Abstract: A collimating arrangement for use in radiotherapy apparatus has a set of mutually contiguous members (8) for substantially attenuating radiation. The positions of the members (8) are adjustable so that edges (8a) thereof form an adjustable aperture (9) for defining the cross-sectional shape of the beam. A lamp (12) illuminates an area including the beam-defining edges (8a). Each of the members (8) is provided with a respective retroreflector (19) for reflecting illumination from the lamp (12) into the camera (13) substantially independently of the position of the beam-defining edges (8a). A detecting arrangement, including a video camera (13), more responsive to the higher intensity of illumination reflected from the retroreflectors (19) than from respectively adjacent regions in the illuminated area, is used to detect the positions of the retroreflectors (19) which are respectively representative of the positions of the edges of the members.

Abstract: The invention relates to a magnetic resonance imaging device comprising a transmitter/receiver which, with the exception of a few components is all digital. The transmitter comprises a digital frequency synthesizer, a single sideband modulator and a selective power amplifier, the single sideband modulator being controlled by a phase locked loop oscillator. The receiver comprises a selective pre-amplifier, a frequency mixing stage which is connected either to an output of the phase locked loop oscillator or to an output of the single sideband modulator, and an analog-to-digital converter which samples the output signal of the frequency mixing stage. The demodulation frequency for the receiver is chosen so that, after demodulation, a frequency band is obtained which is situated to one side of 0 Hz.

Abstract: A circuit which expands monochrome character image patterns to color form for use in a raster scanned computer display system. Monochrome patterns are expanded from one bit per pixel to n bits per pixel. Foreground and background colors are programmable in a pattern generator which uses data from the expanded source patterns to select appropriate colors and characters for a destination pattern to be displayed. The expanded multicolor image is generated by hardware.

Abstract: In a magnetic resonance apparatus a gradient coil system in which "return" arc conductors, which contribute substantially less to the gradient field formation because they are situated further outwards radially and/or axially from the center of the system, are positioned to compensate for stray fields of "effective" are conductors, which are more centrally situated and which contribute more substantially to the gradient field formation. Due to both radial and axial displacement of the return arc conductors relative to the effective arc conductors, the measuring space of the apparatus can be conically shaped, so that a higher patient accessibility is achieved or a smaller diameter can be imparted to a central portion.

Abstract: In a gradient coil system for a magnetic resonance apparatus arc conductors of notably X coils and Y coils are stacked axially or radially so as to form rigid stacks. The arc conductors are interconnected by means of electrical conductors and the stacks are also interconnected, so that a rigid, self-supporting coil system is obtained. Because the coil system is composed of rigid elements, is comparatively open and does not require a coil former, the production of noise in a magnetic resonance apparatus comprising such a coil system is substantially reduced and field disturbances due to coil deformations are also reduced.

Abstract: A method is proposed for the automatic correction of phase errors in NMR spectra. The phase errors are interalia due to deficiencies of the NMR hardware, the time-shifted sampling of a magnetic resonance signal after the appearance thereof. The phase correction is performed by first determining peak locations in a modulus spectrum determined from the complex spectrum and by determining the phases in the peak locations, after which the phase in the peak locations are fitted to a predetermined polynomial by means of a least-squares optimization procedure. The coefficients of the polynomial are thus defined. Subsequently, the NMR spectrum is point-wise corrected by means of the phase polynomial determined. The proposed method can be simply implemented in a NMR device; no severe requirements are imposed as regards the signal-to-noise ratio and the resolution of the spectrum. In practical situations an NMR spectrum usually comprises many spectral lines.

Abstract: A description is given of a data processing network that is constructed as a product network of two or more factor networks. At least one of the factor networks is a chordal ring of at least five stations, or a generalized chordal ring. A generalized chordal ring is formed by dividing each of the stations in a chordal ring (124, 130, 136) into a number of sub-stations. The sub-stations within a station constitute a homogeneous network. The external connections of a station are divided over the relevant sub-stations. In this way an optimum value for the degree (G) and diameter (D) of the network can be chosen on the basis of a selection strategy.

Abstract: An ultrasonic echography apparatus which comprises a first processing circuit (100) of a known type for the processing of the ultrasonic echos in order to display an A-type echogram on a display device (103), and a second processing circuit (200) which is connected parallel to the first processing circuit and which consists mainly of an amplifier (210), a group of n parallel connected channels (220a . . . 220n) each of which comprises at least one band-pass filter (221a . . . 221n) and one envelope detector (222a . . .

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.

Abstract: In NMR images, which are constructed from resonance signals, for example with Fourier zeugmatography, due to coherent interferences, for example, as a result of "leak-through" of NMR signals from one sequence to a next sequence of resonance signals, artefacts can occur in the images, which, depending upon the kind of interference, become manifest in the image as interference lines, ghost images or conspicuous dots. A method is disclosed of reducing the influence of these interferences by smearing the artefacts out over the image as noise. For this purpose, the phase of the reference signals is randomly modulated between measuring cycles of the resonance signals. The reference signal is used to form excitation pulses for producing resonance signals in a body and further in synchronous detection of the resonance signals.

Abstract: A transmit focus generator circuit for pulsing an array of transducers in an ultrasound pulse echo imaging system for transmission of a focused beam of coherent ultrasound energy. A system clock is separated into eight phases. Focusing is achieved by controlling the clock phase delay and burst delay of transmission from each transducer element. Precalculated waveform parameters are stored in a system memory. For each line scan, registers in a transmit focus block for each transducer driver circuit are loaded with the waveform parameters. For each transducer element within the aperture for a particular line scan, the circuit controls the output of pulses to achieve a focused wavefront.

Abstract: A priority processor (1) and a non-priority processor (20) cooperatively access a common memory (30) by means of an address multiplexer (40) which memory and multiplexer are controlled by a control unit (60). The priority processor issues data strobe (DSSN), clock (CLK) and write control (WSN) signals to the control unit to which the non-polarity processor also issues various memory access request signals. By forming a preparation signal (DSSN=0), the priority processor, through the control unit, claims the memory for a memory access cycle if a prior memory access request by the non-priority processor occurred less than about a clock cycle earlier.

Abstract: A lithotripsy workstation which can also be used for X-ray examination includes an X-ray device (5, 6) which is pivotable about a horizontal axis (7), and a shock wave generator (18) which is pivotable about an inclined axis (17) which intersects the horizontal axis. The focal point of the shock wave generator (18) coincides with this point of intersection, even when the shock wave generator is pivoted to the left or to the right to a position which is suitable for crushing a calculus in the left-hand kidney or the right-hand kidney.

Abstract: Images formed by digital subtraction angiography are improved by subtracting a locally deformed image from another image. A subtraction image is obtained which is substantially free from motion artefacts and which contains only the information of a moving contrast medium. To achieve this, a shift vector is determined for various pixels and a reliability criterion is calculated for each direction component of said shift vector.

Abstract: A circuit for performing the EXCLUSIVE-OR function of a signal A and a signal B comprises field effect transistors of the MESFET type normally cut off in the absence of a gate-source signal. The circuit also comprises loads and is integrated on a semiconductor substrate of the group III-V. A signal A which is complementary to the signal A is also applied to this circuit. The circuit is formed by a field effect transistor T'.sub.1 whose gate is controlled by the signal B, whose drain receives the signal A via a load R'.sub.1, and whose source receives the signal A which is complementary to the signal A. The signal representing the EXCLUSIVE-OR function (A.sym.B) is available at the junction of the drain of the transistor T'.sub.1 and the load R'.sub.1 and constitutes the output S.sub.1 of the gate.

Abstract: An MR angiography method in which an angiogram is formed from the difference between amplitude and/or phase information contained in first and second complex images produced by different gradient waveforms in respective first and second types of excitation sequences. The gradient waveforms are chosen so that in the angiogram obtained from the first and second complex images, ideally, signals orginating from excited stationary spin nuclei are not present while the signals orginating from moving spin nuclei, due to flow in blood vessels, are present. However, stationary spin nuclei can be somewhat differently excited in the first and second sequence due to the different gradient waveforms used which cause different eddy currents to flow in metal parts of the apparatus.

Abstract: The invention relates to a volume selective magnetic resonance spectroscopy method. Volume selection is performed after excitation by means of three layer-selective 180.degree. rf pulses which excite the nuclear magnetization in three mutually perpendicular layers. The distance between the three selective 180.degree. rf pulses can be chosen to be as small as possible.

Abstract: Pixel information representing an image for display is encoded using data compression into display data which can be stored on a compact disc. The data compression consists in obtaining the pixel information as a first matrix of high resolution pixel values, subtracting from this first matrix a second matrix composed of lower resolution pixel values, produced by low pass filtering the first matrix, to produce a third matrix of difference values, decimation filtering the second matrix to produce a fourth matrix of less density lower resolution pixel values and encoding the third and fourth matrices. The complementary decoding to obtain the original data consists in restituting the second matrix by interpolation filtering the coded fourth matrix, and combining the restituted second matrix with decoded third matrix.

Abstract: Large-scale time-division switching arrangements often consist of a central switching network and a series of so-called concentrators. For establishing an H1 switching a series of wideband concentrators are connected to a central wideband switching network if the wideband concentrators are of a modular structure and communicate through an internal bus system and an interface circuit with the central wideband switching network connected thereto, a distribution switching in the direction of the subscriber station and a testing of the concentrators while in operation can be effected in a simple way.

Abstract: In a method of aligning objects and in particular, of aligning optically readable disc-shaped information carrier. The objects are preferably optically scanned line-by-line in a direction transverse to their direction of movement. A reference picture line with an optically characteristic picture content is detected to allow alignment relative to known positions. To detect the reference picture line, the picture contents of all the picture lines are compared with each other and the corresponding correlation coefficients are determined. The reference picture line is that picture line whose picture content correlates least with the picture content of any other picture line.