Abstract: The invention relates to a computed tomography method in which the examination zone is scanned along a circular path by means of a conical radiation beam. The computation required for the reconstruction of the absorption distribution in the examination zone can be reduced by taking the following steps: a) rebinning of the measuring data so as to form a number of groups, each group containing a plurality of planes which extend parallel to one another and parallel to the axis of rotation, each plane containing a respective fan beam, b) one-dimensional filtering of the data, produced by the rebinning, of each group in the direction perpendicular to the direction of the planes, and c) reconstructing the spatial distribution of the absorption from the filtered data of different groups.

Abstract: The invention relates to a computed tomography method where the examination zone is scanned by means of a conical radiation beam. The reconstruction volume can be enlarged by reconstructing the absorption of voxels in a first sub-volume by means of a first reconstruction algorithm and that of voxels in a second sub-volume by means of a second reconstruction algorithm, the assignment of the voxels to the sub-volumes being performed in such a manner that the secondary conditions for the reconstruction algorithms used for these sub-volumes are satisfied.

Abstract: The invention relates to a method of and an X-ray device for forming a 3D image (B) of an object (13) to be examined by combining at least two reconstruction images (S1, S2) by weighted addition, said reconstruction images being acquired notably by means of an X-ray device (1) and each reconstruction image (S1, S2) being weighted by a respective weighting function (A1, A2) that describes at least approximately the distribution of noise and/or artefacts in the relevant reconstruction image. The image quality of the resultant 3D image is thus significantly enhanced.

Abstract: The invention relates to a computer tomography apparatus in which the scanning trajectory is shaped as a helix and a conical radiation beam traverses the examination zone. According to the invention, the dimension of the detector window (or the part thereof which is used for the reconstruction) is a factor of 3, 5, 7 . . . larger than the distance between neighboring turns of the helix. Using this geometry, each voxel in the examination zone is irradiated exactly from an angular range of 3&pgr;, 5&pgr;, 7&pgr; . . . when it traverses the cone beam. Such data acquisition yields an improved image quality.

Abstract: The invention relates to a method of forming a series of MR images in which, in the presence of a steady magnetic field, sequences comprising at least an RF pulse and a magnetic gradient field which is varied from one sequence to another are continuously applied to the examination zone, from the image signals thus generated there being reconstructed MR images, the oldest MR signals used for the reconstruction of an MR image being replaced upon reconstruction of the next MR image by the respective newly generated MR signals. Low-artefact reproduction of dynamic processes in the examination zone can be achieved by varying the direction of the magnetic gradient field active during the generation of an MR signal from one sequence to another so that the range of the magnetic gradient field directions required for the reconstruction is distributed between the respective newly generated MR signals. The invention also relates to a device for carrying out this method.

Abstract: The invention relates to an MR method for two-dimensional or three-dimensional imaging of an examination zone, in which a set of raw data is measured repeatedly, an image of the examination zone can be reconstructed from each set, and the raw data of a set is acquired with different measurement parameters, and different sets contain raw data acquired with the same measurement parameters. Improved temporal resolution is achieved in that a set of auxiliary data is formed from at least two sets of raw data in order to produce an image representing the examination zone at a selectable instant, the auxiliary data being derived by interpolation from the raw data acquired with each time the same measurement parameters but at different measurement instants, the weight applied to the raw data entering the interpolation being greater as the time interval between the associated measurement instant and the selectable instant is smaller, the image of the examination zone being reconstructed from the set of auxiliary data.

Abstract: An rf generator for magnetic resonance imaging apparatus including a modulator in which a carrier is modulated with an envelope signal, and a transmitter stage which is connected subsequent to the modulator generator in which the implementation of the modulating signal enables the expenditure for the transmitter stage be substantially reduced in that the modulator comprises a first modulator section in which the envelope signal is converted into a series of equally long digital pulses whose density corresponds to the amplitude of the envelope signal, in that k different kinds of pulses are provided, in that during each pulse of a given kind the carrier is always switched on with a given phase position which deviates from the phase positions of the carrier which are associated with the pulses of the other kinds by 360.degree./k or an integer multiple thereof, and in that the resultant pulse-wise switched, preferably square-wave carrier acts as a switching signal for the transmitter stage.

Abstract: The invention relates to a circuit arrangement for generating rf signals for MR examinations, comprising a read-only memory in which a signal is stored in the form of a series of data words, an address generator for reading data words from the read-only memory with a clock frequency, and a digital-to-analog converter which succeeds the read-only memory. In order to reduce the required storage capacity, a sinusoidal signal in the form of a series of data words is stored in the memory.

Abstract: A magnetic resonance spectrometer in which an analog-to-digital converter in the receiving branch converts the spin resonance signals, or a spin resonance signal transposed to a lower frequency range, into a digital signal, and in which a Fourier transformation circuit is located in a signal path subsequent to the analog-to-digital converter. The signal path between the analog-to-digital converter and the Fourier transformation circuit includes at least one combination of a digital filter and a sampling frequency reducing circuit. The output signal of the reducing circuit has sampling frequency which has been reduced by an integer factor with respect to its input signal and, the reduced sampling frequency is a non-integer factor lower than the frequency of the signal on the output of the digital filter.

Abstract: A magnetic resonance spectrometer in which, at least in the receiving branch, the received spin resonance signal is transposed by successive mixing processes into a transposed signal having a higher frequency range than the baseband. The transposed signal is converted into a digital signal by an analog-to-digital converter.