SPECT scanners using multi-pinhole collimators benefit from modular detectors having a high spatial resolution. Such detectors can be placed closer to the collimator and perpendicular to the pinhole axis (thereby limiting DOI spatial resolution degradation). Current clinical gamma ray cameras have a large area and a poor spatial resolution. This proceeding describes the architecture of SPECTatress, a modular high resolution gamma camera. A brief summary of the electronics and results obtained with the center-of-gravity positioning algorithm have been presented previously (Imaging 2010 conference, Stockholm). Here we present a detailed overview of the pre-amplifiers and the algorithms used in the FPGA. Results using a GPU accelerated MLE algorithm are shown. This measurement indicates a spatial resolution of 1.1mm FWHM in the center of the detector and an energy resolution of 9% FWHM.