Design and development of novel and practical PET detectors for advanced imaging applications

New DOI-measurable PET detectors have been designed, developed and evaluated with advanced silicon photomultiplier (SiPM) and readout technologies. The detector consists of an 8×8 array of 1.5×1.5×20 or 1.5×1.5×30 mm³ LYSO scintillators which is optically coupled to a 4×4 array of 3×3 mm² SiPM array at each crystal array end through a 2 mm thick optical plate. Scintillator surfaces, reflectors and coupling were designed and fabricated to reserve the air-gap to achieve high depth-of-interaction (DOI) resolution and other detection performance. The insensitive edges around each detector is less than 0.2 mm, making it practical to seamlessly tile detectors together to assemble a large size detector panel for developing a PET system. A 16-ch ASIC based PCB readout electronics was developed to solve the challenging SiPM array readout problem. Each compact PCB contains 4 ASIC chips and one detector-level FPGA, with analog signal being inputted from each SiPM array through a flexible printed circuit cable, converted to digital timing pulses, processed online by FPGA to record interaction information (energy, timing, and position), and transferred through a fast LVDS connection to system FPGA for event selection and data acquisition. Initial measurements showed excellent crystal identification with all crystals were clearly separated from each other in a flood source image, with resolutions of energy, timing and DOI were around 17%, 2.7 ns and 2.0 mm (mean value), respectively. Overall, comparing to the previous prototype DOI detectors we developed, the new detector is simplified in design without using complicated light guide yet with significantly improved DOI resolution (from ~5 to ~2 mm), more compact packaging for making a large size flat-panel detector, and more integrated and fast readout electronics. The new detector and readout is expected leading to an advanced PET with leapfrog imaging performance improvement.