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To develop a multi-radionuclide imaging system with a flexible and compact structure that has a potential for breast and other applications, and to evaluate its performances under both positron emission tomography and single photon emission imaging conditions. The plane detector was composed of 5 × 6 blocks with an effective detection area of 168.6 mm × 202.4 mm. Each block consisted of a 16 × 16 LYSO array. The pixel size is 1.9 mm × 1.9 mm × 15 mm. An 8 × 8 silicon photomultiplier (SiPM) array with SensL’s C-30035 sensors was coupled to the LYSO array, separated by a 1.5-mm-thick glass. To minimize the influence of temperature on the detector, the active part of the front-end electronics was kept away from SiPMs. Self-designed data acquisition system and reconstruction software were utilized to evaluate the performances of the whole system. All the blocks had excellent pixels identification. An average energy resolution of 11.39% for 511 keV and 21.37% for 140 keV was obtained. In the PET mode, the best spatial resolution was better than 2 mm and the system sensitivity reached up to 11.05% at 60 mm distance. In the single photon emission imaging mode, a spatial resolution better than 3 mm was obtained. The results indicated that the system has a good overall performance and can be used in breast imaging and other general PET applications. It also has the potential to be used for single photon emission imaging. In pursuit of a better spatial resolution of cross-plane, PSF and DOI technology will be developed in the next work. For specific applications, further improvement of the detector system such as performance evaluation with phantoms will be carried out.

A method has been developed to establish the crystal position look-up table for positron emission tomography with block detectors. It is based on the principle that the counts in crystal position histogram obey the Gaussian mixture model (GMM). This method has taken full consideration of the characteristics of the GMM and the detector itself. The experimental results have proved that it is simple, reliable, and universal.

PET/MR is a new multi-modality imaging system which provide both structural and functional information with good soft tissue imaging ability and no ionizing radiation. In recent years, PET/MR is under major progress because of the development of silicon photomultipliers (SiPM). The goal of this study is to develop a MRI compatible PET insert based on SiPM and LYSO scintillator. The PET system was constituted by the detector ring, electronics and software. The detector ring consists of 16 detector module. The inner diameter of the ring was 151 mm, the external diameter was 216 mm, which was big enough for small animal research, e.g. rat, rabbit and tupaia. The sensor of each module was 2*2 SensL SPMArraySL, coupled with an array of 14 x 14 LYSO crystals, each crystal measuring 2 mm x 2 mm 10 mm. The detector was encapsulated in a copper box for light and magnetic shielding. Resister charge multiplexing circuit was used in the front end electronics. Each detector output 8X and 8Y position signals. One summed timing signal was extracted from the common cathode of all 64 channels. All these signals were transmitted to digital electronic board by a 3 m long coaxial cable from inside of the MR to the outside. Each digital electronic board handled 8 detector modules based on FPGA to obtain the timing, position and energy information of a single event. And then these single events were sent to the coincidence processing board to produce coincidence packets which are prepared for further processing. A 0.2mCi 68Ge line source was used to do the preliminary imaging test. The image was reconstructed by 3D-OSEM algorithm. The initial result proved the system to be feasible as a PET. FDG phantom imaging and simultaneous PET/MR imaging are in progress.