Abstract: Computerized axial tomography is employed with respect to large relatively dense objects such as a solid fuel rocket engine. High energy X-rays, such as a 15 MeV source is used. To develop clean images, a collimator is employed with a relatively minute acceptance angle. Acceptance angles on the order to 1.degree., and in a preferred embodiment 7 minutes of a degree, are used. In a preferred embodiment, the collimator may be located between the object and the detector, although in other embodiments, a pre-collimator may also be used, that is between the X-ray source and the object being illuminated.

Abstract: Computer tomography employs quick back projection, allowing for example software based back projection in a minicomputer. From the line of sight absorption data which is normally taken for computed tomography, the apparatus generates additional data files of more limited resolution, the most limited resolution file has such resolution that software controlled back projection employed in the minicomputer can be completed in a period of time of one minute or less. Thereafter, the operator controls a cursor so that subsequent back projection, on files of higher resolution, employ only a subset of the available data to also limit the processing time.