Purpose: A prototype small animal PET is developed with several novel technologies to measure 3D gamma‐interaction positions and to substantially improve imaging performance. Methods: Each new detector has an 8×8 array of 1.95×1.95×30 mm̂3 LYSO scintillators, with each end optically connected to a solid‐state photo multiplier (SSPM) array through a light guide. This dual‐ended‐readout enables the depth‐of‐interaction (DOI) measurement. Each SSPM array has 16 SSPMs arranged in a 4x4 matrix. Each SSPM has active area about 3×3 mm̂2, with its output read by an ASIC electronics that directly converts analog signals to digital timing pulses which encode the interaction information for energy, timing, crystal of interaction, and DOI calculations. These digital pulses are transferred to and decoded by FPGA‐based TDC for coincident event selection and data acquisition. This independent readout of each SSPM and parallel signal process significantly improve signal‐to‐noise ratio and permit applying flexible data processing algorithms. The current prototype system consists of two rotating detector panels on a portable gantry, with 4 detectors linearly packed together in each panel to provide ∼16 mm axial and variable trans‐ axial FOV with adjustable panel‐to‐panel distance. List‐mode OSEM‐based image reconstruction with resolution modeling was implemented. Both Na‐ 22 point source and phantom were used to evaluate the system performance. Results: The measured energy, timing, spatial and DOI resolutions for each crystal were around 16%, 2.6 ns, 2.0 mm and 5.0 mm, respectively. The measured spatial resolutions with DOI were ∼1.7 mm across the entire FOV in all direction, while those without DOI were much worse and non‐uniform across the FOV, in the range predominately around 3.0 to 4.0 mm. In addition, images from a F‐18 hot‐rod phantom with DOI show significantly improved quality compared to those without DOI. Conclusions: DOI‐ measurable PET shows substantially improved image performance for a compact system. National Institute of Health. University of Texas MD Anderson Cancer Center.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging