Abstract: A method of and an apparatus for tomographic examination by X-ray or gamma ray scanning of structures, intended for the display of images of slices of the structure examined by determination of the electron density in each volume element of these slices.Using an X-ray or gamma ray source, a stationary principal detector and an auxiliary detector which is aligned with the source, for each volume element of each slice two measurements are performed of the diffusion by the Comption effect towards the principal detector and two measurements are performed of the transmission between the source and the auxiliary detector, starting with the slice nearest to the principal detector and proceeding to the slice which is situated furthest from this detector. The measuring results are progressively used for calculating the exact electron density throughout the structure examined.

Abstract: A scintillation camera has photomultipliers and a number of auxiliary radioisotope sources to calibrate the photomultipliers. The calibration circuits can be either analogue or digital.