Advanced hardware architecture for on-line data acquisition in clinical 3-D PET: smart DRAM PCI Card for 14 M event/sec histogramming across terabytes of DRAM

Clinical PET places a demanding burden on the data acquisition architecture - especially when using larger, higher sensitivity detector arrays coupled with demands for high patient throughput. Pure list-mode data acquisition can have limited acceptance due to either too-slow event-packet collection speeds and/or too-slow post-acquisition processing. The typical resolution for this problem has been to perform both LOR-to-bin mapping (rebinning) and histogramming (±unity to memory) in an on-line manner - i.e. projection space "sinograms" are generated during the acquisition while the patient is still in the tomograph. This article describes a new design for very-high-speed online histogramming hardware - the Smart DRAM PCI card. This hardware is significant in the quest to address the needs of fast on-line histogramming into large DRAM arrays. This card has an integral dual-Fibre-Channel interface for receiving (and retransmitting) PET bin-address packets. Also, the card has onboard quad-interleaved ECC DDR SDRAM (4 DIMMs & up to 4 G bytes total per card) with a demonstrated capacity for sustained histogramming rates in excess of 14 M events/sec The retransmit-packets-on-Fibre-Channel feature supports a daisy chain of multiple such Smart DRAM cards. This means the architecture can easily make terabytes of memory available for on-line generation of projection data. Support is planned for time-of-flight and weighted histogramming as well as online gating.