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 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: The problems of selection of objects having complex shapes and usually apprehended by a plurality of facets are solved by making use of curved surfaces, the equation of which is of the second degree. In a test calculation for checking whether a node of an octree decomposition does or does not belong to the surface thus defined, the terms of the second degree are replaced by a constant. It is shown that this approximation permits rapid determination of the complex shapes without having to perform the calculations corresponding to the second degree. The method also permits easy determination of the normal to the object for calculation of shadowing when it is employed for display.

Abstract: A method for elimination of parasitic noise in an x-ray scanner consists of computing the mean value of the signals of the ten first views in a circuit (26). This mean value is subtracted from the signals of the first view V.sub.1 in a circuit (27) so as to obtain the high-frequency components H.sub.1 which are considered as parasitic noise. The signals H.sub.1 are filtered in a high-pass filter before being subtracted from the signals of the view V.sub.1 to obtain signals V'.sub.1 which are free of parasitic components. The signals V'.sub.1 are processed in a sequential circuit (31) in order to obtain signals V'.sub.2 which are free of parasitic component. The same process is repeated for the signals of the other views V.sub.3 to V.sub.m.

Abstract: A method and system to calibrate an X-ray scanner uses a single circular phantom. The circular phantom is off-centered with respect to the axis of rotation of the scanner so as to introduce different paths in the phantom for each channel, depending on the angular positions of the scanner. This results in different attenuation measurements which are compared with values obtained by the computation of the path lengths which depend on the off-centered coordinates r and .PHI. and on the position of the scanner, thus enabling computation of the polynomial approximation coefficients to be applied to the measurements.

Abstract: Medical examination table comprised of plate (5), a frame (4) and intermediate means (6) for moving the plate relatively to the frame in order to introduce it into an examination apparatus (1). The means for moving the plate are provided with an elongated moving element (7) of which one end (8) is movable relatively to the frame and the other end (9) is movable relatively to the plate. Said arrangement increases the clearance of the plate with respect to its frame. Moreover, the driving means are disengageable (25) and allow, by operating a knob (30), an emergency withdrawal of the plate from within the examination apparatus, should the patient become indisposed or in the event of a power failure.

Abstract: A high-voltage connector, in particular for feeding the cathode, two cathode filaments, and two gates of an X-ray tube, wherein the connector comprises five connections, one for power supplying the cathode, two for power supplying the cathode filaments, and the last two for power supplying the two gates, the connections being disposed in such a manner that the distance between the cathode connection and a gate connection and the distance between the two gate connections are greater than the distance between the cathode connection and a cathode filament connection.

Abstract: The vertical displacement of a patient support table for a radiology apparatus is obtained by means of an electromechanical device constituted by arms which are connected to each other and to the support table by means of powered articulations with synchronized movements of rotation. A relatively small minimum height of the order of 60 centimeters is thus obtained.

Abstract: In an x-ray tube of the beam deflection type for a radiology apparatus, the stair-steps of the focusing device of the electron beam are extended by metallic deflecting electrodes placed in parallel relation to said stair-steps and electrically insulated from these latter by means of insulating layers. Said electrodes are brought to different potentials, the polarities and values of which depend on the direction and amplitude of deflection to be obtained.

Abstract: A curved bar probe (1) for an echograph is fabricated by using a thin support (2) on which is placed a bar of piezoelectric crystal. The bar is divided into a plurality of piezoelectric transducers elements (3). The thin support presents the particularity of being rigid at room temperature but is thermodeformable. By subjecting it to a heating-cooling cycle during which it is given a desired curved shape, a rigid bar having an imposed curved shape is obtained. It is then possible to avoid the adhesion of said support to a base (16). This would form a back-reflecting surface for acoustic waves and would create interference harmful to the useful acoustic signal.

Abstract: An optical distributor for deflecting a light beam in different directions comprises a single semi-reflecting mirror 30 carried by a motor-driven turntable 31. The mirror is capable of pivoting about an axis 33 when a stop 46 is withdrawn (position Z of the notch and of the stud 38) and of taking up a position 52 in which it does not intercept the light beam 14. in the other positions (X and Y), the mirror intercepts the beam 14 and deflects it in the desired directions.

Abstract: Disclosed are a device and a method to control the speed of two-phase or three-phase A.C. motors by means of a three-phase converter. The switching-over instants of the switches of the converter for the control of a two-phase motor are computed so that the signals at the common points of each pair of switches are phase shifted with respect to one another and have no low-order harmonic components. The disclosed device and method are applicable to motors driving rotating anodes for X-ray tubes.

Abstract: Movements within volume elements or voxels of a body are depicted by subjecting this body to sequences of electro-magnetic excitation of the SSFP type during an NMR experiment. It is shown that by performing two series of excitation/reading sequences with different sensitization characteristics, it is possible to obtain images of molecular diffusion and/or perfusions in a far quicker and in a far more differentiated way than with standard types of excitation methods, of the spin-echo type for example.

Abstract: The invention relates to detectors of ionizing radiation which use a photoconductor as the detecting element. The invention lies in an electrode moving in a direction OX through a photoconductive medium disposed between two grids of electrodes extending parallel to OX. During the irradiation time, the grid electrodes of one grid are raised to a positive potential relative to the electrodes of the other grid and electrons and positive ions are created in the photoconductor. The electrons are removed by maintaining the positive potential on the electrodes of said one grid for a period of time longer than the irradiation. During displacement of said moving electrode, only the positive ions give rise to current in the electrodes. The invention is applicable to radiotherapy and radiography.

Abstract: In order to make a probe having a concave attack face, a continuous acoustic transition blade (5) is used. Said blade is metallized (7) and is common contact with all the front metallizations (6) of the piezoelectric elements of the probe. The rear metallizations (8) of the elements terminate electrically and independently backwards of the probe. As a result, the electric connection of the piezoelectric elements is simplified. Said probe is usable in experiments with ultrsounds where good focusing is desired.

Abstract: In order to compensate for the influence of magnetic fields on charged-particle beams, in particular in imaging devices provision is made for a coil constituted by a support plate of substantially constant thickness and by patterns deposited on the support in such a manner as to ensure that the absorption of electromagnetic energy is constant over the entire surface of the coil within a predetermined pass-band.In a first embodiment, the patterns are transparent to the electromagnetic energy of a desired frequency band. In a second embodiment, complementary patterns are employed in order to obtain constant absorption over the entire surface of the coil.

Abstract: The invention relates to X-ray tubes, and more particularly to cathodes for such tubes. The invention lies in the cathode, which includes an electron-emitting filament (26), being made in the form of a main body (10) of insulating material having metal electrodes (16 and 19) deposited thereon which are insulated from one another by the main body. The filament (26) and the electrodes (16 to 19) are connected to conductors (27, 21 to 23) which pass through the main body.

Abstract: When making curved bar probes it is necessary, particularly at high frequency, to provide circuits for the connection of piezoelectric elements of the bars which are compatible with the curvature imposed to the bar after it has been fabricated flat. The invention overcomes such difficulty by adjoining on both sides of the elements a generally parallelepipedic relay metallized on at least two (12,13) of its adjacent faces to transpose one connection face (7) situated in plane which must be curved into one connection face (13) which is perpendicular and of which the orientation remains unchanged and parallel to a same plane during the curvature operation. As a result, the connection is simplified.

Abstract: In a nuclear magnetic resonance imaging installation, monitors of the cathode tube type are shielded from the effect of an intense magnetic field. For this purpose, the installation according to the invention has a flat coil which creates a second magnetic field, the direction of which is opposite to that of the intense magnetic field.

Abstract: Problems related to acquistion time with reconstructed image type tomographs are resolved by causing step by step rotations of the X-ray tube/multiple detector set of this tomograph and, at each step, by causing a translational movement of this set in order to scan the entire region to be examined of a body under examination. It is shown that, by using a multiple row multidetector, it is possible, at equal speeds, to improve the quality of the images produced or, at equal quality, to increase the acquisition speed. Furthermore, this mode of operation is especially well suited to the monitoring of radiotherapy action where the practitioner, when acquiring images, needs to be able to touch the patient.