In the case of simultaneous transmission and emission converging tomography a single photon-emission computer-tomography system contains three gamma-camera heads (22a, 22b, 22c) which are mounted on a frame (20) so that they can be rotated about an object (12). An emission radiation source is injected into the object, the emission radiation of which is received by the camera heads. Transmission radiation from a transmission radiation source (30) is limited in cross-section so that it crosses through a central part and not through edge parts of the object and is received by one (22a) of the camera heads simultaneously with the emission data. While the heads and the radiation source rotate, the transmitted radiation passes through various or no parts of the edge parts in various rotational-angle situations. An ultrasonic distance sensor (152) measures an actual edge of the object. By reconstruction (90'') of the transmission data by means of an iterative approximation method and of the measured actual object edge, attentuation properties of the object are determined. The actual edge is used for reduction of artefacts during the reconstruction process, which artefacts are produced by the radiation limiting and the incomplete sampling (scanning) of the edge parts which is connected therewith. An emission-construction processor (112) reconstructs the emission-projection data and attenuation properties to give an attenuation-corrected ... Original abstract incomplete. <IMAGE>
Simultaneous transmission and emission convergence tomography