Digital Tomographic Filtering of Radiographs

Conventional radiographs do not provide information about the depths of details and structures because they are two-dimensional projections of three-dimensional bodies. Taking advantage of the finite size of the X-ray source and the divergent nature of the X-ray beam, a radiograph can be processed by two-dimensional digital filtering techniques, so that the image of a particular layer is improved, while the others are degraded. This technique is referred to as a tomographic filtration process (TFP). This paper develops the mathematical and physical foundations of the method. Based on a model of the radiologic process, which is described in the paper, the equations of image formation in standard tomography, conventional radiography, and tomographic filtering are derived and compared.