Silicon photomultiplier performance tests in magnetic resonance pulsed fields

We are investigating the performance of silicon photomultipliers (SiPM) in a magnetic resonance imaging (MRI) environment with a view to exploiting the potential advantages in a combined positron emission tomography / magnetic resonance imaging (PET/MR) system. SiPMs are attractive for PET because they are compact, provide high gain at low bias voltage, and fast response times. Importantly for combined PET/MR applications, they offer performance comparable to that of the photomultiplier tube (PMT) and are insensitive to magnetic fields. To study the effect of MR static magnetic, pulsed gradient and radio-frequency fields on SiPM performance, we have acquired data whilst switching magnetic fields with the SiPM positioned in the MR system. The wide ´dynamic range´ of SiPMs facilitates their use in both low light level and PET applications; we have acquired ´single photoelectron´ and ²²Na energy spectra to demonstrate SiPM performance for this application. As expected, no degradation in inherent SiPM performance in an MR environment is observed.