Time and DOI resolution measurements of minidetectors for a PET-TOF prostate probe

Prostate cancer (PC) is the most common disease in western countries and a leading cause of cancer death. Powerful techniques and instruments for diagnosis such as CT, MRI, PET/SPECT suffer from limited spatial resolution, sensitivity and/or specificity. Dedicated detectors and techniques are needed. For this reason a new INFN research project (TOPEM) started with the goal of designing, building and testing an endorectal PET-TOF probe compatible with MRI, to be used in coincidence with an external dedicated detector and/or a standard PET ring. Multimodality imaging can play a significant role, merging anatomical and functional details coming from simultaneous PET and MRI (and MRS) scans. Good spatial resolution and Depth Of Interaction (DOI) resolution are needed in order to guarantee high performance in image reconstruction. Here the main focus is a characterization of the elementary detector unit, in terms of energy, timing and DOI resolution. Exploiting the TOF capability allows an increase in the SNR/NECR and also permits elimination of bladder background. Silicon Photo Multipliers (SiPM) are the obvious choice as photodetectors to be coupled with small finger scintillators. Good preliminary results have been obtained both on DOI and Timing resolutions.