Synthesis and enhancement of the radionuclide tomographic section

In principle, it is possible to perfectly reconstruct a two-dimensional density distribution from measurements of one-dimensional projections, subject to certain restrictions on the data, by using one of a number of analytical reconstruction techniques. The radionuclide tomographic section, a map of radiopharmaceutical concentration in a chosen plane of an object, is reconstructed from measurements of the radioactive emission detected at points exterior to the object. However, practical implementation of the procedure means that it is impossible to satisfy all the requirements of the theory, so that the image merely approximates to the original to a greater or lesser extent. We examine the nature and extent of the deviations from the theory and their effect on the reconstructed image; in particular, the problems of sampling, statistics, detector properties, collimation and attenuation are considered in turn. The principles involved in conventional attempts at overcoming major artefacts resulting from the various aberrations are outlined, together with the most significant effects of such corrective procedures. Finally, an improved, system-specific, iterative technique for restoration and enhancement, which we have used in conjunction with the Aberdeen Section Scanner, is described.