Hybrid pixel detectors based on Medipix microchips allow data on the energy of each photon hitting a particular pixel to be obtained in addition to the coordinate information. Their development and wide use in the past decade have renewed interest in multi-energy X-ray computer tomography, opening up a possibility of not only obtaining a high-quality image of the sample under investigation but also determining its elemental composition.
A method for reconstruction of multi-energy X-ray tomographic images based on pre-segmentation and decomposition into basic substances was presented. It was shown that combination of a few detectors with sensors made of semiconductors with different atomic numbers considerably improves quality of energy measurements. A method for adjusting energy thresholds of detector pixels with simultaneous energy calibration with respect to the edge of the X-ray tube radiation spectrum and a procedure for mechanical adjustment of the MARS microtomograph were developed. A mathematical model of the detector was constructed, and its predictions were compared with the experimental data. Results of microtomographic investigations of biological (atherosclerotic patch, abdominal aortic aneurysm) and geological samples were reported.