Simulation and evaluation of a high resolution VIP PEM system with a dedicated LM-OSEM algorithm

Abstract

Over the last two decades there have been a growing number of designs for positron emission tomography (PET) cameras optimized to image the breast. These devices, commonly known as positron emission mammography (PEM) cameras allow much more spatial resolution by putting the photon detectors directly on the breast. PEM cameras have a compact geometry with a restricted field of view (FOV) thus exhibiting higher performance and lower cost than large whole body PET scanners. Typical PEM designs are based on scintillators such as bismuth germanate (BGO), lutetium oxorthosilicate (LSO) or lutetium yttrium orthosicilate (LYSO), and characterized by large parallax error due to deficiency of the depth of interaction (DOI) information from crystals. In the case of parallel geometry PEM, large parallax error results in poor image resolution along the vertical axis. In the framework of the Voxel Imaging PET (VIP) pathfinder project, we propose a high resolution PEM scanner based on pixelated solid-state CdTe detectors. The pixel PEM device with a millimeter-size pixel pitch provides an excellent spatial resolution in all directions 8 times better than standard commercial devices with a point spread function (PSF) of 1 mm full width at half maximum (FWHM) and excellent energy resolution of down to 1.6% FWHM at 511 keV photons at room temperature. The system is capable to detect down to 1 mm diameter hot spheres in warm background.