Various types of cancer remain the second leading cause of death in the world. As a consequence, the detection of these tumors has a vital importance. Optoacoustic imaging (OA), a novel imaging technique, offers high contrast and resolution to detect them by measuring the pressure waves generated by tissues exposed to optical energy. Several algorithms, based on Back Projection (BP) techniques, have been suggested to process OA images in conjunction with signal filtering. In this paper, we compare several BP techniques in combination with different classes of filtering. We apply these techniques first directly to a numerical generated sample image and then to the laser-digitalized image of a tissue phantom, obtaining in both cases the best results in resolution and contrast for a wavelet-based filter.