On-Line Time-of-Flight Mashing: the PDR Card Applied to a Long-Axis PET-TOF System for Reduced Transaxial Angular Sampling with 3-D Nearest-Neighbor Projection-Space Rebinning in Clinical PET/CT

Progress toward more effective time-of-flight (TOF) projection space mapping algorithms has been recently reported. This TOF "mashing" technique (less precise transaxial axial angular sampling) together with single-slice rebinning (SSRB) and reduced MSRB ("M" for multiple) allows much smaller, more optimized TOF projection data space sizes without significant loss in image resolution. This "works in progress" article presents methods for providing both nearest-neighbor rebinning and TOF mashing in general-purpose on-line hardware. Mechanisms to support both TOF axial rebinning and TOF-MSRB are in place but require more validation. The Siemens PDR (PETLINKtrade DMA Rebinner) card has been previously presented for fast and effective LOR-to-projection-space mapping in other PET applications. Here we apply the PDR card for yet another tough and interesting application. In this case, the PDR architecture - which makes use of FPGAs and flash memory - supports nearest-neighbor rebinning, transaxial TOF mashing and TOF-MSRB for the Siemens Long-Axis TOF PET/CT prototype. The TOF PET portion of this PET/CT system supports 52 rings of (4times4times20mm) LSO crystals (624 crystals/ring), a 70 cm dia. FOV with a 22 cm axial length, and a 500 ps FWHM intrinsic TOF resolution. As with previous PDR applications, internal rebinning throughput of 13 to 15 M event packets per second is possible. PDR throughput via PCI to local RAID is in excess of 7 M event packets per second.