Critical review of tomography in radiology and nuclear medicine.

This review covers conventional radiographic tomography, radioisotopic tomography, and a review of computerized transaxial tomography. Simple, reproducible radiographic tomographic methods are increasing in use, and despite their complexity, the diagnostic results are superior to conventional radiographs. There are many different motions of the X-ray tube and the film which can be employed to create a tomogram. The perfect tomographic motion is partly determined by the geometric shape of the object to be imaged and the thickness of the plane of interest. The undirectional tomographic method blurs a point in a linear fashion; the pleuridirectional method blurs a point over a wider surface. Among the most popular directions used are linear, circular, elliptical, and hypocycloidal. The numerous applications of tomography described in this review are an encouraging, broad-based foundation from which the most clinically useful and economically feasible devices will emerge.