Abstract: In order to display the surfaces of internal structures within a solid body from non-intrusively acquired data sets, it is useful to segment the data sets into the internal structures of interest before searching for the surfaces of such structures. To accomplish this, a data segmentation system uses a plurality of sample data points to construct a statistical probability distribution for a plurality of internal structures. Using these probability distributions, each data point is labeled with the most likely structure identification. Searching the thus-segmented data points for surfaces is considerably faster than is possible with the entire data set and produces surface renditions with fewer anomalies and errors. A non-intrusive imaging means is used to obtain a 3D data set. The probability distribution is bivariate and the two data sets are plotted against each other to assist in identifying tissue types.

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 motion imaging method uses magnetic resonance to detect velocity, and an acceleration distribution within moving materials in a subject. Velocity encoding is performed by computing differences of data obtained with modulated motion-encoding magnetic field gradient pulses. Distributions of acceleration are measured responsive to a motion sensitive phase-encoding gradient pulse.

Abstract: A pulsed electromagnetic radiation (EMR) source and an interferometer are used to obtain spectra from the surface of a sample. The pulsed EMR source uses a broadband radiation source and a monochromator to generate monochromatic radiation. Alternatively, a tunable laser can be used as the monochromatic radiation source. The modulated radiation impinges on the surface of interest where it is absorbed. The absorption of radiation causes the surface of the sample to expand. This change in dimension is then detected by an interferometer which employs a monochromatic radiation source to measure the instantaneous distance between the sample surface and the interferometer. The detection system of the interferometer can be an imaging device such as a video camera to obtain the spatial distribution of chemical composition of the sample surface.

Abstract: A method of estimating the quality of a communication channel from a differential phase angle between a received signal and the corresponding transmitted phase angle employs determining a signal to impairment ratio (SIR) as an indicator of channel state information (CSI). A maximum likelihood estimation procedure is employed to calculate this CSI metric as a function of the differential phase angle between the received signal and transmitted signal. An alternate embodiment employs a estimation that incorporates average SIR information for a Rayleigh fading channel. Since CSI is derived from the phase angle of the received signal, and does not require signal amplitude information, it is attractive for use with differential detectors, phase-locked loops (PLLs) and hard-limited signals. The CSI provided can be used for implementing post detection selection diversity, by selecting the signal from a plurality of antennae which has the best SIR.

Abstract: A digital time division multiple access (TDMA) radio communications system employs a digital information source for providing digital information, a transmitter for transmitting encoded digital information in a radio-frequency (RF) signal to a receiver which demodulates the encoded symbols into digital information to be utilized by an output device. The receiver, synchronizes, compensates for frequency drift, samples and divides the samples into halfslots of samples. The halfslots are subdivided into subslots numbered from 1 to N, where N represents the last received subslot. Subslots 1 and N are demodulated into digital information in a forward and reverse direction, respectively with metrics calculated. If the metrics indicate a signal with a larger signal-to-noise ratio from subslot N, subslot N-1 is demodulated in a reverse sense with another reverse metric calculated, and vice versa.

Abstract: An interactive system for producing X-ray fluoroscopic images determines X-ray tube photon count and voltage for producing acceptable quality images while minimizing X-ray radiation dosage to a subject. An image is created and a signal to noise (S/N) ratio is estimated from the image, assuming a Poisson model is assumed for the X-ray image. The S/N ratio is determined by solving several simultaneous equations and the photon count is estimated to produce an image with a desired S/N ratio. Subsequent X-ray fluoroscopy images are produced with the optimum photon count Q, thereby reducing X-ray dosage. The optimization is repeated periodically to readjust the system.

Abstract: A magnetic resonance system employs a sequence of radio frequency pulses and magnetic field gradients to detect and measure the spin-relaxation time T.sub.1 of a selected portion of a sample. Spin-lattice relaxation times are determined by first inverting longitudinal spin magnetization and then detecting the recovery of this magnetization with a series of detection radio frequency pulses. The inversion pulse is applied to the entire sample, but the detection pulses are applied to selected portions of the sample. Each detection pulse is applied in a unique location of the sample, thereby increasing the accuracy of the measurement and permitting the use of multiple detection pulses after a single inversion pulse.

Abstract: A magnetic field gradient apparatus for use in a magnetic resonance (MR) imaging system employing open magnets allows access to a patient while the patient is being imaged. The magnetic field gradient apparatus employs two gradient coil assemblies and a gradient coil amplifier. Each gradient coil assembly has a gradient coil carrier with at least one gradient coil disposed on it. Each gradient coil carrier is comprised of a cylinder with a flange at one end. The gradient coil assemblies are positioned in the bore of each ring of the open magnet and spaced apart from each other allowing access to the patient. The gradient coil amplifier provides current through the gradient coils to create a magnetic field gradient which has high linearity inside an imaging volume. A coil is disposed on cylinders which surround each gradient coil assembly and fit inside the bore of each ring which acts as an active shield and minimizing eddy currents in conductors outside the gradient coil assemblies.

Abstract: A tracking system in which radiofrequency signals emitted by an invasive device such as a catheter, are detected and used to measure the position and orientation of the invasive device. The invasive device has a transmit coil attached near its end and is driven by a low power RF source to produce a dipole electromagnetic field that can be detected by an array of receive coils distributed around a region of interest. The position and orientation of the device as determined by the tracking system are superimposed upon independently acquired Medical Diagnostic images, thereby minimizing the radiographic exposure times. One or more invasive devices can be simultaneously tracked.

Abstract: A shear rate imaging method uses magnetic resonance to detect the distribution of velocities within a subject. Distributions are measured responsive to at least two different field-of-views. Differences of the velocity distribution obtained with one field-of-view and the second field-of-view are computed to give a component of shear rate. The method can be used to obtain velocity measurements in any of three mutually orthogonal directions responsive to field-of-view shifts in as many as three mutually orthogonal directions to give a total of nine shear rate components. Data for each component can be acquired independently or data acquisition can be multiplexed to reduce data acquisition requirements.

Abstract: A low complexity adaptive equalizer for use in U.S. digital cellular radios demodulates .pi./4-shifted differentially encoded quadrature phase shift keyed (DQPSK) encoding in the presence of intersymbol interference (ISI) with reduced decoding complexity by employing an estimated received constellation which takes into account channel changes over time and ISI. The decoding complexity is reduced by tracking a reduced number of estimated reference symbol constellation points and taking advantage of the geometry to estimate the remaining symbol constellation points. Reference symbol constellation points are updated directly to compensate for changes in the channel, instead of determining channel impulse response (CIR) coefficients, and convolving the CIR coefficients with received symbols to determine new reference symbol constellation points.

Abstract: Surgery is performed with pulsed heat means that selectively destroys tissue in a region within a patient. The size of the region destroyed is dependent upon the frequency of the pulses of the pulsed heat means and thermal conductivity of the tissue of the patient. The pulsed heat means can be a coherent optical source that is guided by laser fiber to the tissue to be destroyed. In another embodiment the pulsed heat means is a focussed ultrasound transducer that dissipates ultrasonic energy at a focal point within the region of tissue to be destroyed. A magnetic resonance imaging system employing a temperature sensitive pulse sequence creates an image of the tissue and the region being heated to allow a surgeon to alter the position of the pulsed heat means or vary the pulse frequency.

Abstract: A manually positioned focussed energy transducer system facilitates medical procedures by allowing a physician to manually position the focal point of the focussed energy transducer to a selected tissue. The focal point of the focussed energy transducer is the location which tissue is destroyed when the energy transducer is activated. A tracking device tracks the position and orientation of the ultrasound transducer. An MR imaging system creates an image of internal structures of the patient near the location of the energy transducer. A superposition device receives the position and orientation of the ultrasound transducer from the tracking device and superimposes a symbol on the image corresponding to the position of the energy transducer relative to the patient. This allows the physician to adjust the position of the energy transducer to the appropriate location without the need for energizing the energy transducer.

Abstract: A magnetic resonance (MR) imaging system for use in a medical procedure employs an open main magnet allowing access to a portion of a patient within an imaging volume, for producing a main magnetic field over the imaging volume; a set of open gradient coils which provide magnetic fields gradients over the imaging volume without restricting access to the imaging volume; a radiofrequency coil set for transmitting RF energy into the imaging volume to nutate nuclear spins within the imaging volume and receive an MR response signal from the nuclear spins; and a pointing device for indicating the position and orientation of a plane in which an image is to be acquired; an image control means for operating power supplies for the gradient coils and the RF coils to acquire an MR signal from the desired imaging plane; and a computation unit for constructing an image of the desired imaging plane.

Abstract: A method of configuring an optimum communication system for communicating on adjacent frequency bands with minimal interference between adjacent channels comprises serially coupling a selected encoder to a mapper, a transmit filter, a low pass filter and a modulator, and constructing a receiver with a seriallycoupled receive filter and decoder. The transmit filter is optimized by choosing transmit filter coefficients d.sub.opt which maximize the inband to adjacent-band power. Transmitter coefficients d.sub.opt are obtained by solving an eigenvalue problem which takes into account the power spectrum of the encoder, mapper and receive filter. The optimum transmitter coefficients are then employed in the transmitter to shape the transmitted signal, increasing the adjacent channel interference protection ratio (ACIPR).

Abstract: A magnetic resonance imaging system employs a sequence of radio frequency pulses and magnetic field gradients to detect and measure the spin-relaxation time of moving blood within a subject. Spin-lattice relaxation times are determined by first inverting longitudinal spin magnetization and then detecting the recovery of this magnetization with a series of detection radio frequency pulses. The inversion pulse is applied to the entire subject, but the detection pulses are applied only to a selection portion of the subject. Blood motion causes the blood in the detection region to be replaced for each detection pulse, thereby increasing the accuracy of the measurement and permitting the use of multiple detection pulses after a single inversion pulse. In-vivo application of this invention can be used to assess renal function in individual kidneys.

Abstract: An automated system for determining artifacts in images indicating defects in an imaging device being tested employs a constant radiation source which supplies radiation of spatially uniform intensity to the imaging device to be tested. The imaging device then creates a flood image A.sup.(0). A region of interest (ROI) mask means for all pixel values of flood image A.sup.(0) sets values to zero outside of the imaging devices field of view to produce a flood image A.sup.(1). An image normalization means normalizes flood image A.sup.(1) to have an average value of zero producing a normalized flood image A. A correlation means performs an autocorrelation of normalized flood image A to produce a correlation field which is then masked to select portions of the correlation field.

Abstract: A tracking system employs magnetic resonance signals to monitor the position of a device such as a catheter within a subject. The device has a receiver coil which is sensitive to magnetic resonance signals generated in the subject. These signals are detected in the presence of magnetic field gradients and thus have frequencies which are substantially proportional to the location of the coil along the direction of the applied gradient. Signals are detected responsive to applied magnetic gradients to determine the position of the device in several dimensions. Sensitivity of the measured position to resonance offset conditions such as transmitter frequency misadjustment, chemical shift and the like is minimized by repeating the process a plurality of times with selected amplitudes and polarities for the applied magnetic field gradient.

Abstract: A method of estimating the quality of a communication channel from a differential phase angle between a received signal and the corresponding transmitted phase angle employs determining a signal to impairment ratio (SIR) as an indicator of channel state information (CSI). A maximum likelihood estimation procedure is employed to calculate this CSI metric as a function of the differential phase angle between be received signal and transmitted signal An alternate embodiment employs an estimation that incorporates average SIR information for a Rayleigh fading channel. Since CSI is derived from the phase angle of the received signal, and does not require signal amplitude information, it is attractive for use with differential detectors, phase-locked loops (PLLs) and hard-limited signals. The CSI provided can be used for implementing post detection selection diversity, by selecting the signal from a plurality of antennae which has the best SIR.