A novel TOF-PET MRI detector for diagnosis and follow up of the prostate cancer

Abstract

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

Design, evaluation and comparison of endorectal coils for hybrid MR-PET imaging of the prostate

“…Similarly, from the perspective of PET imaging, conventional and external PET-ring geometries suffer from two significant limitations for prostate imaging-(a) severe attenuation and scatter of photons emitted from the centrally-located prostate, and (b) poor spatial resolution in PET images reconstructed from external ring scanners. Improvements in sensitivity, resolution and efficiency can be achieved by integrating an additional, high-resolution miniature PET detector located close to the prostate in conjunction with external standard resolution detectors (Huh et al 2006, Brzezinski et al 2014, Grkovski et al 2015, Garibaldi et al 2017. It has been demonstrated in various studies that this asymmetric PET configuration provides higher spatial resolution and magnifies the focused region-of-interest (ROI) (Huh et al 2006, Brzeziński et al 2014, Grkovski et al 2015.…”

“…In this work, we explore various endorectal-style coil designs suitable for use in MR-PET prostate imaging and assess their performance in finite integration technique (FIT) simulations and in MR measurements on a 3 T whole-body MRI scanner. We designed a shielded dummy PET insert which has nearly the same geometry as the prototype time-of-flight MR-PET prostate probe (Garibaldi et al 2017), and evaluated the quality of the images acquired using the selected coils by determining SNR as a function of the coil tilting angle against the B 0 direction which, evidently, is the most dominant factor influencing SNR. Although this has not been previously investigated, it is important since this coil will generally not be aligned orthogonally to B 0 due to the location and flexibility of the prostate.…”