Abstract: An RF shield is provided to prevent coupling between the gradient coils and the RF coil of an MR imaging system, wherein the RF field rotates around the RF coil axis. The shield includes a number of coaxial conductive cylinders, and further includes a plurality of cylinders formed of dielectric material, each dielectric cylinder positioned between adjacent conductive cylinders. Each conductive cylinder is formed from sheets of copper, each sheet having a pattern of conductive loops formed therein, and each loop having an associated gap to prevent induction of eddy currents therein by gradient magnetic fields produced by the MR system gradient coils.

Abstract: The present invention, in one form, is a method for detecting reference channel blockage in a computed tomography system. The system includes an x-ray source, a detector and a reference channel. When scanning an object of interest, the x-ray source is supplied with an x-ray source current and projects an x-ray beam toward the detector and the reference channel. The detector, when impinged by the x-ray beam, generates projection data for reconstructing an image of the object of interest. The reference channel is configured to generate an actual reference channel signal when impinged by the x-ray beam. An expected reference signal is determined in accordance with the x-ray source current. The expected reference signal is then utilized to normalize the projection data.

Abstract: The invention is directed to a gradient coil assembly for MR imaging which includes a gradient coil set comprising inner and outer gradient coils, the inner gradient coil located within the outer gradient coil and surrounding or otherwise proximate to an imaging volume. The system further includes means for selectively energizing the inner and outer gradient coils to generate a resultant gradient field in the imaging volume. The energized inner and outer gradient coils are also disposed to collectively generate an eddy current field component in a region between the outer coil and a conductive structure spaced-apart therefrom when the inner gradient coil is displaced along an axis from a specified position with respect to the outer gradient coil.

Abstract: An ultrasound imaging system for displaying edge-enhanced topographic flow power data surrounded by B-mode anatomical data without masking out any significant edge-enhanced topographic flow power data and without displaying any significant flow power background noise. An improved high-pass topographic filter is used to enhance the edges of the flow in the displayed image in both the horizontal (lateral) and vertical (range) directions. The two-dimensional topographic filter is a digital filter with three taps in each dimension and is incorporated in the acoustic line memory. Also, the raw flow power data is compressed down to 7 bits in such a way that the transfer function is shifted away from zero input power. In this way, the system gain can be set to effectively zero out most of the background noise. After the flow power data passes through the high-pass topographic filter, it is mapped to values between -128 and +127 (8 bits) with zero in the middle.

Abstract: The present invention, in one form, corrects any error due to varying detector cell gains in the z-direction represented in data obtained by a scan in a CT system. The CT system includes an x-ray source which emits an x-ray beam from a focal spot, through a collimator aperture, and towards a detector having a plurality of detector cells. The geometry of the x-ray beam, the width of the collimator aperture and the focal spot size are used to determine the z-profile of the x-ray beam across the detector cells. Such z-profile is used to identify effective detector cell gains. The identified effective detector cell gains, rather than actual detector cell gains, are used to correct errors due to varying detector cell gains. Particularly, the identified effective detector cell gains are employed in a known correction algorithm to correct errors. A local average in an x-direction of actual detector cell gain z-profiles is used to determine a non-rectangular norm detector gain z-profile.

Abstract: The present invention, in one form, is a system for obtaining data measurement signals for producing a tomographic image of an object in a multislice scan. More specifically, detector cells in at least one channel of a detector array are electrically coupled, or ganged, so that the ganged channel provides one data measurement signal to be transmitted through the gantry slip ring. The signal distribution in the z-direction for the ganged channel is then determined using signals obtained by adjacent non-ganged detector cells.

Abstract: The present invention, in one form, is a method for improving image quality in Computed Tomography systems by using a partial volume artifact estimation algorithm. In accordance with one embodiment of the algorithm, an object of interest is scanned to generate image data. The image data is segmented into low attenuation data and high attenuation data. A gradient image is generated for two adjacent slices of the image data. The gradient image is then forward projected and squared. The squared gradient image is an estimation of partial volume artifacts in the image data, and therefore is removed from the image data.

Abstract: A device for improving thermal transfer inside an ultrasound probe and reducing heat build-up near the transducer face. The cable components are used as heat conductors which conduct heat out of the probe handle. These heat pipes are coupled to an internal heat conductor which is in heat conductive relationship with the transducer pallet. Thus, heat generated by the transducer array can be transferred, via the internal heat conductor plate and the cable heat conductors, away from the probe surface which contacts the patient. A heat conductive structure can be embedded in the overall shield braid of the cable. Suitable heat conductive structures include thread or wire made of material having a high coefficient of thermal conductivity, as well as narrow tubing filled with heat conductive fluid. Alternatively, inlet and return flow paths for cooling fluid are incorporated in the cable.

Abstract: A method of manufacturing a transducer assembly having a curved transducer array. The method includes the steps of fabricating a laminated assembly by bonding the following layers together: a layer of electrically conductive, acoustic matching material, a layer of piezoelectric ceramic, a flexible printed circuit board and a layer of acoustic damping material. The acoustic damping material changes from an inflexible state to a flexible state when heated. The laminated assembly is then diced to a depth so that the only undiced portion is a portion of the acoustic damping layer. A core body having a curved front face in the shape of a cylindrical section is fabricated. Then at least the undiced portion of the layer of acoustic damping material is heated into a flexible state. The heated undiced portion of the layer of acoustic damping material is flexed to conform to the curved front face of the core body.

Abstract: The present invention, in one form, is a system for performing image reconstruction from projection data acquired in a helical scan. More specifically, the system implements an incremental reconstruction algorithm for helical scan projection data which does not require filtering, weighting and backprojecting such projection data for generating each image. Particularly, an overscan weighting algorithm generates weighting factors to be applied to projection data to generate base image projection data. An update weighting algorithm generates update weighting factors to be applied to the base image projection data to generate subsequent image projection data.

Abstract: A method for designing ultrasonic transducers used in diagnostic ultrasonic imagers, in particular, transducers made up of at least one piezoelectric layer and at least one acoustic matching layer, plus various bonding and backing layers. The method of transducer design uses a particular family of spectra as the basis of the bandpass characteristic. The approach is to specify a transfer function from the Transitional Butterworth Thompson family of spectra. The specification is influenced by trade-offs in bandwidth, transient response and design feasibility. This family is indexed by a design parameter called M. Using the M factor, a designer can more readily make the engineering trade-offs needed. By adjusting this parameter, any dynamic response from maximally flat to Gaussian can be obtained.

Abstract: The present invention, in one form, is a method of determining focal spot position in a computed tomography system using conventional scan data. The computed tomography system includes, in one embodiment, a bowtie filter attenuating an x-ray beam along two symmetrically disposed raypaths. The symmetrical raypaths impinge upon respective detector channels at identifiable path lengths. The raypath lengths are compared to determine whether the focal spot has shifted.

Abstract: An indium gasket having a configuration which allows the indium to reach its yield point at a relatively low contact pressure. The indium gasket is provided with a multiplicity of openings which are filled by the deforming indium during compression between the cryocooler and the cryocooler interface sleeve of a superconducting magnet system. The creation of openings in the gasket has the effect of decreasing the mechanical interface pressure at which the indium yields. The indium flows at a mechanical interface pressure that does not exceed the structural strength requirements of the cryocooler. The indium flows into the empty spaces formed by the openings, thereby providing the necessary thermal conductance between the cryocooler and the interface sleeve. The result is a relatively small temperature difference between the interface sleeve and the cryocooler during cooling of the superconducting magnets.

Abstract: A cryogen recondensing system magnetic resonance imager superconducting magnet and a cryogen recondensing system with a rare earth displacement material cryocooler and superconductive lead bismuth magnetic sleeve provides superconducting current flow of currents induced by movement of the rare earth displacer which generate opposing magnetic fields to shield the superconducting magnet from the magnetic interference of the cryocooler rare earth displacer. Strips of high conductivity wave-shaped aluminum or sapphire rods may be embedded in the surface of the sleeve to lower the thermal resistance of the superconducting shield to enable it to quickly reach superconducting temperature.

Abstract: A magnetic resonance imaging superconducting magnet including a cryostat, a gradient coil and superconducting gradient shield positioned around the gradient coil with an active resistive shimming member contiguous to the cryostat vessel; and the gradient shield being selectively cooled to superconducting operation after the magnetic shimming fields generated by the shimming member for field homogeneity within the bore of the magnetic resonance imaging magnet are induced onto, and maintained by, the superconducting gradient shield and operation of the resistive shimming member discontinued.

Abstract: A whole body RF coil provided for use with an open MR magnet system comprises first and second RF coil components selectively spaced apart from each other on opposite sides of an imaging space disposed to receive a subject, each of the RF coil components comprising a plurality of electrically conductive inner and outer arc segments which respectively lie on corresponding inner and outer circular paths. The RF coil is constructed to allow the subject to pass through the inner and outer circular paths of a selected one of the coil components or alternatively between the spaced apart RF coil components, into imaging space. The first and second RF coils are each energized in quadrature to generate respective corresponding first and second magnetic fields which collectively provide a resultant field comprising the B.sub.1 field component required for imaging.

Abstract: A passively shimmed open architecture magnetic resonance imaging magnet utilizing separated superconducting coil assemblies with open space between including means to obtain a uniform magnetic field in the open space by shaped ferromagnetic bands in the bore of the magnets, the shaping including an axial notch and circumferential holes for attaching passive shims.

Abstract: The present invention, in one form, is a system for modulating x-ray tube current as a function of gantry angle and slice location in a computed tomography system. In one embodiment, a desired noise level for a final image is selected, and a desired minimum x-ray photon reading and a desired average x-ray photon reading are identified to produce an image in accordance with the desired noise level. During scanning, actual x-ray photon readings are used with the desired average x-ray photon reading and the desired minimum x-ray photon reading to generate an x-ray modulating factor. This modulating factor is then used to modulate the x-ray tube current.

Abstract: A method of forming a superconducting joint between the Nb.sub.3 Sn layer of a superconducting tape and a superconducting NbTi wire through use of a Pb-Bi bath, joint securing arrangement and mold around the joint.