Background: Virtual-Pinhole PET is one of the methods to achieve high-resolution animal PET image

which suggests to integrate high-resolution detectors into existing PET scanner. Purpose: To validate the Virtual-Pinhole PET concept

we aimed to improve the image resolution of PET system to sub-millimeter range. Methods: Monte Carlo simulation code GATE (Geant4 Application for Emission Tomography) was applied to study the imaging resolution of a full ring Micro Insert system integrated with the SIEMENS MicroPET Focus-220. The track of gamma ray in both Insert detectors and PET Scanner detectors of Focus-220 was obtained simultaneously in one data taken. Three types of coincidence detections for gamma ray interactions in PET Scanner detectors and Insert detectors were selected

which represented coincidence detections between PET Scanner and PET Scanner (SS)

coincidence detections between PET Scanner and Insert (IS)

and coincidence detections between Insert and Insert (II). The filtered back-projection (FBP) algorithm was employed to reconstruct the PET images of Na-22 point sources. Results: The image resolutions of GATE simulated data show 1.0?1.5 mm

0.9?1.1 mm

and 0.5?0.9 mm at FWHM for SS

IS and II

respectively. These simulated results are kept good agreements with the experimental results of Micro Insert system obtained at Washington University. Conclusion: The image resolution of animal PET can be improved to sub-millimeter range by using Micro Insert PET system. Abstract