Empirical effects of angular sampling and background content on image quality in dedicated breast SPECT

This study investigates the effects of varying the azimuthal and polar sampling of the acquisition trajectory with the dedicated breast SPECT imaging system developed in our lab. In addition, the frequency quality (density and distribution) of the background is considered. The SPECT system consists of a 16 times 20 cm² CZT gamma camera with 6.7% FWHM energy resolution at 140 keV, which can accommodate fully 3D simple or complex trajectories about a pendant, uncompressed breast. Trajectories used in these studies are vertical axis of rotation, tilted parallel beam and sine wave projected onto a hemisphere. Various geometric and anthropomorphic phantoms containing lesions are imaged to evaluate the effects of sampling and background distributions on signal (lesion) visualization. In general, sufficient counting statistics limit the quality of the image and thus an optimization between the number of projections and the number of detected events is being explored. Reconstructed images of anthropomorphic breast phantoms did not appear to have distortion artifacts in regions inside the breast phantom containing a variety of spatial frequencies, but distortions did appear in some instances in the high frequency outer edge of the phantom in reconstructed images.