive NaI(Tl) detectors, which results in a 50 cm transverse field-of-view and a 12.8 cm axial field-of-view. The fine spatial sampling in the axial direction allows the data to be sorted into as many as 64 transverse planes, each 2 mm thick. A large axial acceptance angle, without interplane septa, results in a high-sensitivity and low-randoms fraction, with a low-scatter fraction due to the use of a narrow photopeak energy window. This work emphasizes those performance measurements that illustrate the special characteristics of a volume imaging scanner and how they change as the axial length is increased.
ABSTRACT
A volume imaging positron emission tomography (PET) scanner with a large acceptance angle, such as the PENN-PET, offers fine spatial sampling and resolution in three dimensions, and a high sensitivity because of the inclusion of all cross-plane rays. The signal-to-noise ratio (SNR) is used to evaluate image quality for different scanning conditions of the PENN-PET using an activated cylindrical phantom with cold spheres of various sizes. Raising the energy threshold to 400 keV improves the SNR by lowering the scatter fraction, though it also reduces the sensitivity. Increasing the axial acceptance angle from +/-1.3 degrees to +/-6.5 degrees improves the SNR by increasing the sensitivity, even with a two-dimensional reconstruction algorithm, which compromises spatial resolution in the axial direction for points at the edge of the radial field of view. Initial results show that a three-dimensional reconstruction offers an improved SNR over a two-dimensional reconstruction that does not use all cross-plane rays.