An event driven read-out system for a novel PET scanner with Compton enhanced 3D gamma reconstruction

The design of a data acquisition system (DAQ) for a novel positron emission tomography scanner is reported. The PET system, based on long axially oriented scintillation crystals, read out by hybrid photon detectors (HPD), allows 3D parallax-error free Compton enhanced gamma reconstruction. The DAQ system is composed of several read-out cards, each one associated with a module of the PET scanner, and of a main card that controls the whole system. Using fast triggering signals from the silicon sensor back-planes, the main card performs the coincidence analysis, and, in case of coincidence, it enables the read-out of the two modules involved. The other modules are left free to perform new acquisitions. This concept based on several independent, event driven and parallel read-out chains, drastically reduce the acquisition dead time. Each enabled readout card digitizes, encodes and stores data from the respective module. Data are stored in a local FIFO and then are transferred through a network into a single computer. The system is designed according to the specifications of IDEAS VaTaGP5 chip. Each read-out card is able to accommodate all the chip read-out modes and the test procedures and can be used as a standalone read-out system that allows reading out up to 16 daisy chained chips per channel. We describe a simplified DAQ system, designed for a two module demonstrator set-up, developed to study and optimize the essential design parameters.