Positron emission tomography (PET) imaging is based on detecting two time-coincident photons from the emission of a positron-emitting radioisotope. The PET ring consists of several acquisition modules where photon events are detected and digitized to record the energy, position, and time information. A concentrate and coincidence module collects events from acquisition modules and performs coincidence detection and data aggregation.
In this case, each acquisition module uses a single White Rabbit link to synchronize and transmit the digitized data, the concentrate and coincidence process is embedded inside the White Rabbit switch and only the true coincidence events on line of response (LOR) are further transmitted for image reconstruction. This provides a modular, scalable solution for PET acquisition system.
Preclinical PET is a noninvasive imaging tool for studying disease development/progression and the development of novel radiotracers and pharmaceuticals for clinical applications. When a positron is emitted from the nucleus, it produces two photons of 511 keV essentially in opposite directions. The two photons are detected in coincidence by the PET scanner. The locations of the two points of interaction with the scintillators form a line of response (LOR). Acquisition of large number of coincidence events along all lines of response can provide enough information to reconstruct the underlying distribution of the radioisotope. Coincident events are defined as two photons detected within a very short time interval, or coincidence window, typically set at approximately 6 to 12 nanoseconds.
A Cute-WR mezzanine is integrated inside each acquisition module to provide the sampling clock and timestamp and a TCP/IP stack engine. In the White Rabbit switch, a special demux logic on each downstream port checks the packets from each acquisition module, the data frames containing photon events are directed to a dedicated PET coincidence logic where the true coincidence event on LOR are checked and packeted; the other PTP packets and status/configuration packets are unaffected and routed to the WR SWcore.
With this deeply customized WR switch, an elegant and compact architecture is able to provide both time synchronization and coincidence processing and shows great scalability and modulization for PET instrument.
