Low energy gamma ray imaging with a detector array

Abstract

Methods such as Compton imaging can be used to image a radiation field, including localizing different radioactive isotopes. Depth of interaction detection enables Compton imaging using Cadmium Zinc Telluride (CZT) detector for gamma ray energies above ∼300 keV. We have developed an imaging technique for low energy gamma rays, using an array of CZT sensors, based on the non-uniform penetration of radiation into the interior of individual crystals, and radiation “shadows” cast by one detector crystal onto its neighbors. This mask-free imaging technique is ideal for a hand-held detector system because it avoids the need for the heavy collimator or masks typically used to image at low energies. A radiation source direction is reconstructed from the unique geometric shadow that develops when illuminating detector array. This shadow is based on the path length attenuation of the gamma as it passes through the detector material. This self-shielding technique can also be combined with high energy gamma ray Compton imaging to enhance radioisotope localization. We demonstrate this approach using simulations and measurement on a multi-crystal CZT detector.