  We are investigating a prototype virtual pinhole positron emission tomography
(VP-PET) system for small animal imaging applications. The PET detector modules
were made up of 1.3 mm lutetium-yttrium oxyorthosilicate (LYSO) arrays, and the
insert detectors consists of 0.6 mm pixelated Cadmium Zinc Telluride (CdZnTe).
To validate the imaging experiment, we conducted a Monte Carlo simulation for
the VP-PET system in Geant4 Application for Emission Tomography (GATE). For a
point source of Na-22 with 0.5 mm diameter, the filtered back-projection (FBP)
algorithm reconstructed PET image shows a resolution of 0.7 mm
full-width-at-half-maximum (FWHM). The system sensitivity is 0.46 cps/kBq at
the center of field view (CFOV) of the PET system with a source activity of
0.925 MBq and an energy resolution of 350-650 keV. A rod source phantom and a
Derenzo phantom with F-18 were also simulated to investigate the PET imaging
capability. GATE simulation indicated that two point sources with 0.5 mm
diameter 2 mm apart could be clearly separated using 0.6 mm pixelated CdZnTe
detectors as insert devices in a VP-PET system.
