Abstract: A minicamera detects at least one .beta. and .gamma. nuclear radiation (or assimilated) emitted by a radioisotope present in a body (1, 2). Its image pick-up head (300) includes a collimator (301), a scintillator (302) and a photodetector assembly (303 to 309). In accordance with the invention, the image pick-up head (300) also includes a modulating grid (312) with holes which is arranged between the collimator (301) and the scintillator (302). The grid can completely open or close the collimator under the influence of a suitable mechanism (313). The signals acquired by the photodetector assembly in the open position are applied to a first image memory (423) whereas those acquired in the closed position are applied to a second image memory (424). Comparison and calculation means (421) provide the desired useful signal by simple subtraction of the contents of the two memories (423, 424).

Abstract: The invention relates to a gamma camera comprising a scintillation crystal, a light intesifier, an optical guide for dispersing the light, and a scintillation localizer. The light intensifier comprises a mosaic of independent, juxtaposed, identical modules, each of which comprises an entrance face and an exit face. The entrance face is provided with a photocathode and is optically coupled to the exit face of the scintillation crystal. The exit face is provided with a screen and is coupled to the scintillation localizer.

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: The peripheral part of the optical block of a gamma camera, which is formed by the scintillation crystal and the optical conductor, is provided with a diffusive light reflector, the reflection and optical diffusion properties of which are combined in relation to the wavelength of the scintillation light so that signal/distance curves for each of the photomultipliers used are substantially coincident within the useful field of the camera. This improvement results in a suitable compromise between on the one hand linearity and spatial uniformity and on the other hand spatial and energetic resolution of the gamma camera.

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.