Abstract: A magnetic resonance (MR) active invasive device system for imaging blood vessels employs an integrated polarizing and imaging magnet which is comprised of a small, high-field polarizing magnet whose flux return path is routed through pole structures to produce a large substantially uniform low-field magnetic region suitable for low-field magnetic resonance imaging. A subject is positioned in the uniform low-field region. A catheter is inserted into the patient at or near the root of a vessel tree to be imaged. A fluid, intended to be used as a contrast agent is first passed through the small high-field polarizing magnet, creating a large net longitudinal magnetization in the fluid. The fluid is then introduced into the subject is through the catheter. Radiofrequency (RF) pulses and magnetic field gradients are then applied to the patient as in conventional MR imaging.

Abstract: The present invention is a method for visualizing a two dimensional field of orientation data on a surface which may be (flat or curved). A unit polyhedron is constructed which approximates a unit sphere centered at a point on the surface corresponding to the orientation vector. Colors are assigned to facets of the polyhedron such that adjacent facets have similar colors. Orientation vectors are projected onto facets of the polyhedron, and the surface point which is associated with the orientation vector is color coded with the color of the intersected facet. The method can be used in geology, metallurgy, stereology, and any other domain where a large set of orientation data is collected.

Abstract: Imaging parameters, such as the location, orientation and field of view of an imaging plane are selected. These parameters are provided to a pulse sequencer of a magnetic resonance (MR) scanner which modifies an MR pulse sequence to acquire an image at the selected imaging plane. The pulse sequencer controls an RF transmitter and gradient amplifiers to cause an MR image of the subject at an imaging plane to be acquired. The MR image is displayed on a display device. An interface device receives and reduces the MR image to an image icon and saves the image icon along with the corresponding imaging parameters. The image icons are displayed on the periphery of the screen around an MR image. An operator may then view and select one of the image icons, employing the pointing device. This causes the imaging parameters corresponding to the selected image icon to be sent to the pulse sequencer thereby causing an MR image to be acquired with these imaging parameters.

Abstract: Time sampled data from many hundreds of sensors spatially arranged on a subject is acquired, displayed and archived in real-time. A redundant array of acquisition processors coupled to temporary storage device are controlled by a system control processor. As the data is acquired, an operator interacts with a display processor to select sensors mapped on a computer model of the subject. The selected sensors are displayed as real-time `postage stamp` traces each located in a position reflecting their position on the subject. During acquisition in the background, or at some time later, the acquired data is archived onto a slower, but much larger data storage device such as a stream tape, or optical disk.

Abstract: A tracking system monitors the position of a device within a subject and superimposes a graphic symbol on a diagnostic image of the subject. Registration of the tracked location with the diagnostic image is maintained in the presence of subject motion by monitoring subject motion and adjusting the display to compensate for subject motion. Motion monitoring can be performed with ultrasonic, optical or mechanical methods. The display can be adjusted by modifying the displayed location of the device or it can be adjusted by translating, rotating or distorting the diagnostic image.

Abstract: A multi-planar imaging method employs magnetic resonance to detect image data from multiple planes within a subject. Data from each plane are detected in response to the same readout gradient and are simultaneously detected. The image planes can be arbitrarily oriented with respect to each other and with respect to the readout and phase-encoding image formation magnetic field gradient pulses if desired. Overlap of image data from each of the excited image planes in the acquired image is prevented by employing a thick refocusing slab oriented orthogonal to the readout and phase-encoding directions, or by choosing planes which intersect outside the subject's anatomy.

Abstract: The present invention provides a novel Geometric Harmonic Modulation (GHM) system. The GHM system operates in two modes, a preamble mode and a traffic mode. During the preamble mode, n+1 frequencies are each offset by a predetermined phase offset in the transmit unit and passed through a channel to a receive unit. The set of phase offsets is used as the spreading code in the transmit unit, and also acts as an `address` of receive units to transmit to. The receive unit monitors preamble signals to determine the phase offsets. When it recognizes a set of phase offsets, or `address`, which pertains to itself, the receive unit stores the phase offsets and uses these phase offsets to despread and decode the appended message. After the preamble mode is finished, the GHM modulator enters the traffic mode and requests the message to be transmitted from the message source. A traffic carrier waveform is created by multiplying tones, each having its specific phase offset.

Abstract: A traffic carrier waveform W.sub.n (.PHI.,R;t) being the product of a number of tones is employed in transmitting blocks of information from a transmit unit to a receive unit. The tones are geometrically increasing multiples of a frequency of a fundamental tone. Each tone incorporates a tone phase. The selection of these tone phases uniquely identifies each transmitted signal. The tone phases also is used as a `key` in converting a message signal into a direct wide spectrum signal for communication. To insure that third parties do not decode the transmitted message, the tone phases are transformed to seed phases by a method known to both the transmit and receive units, but not to third parties. The seed phases are then transmitted by intermittent preamble carrier waveform to the receive unit which transforms these into the tone phases and decodes the message signal. The seed phases may be dynamically changed according to a sequence known or generated by both the transmit unit and receive unit.

Abstract: The present invention provides a novel frequency Interlaced Geometric Harmonic Modulation (IGHM) system. The IGHM system operates in two modes, a preamble mode and a traffic mode. During the preamble mode, n+1 frequencies are each offset by a predetermined phase in a transmit unit and passed through a channel to a receive unit. The set of phases is used as the spreading code in the transmit unit, and also acts as an `address` of desired receive units. The receive unit monitors preamble signals to determine the phases. When it recognizes a set of phases, or `address`, which pertains to itself, the receive unit stores the phases and uses these phases to despread and decode the appended message. After the preamble mode is finished, the IGHM modulator enters the traffic mode and requests the message to be transmitted from the message source.

Abstract: The present invention provides a system for determining, and correcting for, channel-induced distortion in transmitted wideband carrier signals. During a synchronization, or sounding mode, known as the preamble mode, a wideband signal consisting of a number of tones, which may be those of geometric harmonic modulation (GHM), each having a phase of zero are transmitted to a receive unit. At the receive unit, the phases for each tone are extracted. Since each tone is at a different frequency, a snapshot of the change in phase over a number of frequencies can be determined. These phase changes are employed in determining the generalized phase distortion over frequency equation which is used to remove the phase distortion induced by the channel before decoding of the signal. The device then operates in its traffic mode thereby transmitting information to a receive unit which uses the phase distortion information to remove phase distortion induced by the channel and then decode a message signal.

Abstract: The present invention provides a novel Geometric Harmonic Modulation (GHM) method. The GHM method functions in two modes, a preamble mode and a traffic mode. During the preamble mode, n+1 frequencies are each offset by a predetermined phase in a transmit unit and passed through a channel to a receive unit. The set of phases is used as the spreading code in the transmit unit, and also acts as an `address` of intended receive units. The receive unit monitors preamble signals to determine the phases. When it recognizes a set of phases, or `address`, which pertains to itself, the receive unit stores the phases and uses these phases to despread and decode the appended message. After the preamble mode is finished, the GHM modulator enters the traffic mode and requests the message to be transmitted from the message source. A traffic carrier waveform is created by multiplying tones, each having its specific phase. An analog or binary message is encoded by modulating the traffic carder waveform.

Abstract: Magnetic field gradient coils, such as those typically employed in magnetic resonance (MR) imaging employ folded loop current paths in which a first section carries current along a path close to an imaging volume. This produces a magnetic field gradient within the imaging volume. A second section, being a further radial distance from the imaging volume, carries current in a return path, in a substantially opposite current direction as the first section, thereby reducing stray magnetic fields outside of the second section. The second preferable has the same current pattern, but is slightly larger to contain magnetic fields at the fringes. A third section connects each turn of the coils in the first section to a corresponding turn of coils in the second section. This third section is disposed in a partially radial direction to connect the first and second sections.

Abstract: A graphic workstation converts a polygonal model generated with computer aided design (CAD) software or volumetric data into a more compact polygon strip list having multiple strip sublists. The strip list, in addition to being more compactly stored, is displayed much more rapidly than conventional polygonal models since much of the redundant redrawing is eliminated. Shared point of adjacent polygons are eliminated. The strip list consists of a number of strip lists, each list having vertices of a first, or initial, polygon and subsequent vertices defining remaining portions of polygons to be `built onto` the polygon strip in the strip direction. Since this method of model storage and display is much more efficient, less powerful graphic workstation could be implemented in place of more powerful graphics workstations; or alternatively, existing graphics workstation would become faster and have more free memory available for other functions.

Abstract: A method of reconstructing selected features of a part manufactured according to a CAD model involves acquiring a set of linear push broom (LPB) projection images of the part acquired at different angles about an axis of rotation passing through the part. Acquiring a set of matrices M.sub.j j=1 . . . N, each of which maps 3D coordinates of the part to screen coordinates of one of the projection images. Reconstruction of 3D structures from the projection images requires identification of screen coordinates of each image which correspond to a point of the structure of the part to be reconstructed. Back projecting these screen coordinates modified by the distortion inherent in the LPB imaging device. This is accomplished by selecting a screen coordinate on a feature desired to be reconstructed. Computing a ray passing through the selected screen coordinate through an imaging center. Using each M matrix to map this ray to a hyperbola on the other images.

Abstract: A system for testing the integrity of critical circuitry, lines and wires employs a differential amplifier having an input resistance R.sub.in and a feedback loop with a resistance R.sub.fb. The critical wires being tested must be a signal wire series connected to a resistance R.sub.S, which is in turn series connected to a return wire. A test voltage source is connected to the noninverting input of the differential amplifier. The signal wire is connected to the inverting input of the differential amplifier. The test voltage source is activated by a test control unit. When activated, the test voltage source provides two distinct outputs allowing computation of a test gain in the presence of other functional signals. The test control unit measures the output V.sub.out of the differential amplifier and computes the value of the test gain. A break in either the signal wire or the return wire will result in a test gain of 1. If the signal and return wires are shorted, the test gain will be 1+R.sub.fb /R.sub.in.

Abstract: A method of calibrating a linear pushbroom imaging device used in non-destructive testing of a part manufactured according to a CAD model involves identifying the location of fixed reference points, such as tooling balls in the CAD model. Positioning the part on a fixture having tooling balls fixed relative to each other in the same manner as those in the CAD model. Adjusting the part on the fixture such that points on the surface of the part known to be accurate have the same locations relative to the tooling bails as the CAD part is to the CAD tooling balls. Obtaining several projection images of the part and tooling balls at different angles about an axis of rotation passing through the part. Using the known 3D locations of the center of the CAD tooling balls and the corresponding measured screen locations of the is actual tooling balls, transformation matrices, G, M.sub.

Abstract: An enhanced reality maintenance system for operating in a hazardous or inaccessible environment employs an environment modeler which is supplied with spatial parameters of a given environment and creates a computer model of the environment. An environment renderer creates a plurality of images, each corresponding to a viewing location and orientation, `viewpoint`. A remotely operated vehicle (ROV) attached to a base unit by a tether cord or radio link navigates in the environment. The ROV has a spatial imaging device, such as a video camera, and actuators which propel it through the environment. Its position and orientation are determined by a position and attitude (P&A) sensing unit, and are passed to an ROV renderer which creates an image of a prestored model of the ROV having the same location and orientation as the ROV and viewed from a specified viewpoint. The viewpoints may be predetermined, provided to the system or may be interactively determined as an offset from the ROV position and orientation.

Abstract: A frequency-shift keying (FSK) demodulator demodulates a binary signal encoded in an FSK signal. The present invention employs a bandpass filter to filter out noise and pass the frequencies used in the modulation. A comparitor converts the received signal into a square wave. A divider reduces the frequency of the square wave signal by a dividing factor. A counter counts the number of square wave transitions in a predetermined time period. A decision device receives the dividing factor from the divider, and uses this factor to adjust the count measured. The adjusted count is compared to counts pertaining to modulated frequencies to select a frequency. A bit value associated with the selected frequency is output for the time period being demodulated.

Abstract: A multi-planar imaging method employs magnetic resonance to detect image data from multiple planes within a subject. Data from each plane are detected in response to the same readout gradient and are simultaneously detected. The image planes can be arbitrarily oriented with respect to each other and with respect to the readout and phase-encoding image formation magnetic field gradient pulses if desired. Overlap of image data from each of the excited image planes in the acquired image is prevented by modulating the phase of each RF excitation pulse in concert with the amplitude of the phase-encoding gradient pulse to cause the image data from each excitation plane to be displaced by a unique amount in the phase-encoding direction.

Abstract: A method of determining surfaces of swept volumes, which defines a region reserved for the removal of an object, or the motion of an object, is determined employing implicit modeling. A definition of an object and the trajectory in which it is to be moved are provided to the swept surface display device. An implicit model is created by determining shortest distance from each voxel of a object volume to a surface point of the object. A workspace volume has voxels each initialized with distances which are much larger than any distance envisioned. The implicit model space voxels are transformed relative to the workspace voxels according to the trajectory at a time t. Workspace voxels are updated with corresponding implicit model space voxels when the value of the implicit model space voxel is lower than the workspace voxel value. The implicit model space voxels are transformed relative to the workspace voxels for another time t and the number of workspace voxels are again updated.