Data Acquisition for a Preclinical MR Compatible PET Insert Using the OpenPET Platform

OpenPET has recently been developed as a modular, flexible data acquisition (DAQ) platform for nuclear imaging applications. We present a description of the system architecture and DAQ implementation using OpenPET for a small animal positron emission tomography (PET) insert designed for hybrid PET/magnetic resonance imaging (MRI) at 7T. The PET insert consists of 16 silicon photomultiplier-based detector modules, creating a total of 64 analog channels. The OpenPET system used consisted of four 16 channel detector boards connected to one support board (SB), in turn connected to a Host PC via a USB2.0 interface. Both detector and SBs contain field-programmable gate arrays, allowing customized firmware for both. The initial OpenPET firmware release allowed data capture in oscilloscope mode only, limiting data collection to a system single events rate of 18.8 kcps. Customized firmware changes were implemented in four revisions, resulting in a final version using an 8 byte data packet and supporting a system single events rate of > 4.5 Mcps. Noise equivalent count rate (NECR) results are presented for each firmware revision, showing improvement from peak NECR of 1.0 kcps @ 0.6 MBq to 19.5 kcps @ 15.3 MBq. The final version of the firmware enables its routine use in small animal PET/MRI.