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Cortical magnetic and electric fields associated with voluntary finger movements

Brain Topography 1994年第3期6卷 175-183页

作者： Nagamine, Takatshi Toro, Camilo Balish, Marshall Deuschr, Günther Wang, Binseng Sato, Susumu Shibasaki, Hiroshi Hallett, Mark Department of Brain Pathophysiology Kyoto University School of Medicine Kyoto 606 Sakyo-ku Japan Human Motor Control Section Medical Neurology Branch National Institute of Neurological Disorders and Stroke National Institutes of Health Bethesda MD United States Neurophysiology Unit Epilepsy Research Branch National Institute of Neurological Disorders and Stroke National Institutes of Health Bethesda MD United States Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health Bethesda MD United States State University of Campinas Campinas SP 13081 Brazil

Multichannel recordings of both movement-related magnetic fields (MRMFs) and movement-related cortical potentials (MRCPs) were simultaneously recorded in association with voluntary unilateral self-paced index finger abduction movement in two normal volunteers. 1) Slow magnetic field (readiness field;RF) can be detected several hundred msec before the movement onset, and its field distribution indicates the existence of the largest generator source over the contralateral primary motor area. Taken together with the vertex-maximal Bereitschaftspotential which corresponds to the earlier part of the RF, the complexity of this magnetic field suggested by relatively low correlation value in single dipole model indicates the co-activation of other underlying generators besides this largest dipole. 2) The utilization of MRMF with MRCP facilitates the separation of two distinct electrophysiological events in proximity to the movement onset, which are difficult to be determined by the technique of MRCP only. Those are the motor field (MF) and the movement evoked field I (MEFI) in MRMF, and the parietal peak motor potential (ppMP) and the frontal peak motor potential (fpMP) in MRCP, which occur approximately 20 and 100 msec after EMG onset, respectively. These two subcomponents may imply the culmination of motor cortex and sensory feedback activation, respectively. Combined study of MRMF and MRCP will provide better definition of cortical events related to voluntary movement than the study of either modality alone. © 1994 Human Sciences Press, Inc.

关键词： Magnetoencephalography Motor field Movement evoked field Movement-related cortical potential Movement-related magnetic field Readiness field

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ON THE OPTIMALITY OF IDEAL FILTERS FOR PYRAMID AND WAVELET SIGNAL APPROXIMATION

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 1993年第12期41卷 3591-3596页

作者： UNSER, M Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health Bethesda MD USA

The reconstructed lowpass component in a quadrature mirror filter (QMF) bank provides a coarser resolution approximation of the input signal. Since the outputs of the two QMF branches are orthogonal, the transformation that provides the maximum energy compaction in the lowpass channel is also the one that results in the minimum approximation error. This property is used as a common strategy for the optimization of QMF banks, orthogonal wavelet transforms, and least squares pyramids. A general solution is derived for the QMF bank that provides the optimal decomposition of an arbitrary wide sense stationary process. This approach is extended to the continuous case to obtain the minimum error approximation of a signal at a given sampling rate. In particular, it is shown that the sine-wavelet transform is optimal for the representation at all scales of signals with non-increasing spectral density.

关键词： Channel bank filters Least squares approximation Mirrors Filter bank Energy resolution Signal resolution Compaction Approximation error Continuous wavelet transforms Wavelet transforms

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A FAMILY OF POLYNOMIAL SPLINE WAVELET TRANSFORMS

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SIGNAL PROCESSING 1993年第2期30卷 141-162页

作者： UNSER, M ALDROUBI, A EDEN, M Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health Bethesda MD 20892 USA

This paper presents an extension of the family of orthogonal Battle/Lemarie spline wavelet transforms with emphasis on filter bank implementation. Spline wavelets that are not necessarily orthogonal within the same resoluton level, are constructed by linear combination of polynomial spline wavelets of compact support, the natural counterpart of classical B-spline functions. Mallat's fast wavelet transform algorithm is extended to deal with these non-orthogonal basis functions. The impulse and frequency responses of the corresponding analysis and synthesis filters are derived explicitly for polynomial splines of any order n (n odd). The link with the general framework of biorthogonal wavelet transforms is also made explicit. The special cases of orthogonal, B-spline, cardinal and dual wavelets are considered in greater detail. The B-spline (respectively dual) representation is associated with simple FIR binomial synthesis (respectively analysis) filters and recursive analysis (respectively synthesis) filters. The cardinal representation provides a sampled representation of the underlying continuous functions (interpolation property). The distinction between cardinal and orthogonal representation vanishes as the order of the spline is increased;both wavelets tend asymptotically to the bandlimited sinc-wavelet. The distinctive features of these various representations are discussed and illustrated with a texture analysis example.

关键词： WAVELET TRANSFORM BETA-SPLINES POLYNOMIAL SPLINES INTERPOLATION BINOMIAL FILTERS QUADRATURE MIRROR FILTERS (QMF) BIORTHOGONALITY MULTIRESOLUTION SIGNAL ANALYSIS

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DISCOVERING SWITCH PHARMACEUTICALS FROM MULTISTATIONARY BIOCHEMICAL NETWORKS

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JOURNAL OF THE NATIONAL CANCER INSTITUTE 1993年第7期85卷 518-518页

作者： MORRISON, PF DEDRICK, RL Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of HealthBethesda Md

An editorial discusses an approach to finding effective pharmaceutical agents. Researchers have suggested that the behavior of biochemical networks may provide an approach for discovering pharmaceuticals.

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THE VISUALIZATION OF RF PROBE ELECTRIC-FIELDS

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MAGNETIC RESONANCE IN MEDICINE 1993年第3期29卷 386-390页

作者： CHEN, CN HOULT, DI Biomedical Engineering & Instrumentation Program National Center for Research Resources National Institutes of Health Bethesda Maryland

An assembly of resistive paper and liquid crystal sheet, conveniently and cheaply constructed for visual detection of the electric fields associated with an rf probe, is presented. Electrical asymmetries, and “hot-spots” usually associated with conservative electric fields, are easily visualized by the color patterns displayed. The device is of considerable assistance in probe design and the minimization of dielectric loss.

关键词： RF PROBE ELECTRIC FIELDS NMR

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B-SPLINE SIGNAL-PROCESSING .1. THEORY

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 1993年第2期41卷 821-833页

作者： UNSER, M ALDROUBI, A EDEN, M INSERM U.2 Hôpital Henri-Mondor Creteil France Biomedical Engineering and Instrumentation Program National Institutes of Health DHHS Bethesda MD USA

This paper describes a set of efficient filtering techniques for the processing and representation of signals in terms of continuous B-spline basis functions. We first consider the problem of determining the spline coefficients for an exact signal interpolation (direct B-spline transform). The reverse operation is the signal reconstruction from its spline coefficients with an optional zooming factor m (indirect B-spline transform). We derive general expressions for the z transforms and the equivalent continuous impulse responses of B-spline interpolators of order n. We present simple techniques for signal differentiation and filtering in the transformed domain. We then derive recursive filters that efficiently solve the problems of smoothing spline and least squares approximations. The smoothing spline technique approximates a signal with a complete set of coefficients subject to certain regularization or smoothness constraints. The least squares approach, on the other hand, uses a reduced number of B-spline coefficients with equally spaced nodes;this technique is in many ways analogous to the application of antialiasing low-pass filter prior to decimation in order to represent a signal correctly with a reduced number of samples.

关键词： Spline Signal processing Nonlinear filters Least squares approximation Filtering Smoothing methods Interpolation Noise reduction Data compression Maximum likelihood detection

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Generalized sampling theory and application to multiresolutions and wavelets of L2

Generalized sampling theory and application to multiresoluti...

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Mathematical Imaging: Wavelet Applications in Signal and Image Processing 1993

作者： Aldroubi, Akram Unser, Michael National Institutes of Health Biomedical Engineering and Instrumentation Program BethesdaMD20892 United States

We use approximation theory to generalize the classical sampling procedure of Shannon. We give a link between this theory and the theory of wavelet transforms. As an application, we give a general method for construct... 详细信息

关键词： Wavelet transforms

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Portraits of frames: Overcomplete representations with applications to image processing

Portraits of frames: Overcomplete representations with appli...

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Mathematical Imaging: Wavelet Applications in Signal and Image Processing 1993

作者： Aldroubi, Akram National Institutes of Health Biomedical Engineering and Instrumentation Program BethesdaMD20892 United States

We present two methods for generating frames of a Hilbert space 7i. The first method uses bounded operators on H to transform a frame into another frame of H1 ⊂ H. The other method uses bounded linear operators on l2 to generate frames of H. We characterize all the mappings that transform frames into other frames. We also show how to construct all frames of a given Hilbert space 7i starting from any given frame. We show how to apply the theory to obtain shift-invariant tight frames, and shift-invariant tight multiresolution. We also show how to obtain scaling function and wavelets with prescribed properties. Finally, We discuss the noise reduction properties of frames. © 1993 SPIE. All rights reserved.

关键词： Hilbert spaces

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ELECTROOPTICAL SIMULATOR FOR PULSE OXIMETERS

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MEDICAL & BIOLOGICAL engineering & COMPUTING 1993年第5期31卷 534-539页

作者： ZHOU, GX SCHMITT, JM WALKER, EC 1. National Center for Research Resources Biomedical Engineering and Instrumentation Program National Intitutes of Health Building 10 Room B2S245 20892 Bethesda MD USA

Although pulse oximeters have gained widespread acceptance as intensive-care monitors, a convenient method for testing the operation of instruments sold by different companies does not yet exist. In this note, the authors introduce a simple simulator that takes advantage of the intrinsic wavelength dependence of a twisted-nematic liquid-crystal retarder (the type of retarder most frequently employed in liquid-crystal displays). This new approach eliminates the need to split the red and infrared light into two separate collimated beams before straightforward and no customized components or lithography are required. By properly selecting the type and orientation of the polarizers, the optical-density variations that it produces can be made to resemble those of blood-perfused tissue.

关键词： LIGHT LIQUID CRYSTAL OXIMETRY OXYGEN SATURATION POLARIZATION PULSE OXIMETRY SIMULATOR

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Design considerations in making a broad-range fiber-optic pH sensor

Design considerations in making a broad-range fiber-optic pH...

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Fiber Optic Sensors in Medical Diagnostics 1993

作者： Peterson, John I. Netto, Eden J. Biomedical Engineering and Instrumentation Program NCRR National Institutes of Health Building 13 Room 3N17 BethesdaMD20892 United States

The general background and theoretical aspects involved in making a broad-range fiber-optic pH sensor will be discussed. © 1993 Proceedings of SPIE - The International Society for Optical engineering. All rights ... 详细信息

关键词： Fiber optics

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