Abstract: Two scanning systems are described to X-ray sections of a body and obtain a plurality of radiographic projections suitable for reconstruction as models of the body. The transmitted X-rays are recorded in any convenient form to produce data proportional to their intensities, and the data are converted to logarithmic form, stored and processed by a computer according to a predetermined set of original algorithms. The computer calculates a two-dimensional matrix from any set of linear arrays of data which represent the projection values of a body section. Such a matrix represents an estimate or approximation of the two dimensional distribution of the absorption or transmission coefficients of the X-rayed body section. The computer outputs are used to display pictures of the X-rayed body sections in any convenient visual or numerical form.