Near-field high-resolution coded aperture gamma-ray imaging with separable masks

Abstract

A coded aperture gamma camera based on a novel imaging model which decomposes the mask projections as a superposition of two separable functions was proposed for near-field high-resolution gamma-ray imaging. In this system, a separable mask was used to reduce the complexity of calibration and the computational burden of image reconstruction. The performance of the system was investigated by using GEANT4 Monte Carlo simulations. The quality of the reconstructed image depends on both mask thickness and gamma-ray energy. High quality reconstructed images of different energy planar sources were obtained. When the aperture diameter was 2.0 mm and the mask thickness was 20.0 mm, the estimated spatial resolution (full width at half maximum) were 2.1, 3.2, 8.4 and 10.2 mm for 140, 356, 662 and 1170 keV photons, respectively. The analysis results of reconstructed images indicate that, unlike using the cross correlation method, the performance of the system was not affected by the aperture collimation effects. The mask and anti-mask technique can help to increase the quality of reconstructed images when the counting statistics were large.