Abstract: The invention relates to X-ray tubes. The cathode for an X-ray tube has two filaments associated with a deflecting and focusing device which comprises at least three metal parts which are electrically insulated from one another and which are raised to electrical voltages. First and second ones of the metal, parts are associated with a first filament, while the second metal part and a third metal part are associated with the second filament.

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: The disclosure concerns X-ray scanners and, more particularly, a method to measure the bone density of a patient that takes his or her build into account. The disclosed method consists in performing a calibration of the bone density measurement by means of a phantom that simulates the patient's body and the vertebra an calibration phantom comprising a water insert and an insert with a high concentration of K.sub.2 HPO.sub.4. A measurement is made of the densities of several inserts of different concentrations and of the concentration of the water insert and of the K.sub.2 HPO.sub.4 high concentration insert, in the presence and without the presence of the bag of water, enabling the computation of corrections of the measured density of the patient's vertebra depending on his or her build.

Abstract: To enable a biopsy needle to be inserted into a breast under examination on a mammograph, a crank handle-shaped structure is provided which is vertically supported by a shaft and which carries a needle carrier on its handle portion, the vertical axis of rotation passing through a tumor whose position within the breast has been calculated. It is shown that the insertion distance of the needle can be predetermined and that under these conditions a variety of ways of reaching the tumor are made available by rotating the crank-handle shape about its axis. The insertion direction can be selected as a function of criteria applicable to the subsequent surgery and not solely as a function of the structure of the mammograph itself.

Abstract: The disclosure concerns radiology instruments that include an X-ray source, a receiver of the film or film-screen type, a detection cell and means to compute the yield at the cell. The method consists of performing measurements of the yield at instants t.sub.1, t.sub.2, . . . t.sub.3 during the exposure, so as to determine the lumination or luminous exposure (the quantity of the light received multiplied by the exposure time) on the film and then computing the lumination remaining to be acquired to obtain the chosen optical density on the film.

Abstract: In order to carry out a three-dimensional reconstruction of an object acquired by a series of conical projections on a two-dimensional multidetector, the object is estimated by a sampled function. The sampled function is projected and the projections of the sampled function are compared with the measurements resulting from acquisition on the 2D multidetector. A new estimation of the object is deduced therefrom and these operations are repeated until the comparison is satisfactory. In order to project, the sampled three-dimensional object is decomposed on a space of Gaussian basis functions. The contribution of the basis functions is computed for each image of the projection images, these contributions being equal to the integral of the product of the basis functions and of a support for illumination of the image element.

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: Problems of homogeneity of the resonant field of an NMR machine are solved by differentiating the polarization and resonance functions assigned to coils of the field of said machine. In order to produce a magnetization, use is made of a polarization coil which produces a high field. This polarization field does not need to be homogeneous. Before making measurements, during sequences of excitation-measurement of the electromagnetic wave within the body under examination, the polarization field is switched in order to be cancelled and the body is subjected to a resonance field. This resonance field can be of much lower strength but is on the other hand much more homogeneous. By thus making use of switching of the orienting field, it is shown that the signal-to-noise ratio of the detected signal is maintained.

Abstract: In X-ray tubes with a rotating anode, the shielding of the stator is obtained by a first conductive layer that is deposited on the external wall of an insulating bell-shaped part and has an electrical discontinuity, and by a second conductive layer that is deposited on the internal wall of an insulating cup-shaped or bowl-shaped part, the bell and the bowl encasing the stator and thus creating an electrostatic screen against the high frequency oscillations that result from the "crackling" of the tube. The device can be applied to X-ray tubes for radiology instruments.

Abstract: Disclosed is a device that can be used to obtain voltages for the biasing of the electrodes used to deflect the electron beam emitted by a cathode of an X-ray tube. Four DC voltages .+-.V.sub.1 and .+-.V.sub.2 are generated and applied to a mixing circuit in which they are added by using diodes to floating reference pulse voltages .+-.V.sub.3 so as to obtain voltages VS.sub.1, VS.sub.2, VS'.sub.1, VS'.sub.2 for the charging of capacitors such that:VS.sub.1 =V.sub.3 -V.sub.1 and VS.sub.2 =-V.sub.3 +V.sub.2VS'.sub.1 =-VS.sub.3 +V.sub.2 and VS'.sub.2 =V.sub.3 -V.sub.

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: The disclosure relates to devices for supplying current to X-ray tube cathode filaments. The filament of a cathode is supplied with high-frequency current pulses given by a hyporesonant type DC/AC converter, the transistors of which are controlled by a regulation circuit. This regulation circuit carries out a high-frequency regulation.

Abstract: A change-over switch comprises four input terminals connected in pairs to one of the two poles +HT and -HT of a high voltage generator and four output terminals connected in pairs to one of two X-ray tubes. It includes two identical half change-over switches with coupled control, each half change-over switch comprising two contact devices, each constituted by a fixed contact element and a movable contact element between which there is interposed an insulation device when the electrical contact is open. The movable contact elements and the insulation device of each half change-over switch are connected to one another to have combined movements.

Abstract: In a radiological apparatus using an antiscatter grid, this grid is kept fixed instead of being movable, and its image is removed by irradiating it as well as the object to be examined by two X-ray sources that have to be separated by a distance b determined by the first zero of the modulation transfer function of this two-source system. To take account of the magnification G, the distance b can be adjusted by means of a cathode emitting two electron beams with adjustable deflection.

Abstract: An assembly is made enabling an inverter of a high-voltage generator to pass from a full-bridge use to a half-bridge use, in replacing a connection circuit of a mid-point of a first rectifier of this generator at a mid-point of the inverter by a circuit that is frequency controlled at the rate at which the inverter itself is controlled. By this approach, the two assemblies are made compatible and it becomes possible to pass from one assembly to the other as a function either of a high power to be supplied or of a ripple, which cannot be tolerated, of a residual voltage rectified by a second rectifier.

Abstract: The invention applies to radiological apparatuses for angiographic examination. The invention lies in the fact that an X-ray attenuation filter is disposed between the X-ray source and the patient, said filter introducing attenuation on the path of each X-ray such that the total attenuation to which each X-ray is subjected on its path to the receiver is substantially the same for all of the paths in the X-ray beam, thereby homogenizing the exposure of the image-forming receiver.

Abstract: In order to reconstruct an angiographic arborescence, two images are acquired according to orientations substantially perpendicular to each other of an arborescence (IVA,CX) to be reconstructed. By a follow-up operation of the segments, the coordinates of the arborescence segments are reconstructed. Indeterminations resulting from the too small number of acquisitions effected are removed by emitting hypotheses (AV, IV) on forms deductible from the recorded acquisitions and by verifying those hypotheses with respect to a model. The model has the particularity of being structural, that is to say substantially descriptive. In this structural model, each arborescence segment is characterized by a number, by a direction (49-54), and by the numbers, direction and number of segments preceding or following it. By operating in this way, it has been proved that angiographic images may be reconstituted in a more rapid and simple way.

Abstract: In an imaging process and system by transillumination of a medium illuminated by transparency by a beam, an acoustic transducer emits an acoustic wave in the medium which interferes with the beam. The frequency of the light passing through the medium is then shifted from the value of the frequency of the acoustic wave. A collimating device whose object focus is located at the intersection of the acoustic wave and the light beam collects the light diffused by the medium.

Abstract: The invention concerns radiology systems and, more particularly, in such systems, to a method to determine and calibrate the lumination (namely the quantity of light received multiplied by the exposure time) received by the radiographic film in order to obtain a given blackening of the film. This method consists in carrying out a certain number of calibrations of the radiology system, and then in making a sensitogram of the type of film used. Then, a radiographic shot is taken with an object of a known thickness E.sub.o and, to obtain a reference optical density DO.sub.refo, the optical density DO.sub.m of the shot obtained is measured and compared with DO.sub.refo on the sensitogram to determine L.sub.ref.