Computerized Transmission Tomography: CT and Digital Volume Scanning

Abstract

The formation of radiographic images results from the interaction of X-ray beams with the tissue of a patient. The image which results is a representation of the distribution of interaction within the body. The degree of interaction can be determined by measuring and recording either the number of photons which are transmitted through a body or alternatively the distribution of scattered photons (1). In this paper only those methods which rely on transmission measurements will be considered. It will be shown that all high efficiency methods produce data with a very wide dynamic range which is difficult to transmit into the eye and brain of an observer. Computer tomography represents one solution to the problem and can be regarded as a method for compressing the dynamic range of relevant data. Other solutions are probably possible and the construction of versatile high efficiency X-ray systems which give most of the advantages of current C.T. systems should be possible. The basic arguments which lead to this conclusion will now be developed.