Development of a simultaneous PET/Ultrasound imaging system with near real-time reconstruction capability for point-of-care applications

In this project, we propose to investigate the feasibility of a novel technology that will bring both PET and ultrasound imaging to the patient bedside to support point-ofcare(PoC) molecular imaging applications. The system will comprise of a panel detector placed behind the patient and a maneuverable probe that consists of a PET detector and an ultrasound transducer. The probe can be moved around a region-of-interest in the patients' body to collect both PET coincidence events and ultrasound signals. The location of the maneuverable probe relative to the back panel detectors is tracked in real-time as coincidence events are recorded. These events are used for list-mode image reconstruction in near realtime to provide visual feedback to the operator who can interactively control the probe to collect additional counts from the most critical locations and/or angles in order to dynamically optimize the image quality. To prove the concept, we developed a prototype that consists of a single channel SiPM(SensL FB30035) coupled to a 3.0 \times3.0\times20.0 mm^{ 3} LSO crystal as the back detector. The maneuverable probe consists of an ultrasound transducer and a PMT(Hamamatsu H8500) coupled to 48\times48 LSO crystals of 1.0\times1.0\times10.0 mm^{ 3} each. A robotic arm allows us to position the probe at arbitrary locations. Coincidence timing resolution of 470 ps FWHM has been achieved. We have implemented a GPUbased fully 3D list-mode Time-Of-Flight image reconstruction algorithm that can model the dynamically changing geometry of this PoC system. In this study, we report preliminary results from both actual experiments using this prototype and simulations using GATE. Detector modules with larger sensitive volume will be fabricated and tested to perform more imaging studies in order to explore the capability of this class of system.