Development of a PET subsystem for next generation preclinical PET/EPR for studying tumor hypoxia

Previously, we reported a PET/EPR hybrid imaging system aiming to study and improve the efficacy of PET hypoxic tumor imaging using EPR oxygen imaging as a ground truth. Encouraged by the successful results with this exploratory system, we launched a PET subsystem development for the next generation PET/EPR scanner that has more suitable features for small animal imaging. The distinctive features of the new PET system include an ~4 times larger axial field-of-view (~106 mm) to allow whole body imaging of rodents, and a potentially sub-millimeter resolution by use of ~1 mm width LYSO scintillators. We devised a new signal multiplexing method to efficiently handle the significantly increased number of silicon photomultiplier outputs of this new system. The design of the detector module (DM) of the system has undergone several iterations. In the final design, the DM consists of 8 detector units (DU) on a 175mm x 20 mm printed circuit board, and each DU is made of a 12x12 LYSO crystals (1x1x10 mm
³
) coupled to a Hamamatsu 14161-3050HS-04 MPPC array (4x4 3.2 mm pitch). The new signal multiplexing method produces only 6 outputs for each DM: two outputs for coincidence time and DU identification, and four outputs for pixel crystal identification within a DU. Fourteen (14) DMs have been developed and successfully assembled into a PET ring whose inner and outer diameters are 60 mm and 115 mm, respectively. Evaluation tests were conducted by using a Brightonix BASP-10011 data acquisition board that provides high-throughput 16 12-bit 80 MSPS analog-to-digital converter (ADC) and 16 time-to-digital converter (TDC) channels. The initial results indicate that when using the BASP-10011 resulting DM performance properties were as good as those obtained by using the CAEN 5742 waveform sampler operating at 0.7 GSPS. At the meeting, we will present the development of the PET system employing the BASP-10011 DAQ and its performance measurement result.