Abstract: A magnet for magnetic resonance imaging of the type arranged to provide fields suitable for imaging in an imaging region outside of the physical structure of the magnet, such as a magnet including plural concentric superconducting coils, generates a field having near-zero radial curvature at one location. Shim coils are actuated to adjust this location in synchronism with tuning of the RF transceiver for slice selection, so that when each slice is selected, that slice is coincident with the location of near-zero radial curvature.

Abstract: A system and method for phase sensitive MRI reconstruction using partial k-space data to reduce either scan time or echo time, depending on whether partial echo or partial NEX MR data is acquired, that retains phase information and reduces edge blurring in a magnetic resonance image. Phase sensitive partial k-space data reconstruction improves upon the homodyne reconstruction process to estimate and correct for an edge blurring convolution error term in a partial echo or partial NEX data while preserving phase information. The phase sensitive partial k-space reconstruction includes Fourier transforming and filtering the partial k-space data through high and low-pass filters, and a linear combination of both, and estimating a blurring correction term, representative of a convolution error factor, from a portion of the filtered data set.

Abstract: A diagnostic imaging apparatus such as a magnetic resonance imaging (MRI) device includes a vacuum vessel (24) having a central helium reservoir (16) in which superconducting magnetic coil windings (10) are maintained at a superconducting temperature. The vacuum vessel defines a bore (12) within which a gradient tube assembly (30) and an RF coil (32) are received. The gradient tube assembly includes an integral tongue (66) extending from a patient end (48) thereof. A first constraint (70) retrains the gradient tube assembly in a “push-pull” arrangement in both directions along the z-axis. The constraint (70) is mounted to a patient-end of the vessel (24) at a lowermost (i.e., six o'clock) position. The constraint includes vibration isolators (94) interposed between the tongue and a saddle mount (72) to reduce vibration transmission from the gradient tube assembly to the vessel.

Abstract: A method for automatic modelling of the stratigraphic structure of an underground zone with fast adjustment of the parameters of the model with observed or measured data is disclosed.

Abstract: The processing of surface seismic data may be monitored where vertical seismic profile data are available for the same region. A trace (45) of the vertical seismic profile data recorded from a geophone at the surface is compared with data generated by the data processing before completion of migration and provides a measure of the quality of the data processing. Alternatively, a derived trace may be derived by taking sections of the vertical seismic profile data traces along a section curve (47). The derived trace may be thought of as partially migrated data and may similarly be used for monitoring the quality of surface seismic data processing.

Abstract: A dual mode gradient coil system in which amplifiers powered by a single signal source are connected by a switch to a plurality of coils. The switch selectively serves to place the coils in series with said amplifiers placed in parallel for a high change in magnetic field per unit distance or, alternatively, to allow each coil to be driven by a separate amplifier for a high change in magnetic field per unit time.

Abstract: A flexible, low-loss, low-capacitance, high-voltage, high-current, moderate-impedance, unshielded, balanced, rf-pulse transmission twinline is produced by etching parallel copper traces on opposite sides of a flexible substrate, spaced apart such that the distance between the conductors is greater than four times the substrate thickness and at least one of the conductors has a width greater than half of the separation between the conductors. A second, similar twinline may be etched on the same substrate beside the first twinline and paralleled at both ends with the first twinline to form a lower-impedance quadline such that alternate conductors in the quadline are on alternate sides of the substrate and have opposite current phases. Both surfaces may be coated with a thin, flexible dielectric to increase the voltage rating for a given conductor separation with minimal affect on propagation factor, attenuation constant, or flexibility.

Abstract: A system for detecting a target substance within a class of explosives and narcotics containing quadrupolar nuclei through the use of nuclear quadrupole resonance (NQR). The system applies an RF signal to a coil (34) to excite the substance under test. If the target material is present, an NQR signal will be picked up by the same coil, That signal is compared with known NQR signals in frequency and amplitude. A signal is displayed in an appropriate way if a threshold value of the NQR signal is equalled or exceeded. The empty coil is statically tuned by means of adjusting the location or capacitance values, or both, of static tuning capacitors (102) in the coil. The coil is tuned after the specimen is inserted into the coil by means of an auto-tune feature (36). Effective RFI shielding (37) is provided to prevent external contaminating signals from being detected by the coil and to prevent RF signals from escaping from the scanner. The invention also includes the method for performing tests with the system.

Abstract: An improved micro-actuator position sensor which provides an accurate position signal for higher bandwidth control of a micro-actuator. The position sensor allows closed loop control of the micro-actuator position. Preferred embodiment micro-actuator sensors include a piezo-resistive stress sensor integrated within the springs, a capacitance sensor and magnetic reluctance sensor. Embodiments of the present invention are described in detail as integrated sensors for a micro-actuator used in hard disk drives. The sensor is integrated with a micro-actuator at the tip of the conventional actuator arm to improve the precision seeking capability of the actuator arm.

Abstract: A toroid cavity detector includes an outer cylindrical housing through which extends a wire along the central axis of the cylindrical housing from a closed bottom portion to the closed top end of the cylindrical housing. In order to analyze a sample placed in the housing, the housing is placed in an externally applied static main homogeneous magnetic field (B0). An RF current pulse is supplied through the wire such that an alternately energized and de-energized magnetic field (B1) is produced in the toroid cavity which B1 field is oriented perpendicular to the B0 field. Following the RF current pulse, the response of the sample to the applied B0 field is detected and analyzed. In order to minimize the detrimental effect of probe ringing, the cylindrically shaped housing is elongated sufficiently in length so that the top and bottom portions are located in weaker, fringe areas of the static main magnetic B0 field.

Abstract: A sensor for measuring linear or angular dimension. The sensor can be moved with respect to a magnetized scale with a period &lgr;. It is equipped with magnetoresistive electrodes provided with barber-pole structures and connected so as to form n measuring bridges, each measuring bridge formed by four sets of magnetoresistive electrodes. The magnetoresistive electrodes making up each set are connected in series, the magnetoresistive electrodes being distributed spatially so as to constitute x groups. Each group being formed by more than eight consecutive magnetoresistive electrodes coming from two sets of a same measuring bridge.

Abstract: A method of compensating for an eddy field according to measurements of the field. The method includes fitting the measurements of the field to a plurality of candidate models of the field. A stability value indicative of the stability of the fitted model to changes, is assigned to each of the fitted candidate models. A model is selected from the candidate models responsive to the stability values of the candidate models and the eddy fields are compensated responsive to the selected model.

Abstract: A seismic sensor array includes a means for passive electrical to optical energy transformation and transmission. This transformation is used remotely with traditional sensor arrays, which may include hydrophones, geophones, or a combination of them. The transformation means is used to develop an optical signal in a fiber which then conveys the seismic signals to a recording center or data accumulator. The transformation means preferably comprises a stack of piezoelectric elements capped on each end by a rounded crown to accommodate an optical fiber wound around the stack and the crowns.

Abstract: The method and apparatus of the invention determines earth formation resistivity at extended depths into the formation by the use of telemetry transmission signals to measure the formation resistivity. The telemetry transmission signals carry measurement data from downhole sensors through the formation to an uphole receiver. The signal transmission is by means of induction telemetry. At the receiver, the signal is demodulated to obtain the transmitted measurement data. During the detection of the signal at the receiver, the signal amplitude is also extracted and is used to determine the formation resistivity. In addition, changes in the signal amplitude are also used to indicate formation boundaries for determining well location during directional drilling.

Abstract: A current sensor assembly includes a sensor coil, an electrostatic shield coil, a core, a housing, and a magnetic shield. The sensing coil, electrostatic shield coil, core, housing, and magnetic shield can be of toroidal symmetry and arranged coaxially about a pair of primary current conductors. The conductors can be either asymmetric or symmetric with respect to the geometric center of the remaining sensor assembly. The core and a secondary winding make up a current sensor. The core is cylindrically shaped and fabricated of non-magnetic material. The secondary winding is wound over the cylindrical core to form a toroidally shaped winding. When assembled into the current sensor assembly, the core and windings are disposed around two single turn primary windings through which AC currents to be measured flow. Alternatively, the conductor can be flat and the sensor can be a solid state sensor that includes an electrostatic shield.

Abstract: Disclosed is an apparatus and a method for three dimensional magnetic resonance data acquisitions using a fast 3D sequence to acquire volumetric data in a cine mode. The entire heart can be imaged in the same amount of time that a conventional cine scan requires for a single section. The true temporal resolution is similar to that of the segmented k-space acquisition. The sequence uses very short repetition times (TR), and hence the inherent contrast is poor. This problem is overcome with the use of a T1 shortening agent. Since contrast between blood and the myocardium is no longer flow dependent, it is more stable throughout the heart cycle.

Abstract: A new two-dimensional NMR carbon-proton chemical shift correlation experiment, the MAS-J-HMQC experiment, is proposed for rotating solids. The magnetization transfer used to obtain the correlations is based on scalar heteronuclear J couplings. The 2D map provides through-bond chemical shift correlations between directly bonded proton carbon pairs in a similar way to corresponding high-resolution liquid state experiments. The transfer through J coupling is shown to be efficient and more selective that those based on heteronuclear dipolar couplings. The experiment, which works at high MAS spinning rates, yields the unambiguous assignment of the proton resonances. The experiment is demonstrated on several organic compounds.

Abstract: Navigator echo signals are acquired during an MRI scan in which image data is acquired. The navigator echo signals are used to estimate an initial correction of the acquired image data for patient motion during the scan. The initially corrected image data is then autocorrected in an iterative process which measures image quality and makes further corrections to the image data until the measured image quality is within tolerance.

Abstract: The invention provides a method for imaging the distribution of n-acetylaspartic acid (NAA) in mammalian neuronal tissue, by a) exciting the neuronal tissue to generate magnetic resonance signals, including signals corresponding to NAA; b) suppressing non-NAA magnetic resonance signals by a combination of band selective inversion with gradient dephasing, and chemical shift selective pre-excitation; c) encoding a first spatial dimension of the NAA signal with readout encoding and a second spatial dimension of the NAA signal with gradient phase encoding, and d) using the encoded first and second spatial dimensions to image, by reconstrucion, the distribution of NAA in the tissue.

Abstract: The present invention relates to a method of manufacturing a human tissue phantom for evaluation of electromagnetic wave environment. The present invention suggests the human tissue phantom having reproductibility, being different from liquid type, after elapse of a certain period and preventing the air-gap occurring after insertion of probe, by using a composite material which is composed of a shape memory polymer as a base material and a dielectric material and a conductive material as the fillers, and also suggests the method of manufacturing the whole human body phantom.