Different methods of image reconstruction for portable X-ray and gamma-ray imager with coded aperture

The coded aperture imaging increases device sensitivity for the same detector and angular resolution. The hexagonal URA masks of ranks 6 and 9 have been used for portable gamma-ray imager instead of pinhole collimator. The combined detector: scintillator+image intensifier+CCD matrix and hexagonal URA masks with step of pattern 1.5-2.5 mm were used. The images of point objects and complex circular objects of different diameters were obtained. With tantalum mask of thickness 12 mm (total FOV-23×22 degrees, resolution-1.5 degree) system is able to detect 1 MBq Cs-137 point source at distance 1 m in time 10 min. With SNR>5. The aperture of the device is not limited by angle of fully coded aperture and sources out of this region may input into coded shadow picture. For correct image reconstruction in this case the authors consider possibility of extension of decoded image size out of fully coded aperture. The approaches to image decoding in this extended area based on a least squares fitting of estimated image to experimental data were studied