1. An improved device for computing and displaying the spatial distribution of physical characteristics in a layer of a body from signal values which are derived from measurements made by a radiation source and one or more radiation detectors in a multiplicity of measuring series along a corresponding multiplicity of directions in the layer comprising: an allocation device which, for each measuring series, assigns one of the signal values to each of a multiplicity of image points, each assigned signal value having been produced in the same strip in which the associated image point is siturated; storage means connected to accumulate and store all of the assigned signal values for each image point; summing means connected to receive and superpose all of the signal values for each image point to produce a superposed value for that image point; and display means connected to receive the superposed values and to produce therefrom a display wherein the values of displayed points correspond to the mean-value of the superposed values of image points in the region of each displayed point.