In this study, we designed a depth of interaction (DOI) detector module for use in a magnetic resonance imaging (MRI) system. The detector uses a semiconductor photosensor that is unaffected by a magnetic field. The
detector module consists of two layers of a crystal array that have different l ight sharing characteristics. To verify the performance of the detector module, simulations of the optical photon transport in the crystal array
were performed with a DETECT2000 tool. Various combinations of the parameters, such as the reflector used and the treatment of crystal surfaces, were simulated and the characteristics were evaluated through a reconstructed flood image. In certain combinations of the simulation conditions, all of the crystal pixels could be identified along all directions. Thus, the proposed DOI detector module could extract the three-dimensional
gamma ray interaction position from the two-dimensional flood image.