Development of an MRI compatible digital SiPM based PET detector stack for simultaneous preclinical PET/MRI

We developed the world´s first MRI compatible PET detector based on digital silicon photomultiplier technology (digital SiPM). In this work we present our stack design and initial measurement results. The design of the detector stack considers all aspects of MRI compatibility and allows for the first time to operate digital SiPMs inside an MRI. The detector stack is composed of two layers. The top layer contains an 8 x 8 channel digital SiPM array with 4 mm pitch. The bottom layer hosts an FPGA for data acquisition and configuration as well as a circuit to control and monitor the bias voltage. We tested the detector stack in combination with an L YSO scintillator array containing 30 × 30 crystals with a pitch of 1 mm and 12 mm length. We build up highly integrated detector modules and tested the detector stack in a clinical 3 Tesla Philips Achieva MRI system. Our measurements indicate that the performance of the digital SiPM is unaffected by the MRI system even under extreme conditions. The presented detector stack is used to build up the Hyperion IID preclinical simultaneous PET/MRI insert for rodent studies within MEC and ForSaTum project.