Novel electro-optically coupled MR-compatible PET detectors

A new magnetic resonance(MR) compatible PET detector design is being developed that uses electro-optical coupling to bring the amplitude and arrival time information of high speed scintillation pulses out of an MR system. The electro-optical coupling consists of a magnetically insensitive photodetector connected to a non-magnetic vertical cavity surface emitting laser (VCSEL) diode. This scheme essentially acts as an optical wire. When compared to signal transmission over standard co-axial cables, electro-optical coupling will have little influence on a MR system because the optical fibers are not conductive. A single 3 mm × 3 mm × 20 mm LYSO crystal coupled to a SENSL SPMArray 3035G16 was placed in coincidence with a 4 mm × 4 mm × 4 mm LSO crystal coupled to a R9779-20 Hamamatsu PMT with and without non-magnetic VCSEL laser coupling. No change was measured in energy resolution of 15.6 +/− 0.4 % with electro-optical coupling versus coax-coupling energy resolution 15.5 +/− 0.4%. Also, no change in coincidence time resolution was measured between electro-optical coupling with 1.30 +/− 0.01 ns FWHM versus coax at 1.32 +/− 0.02 ns FWHM. High speed analog modulation using the VCSEL laser was successful and paves the way for a MR compatible PET block detector that has a significantly reduced electronic footprint than a standard MR compatible PET detector. This may provide the way to create a large axial FOV whole body clinical PET system that will have very little influence on a whole body clinical MR system performance.