A tomograph VMEbus parallel processing data acquisition system

The authors describe a VME-based data acquisition system suitable for the development of positron volume imaging tomographs which use 3-D data for improved image resolution over slice-oriented tomographs. The data acquisition must be flexible enough to accommodate several 3-D reconstruction algorithms; hence, software-based system is most suitable. Furthermore, because of the increased dimensions and resolution of volume imaging tomographs, the raw data event rate is greater than that of slice-oriented machines. These dual requirements are met by the proposed data acquisition system. Flexibility is achieved through an array of processors connected over a VMEbus, operating asynchronously and in parallel. High raw data throughput is achieved using a dedicated high-speed data transfer device available for the VMEbus. The device can attain a raw data rate of 2.5 million coincidence events per second for raw events which are 64-bits wide