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 s...
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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, conti...
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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 ex...
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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-dimensi...
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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".
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 wave...
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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...
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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.< >
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. exhi...
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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.
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...
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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.
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 vi...
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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