Abstract: In a computerized tomographic radiographic apparatus a source of radiation projects radiation through a patient to be incident on at least some of a plurality of detector devices. To project the radiation from different directions the source moves relative to the body and also relative to the detectors to irradiate different detectors. Collimators, moving with the source, are provided to reduce the incidence of scattered radiation on the detectors. The collimators take the form of baffle plates which are arranged, to present substantially the same exit aperture to each detector despite the relative movement.

Abstract: A data processing arrangement includes first storage means having storage locations arranged in a plurality of rows and second storage means comprising a single column of locations, one location being provided in said second storage means for each row of the locations in said first storage means. In order that the data stored in the two storage means can be correlated such that a combination of the data held in various locations of the first storage means can be compared with a corresponding value in a location of said second storage means, there is provided means for shifting the data held in the first and second storage means, at individually controllable rates, along said rows and said column respectively.