Development of a singles-based scalable data acquisition system for the whole-body OpenPET

Abstract

One of the challenging applications of PET is implementing it for in-beam PET, which is an in situ monitoring method for charged particle therapy. For this purpose, we previously proposed the world's first open-type geometries which we named OpenPET. For in-beam PET, careful designing and testing of detectors are important because secondary particles generated in a target degrade detector performance in the OpenPET geometries. We are now developing a whole-body OpenPET. In this work, we developed a data acquisition (DAQ) system for the whole-body OpenPET. In order to increase scalability and maintain the possibility for future development of complicated coincidence algorithms to reject background signals, our designed DAQ system has no coincidence circuit and only singles list-mode data acquisition circuits. The DAQ system makes a judgment on coincidence based on software, where the singles listmode data include 6 bits energy and 500 ps tags for timing information. First, calculation speed of the developed software coincidence algorithm was tested using GATE simulation data, and we confirmed that calculation time of the software-based coincidence process was less than measurement time for in-beam PET. Then, the developed DAQ was partially tested in HIMAC experiments, where the 12C beams of 290 MeV/u with 105 − 108 particles per second (pps) were irradiated onto a water phantom. We placed a detector at the position of risk, where the largest number of secondary particles are incident, and we obtained sufficient crystal identification performance even with a typical clinical beam intensity of 108 pps.