Design and Implementation of Digital Tomographic Filters

A technique is proposed which allows the selective filtering of conventional radiographs in order to obtain depth-dependent information by utilizing the depth-dependent information contained therein. This technique, referred to as tomographic filtering or tomographic filtration process (TFP), takes advantage of the finite size of the X-ray source, so that after processing, the image of a particular layer is improved while the others are not. This paper starts with a brief review of technique and then concentrates on the design and implementation of digital tomographic filters. Examples are shown, including images of simulated radiographs processed with such filters. Evaluations of the performance of these filters show that the image quality cannot be as good as that of standard tomography or multiprojection reconstruction techniques; nevertheless they represent an improvement over conventional radiology, and highlight additional depth-dependent information contained in radiographs. This paper concludes with suggestions for further research in this area.