A novel method to determine the directionality of radiation sources with two detectors based on coincidence measurements

ICx Radiation has developed a novel method to determine the direction of radiation with a device containing only two detectors by comparing and analyzing the paired-energy distributions of coincident events. The method does not require complex image reconstruction but rather extracts the directionality from the means and skewness of the two coincidence spectra. All energy data contribute to the energy spectrum, while events that occur within the coincidence time window are also added to a separate time-dependent buffer that represents the “reduced” spectra from each detector. These spectra contain counts only from true Compton events. The mean and skewness of each detector's reduced spectra subset is then calculated. Equal skewness and means correspond to the source being in front of the device. Opposite polarity skewness correspond to the source being located to the left or right of the device. For low count rates due to weak sources or sources located far away from the detectors, the skewness comparison gives fast indication for the hemisphere in which the source is located, while increased count rates or increased acquisition times reduce the uncertainties and allow a detailed angular detection of the source position. The simulations, experimental results and the angular resolution as a function of the strength, source energies and distance of the radiation source are discussed.