Abstract: The present invention, in one form, is a system for reducing noise artifacts in three-dimensional image reconstruction using data acquired in a helical scan. More specifically, a standard deviation ratio of reconstructed images with and without helical weighting is identified. Such standard deviation ratio is then used to generate filter coefficients, which are then applied to the data in an adaptive smoothing algorithm.

Abstract: The present invention, in one form, is a method for detecting a partial volume artifact in scan data acquired during a tomographic scan. In accordance with one embodiment of the algorithm, an object of interest is scanned to generate scan data. Sampling pairs of the scan data are identified and used to generate an inconsistency map. The inconsistency map is weighted and filtered to generate a partial volume signature which identifies partial volume artifacts.

Abstract: Susceptibility artifacts in slice selective volume magnetic resonance spectroscopy are reduced by applying phase encoding at a nominal resolution equal to or larger than the slice selection dimensions. In a preferred embodiment of the method, phase encoding is applied along the axes of the first and last RF slice selections. The volume of interest is contained completely within a single pixel defined by the 2D phase encoding. Unsuppressed water reference signal from the volume of interest is relatively unaffected by these artifacts and is collected without phase encoding.

Abstract: The present invention, in one embodiment, is an interference detection assembly for detecting patient and patient table interference with a gantry of a computed tomography system. The assembly, in one form, includes a frusto-conical capacitive plate secured to a leading frusto-conical surface of the gantry bore. The capacitive plate is coupled to a control unit which detects changes in the capacitance of the capacitive plate. When the plate is discharged below a threshold charge, the control unit generates a signal which may be used to automatically interrupt a scan.

Abstract: A method for optimizing the beam distribution to obtain the highest frame rate together with the least amount of acoustic noise while limiting the spatial aliasing to an acceptable level. The beam distribution is adjusted according to the scan format and as a function of the beam width, which is proportional to the product of the F number and the operating wavelength. As the F number changes in going from the shallow depth to a deeper depth, the number of beams fired to construct an image would change correspondingly. In addition, if the F number is changing in going from the center of image to the edge of the image, the separation of the fired beams would change. Alternatively, if the operating frequency is being changed in going from shallower depths to deeper depths or in going from the center of image to the edge of the image, the beam spacing is changed in order to fire the optimum number of beams at all times, and thereby obtain the highest frame rate.

Abstract: The present invention, in one form, is a brake assembly for a tilting gantry. The brake assembly is coupled to the gantry in substantially the same manner as a driving actuator is connected to the gantry, and includes a hydraulic cylinder, a piston, a reservoir and a valve. The cylinder includes a first end, a second end, and a sidewall extending between the first end and the second end to define a chamber. The piston includes a head and an arm which is configured to couple to the gantry. The piston is positioned within the hydraulic cylinder so that the head of the piston is in the cylinder chamber and the piston arm extends through a piston opening of the first end of the hydraulic cylinder. The reservoir is configured to retain hydraulic fluid, and the valve is connected in series circuit between the hydraulic cylinder and the reservoir.

Abstract: A phased array sector scanning ultrasonic system includes a separate beamformer channel for each respective element in an ultrasonic transducer array. Each beamformer channel has a three-stage complex FIR filter downstream of an analog-to-digital converter. Each filter circuit stage has a register pipeline, an in-phase FIR filter and a quadrature FIR filter. The first stage only has real samples, so there is a single pipeline. The other stages have complex inputs composed of in-phase (real) and quadrature (imaginary) samples, requiring a pipeline for each. Each register pipeline is made up of a multiplicity of registers connected in series. The number of registers in a given pipeline must equal the number of taps being used on the FIR filter immediately downstream of the register pipeline. The registers are clocked in synchronism and store successive echo data samples. Each register in the pipeline has an output connected to a respective tap of the corresponding FIR filter.

Abstract: The present invention, in one form, is a scatter collimator for a computed tomography system including an x-ray source. The scatter collimator is positioned between a detector array and an object to be imaged. The scatter collimator includes a housing, a plurality of attenuating blades and a plurality of attenuating wires. The blades and wires are mounted to the housing, and oriented substantially perpendicular to each other. Particularly, the blades and wires form a two-dimensional shielding grid. The blades also are oriented so that they are radially and focally aligned with the x-ray source. A detector element of the detector array is secured to the housing so that the blades and wires are between the detector element and the x-ray source. The detector element, in one form, includes a scintillation element which is coated with a light-retaining material.

Abstract: A method is used for interfacing dissimilar materials in an X-ray tube. The X-ray tube includes a rotor assembly to distribute heat generated in the X-ray tube. The X-ray tube is sealed within a glass material which has a first expansion coefficient. An interface is provided between the rotor assembly and the glass material to absorb temperature coefficient stresses. Preferably, the glass material is Borosilicate and the interface comprises a metal material and a ceramic material. The ceramic material has a second expansion coefficient that closely matches the first expansion coefficient. The metal material is preferably Kovar, and the ceramic material is preferably Mullite. Temperature coefficient stresses are then absorbed within the ceramic and metal structure.

Abstract: A CT cone beam imaging system is provided wherein a source of cone beam radiation and a detector array are mounted for movement with respect to an object, to provide a reconstructed image of the object. Relative movement is established between the cone beam source and the object along a scan path comprising a circular component and a linear component. The source is operated to irradiate the object during such movement to project cone beam data onto the detector, the projected data comprising linear and circular data sets which respectively correspond to the linear and circular components of the scan path. To significantly minimize processing requirements, a subset of data elements is selected from the linear data set, wherein each of the selected data elements is associated with a set of spatial parameters which define spatial regions contained within a hypothetical sphere in the Radon space, but which are not intersected by a Radon shell defined by dimensions of the circular path and the cone beam.

Abstract: A helium cooled superconducting magnet assembly with helium gas recondensing apparatus to return liquid helium to the helium supply in the helium vessel in which the recondensing apparatus positioned within the space between the vacuum vessel and surrounding vacuum vessel in thermal contact with a cryocooler within a fixed cryocooler sleeve in the vacuum vessel with the cryocooler positioned to minimize magnetic disturbances to the magnet assembly magnetic field and the recondenser connected through thin corrugated steel tubing to the helium vessel with the tubing sized to provide thermal and vibration isolation of the helium vessel.

Abstract: A phase unwrapping method is provided comprising a post-processing MR operation for an array of phase-related MR data elements. The method includes the steps of defining a Region of Interest, of comparing each data element with the first and second data elements which are adjacent thereto in the array, in order to generate respectively corresponding first and second gradient values. A subset of the data elements is constructed, wherein a data element is assigned to the subset only if its corresponding first and second gradient values are less than a selected threshold value VENC/2. The data element subset is employed to generate a fitted phase function having a value at the position of each data element in the array, and the value of the fitted function thereof, for a given data element, is subtracted from the measured value thereof.

Abstract: An x-ray unit is provided which includes an x-ray device for producing x-rays. A base holds the x-ray device, which comprises an x-ray source for positioning over an area of concern, and a rotatable x-ray source support column for allowing movement of the x-ray source. The total rotational motion of the support column is greater than 360.degree. relative to the base. Mechanical end of rotation stops mechanically defining total rotational motion of the support column. The x-ray source is capable of clockwise and counterclockwise movement from a parked position.

Abstract: A method and an apparatus for three-dimensional imaging of ultrasound data by reducing speckle artifact data before the acquired data from a volume of interest is projected onto an image plane. An ultrasound scanner collects B-mode or color flow mode images in a cine memory, i.e., for a multiplicity of slices. The data from a respective region of interest for each slice is sent to a master controller, such data forming a volume of interest. The master controller performs an algorithm that iteratively projects the pixel data in the volume of interest onto a plurality of rotated image planes using a ray-casting technique. Prior to projection, the master controller smooths the speckle contained in the pixel data filtering using a convolution filter having a nine-point kernel.

Abstract: Methods and systems for performing a tomographic scan which allow an operator to define a non-circular orbit so that a detector can be positioned close to a patient at each view are described. Such methods and systems provide that the patient to detector distance is reduced, which improves spatial resolution for the scan. In one embodiment, and to achieve a non-circular orbit, the camera and table/patient are moved with respect to one another. Specifically, the table is pinned in position and set to lateral and vertical positions during set-up. The same lateral and vertical table positions are maintained during the scanning phase. To get the camera closer or farther from the patient/table, the camera is pitched in or out. The camera head is tilted to achieve a tilt angle of zero degrees for all changes in pitch. As the camera pitches in and out, the central axis of the camera moves along the longitudinal axis of the table.

Abstract: An induction motor rotor particularly for x-ray tube applications comprises a series of hollow cylinders fitting concentrically on each other and on a motor shaft. The first cylinder is a highly heat resistant and electrically insulating material. The next cylinder is a highly magnetic material cylinder fitting on the first cylinder. The next and outermost cylinder is an electrically conductive material providing the armature conductor of the induction motor rotor.

Abstract: The present invention, in one embodiment, is a system for performing image reconstruction from raw projection data acquired in a tomographic scan. More specifically, the system implements an estimation algorithm for raw projection data which does not require fully pre-processing all raw projection data for image reconstruction. Particularly, raw projection for a base view is pre-processed to generate pre-processed projection data for the base view. A linear calibration algorithm generates a linearization vector using at least a portion of the fully pre-processed projection data for the base view. The linearization vector is then applied to raw projection data for subsequent views to generate estimated pre-processed projection data for such subsequent views.

Abstract: The present invention, in one embodiment, is a system for performing image reconstruction from unfiltered scan data acquired in a tomographic scan. More specifically, the system implements an algorithm for unfiltered scan data which eliminates the requirement that the scan data for a particular view be fully filtered for image reconstruction. Particularly, unfiltered scan data for a base view is fully filtered to generate filtered scan data for the base view. At least a portion of the filtered scan data for the base view is then used for subsequent views. Particularly, for a subsequent view, only the high frequency components of unfiltered scan data for that view are filtered with a short filter. The filtered high frequency components then are added to the low frequency components of the filtered base view scan data to estimate fully filtered scan data for the subsequent view.

Abstract: A method and system are provided for controlling a motor to rapidly accelerate and synchronize with an external synchronization pulse. First, the motor is accelerated to only half of the desired speed. At this point, the phase error with the sync pulse is calculated, and the motor continues "cruising" at half speed until the phase discrepancy diminishes. Then the motor rises to the full desired speed at the optimal time such that it is in phase with the sync pulse just as it reaches full speed. The acceleration is performed at a constant, yet slow enough, rate to receive at least three speed feedbacks. Then the instantaneous speed can be accurately measured and the next (and final) speed command during acceleration is interpolated between the ideal command for rising and the ideal command for cruising at the desired speed.

Abstract: The present invention, in one form, is a method for improving grey-white matter differentiation between regions of an image to be reconstructed from data obtained by a CT scan. More particularly, in accordance with one form of the present invention, a re-mapping function is utilized to generate CT numbers. In accordance with such function, CT numbers that are outside the grey-white matter region are not "stretched". The CT numbers within such region are "stretched" with the larger "stretch" centered on the grey-white matter region and tapering off at the boundary. Using such a function, grey-white matter differentiation is improved without adversely affecting quality and accuracy.