摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
An examination bed, notably for RMN or tomodensitometry, which includes a chassis, an examination plateau, and a mechanism for driving movement of the plateau with respect to the chassis and with respect to the apparatus wherein the moving mechanism includes a moving assembly with respect to the plateau and the chassis, elongated in its shape with one end being movable with respect to the chassis and whose other end is movable with respect to the plateau.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
Gradient pulses are applied during the common periods and with homothetic shapes on each of three imaging axes of an NMR machine in order to form oblique images. This results in a simplification of programming of the supplies of the gradient pulse application device.