A data acquisition system for a ring Compton camera

A data acquisition system has been developed to acquire coincidence data from a ring Compton camera. The ring Compton camera is composed of a silicon pad detector and a ring sodium iodide (NaI) detector. A useful coincidence event is one in which a gamma-ray photon from the source Compton scatters in the silicon detector, and is then captured or absorbed in the NaI detector. To determine whether interactions in two detectors belong to a coincidence event, the coincidence detection circuit compares timing signals from both detectors to determine if they arrive almost simultaneously. Coincidence interrupts generated by this circuit notify a personal computer and initiate the data transfer for each event. The data acquisition software implemented in Visual Basic and C++ has been developed to provide system control and data collection. Tomographic imaging results of a ¹³¹ I line source show that the reconstructed spatial resolution is 2.2 mm FWHM at 9.54 cm