Abstract: An emission computed tomograph provided with a collimator ring rotatable about an object being examined and having a plurality of slits for defining the direction of incidence of the radiation emitted from the objection the radiation detectors. The slits are arranged circumferentially of the ring and directed at successively different angles relative to the radial direction of the collimator ring, so that as the ring is rotated, the object is tomographically scanned. The collimator ring may be divided into a plurality of equal arcuate portions, in each of which the slits are directed toward the object in parallel with each other, so that as the collimator ring is rotated to scan the object, only the parallel profile data thereof can be obtained.

Abstract: Emission computed tomograph wherein a pluralty of detectors surround an object to be examined so as to detect X- or gamma radiation emitted by said object. In front of each of said detectors there is provided a collimator which comprises a pair of main plates and a subsidiary plate interposed therebetween. The plates are made of a material capable of blocking penetration of the radiation therethrough and so supported as to be swingable over an angle sufficient to cover the whole of said object. The plates of all the collimators are simultaneously swung to the same side and at the same angular speed thereby to change the direction of incidence of said radiation on each of said detectors.

Abstract: An emission computed tomograph provided with different types of collimators for selective use with different kinds of radionuclides. The different collimators are alternatively brought into operative position in front of the radiation detector in accordance with the kind of radionuclide being used.