Abstract: The calibration method consists in measuring the efficiency D of a detector cell placed behind the object as a function of various phantom thicknesses E.sub.p and various X-ray tube supply voltages V.sub.m. These measurements enable an analytic model D=f(V.sub.m, E.sub.p) to be determined describing the resulting curves. The inverse function of this analytic model can be used for calculating thickness E.sub.p as a function of the measured efficiency D and the known supply voltage V.sub.m.

Abstract: In order to display a portion of a physical structure on a screen, an intermediate "pointer" memory is created. The addresses of memory words in the pointer memory correspond to the coordinates of pixels on a display screen, or in equivalent manner to the corresponding addresses of memory words in an image memory. The information loaded into the memory words of the pointer memory is representative of addresses in an "original" memory whose collection of memory words represents the structure under investigation. It is shown that by using the pointer memory it is possible for each voxel of the structure to establish quickly the coordinates of the position at which it ought to appear on the screen, and thus the address of the corresponding memory words in the pointer memory, by using previously-calculated memory addresses for the pointer memory.

Abstract: By associating an open conductive shield with a radiating loop, it is possible to limit transmission of the electric field for the benefit of transmission of a magnetic field alone. It is shown in particular in the nuclear magnetic resonance imaging field that the antenna becomes less sensitive to the dielectric behavior of the zone in which the emitted field is radiated.

Abstract: The invention relates to radiology systems and, more particularly in such systems, to a method that enables the effect of non-reciprocity of the radiographic film to be determined. This effect of non-reciprocity is expressed by coefficients CNRD(d.sub.i) which are a function of the photon dose rate (d.sub.i) on the film, the coefficients CNRD(d.sub.i) being obtained from the coefficients CNRT(t.sub.i) and the determination of the reference lumination L.sub.ref received by the film.

Abstract: A medical examination table comprises a pedestal to which an end of a rocker is hinged. An underframe is fixed rotationally to the other end of the rocker. By acting on the two axes of rotation, the table may enable motions that are as different as a simple raising motion and tilting motions of various amplitudes in one direction or another. The advantage of the invention is that it provides a simplification of the industrial-scale manufacturing of tables with or without a rocker.

Abstract: In order to analyze an image, a search is made, for all the minima of the image, for the dynamic of these minima. When the dynamic of these minima is small it corresponds finally to noise. If this measured dynamic is large, the minimum is regarded as being representative of a sufficiently significant irregularity in the image signal.

Abstract: Process to correct distortion of radiological images by obtaining the image of a regular test chart and assessing the distortions to which the image is subjected. This assessment is used to correct normal images obtained with the installation. One obtains automatically the distortion corrections to be applied to the image elements by eliminating (55) the image background by creating (63) images of similar columns, by labelling (66) the columns detected and by calculating (71) the co-ordinates of the intersections of these columns. The calculation of the intersection co-ordinates is improved by replacing (89) these columns by straight segments whose position is calculated by a regression of least error squares over all the image elements belonging to this column and situated near this intersection. Preferably, all these calculations should be made through implementing mathematical morphology operations.

Abstract: An X-ray tube is enclosed in a casing containing a cooling fluid. At least one terminal part of the casing is elongated to house a high-voltage power supply device comprising a high-voltage output terminal connected to the anode and/or the cathode and low-voltage input terminals connected to low-voltage contact elements for connection to a low-voltage supply source that is located outside the casing.

Abstract: To carry out an automatic processing operation on radiographic images in mammography, it is shown that it is possible to correct the harmful effects of the linearity defect of the characteristic curve of sensitivity of the radiographic film used for this radiograph by making a statistical study of the noise in this image. It is shown that this statistical study enables the correction elements to be deduced directly using a top hat transformation. The processing is then independent of any prior knowledge that might be had of the sensitivity of the film or of the conditions in which the examined radiographs were acquired as well as subsequently developed.

Abstract: An x-ray identification module includes a strip having recesses formed in opposite surfaces thereof. An opaque x-ray marker is received within one of the recesses, and a lateral strip portion is defined adjacent each recess. At least two suction cups are mounted to the lateral portion adjacent each recess, in non-overlying relationship to the marker-so as to avoid adding thickness to the strip in the area of the marker. The module is particularly useful for mammography.

Abstract: In voludensitometry and in cases in which it is necessary to acquire only a small number of views, the artifact ratio resulting from reconstructions is reduced. There is acquired at least one view of the object to be reconstructed, the principal direction of irradiation of which is oriented substantially at right angles to a plane formed by or containing the other directions of irradiation corresponding to the other views.

Abstract: A safety device for an X-ray unit comprises an X-ray tube protected by a casing and cooled by a fluid circulating between the tube and the casing. This device is aimed at preventing any excess pressure of the cooling fluid in the casing. It comprises a rigid, hermetically sealed and vacuum-tight cavity connected to the circuit of the fluid by a hydraulic connector with a high flow rate, designed to open mechanically and automatically under the effect of the fluid, by a pressure that exceeds a predetermined threshold.

Abstract: A mobile radiology machine that meets anti-toppling standards is made by limiting the unfolding of the structure that holds the X-ray tube, so that this unfolding occurs as a function of the angle of orientation of this structure about a vertical axis of exploration. It is shown that, under these conditions, it is possible to obtain satisfactory operation from a mobile radiology machine that weighs less and can be moved, if necessary, without the use of motors.

Abstract: In a high-voltage power device for X-ray tubes, a single magnetic circuit is used to couple a primary circuit to two separate secondary circuits. Each of these secondary circuits comprises a series of secondary windings, each connected to a rectifier-doubler circuit constituted by diodes, borne by a printed circuit, and by capacitors, borne in a cellular compartment. This arrangement makes it possible notably to double the output high voltage or to obtain perfectly symmetrical high voltages in a device that occupies less space.

Abstract: The segmented object is represented in terms of a numerical volume by calculating the gradients of the physical quantities loaded into the volume elements of this numerical volume. The gradients are shown to be perpendicular to the true surface of the object to be segmented and that they determine a surface more precisely than a treatment carried out on the surface of the segmented object. To eliminate the artefacts of a contour line which are visible in particular in the regions of low relief, the gradients assigned to volume elements of the surface of the object are weighted with respect to gradients assigned to volume elements adjacent to these volume elements by apparent facets of this segmented object.

Abstract: A light box for X-rays is made by using a graphics screen (20) coupled to a microprocessor (23), with the screen being used with inverse brightness. Under these conditions, the graphics screen emits light at nearly all points, other than special locations (I.sup.25) whose positions can be controlled by means of a control box (24). An X-ray negative (6) to be examined is placed over the graphics screen. The control box is used to move the non-illuminated regions of the screen to point to special locations in the negative. The light box is particularly applicable t studying stereographic negatives for mammography. It makes it possible to determine more quickly and more accurately the locations of lesions in breasts under examination.

Abstract: Disclosed is a device to obtain a DC voltage V.sub.p that is adjustable in a wide range of values. To a rectifying and filtering circuit, there are applied AC pulses. The quantity of electricity of these AC pulses is constant for each pulse, and their frequency F varies as a function of the voltage V.sub.p to be obtained. To this effect, a DC/AC converter of the hyporesonant type is used. The device can be used for providing bias for a focusing element of an X-ray tube.

Abstract: In order to reconstruct the structure of a body by way of iterative algorithms, the first iterations are carried out with lower resolution in order to limit the number of calculations. The image can then be reconstructed when the calculation time is reduced to one-third or even one-quarter. The image thus reconstructed is of better quality than images reconstructed using only a single resolution.

Abstract: In an NMR experiment, the movements of an object are represented by carrying out a harmonic analysis of the images based on a resolution of the movement of the object into a Fourier series. There is then obtained a set of images which is representative of the Fourier components of this movement. The images are then recombined at will so as to produce either a general moving image, or an image of those parts which are motionless in the object, or finally an image of only those parts which are in motion.

Abstract: The disclosure relates to high-voltage change-over switches that are used to apply high voltage alternately to two X-ray tubes. Each of the four switch devices constituting a change-over switch includes a fixed contact element connected to an input terminal of the high voltage and a movable contact element connected to an output terminal by a curved, flexible strip, the shifting of which is obtained by a hinged arm that is actuated by an insulator sleeve surrounding the strip. The rotation of the sleeve in one direction causes contact through a hole in the wall of the sleeve while rotation in the reverse direction causes the contact elements to move away from each other and gives rise to the interposition of the insulator wall between the contact elements at a distance. The disclosed device can be applied to radiology installations.