Abstract: A C-shaped superconducting magnet for use in magnetic resonance imaging (MRI) equipment is disclosed. The magnet includes flux concentrators on opposing sides of the gap, for generating a vertical field therein; the flux concentrators include a plurality of coils, for carrying current in opposing directions, so as to generate an inwardly directed field to compensate for the gap. Injection correctors, each consisting of a horizontal coil, are disposed adjacent the flux concentrators. A flux return body, for example a superconducting solenoid or an iron yoke, provides a return path on the opposite side of the magnet from the gap. Flux deflectors guide return flux in a curved path from the flux return body to the injection correctors.

Abstract: An acoustic transducer assembly is provided having a one or two dimensional array of transducer elements, an electrical circuit element such as a circuit element and a backing for interconnecting transducer elements to corresponding contacts or traces of the circuit element. The backing is a block of acoustic attenuating material having a conductor extending therethrough between each transducer element and the corresponding circuit contact. The block has acoustic properties, including acoustic impedance and acoustic velocity, to achieve a desired degree of acoustic match with the transducer elements and/or to permit coupling of acoustic energy from the conductors into the block. The block may be of a single material or may have different volumes of two or more materials having different acoustic properties to achieve desired results. Multiple thin conductors or conducting fibers or foils may be utilized for each transducer element to reduce or eliminate acoustic coupling into the conductors.

Abstract: Apparatus and method for compensating for differences in time at which an incoming acoustic wave is received by an array of acoustic signal receivers to take account of the shape of the incoming wave and the non-zero incidence angle of its approach. Each receiver is provided with a time delay module that introduces a large or coarse scale time delay .DELTA.t.sub.L plus a small or fine scale time delay .DELTA.t.sub.S, where .DELTA.t.sub.L is an integral multiple of a coarse scale time interval length .DELTA.t.sub.c and .DELTA.t.sub.S may be varied continuously from 0 to a predetermined time interval length (.DELTA.t.sub.S).sub.max that may be made at least as large as .DELTA.t.sub.c.

Abstract: Apparati and methods for magnetic resonance imaging a selected interrogation volume in a tissue of a human or animal body, to provide increased signal-to-noise ratios for fixed data acquisition times. The method involves excitation of magnetic resonance in a selected interrogation volume that may be as small as 500-3,000 cm.sup.3, through controllable focusing or steering of a rotating magnetic field signal used to induce magnetic resonance. The response signals issued by the excited volume element are then collected by focusing of these response signals, using a phased array of antennae for this purpose. Use of the invention with well known nuclear magnetic resonance excitation procedures, such as spin echo, echo planar, gradient recalled and backprojection, are discussed.

Abstract: A two-dimensional phased array ultrasound imaging system distributes signal delays between its probe and its base section. The transducer elements are grouped and relative delays between elements of a group are introduced within the probe. Once the intragroup delays are introduced, the signals from the elements of a group are combined to generate a group signal. A group signal is generated for each group and, collectively, the group signals are transmitted to the base section via a multi-wire cable. Delays between groups are introduced at the base section. This distribution of delays maintains power dissipation within the probe at a tolerable level while requiring only a manageable number of data and signal lines between the probe and base section.

Abstract: Apparati and methods for magnetic resonance imaging a selected interrogation volume in a tissue of a human or animal body, to provide increased signal-to-noise ratios for fixed data acquisition times. The method involves excitation of magnetic resonance in a selected interrogation volume that may be as small as 500-3,000 cm.sup.3, through controllable focusing or steering of a rotating magnetic field signal used to induce magnetic resonance. The response signals issued by the excited volume element are then collected by focusing of these response signals, using a phased array of antennae for this purpose. Use of the invention with well known nuclear magnetic resonance excitation procedures, such as spin echo, echo planar, gradient recalled and backprojection, are discussed.

Abstract: Apparatus and method to provide a controllable one-dimensional array or two-dimensional array of delay times for an array of acoustic signals propagating in a plurality of bodies of piezoelectric material. Each piezoelectric body is provided with three or more pairs of electrodes, with the first and second electrodes of a pair being spaced apart and positioned on first and second surfaces, respectively, of the piezoelectric body. As an acoustic wave propagates longitudinally in the piezoelectric body, an electrical voltage signal is generated between each electrode pair as the wave passes between the two electrodes of that pair. Time delay is controlled by choice of the longitudinal position of each electrode pair along the piezoelectric body.

Abstract: Apparati and methods for magnetic resonance imaging a selected interrogation volume in a tissue of a human or animal body, to provide increased signal-to-noise ratios for fixed data acquisition times. The method involves excitation of magnetic resonance in a selected interrogation volume that may be as small as 500-3,000 cm.sup.3, through controllable focusing or steering of a rotating magnetic field signal used to induce magnetic resonance. The response signals issued by the excited volume element are then collected by focusing of these response signals, using a phased array of antennae for this purpose. Use of the invention with well known nuclear magnetic resonance excitation procedures, such as spin echo, echo planar, gradient recalled and backprojection, are discussed.

Abstract: In ultrasonic apparatus has a large aperture annular transducer array which is mechanically rotated in a scanning motion. The ultrasound beam is electronically steered to compensate for angular position error caused by the scanning motion by means of preselected delay patterns to thereby produce an ultrasound beam which undergoes a discrete step scan pattern of an object of interest. Also disclosed is a method of manufacturing the transducer array which involves segmenting the transducer after assembling the transducer components.

Abstract: The acoustic imaging transducer described herein incorporates an acoustic stack contained in an alumina housing which also provides structure for electrically connecting the transducer array elements to system signal processing electronics.

Abstract: A method is provided to connect individual conductive traces to an array of individual piezoelectric elements by bonding a flexible circuit board containing conductive traces to the piezoelectric elements. The resultant bonded elements provide an array for an acoustic transducer.

Abstract: Spurious emissions caused by a newly-described vibration mode in an acosutic imaging transducer are suppressed by cancelling the net displacement of the center of mass of each piezoelectric element in the transducer array.