Abstract: A method and an apparatus for improving the contrast of the displayed image data in a B-mode ultrasound imaging system. An adaptive gray mapping is based on the actual raw imaging data instead of assumptions about that raw data. The user specifies a region of the image (or the entire image) with a graphical region-of-interest (ROI) marker. When prompted by the user, a software program in the master controller analyzes the raw data within the ROI and constructs a new gray map based upon the analyzed data. This mapping can be created by transforming an old gray map or by generating a new gray map. This new gray map is then used by the ultrasound system during imaging. Optimum contrast is achieved by automatically adjusting the brightness and contrast levels of the image based on the values of the raw data.

Abstract: Methods and apparatus for reducing the amount of computation required by nonlinear operations in medical ultrasound imaging by using lower-order polynomials to approximate the nonlinear functions. The method can be applied to envelope detection, phase detection, logarithmic compression and other nonlinear functions. Various pre-processing techniques (e.g., pre-reducing the data range and pre-dividing an entire range of the input into a number of subranges) can optionally be used prior to the polynomial approximation to achieve better accuracy, further reduce the polynomial order, and/or simplify the implementation.

Abstract: An ultrasound color flow imaging system is programmed to operate in an adaptive manner. The operational adjustments are made based on the system gain setting or the transmit packet size or both. Based on these operator inputs, the transmit burst length is adjusted for optimum operation. In addition, the transmit peak amplitude and the bandwidth of the receive filter are adjusted as a function of the burst length adjustment.

Abstract: A method is provided for acquiring MR image data, which comprises the steps of applying a succession of RF excitation pulses to a selected region of an imaging subject to produce a corresponding succession of MR data signals, generating a readout gradient in association with each of the MR data signals, and acquiring sets of data points from the MR data signals to provide views respectively corresponding thereto. The data points of a view are respectively identified by positions in k-space along a first k-space axis, each of the positions along the first k-space axis having a time offset with respect to a reference.

Abstract: An MRI system performs a scan to acquire NMR signals from which an image can be reconstructed. The NMR signals are compressed prior to digitization by a nonlinear preamplifier, and after digitization, the signal is restored to the correct amplitude by a decompression process. The SNR of the reconstructed image is improved without increasing the size of the analog to digital converter.

Abstract: A thermally insulating joint for multilayer insulating blankets for a superconducting magnet with layers of low thermal emissivity material separated by low conductivity spacers staked together with adjacent joints and vents offset from each other and with low emissivity adhesive strips overlying the remote ends of adjacent layers of the joined blankets.

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, a segmentation algorithm divides the projection into a plurality of segments so that subsequent images are generated by generating image data only for those segments that have changed from the base image.

Abstract: The present invention, in one form, is a method for correcting for artifacts caused by highly attenuating objects in a CT image data using a correction algorithm. In accordance with one embodiment of the algorithm, the highly attenuating objects are identified in the image data using the CT numbers from the image data. The segmented image data for each highly attenuating material are used to produce separate component images for each material. The component image data for each material is then separately forward projected to generate projection data for each material. The projection data for each material is then adjusted for the attenuation characteristic of the material to generate projection error data for each material. The resulting projection error data are then filtered and backprojected to produce error-only image data. The error-only image data are then scaled and combined with the original image data to remove the highly attenuating object artifacts.

Abstract: A cryogen recondensing magnetic resonance imager superconducting magnet utilizing a rare earth displacement material cryocooler with a superconducting sleeve surrounding a portion of the circumference of the cold end of the cryocooler to provide superconducting current flow of currents induced by movement of the rare earth displacer to generate opposing magnetic fields which shield the imaging region of the superconducting magnet from magnetic interference generated by movement of the cryocooler rare earth displacer.

Abstract: A multiband RF pulse is produced using the SLR method. A single-band RF pulse is produced and employed to determine correction factors. The SLR polynomial coefficients for each excited band are calculated and corrected, and then combined to form a composite SLR polynomial from which the multiband RF pulse is produced.

Abstract: An ablation system includes a catheter adapted to be inserted into the heart of a patient. The catheter has a distal end and a plurality of electrodes disposed adjacent the distal end. One of the electrodes being an ablation electrode. An ablation RF energy source connected to the ablation electrode, a patient interface is connected to at least some of the electrodes for acquiring intracardiac ECG signals and a stimulator is connected to the catheter for providing pacing signals thereto. A phase balanced all pass filter is connected between the catheter and the patient interface for suppressing the interference to the intracardiac ECG signals by the RF ablation energy signal.

Abstract: An MRI system performs a calibration prescan in which NMR projection signals are produced using a calibration pulse sequence. The readout gradient employed during the acquisition of each NMR projection signal is rotated during the signal sampling such that the projection angle changes during the acquisition. The center of the field of view is weighted more heavily in the calculation of the optimal RF transmit power to provide a more accurate setting when using local coils.

Abstract: A method is provided for measuring the weight of a medical imaging scanner patient. The scanner has a bore portion for receiving and housing the patient during a scan. Initially, a reclining apparatus associated with the scanner is provided, on which the patient can recline during the scan. A hydraulic lift mechanism is then used to position the reclining apparatus and the patient at bore level. The pressure within the hydraulic lift mechanism can then be measured as a function of downward force exerted by the reclining apparatus and the patient surface. Alternatively, the automatic measuring of patient mass, associated with the movement of the reclining apparatus and patient into the bore, can be determined by calculating instantaneous acceleration of the reclining apparatus and patient as the reclining apparatus and patient are slid into the bore.

Abstract: An MRI system performs a calibration procedure to calculate optimal compensation parameter values for a pre-emphasis filter that alters the shape of gradient waveforms. The gradient field errors are measured using a series of pulse sequences in which different compensation parameter values are sampled. The measured errors are used to calculate a gradient error function and the optimal compensation parameter values are calculated by finding the minimum in the gradient error function.

Abstract: A method and an apparatus for enhancing the side-lobe performance of a sparse ultrasonic transducer array using harmonic imaging to reduce all beam sidelobe (including grating lobe) levels. Harmonic imaging consists of using the active transducer elements to transmit an ultrasound signal (wideband or narrowband) of center frequency f.sub.0 and receive at one or more harmonic frequencies nf.sub.0, where n.gtoreq.2.

Abstract: A system and method for improved water and fat separation in magnetic resonance imaging (MRI) is disclosed using a set of low-resolution images to correct phase errors with overall reduced scan time and post-processing time and enhanced reliability. Several embodiments are disclosed whereby reliable water and fat separation is achieved in nearly one NEX, Two NEX, or Three NEX regular imaging times. In the one embodiment, a regular image data set having water and fat phase-shifted by 90.degree. is acquired, along with two low-resolution image data sets where water and fat are phase-shifted by 0.degree. and 180.degree. are acquired. In another embodiment, two regular image data sets having water and fat phase-shifted by 0.degree. and 180.degree. are acquired, and a low-resolution imaging data set having water and fat phase-shifted by 90.degree. is acquired.

Abstract: A correction coil current adjustment circuit for a superconducting magnet to selectively switch various coils in circuit with a power source to provide the desired superconducting current flow and magnetic field homogeneity for magnetic resonance imaging eliminating the need for some of the mechanical leads which extend from the exterior of the magnet to the interior of the cryogen vessel minimizing thermal leak paths and including simplified switching of the various main and correction magnet coils to provide the desired current flow. Inductive coupling from outside the magnet to induce correction coil current flow eliminates additional mechanical leads.

Abstract: A method and an apparatus for tracking scan plane motion in free-hand three-dimensional ultrasound scanning using adaptive speckle correlation. The method employs a correlation index which adapts to different display dynamic range and post-processing filters. The method may include the following steps: choosing a kernel within each frame image for correlation calculations; rejecting duplicate image frames; measuring the degree of correlation between successive image frames; rejecting correlation estimates which may be associated with hand jitter and other artifacts; and computing the average frame-to-frame (i.e., interslice) spacing based on the average correlation estimate. This image-based motion tracking technique enables three-dimensional reconstruction with good geometric fidelity, without use of any external position-sensing device.

Abstract: A suspension system for a superconducting magnet for supporting and spacing the thermal radiation shield and vacuum vessel about the cryogen vessel utilizing a carbon fiber reinforced composite assembly with a first frustro-conical member positioned between the cryogen vessel and radiation shield and a second frustro-conical member extending from the vacuum vessel to overlap the radiation shield with a radially extending connecting member between the interior ends of the members to provide a tortuous generally Z-shaped lengthened thermal path and thermal resistance plus mechanical support in both the axial and radial directions.

Abstract: An open architecture magnetic resonance imaging permanent magnet assembly with moveable magnets and adjustable field inclination with automatic magnetic field homogeneity shimming to enhance imaging and positioning of the magnetic field about the portion of the patient to be imaged while enabling interventional physician access.