Abstract: An emission tomographic system which includes a gantry and a detector is described. The system automatically adjusts the detector attitude to maintain the detector at a desired orientation with respect to a patient during a scan. The system includes a tilt drive and processor coupled to the gantry and the detector. The processor receives signals indicative of changes in the gantry pitch angle, and uses such signals to determine appropriate changes in detector tilt. For each change in gantry pitch angle, the processor executes an algorithm relating gantry pitch angle to detector tilt angle, and determines an appropriate responsive change in detector tilt angle. The tilt drive then tilts the detector in accordance with the appropriate responsive change.

Abstract: A method and an apparatus for improving the signal-to-noise ratio (SNR) and/or resolution in color flow ultrasound imaging by using complementary-coded excitation of the transducer array. The SNR is improved by transmitting a pair of Golay-coded pulse sequences in alternating sequence at the same transmit focal position over multiple firings and then partly decoding the beamsummed data. The partly decoded data is then vector summed and high pass filtered. The summed and high-pass-filtered data is optionally decimated by a factor of two. The decimated or undecimated data is then input to the parameter estimator, which provides imaging signals representing the flow in a scan plane. Those imaging signals are then displayed as color information on a display monitor.

Abstract: The present invention, in one form, is a system for performing image reconstruction using data acquired from a single detector row in a helical scan. More specifically, a modified weighting factor W.sub.f (.beta.,.gamma.), which is a shifted and weighted average version of the single slice helical weighting factor, is generated. The modified weighting factor is then applied to data to reduce image noise and artifacts and/or increase image sharpness.

Abstract: A method and apparatus for adjusting the shape of a region of interest (ROI) in a frame of imaging data in response to an operator-actuated change in the depth of the ROI. The displayed image has a background region of data acquired using a first imaging mode and an ROI of data acquired using a second imaging mode. The ROI is surrounded by the background region and bounded by an ROI graphic. The adjustment in the shape of the ROI is accomplished by programming the imaging system with an algorithm that maintains the height and the bottom width of the ROI substantially constant. Only the top width of the ROI and the angles of the edge lines are automatically changed in response to the operator-actuated change in ROI depth.

Abstract: A superconducting magnet utilizing a pair of donut-shaped annular magnet assemblies including in each a cryogen pressure vessel with a non-magnetic cylindrical divider forming pairs of concentric chambers. Pairs of axial non-magnetic strut members spaced about the interior of the pressure vessel extend at an angle within the concentric chambers between the end flanges of each assembly to resist forces generated within and between the pair of magnet assemblies.

Abstract: A method is provided for maximizing substrate usage in the fabrication of flat panel displays or detectors, while also maximizing electrostatic protection for the displays or detectors. Initially, at least two detectors are positioned on the substrate, with each of the detectors having a guard ring of a certain width. At least a section of the guard ring width of one detector is approximately adjacent to a section of the guard ring width of another detector. The approximately adjacent guard ring width sections are then positioned such that a maximum overlap of the adjacent guard ring width sections is achieved, while still providing each display or detector with electrostatic discharge protection. Each of the detectors is separated from the other detectors and the remainder of the substrate by the process of scribing partially through the substrate and breaking at the scribe mark or by sawing.

Abstract: A method and an apparatus for adaptively suppressing incoherent data in a coherent imaging system. A focused ultrasound beam is transmitted with conventional transmit beamforming time delays. The returning echo signals are processed along two separate receive signal processing paths. The time delays along one processing path are set for traditional coherent receive beamforming, while the time delays along the other processing path are set to apply incoherent summing to the same set of return signals (e.g., time delays equal to zero). Then at each point in the receive beam or vector, the coherent and incoherent summation signals are compared. If the coherent and incoherent summation signals are of like amplitude, the beamformed signal of the first processing path is deemed incoherent, and its display is suppressed in the final image.

Abstract: An ultrasound color flow imaging system is programmed to optimize display images of power and velocity by automatically adjusting thresholds by using histograms and samplings of color flow data.

Abstract: A method is provided for correcting for effects of translational motion or movement of an object in MR imaging. In accordance with the method, an MR point source is joined to the object for translational movement in unison therewith, the point source being maintained in selectively spaced-apart relationship with the object. The method further comprises acquiring a set of k-space data representing images of the object and point source collectively, and deriving a function representing the square of the magnitude of the k-space data set. An inverse Fourier transform operation is applied to the derived function to generate a correlation function with a number of correlation components, a specified one of the correlation components comprising the cross-correlation of the object and the point source.

Abstract: A method for automatic Doppler angle estimation based on the B-mode and color flow (if available) image. The method uses an algorithm for automatic vessel slope measurement which first finds an optimal initial point within the sample volume or range gate, and then searches for the most reliable pixel points (near or far walls) based on a combination of intensity-only and intensity-difference thresholds, before performing a slope estimation. B-mode intensity data and, optionally, color flow velocity or power data (before gray/color mapping) are used. The algorithm may also be applied to methods for automatic tracking of vessel diameter and flow rate calculations, although the primary objective is to achieve automatic Doppler angle estimation in an ultrasound scanner.

Abstract: The present invention provides for an adherent and durable coating for a lead-lined x-ray tube casing which is exposed to dielectric cooling oil. Electroplating lead radiation shield material with a corrosion resistant and nontoxic material having excellent solderability, softness and ductility, provides a clean corrosion resistant surface which is inert to the oil, independent of temperature and x-ray irradiation. The electroplating material preserves the lead surface from flaking and corroding to the oil. The electroplating material is preferably selected from the group consisting of tin, silver, copper and nickel, or various combinations of those or other materials capable of providing an adherent and durable coating for the x-ray tube casing.

Abstract: Two methods are disclosed to remove the image artifacts produced by Maxwell terms arising from the imaging gradients in an echo planar imaging pulse sequence. In the first method, the frequency and phase errors caused by the Maxwell terms are calculated on an individual slice basis and subsequently compensated during data acquisition by dynamically adjusting the receiver frequency and phase. In the second method, two linear phase errors, one in the readout direction and the other in the phase-encoding direction, both of which arise from the Maxwell terms, are calculated on an individual-slice basis. These errors are compensated for in the k-space data after data acquisition.

Abstract: A method and an apparatus for enhancing edges in computer-generated images. Each image frame is divided into non-overlapping blocks of pixels. Each block is characterized by a value proportional to the contrast of the block. Each block is checked to see if its contrast is greater than a user-selectable contrast threshold. If the block contrast is greater than the threshold, a window level operation is performed upon that pixel block. This method restricts the window level edge enhancement function to just the set of pixel blocks that have a high contrast value and may contain an edge.

Abstract: In a method for providing an MR image of a section taken through an object, wherein the section is acquired in the presence of in-plane translational motion of the object, an MR system is operated to acquire a set of imaging data points from the section, the set of imaging data points being contaminated by phase errors resulting from the motion. The MR system is further operated to acquire a plurality of correction data point sets, each correction data point in one of said sets being acquired along an alignment line or other trajectory and at a location coinciding with the location of one of the imaging data points. The imaging data points respectively coinciding with the correction data points comprise, collectively, a subset of the imaging data points. The phase difference between each correction data point set and its corresponding subset of imaging data points is determined, and then used to remove the phase errors from the set of imaging data points.

Abstract: A method and an apparatus for imaging the nonlinear components of an ultrasound signal returned from ultrasound scatterers in tissue or contrast agents in blood. The method employs a code-modulated wavelet for transmission combined with correlation filtering on reception. Coding methods are used to simultaneously manipulate the linear and nonlinear terms. The manipulations affect the magnitude and temporal arrangement of the resulting decoded waveforms. Among the simultaneous manipulations of linear and harmonic decoded signals are: orthogonal linear terms, finite linear terms, minimum sidelobe with optimal peak harmonic terms and optimally compressed harmonic terms.

Abstract: An X-ray tube comprises an anode assembly having an associated anode and a cathode assembly for providing a focused electron beam directed to the anode. An anode target, associated with the anode assembly, accelerates the electron beam and produces X-rays upon electron impact with the anode target. Off-focal radiation tends to be most intensely emitted by the top surface of the target. In conventional X-ray tubes, the off-focal radiation as seen by the detector encompasses almost the entire top surface of the target assembly. In accordance with the present invention, the anode target comprises a cut-out top surface for reducing off-focal radiation, by blocking the off-focal radiation from the top surface from reaching the detector. Blocking the radiation produced at the top surface becomes more important as the ratio of the track area visible at the detector decreases with respect to the top surface area.

Abstract: A self-tuning crystal notch filter suitable for rejecting a carrier signal in a receiver channel of a receiver of an ultrasound imaging system. The crystal notch filter has a resonant frequency which is electronically tuned. Tuning is done under software control without operator intervention. The software instructs a channel other than the one being tuned to transmit into the transducer. The receive channel being tuned amplifies the received signal and then passes the amplified signal through the notch filter and the TGC amplifier to the corresponding digital signal processing (DSP) circuit via an analog-to-digital converter. The software reads the amplitude of the digital receive signal output from the DSP circuit. By programming a D/A converter incorporated in the notch filter, a value can be found that minimizes the amplitude of the signal output by the DSP circuit, i.e., maximizes the amount of carrier signal being rejected. This value is then used during subsequent imaging data acquisition.

Abstract: A method and an apparatus for increasing the contrast resolution of computer-generated images using fractal enhancement techniques. Each image frame is divided into blocks of pixels which are sorted into source and destination lists based on their distance from the transmit focal zone. The source list contains overlapping pixel blocks corresponding to ranges within a predetermined distance of the transmit focal zone (i.e., blocks of high resolution). The destination list contains non-overlapping blocks corresponding to ranges outside the focal zone area (i.e., blocks of lower resolution). For each low-resolution block, a computer searches for a high-resolution block having the same brightness and contrast classes, but having a greater block contrast. The high-resolution block meeting these criteria and having the greatest block contrast is substituted for the corresponding low-resolution block in the image frame.

Abstract: A method and an apparatus for three-dimensional ultrasound imaging of a needle-like instrument, such as a biopsy needle, inserted in a human body. The instrument is visualized by transmitting ultrasound beams toward the instrument and then detecting the echo signals using a linear array of transducer elements. The problem of ultrasound being reflected from a biopsy needle in a direction away from the transducer array is solved by steering the transmitted ultrasound beams to increase the angle at which the beams impinge upon the biopsy needle. Ideally the ultrasound beams are perpendicular to the biopsy needle. This increases the system's sensitivity to the needle because the reflections from the needle are directed closer to the transducer array. This can be accomplished using either the B mode or the color flow mode of an ultrasound imaging system.

Abstract: Gamma transmission apparatus for use with a gamma camera for reducing transmission imaging period duration, wherein a camera processor is only capable of a maximum number of calculations per second, each photon detected by the camera requires a specific number of calculations and some of the detected photons are not useful for imaging purposes, the apparatus modifying the effective length of an imaging beam to reduce transmission line length thereby eliminating photons which cannot be used for imaging and freeing processor time to process photons useable for imaging thereby increasing imaging speed.