Abstract: An x-ray examination apparatus comprises an x-ray source for generating an x-ray image and an image analysis system derives brightness variations from the x-ray image and derives a dose control signal dependent on said brightness variations in order to control the x-ray source. The image analysis system derives a distribution of said brightness variations and derives the dose control signal from the distribution of brightness variations. Preferably, the image analysis system is arranged to derive the brightness variations from the processed image and a histogram analysis is employed to derive the dose control signal.

Abstract: The invention discloses a method of processing an image including the steps of decomposing the image into detail images at successive resolution levels. The detail images at successive resolution levels contain image information at respective spatial scales. Filtering of detail images is carried-out in dependence on at least one subsequent detail image having a lower resolution level than the current detail image. A processed image is reconstructed from the filtered detail images.

Abstract: A radio transmission system having a base station and a mobile station is disclosed. A controller dynamically changes in real-time the allocation of channels in response to changes in signal propagation and traffic conditions between the base and mobile stations. The allocation of channels is based on use of a Kohonen model and is determined by a space-dependent component and/or a time-dependent component. The space-dependent component is determined by signal strengths received by the base and mobile stations and the time-dependent component are determined by activity of the channels.

Abstract: An image is processed taking into account the direction of a predominant structure of the image. Said predominant direction is derived from image information in the image. In particular, the covariance matrix having matrix elements depending on products of differences between pixel-values in separate directions is calculated. The eigenvectors of the covariance matrix correspond with the predominant direction of the image structure and the eigenvalues of the covariance matrix represent the strength of the structure in the image. The covariance matrix is computed locally, i.e. for separate regions in the images so as to take variations of the direction of predominant structures into account.

Abstract: A spread-spectrum based cellular mobile radio system resolves average mutual interferences (I.sup.u (j).sub.av, I.sup.d (j).sub.av) between radio zones j, j') from a total interference experienced in a radio zone (j), using statistical methods. First, interference measurements are carried out in the radio zones (Z1, Z2), and data is transmitted to a central control arrangement (CA) which resolves the average mutual interferences. Then, these average mutual interference (I.sup.u (j).sub.av, I.sup.d (j).sub.av) are used in an optimization process for acquiring access control parameters (x) for controlling traffic per radio zone (Z1, Z2). In the optimizing process various objective functions may be applied so as to fulfil system operator demands. Thus, system overload is avoided, and further, a flexible tool is provided for satisfying operator demands.

Abstract: A cellular mobile radio systems includes fixed stations and mobile stations, a radio cell being subdivided into sub-cells and each sub-cell being assigned its own allocation of radio channels. The values of radio parameters of the fixed stations are measured and evaluated for assigning a mobile station to a sub-cell. To achieve an additional increase of the radio channel capacity of such system, a position vector is assigned to each respective mobile station which is derived from the measured parameters. A mobile station is then assigned to a specific sub-cell on the basis of its position vector.

Abstract: In a method of processing an image the image is divided in one or more blocks. Separate blocks are spatially frequency transformed in that pixel-values of the blocks are transformed into spectral coefficients. A noise level of the image is estimated and reduced spectral coefficients are derived from spectral coefficients and the estimated noise level. Pixel-values for a processed block are synthesized from the reduced spectral coefficients and the processed blocks are assembled into a processed image. The noise level is estimated from the image information within the image. Preferably, a few parameters relating to the circumstances under which the image was acquired are also taken into account for estimating the noise level.

Abstract: An image processing method includes multi-resolution decomposition to decompose an input image into frequency-band images, which are subsequently filtered according to an order statistics filtering. Preferably, a finite impulse response median hybrid is employed. The filtered frequency-band images are synthesized to form the filtered output image.

Abstract: In a cellular mobile radio network a limited number of available channels must be allocated among the various cells, and the efficiency of such allocation is highly variable with changing traffic conditions in the network. To solve this problem the invention determines all possible radio situations which may arise in the network, including the radio positions of a mobile station and occupancy of the various channels. The individual components of each possible radio situation are then compared with predetermined thresholds so as to reduce the multiplicity of such situations to a relatively small number of classified radio situations each of which has its own channel list allocated thereto. When a channel is requested for a mobile station, the relevant classified radio situation is determined and channel assignment is made from the channel list applicable to that classified situation.

Abstract: A mobile radio system includes fixed stations and mobile stations, a free channel for establishing connection to a mobile station being selected from a predetermined channel list for each fixed station. The individual station lists are initially assigned in a radio network planning phase. To adjust to changes in the system which only occur after it is in operation, the assignment of radio channels is modified on the basis of measured data obtained during actual operation of the system. In this way the system becomes self-adaptative.

Abstract: In order to suppress a doublet structure in a carbon spectrum due to J-coupling between carbon and hydrogen spins in compounds containing at least one CH group, a first magnetic rf field having a frequency equal to the Larmor frequency of carbon is generated, after which a second magnetic rf field having the Larmor frequency of the hydrogen in the relevant CH group is applied to the examination zone, and the spin resonance signal generated is detected. Decoupling is achieved with a reduced rf load in that a magnetic rf pulse having the duration T and the amplitude B.sub.p is generated a predetermined period of time dt after the end of excitation of the carbon, after which the amplitude of the rf field is immediately reduced to a value B.sub.c and the spin resonance signal is detected, the parameters dt, Bc and Bp being chosen so that the modulation of the spin resonance signal caused by the J-coupling is exactly eliminated.

Abstract: A method of and a system for, determining the nuclear magnetization distribution, where a plurality of sequences act on an examination zone in the presence of a uniform, steady magnetic field, each sequence comprising an r.f. pulse whereby, in conjunction with a magnetic gradient field, the nuclear magnetization in the zones situated on both sides of a layer to be examined is excited and possibly dephased. The r.f. peak power can be reduced by modulating a signal on a carrier whose frequency corresponds to the Larmor frequency in the center of the layer to be examined, the frequency of said signal varying in a range which corresponds to differences between said Larmor frequency and the Larmor frequencies in one of the zones.

Abstract: The invention relates to a nuclear magnetic resonance examination method for the selective excitation of a limited volume of a body under examination, in which the excitation is effected by three successive frequency-modulated pulses the first and the third of which are equal to one another and the second of which is a 180.degree. pulse. A gradient magnetic field, the gradient of which runs each time in one of three directions perpendicular to one another, is active during each of the three pulses.

Abstract: The invention relates to a method of generating separate fat images and water images and to an apparatus for performing this method. Separate fat images and water images are obtained by means of a sequence consisting of three high-frequency pulses, the second and the third high-frequency pulse having an identical flip angle and being situated at a distance in time from one another which corresponds to half the reciprocal value of the difference between the Larmor frequencies of water-bound hydrogen protons on the one hand and fat-bound hydrogen protons on the other hand, or to an odd multiple thereof.

Abstract: The method and device for NMR Fourier zeugmatography utilizes amplitude-modulated r.f. pulses (90.degree. and 180.degree. pulses) for the excitation of nuclear spins and the generating of nuclear spin echo signals. For three-dimensional Fourier zeugmatography, r.f. pulse having a large bandwidth (for example 10-50 kHz) are desired. The use of amplitude-modulated signals then implies an undesirably high peak power of the r.f. generator. In accordance with the invention, use is made of a frequency-modulated signal which can have a substantially constant amplitude and which preferably covers the desired frequency spectrum at a uniform speed.

Abstract: The invention relates to an MR tomography apparatus, comprising three coil systems for generating a magnetic field which extends in the direction of a steady, homogeneous main field and which varies linearly as a function of the location. In addition, there is provided at least one further coil system which generates a magnetic field which also extends in the direction of the homogeneous magnetic field but which varies non-linearly as a function of the location. The coil systems are supplied with a current which is always proportioned so that the superposition of the magnetic fields of the coil systems produces the desired variation in time and space of the magnetic flux density of the steady field. The effect of eddy currents or other inaccuracies can then be reduced by the additional coil system.