Nearest-neighbor rebinning in clinical PET: fast and accurate on-line 3-D LOR-to-bin mapping on the HRRT with the new PDR card

A fundamental requirement for 3D PET is the proper positioning of each coincidence event into the 3D projection data space. When this positioning calculation - i.e. nearest-neighbor LOR-to-projection-bin mapping or "rebinning" - is performed rapidly, higher patient throughput results. High-sensitivity, high-resolution PET - such as the CPS HRRT - requires that more complex rebinning calculations be performed at higher rates. These requirements place increasing demands on the data acquisition electronics. This article describes a new PCI card for on-line translation of 64-bit detector-pair event packets into (32-bit or 64-bit) bin-address packets at 15 M packets/sec. The PDR (PETLINK/spl trade/ DMA Rebinner) receives and/or transmits event packets on dual Fibre Channel fiber-optic links as well as a 64/66 PCI interface. The PDR contains flash memory and FPGA devices to form a digital pipeline. This pipeline delivers nearest-neighbor rebinning calculations at 15 M event-packets/sec. The combination of flash memory (a set of 20 chips -each with 4 M/spl times/16-bit capacity and 60 ns access time) and large-capacity FPGAs (set of 3 - each with >600 user I/O pins) results in extreme flexibility for complex PET applications. The main focus of this article is the application of the PDR to the HRRT. The PDR delivers accurate axial and transaxial LOR nearest-neighbor rebinning. Even the more oblique HRRT LOR are mapped into the proper sinogram bins. This accurate rebinning is significant for optimal resolution in HRRT images.