Abstract: In a fuel dielectric constant detecting apparatus, a high frequency signal is applied to an element for subjecting the high frequency voltage signal to resonance corresponding to the dielectric constant of the fuel. A DC voltage is applied to the subjecting element so that the duty of the high frequency signal be 50%, and the high frequency signals are so controlled that the phase shift between the signals provided at both ends of the resistor be a predetermined value. Alternatively, in the apparatus, the high frequency signal applying member includes a high frequency signal applying section and a reference high frequency signal applying section.

Abstract: An MRI technique in which the similarity of samples from different portions of a body is determined and displayed. In one embodiment, the method can be used to track the spread of a known primary tumor to other portions of a patient's body. The MRI apparatus is used to produce a training set comprising one or more training samples. The training set is formed from a plurality of congruent first images of a training region of the body. Each first image is produced using an MRI pulse sequence different from the pulse sequences used to produce the other first images. Each first image comprise an array of pixels, and each training sample comprises a spatially aligned set of pixels from each first image. The same technique is used to produce a plurality of test samples corresponding to a test region of the same body. The test samples are produced using the same pulse sequences as the training samples.

Abstract: Disclosed is a method for automatically removing blur in magnetic resonance image signals introduced due to inhomogeneity in the magnetic field and variations in magnetic susceptibility of an object being imaged. Detected signals are demodulated at several different frequencies and reconstructed to create a series of base images. The amount of blur is determined by establishing a focusing measure for each point or part in each base image, and a composite image is then constructed using only the unblurred regions from each base image. Focusing criterion can include minimization of the imaginary part of the complex MRI after removal of constant and low frequency phase information.

Abstract: An apparatus serves to excite and/or measure magnetic resonance in samples, in particular in relation to whole body tomography. A probehead (10) incorporates a high frequency system to transmit and/or to detect a high frequency magnetic field of a predetermined measuring frequency. The probehead (10) further incorporates a coil system to produce a magnetic field of predetermined inhomogeneity inside an inner space (13) of the probehead (10) varying according to a predetermined time program. Elements of the high frequency system are combined with elements of the coil system into common construction units. In addition, a signal processing unit for measured resonance signals is provided for. The construction units are in the form of hollow bodies (20). Coils (33) of the coil system are located inside the hollow bodies (20). Conductive outer walls (21) of the hollow bodies (20) form the high frequency system.

Abstract: For the purpose of constructing a transversal gradient coil, formed by a conductor, for producing a target field distribution with a prescribed current in a magnetic resonance imaging system, a series of points defining the locations of the coil conductor on a carrier are identified by placing a grid mesh network of elementary saddle coils over the carrier, calculating the magnetic field of these elementary saddle coils and defining a number of ampere-turns for each elementary saddle coil with a fit algorithm on the basis of the target field distribution. The discrete conductor position points are then identified by integration which, in combination, define the path of the coil conductor on the carrier.

Abstract: A magnetic-resonance imaging apparatus has superconducting magnets for generating a large uniform magnetic field within a predetermined volume. Within that volume, coils for generating magnetic field gradients are supported on a bobbin, enabling an object within the bobbin to be investigated. The coils on the bobbin are subject to forces but are rigidly connected to the bobbin. Therefore, energy is transmitted to the bobbin which can cause the bobbin to vibrate and so generate noise. To dissipate that energy, the coils are attached to tubes, or other hollow members, on the bobbin, which tubes or hollow members contain movable bodies such as particulate material. The energy due to the forces on the coils cause the movable bodies to move and collide, so dissipating the energy and reducing the noise.

Abstract: A method and apparatus to reduce the noise in three-dimensional phase contrast magnetic resonance velocity measurements exploits the property that blood is incompressible and therefore the velocity field describing its flow must be divergence-free. The divergence-free condition can be incorporated by the projection operation on Hilbert space where the velocity measurements are projected onto the space of divergence-free velocity fields. The reduction of noise is achieved since the projection operation eliminates the noise component that is not divergence-free. Higher quality angiograms are produced due to the noise reduction in the velocity measurement signals.

Abstract: A method for MR imaging in an inhomogeneous magnetic field substantially without inhomogeneity induced artifacts is disclosed. The method includes acquiring more than one line of K-space per pulse sequence. The K-space data is acquired in partial line segments. The method allows shorter imaging times and higher image quality than conventional imaging methods for inhomogeneous fields.

Abstract: An NMR excitation coil includes a plurality of conductive elements having varying lengths and arranged parallel to one another to define cylindrical volume. A planar loop connects one end of the conductive element together with the conductive segments between pairs of the conductive elements. A non-planar loop connects the other ends of the conductive elements with a series of conductive segments between pairs of the conductive elements. Some of the non-planar loop segments are formed by a coaxial cable having a central conductor connected between ends of two conductive elements and a shield the electrically floats. A separate capacitor is located in those segments of the two loops that are not formed by coaxial cables. Each capacitor has a capacitance which is defined by the inductance of the conductive elements connected to that capacitor.

Abstract: Magnetic field generating apparatus having a solenoid arranged to generate a steady magnetic field gradient along its axis. The arrangement is such that in use contours of constant field are formed within the solenoid. The contours extend generally radially outwardly from the axis of the solenoid and asymmetrically with respect to the center plane of the solenoid orthogonal to its axis. Regions of substantially homogeneous magnetic field suitable for performing an NMR experiment exist about each contour, the regions having substantially constant thickness along the contours.

Abstract: MRI T1 relaxometry is performed using a single fixed strength magnetic background field for RF signal transmission and reception thus greatly simplifying RF circuitry design and/or adjustment Switched differing strength background magnetic fields are employed at other times in the relaxometry cycle so as to predominate the NMR T1 relaxation parameter value and thus permit relaxometry determinations of T1 values versus magnetic field strength (or the equivalent corresponding NMR RF frequency) at N data points using as few as N+1 measurement cycles. In one embodiment, the booster field is switched on for fixed time intervals .tau. while variable initial NMR nutation pulses .alpha. are utilized as the controlled relaxometry variable parameter. Process and apparatus are disclosed for thus efficiently achieving in vivo NMR relaxometry (including magnetic resonance imaging if desired).

Abstract: This invention relates to a superconducting magnet of the type that has a relatively small imaging volume. Such structures of this type, generally, allow the operator to image human limbs without the use of a larger, more costly superconducting magnet.

Abstract: A capacitive position sensor has a scale (10), having hollow or raised topographical features, and a cursor (20) having an electrode array comprising at least two transmitting electrodes (21a, 21b) and at least one receiving electrode (21c) separated by shielding electrodes (21g). The coupling capacitances (Cac, Cbc) between transmitting and receiving cursor (20) electrodes are modified as a function of the position (x) of the scale topographic feature (11) relative to the cursor, the evaluation of the variation of the signals picked up by the receiving electrode permitting a precise measurement of the relative displacement between scale and cursor.

Abstract: A novel method of magnetic resonance imaging is disclosed, in which a single high-frequency magnetic field signal synthesized from a plurality of high-frequency components associated with a plurality of slice sections respectively is applied to a subject to excite the slice sections at the same time, and a phase encode pulse is applied in the direction perpendicular to a slice section. Information corresponding to the position of a slice section is applied to the phase of an excited spin and a measurement signal is subjected to Fourier transformation thereby to produce a data corresponding to each slice section. The phases of a plurality of high-frequency components of a high-frequency magnetic field signal are controlled to be in a predetermined relationship to each other at a predetermined timing.

Abstract: A remotely positionable device for use in magnetic resonance imaging includes a magnet which is juxtaposable against the object to be imaged without actually surrounding to object. When so positioned, the magnet generates a static nonhomogeneous magnetic field having a determinable measurement surface wherein both the magnitude and the gradient of the field are substantially constant. Additionally, the device includes an RF antenna for periodically pulsing nuclei in the measurement surface with pulses of the Larmor frequency to initially tilt the nuclei and to subsequently refocus the nuclei. The device also includes a pair of gradient coils which generate a gradient fields that are superposed on the static field to encode the nuclei. The RF antenna subsequently receives a plurality of encoded spin echo signals from the refocussed nuclei which are averaged by a computer to create a measured response.

Abstract: A local gradient coil adapted for use with stereotaxic devices includes an opening in the coil form positioned to minimize the disruption to the gradient fields and a bearing for moving the form with respect to the stereotaxic frame so that the opening may be limited in area and yet provide essentially unrestricted access to the patient. The windings in the neighborhood of the opening may be diverted by modifying the stream function of the windings in a manner to minimize the effect of the opening on the gradient field.

Abstract: Method for MR imaging of an object in which various RF and magnetic field gradient pulse sequences are used to produce transverse magnetization and to generate echoes. The RF pulse sequence may include a sinusoidal waveform component defined by either y=sin x, 0.ltoreq.x .ltoreq.4.pi.; y=cos x, 0.ltoreq.x .ltoreq.4.pi.; or y=sin x, 0.ltoreq.x.ltoreq..pi./2, y=cos x, .pi./2.ltoreq.x.ltoreq..pi.; and a phase component defined by either y=0, 0.ltoreq.x.ltoreq.2.pi., y=.pi., 2.pi..ltoreq.x.ltoreq.4.pi.; or y =-2.pi.cos x, 0.ltoreq.x.ltoreq..pi./2, y=-2.pi.sin x, .pi./2.ltoreq.x.ltoreq..pi.. The selected waveform and phase components may be combined to form a first, composite RF signal and the Hilbert transform of the composite RF signal selected as a second RF signal. Alternately, the second RF pulse sequence may be comprised of first and second phase shifting linear ramps. The selected gradient magnetic field pulse sequences may include a first sinusoidal readout pulse sequence defined by y=ax sin x, 0.ltoreq.x.

Abstract: In nuclear magnetic resonance tomography apparatus operable with a pulse sequence according to the echo-planar method, only a part of the k-space is scanned in the phase-coding direction per data acquisition, i.e., per radio-frequency excitation pulse. A phase-coding gradient is used such that regions of the k-space which are interleaved relative to each other are scanned in successive data acquisitions in the phase-coding direction. The number of echoes employed for the raw data matrix, and thus the resolution in phase-coding direction, or the length of the individual pulses of the read-out gradient, and thus the resolution in read-out direction, can thereby be enhanced.

Abstract: Improved NMR sample tube shapes and inserts for standard tubes to shape the sample for greater homogeneity to provide symmetry of liquid sample and tube to a greater distance from the observe region for the same volume of sample as used in the prior art.

Abstract: In a method for compensation of time variant field disturbances in magnetic fields of electromagnets with high field-homogeneity, in particular in sample volumes of superconducting electromagnets for measurements of magnetic resonance, the dispersion signal u.sub.x of the nuclear signal of a reference substance is acquired and taken into consideration for compensation by generation of a current dependent on the dispersion signal in a field correction coil of the electromagnet. The method is characterized in that the absorption signal u.sub.y of the reference substance is additionally acquired and that the compensation is carried out in dependence on the quantity u.sub.x /u.sub.y and/or (1/u.sub.y)(du.sub.x /dt). These are substantially independent of many influencing quantities.