  Prostate cancer is the most common disease in men and the second leading
cause of death from cancer. Generic large imaging instruments used in cancer
diagnosis have sensitivity, spatial resolution, and contrast inadequate for the
task of imaging details of a small organ such as the prostate. In addition,
multimodality imaging can play a significant role merging anatomical and
functional details coming from simultaneous PET and MRI. Indeed,
multi-parametric PET/MRI was demonstrated to improve diagnosis, but it suffers
from too many false positives. In order to address the above limits of the
current techniques, we have proposed, built and tested, thanks to the TOPEM
project funded by Italian National Institute of Nuclear Phisics a prototype of
an endorectal PET-TOF/MRI probe. In the applied magnification PET geometry,
performance is dominated by a high-resolution detector placed closer to the
source. The expected spatial resolution in the selected geometry is about 1.5
mm FWHM and efficiency a factor of 2 with respect to what obtained with the
conventional PET scanner. In our experimental studies, we have obtained timing
resolution of ~ 320 ps FWHM and at the same time Depth of Interaction (DOI)
resolution of under 1 mm. Tests also showed that mutual adverse PET-MR effects
are minimal. In addition, the matching endorectal RF coil was designed, built
and tested. In the next planned studies, we expect that benefiting from the
further progress in scintillator crystal surface treatment, in SiPM technology
and associated electronics would allow us to significantly improve TOF
resolution
