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INTERNATIONAL CONF ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING

作者： UNSER, M ALDROUBI, A Biomedical Engineering and Instrumentation Program Bldg. 13 National Institutes of Health Bethesda 20892 MD United States

ISBN: (纸本)0780305329

We describe new digital filtering algorithms for the processing and representation of signals using polynomial splines. We first consider the classical polynomial spline interpolation problem and show that it can be solved efficiently by recursive digital filtering. This result also yields a simple procedure for signal differentiation. We then derive filters that efficiently solve the problem of smoothing spline approximations. This technique is a regularized version of spline interpolation and is therefore less sensitive to noise. It is applied to the design of a robust edge detection algorithm with an adjustable scale parameter. Finally, we describe a filtering/sampling algorithm for least squares spline approximation. This data reduction technique is applied to the generation of a cubic spline image pyramid that is found to compare favorably with the Gauss/Laplace pyramid. © 1992 IEEE.

关键词： Interpolation

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Cardiac tissue in an electric field: A study in electrical stimulation

Cardiac tissue in an electric field: A study in electrical s...

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1992 IEEE Conference on Computers in Cardiology, CIC 1992

作者： Trayanova, Natalia A. Roth, Bradley J. NSF/Engineering Research Center Department of Biomedical Engineering Duke University DurhamNC United States Biomedical Engineering and Instrumentation Program NIH BethesdaMD United States

ISBN: (纸本)0818635525

This present an overview of possible mechanisms for cardiac stimulation. Changes of the transmembrane potential in the myocardium in response to an applied electric field are produced by two types of mechanisms, continuous or discrete, depending on whether they are associated with complete or incomplete current redistribution between the intracellular and extracellular spaces. Another way of classifying these mechanisms is whether they produce a membrane polarization only at the heart surface, or both at the surface and throughout the bulk of the heart. These categories provide a unifying framework for future studies on the mechanisms of field stimulation of the heart. © 1992 IEEE.

关键词： Heart

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Dose-dependent smooth muscle cell proliferation induced by thermal injury with pulsed infrared lasers 14

Dose-dependent smooth muscle cell proliferation induced by t...

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14th Annual International Conference of the IEEE engineering in Medicine and Biology Society, EMBS 1992

作者： Douek, Philippe C. Correa, Rosaly Unger, Ellis F. Neville, Richard Banai, Shmuel Epstein, Stephen E. Leon, Martin B. Bonner, And Robert F. Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health BethesdaMD United States

ISBN: (纸本)0780307852

Pulsed infrared laser irradiation induced localized thermal lesions in arteries by transiently heating to ∼30°C above ambient and subsequent SMC proliferation in rabbits by 3-4 weeks. Neointimal proliferation exhibited a clear dose dependence both as laser fluence was increased (R=0.83) and for a fixed surface irradiation as the depth of the nearest arterial media was decreased (R=0.95). Thermal injury to the arterial wall is shown to be potent stimulus for SMC proliferation, favoring reduction in energies used in laser or thermal angioplasty. © 1992 IEEE.

关键词： Cell proliferation

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HOW THE ANISOTROPY OF THE INTRACELLULAR AND EXTRACELLULAR CONDUCTIVITIES INFLUENCES STIMULATION OF CARDIAC-MUSCLE

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JOURNAL OF MATHEMATICAL BIOLOGY 1992年第6期30卷 633-646页

作者： ROTH, BJ 1. Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health Bldg. 13 Rm. 3W13 20892 Bethesda MD USA

The bidomain model, which describes the behavior of many electrically active tissues, is equivalent to a multi-dimensional cable model and can be represented by a network of resistors and capacitors. For a two-dimensional sheet of tissue, the intracellular and extracellular conductivity tensors can be visualized as two ellipses. For any pair of conductivity tensors, a coordinate transformation can be found that reduces the extracellular ellipse to a circle and aligns the intracellular ellipse with the coordinate axes. The eccentricity of the intracellular ellipse in this new coordinate system is an important parameter. It can have two special values: zero (in which case the tissue has equal anisotropy ratios) or one (in which case the tissue is comprised of one-dimensional fibers coupled through the two-dimensional extracellular space). Thus the bidomain model provides a unifying framework within which the electrical behavior of a wide variety of nerve and muscle tissues can be studied. When the anisotropy ratios in the intracellular and extracellular domains are not equal, stimulation with an anode always causes depolarization of some region of tissue. An analogous effect occurs in models that describe one-dimensional fibers, in which an "activating function" determines the site of stimulation. Experiments indicate that cardiac muscle does not have equal anisotropy ratios. Therefore, models developed to describe stimulation of axons may also help in understanding stimulation of two- or three-dimensional cardiac tissue, and may explain the concept of anodal stimulation of cardiac tissue through a "virtual cathode".

关键词： BIDOMAIN VIRTUAL CATHODE CONDUCTIVITY ANISOTROPY CARDIAC MUSCLE

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Spline multiresolutions and wavelet transforms

Spline multiresolutions and wavelet transforms

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1992 IEEE-SP International Symposium on Time-Frequency and Time-Scale Analysis

作者： Unser, M. Aldroubi, A. Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health Bldg. 13 Room 3W13 BethesdaMD20892 United States

ISBN: (纸本)0780308050

We present an extension of the family of BattlefimariB spline wavelet transforms. By relaxing the intra-level orthogonality constraint, we show how to construct generalized polynomial spline scaling functions and wavelets that span the same multiresolution spaces, but can also exhibit very distinct properties. Particular examples in this family include the Bspline wavelets of compact support that are optimally localized in time-frequency;the cardinal spline wavelets that have the fundamental interpolation property;and the dual spline wavelets (the biorthogonal complement of the B-spline wavelets). We provide a full characterization of the digital filters for the corresponding fast wavelet transform algorithms. We also discuss the asymptotic properties of these representations, and indicate the link with Shannon's sampling theory and the Gabor transform. © 1992 IEEE.

关键词： Digital filters

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Cardiac tissue in an electric field: a study in electrical stimulation

Cardiac tissue in an electric field: a study in electrical s...

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Computers in Cardiology (CinC)

作者： N.A. Trayanova B.J. Roth NSF/Engineering Research Center and Department of Biomedical Engineering Duke University Durham NC USA Biomedical Engineering and Instrumentation Program National Institutes of Health DHHS Bethesda MD USA

The authors present an overview of possible mechanisms for cardiac stimulation. Changes of the transmembrane potential in the myocardium in response to an applied electric field are produced by two types of mechanisms, continuous or discrete, depending on whether they are associated with complete or incomplete current redistribution between the intracellular and extracellular spaces. Another way of classifying these mechanisms is whether they produce a membrane polarization only at the heart surface, or both at the surface and throughout the bulk of the heart. These categories provide a unifying framework for future studies on the mechanisms of field stimulation of the heart.< >

关键词： Cardiac tissue Electrical stimulation Heart Polarization Biomembranes biomedical engineering Myocardium Extracellular Electrodes Defibrillation

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Dose-dependent smooth muscle cell proliferation induced by thermal injury with pulsed infrared lasers

Dose-dependent smooth muscle cell proliferation induced by t...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： Philippe C. Douek Rosaly Correa Ellis F. Unger Richard Neville Shmuel Banai Stephen E. Epstein Martin B. Leon Robert F. Bonner Biomedical Engineering and Instrumentation Program National Center of Research Resources National Institutes of Health DHHS Bethesda MD USA

Pulsed infrared localized thermal lesions heating to 30°C above SMC proliferation in Neointimal proliferation laser irradiation induced in arteries by transiently ambient and subsequent rabbits by 3-4 weeks. exhibited a clear dose dependence both as laser fluence was increased (R=0.83) and for a fixed surface irradiation as the depth of the nearest arterial media was decreased (R=0.95). Thermal injury to the arterial wall is shown to be potent stimulus for SMC proliferation, favoring reduction in energies used in laser or thermal angioplasty.

关键词： Lesions Ear Transient analysis Heating Lasers Arteries Surgery

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Letter to the editor: Letter to the editor

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Cancer Investigation 1992年第2期10卷 187-188页

作者： Miller, Donald L. Lutz, Robert J. Diagnostic Radiology Departmentm Warren Grant Magnuson Clinical Center Bethesda MD 20892 United States Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health Bethesda MD 20892 United States

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CLASSIFICATION OF NATURAL TEXTURES BY MEANS OF 2-DIMENSIONAL ORTHOGONAL MASKS - COMMENTS

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 1991年第4期39卷 1005-1006页

作者： UNSER, M Biomedical Engineering and Instrumentation Program National Institutes of Health DHHS Bethesda MD USA

The correspondence of Cohen et al. describes a texture analysis method that is a special use of the approach reported in [3]. Moreover, the derivation of the optimum set of masks presented by these authors is based on an incorrect assumption;the correct solution should be the local Karhunen-Loeve transform which is generally different from a 2 x 2 Hadamard transform (2 x 2 DHT). However, this error has relatively minor effects from a practical point of view since the ability of the 2 x 2 DHT to decorrelate real texture images is usually excellent.

关键词： Signal processing algorithms Speech processing biomedical signal processing Frequency estimation Spectral analysis Inspection Prediction algorithms Algorithm design and analysis biomedical engineering Instruments

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SPECTRAL LOCALIZATION WITH OPTIMAL POINTSPREAD FUNCTION

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JOURNAL OF MAGNETIC RESONANCE 1991年第2期94卷 268-287页

作者： VONKIENLIN, M MEJIA, R In Vivo NMR Research Center Biomedical Engineering and Instrumentation Program NCRR National Institutes of Health Bethesda Maryland 20892 USA

The SLIM experiment ( X. Hu, D. N. Levin, P. C. Lauterbur, and T. Spraggins, spectral l ocalization by im aging, Magn. Reson. Med. 8 , 314, 1988 ) promises to be an efficient technique for localized spectroscopy in vivo , allowing simultaneous acquisition of regional spectra from several, arbitrarily shaped compartments. In the present contribution, we evaluate how sensitivity is affected in this experiment, and we identify a source of localization errors stemming from inhomogeneities within the compartments. We present SLOOP (“spectral lo calization with o ptimal p ointspread function”) as an extension of the SLIM technique. SLOOP optimizes sensitivity and minimizes localization errors by choosing an optimal set of phase-encoding gradients that matches the pointspread function to the shape of the volumes of interest. Experimental results obtained in vitro on a rabbit kidney are shown. SLOOP is also compared to Fourier series localization techniques and to spectroscopic imaging and is presented as a generalization of both of these that samples k space in a nonuniform fashion.

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