The reconstruction of objects from shadowgraphs with high contrasts

摘要

It is demonstrated that the presence of regions with high contrast in the projections can seriously alter the performance of algorithms designed for the reconstruction of objects from their shadowgraphs. The demonstration uses two test patterns: one based on a cross section of the thorax, the other based on a cross section of the head. An algebraic reconstruction technique is proposed, which is capable of reconstructing such cross sections with reasonable accuracy from a limited number of projections. The method is compared with an earlier algebraic technique, the iterative least squares method and two versions of the convolution method.