Method and apparatus of biosignal spatial analysis
First Claim
1. A method of measuring, analyzing and visualizing electrical activities in a system comprising the steps of:
- (a) collecting signals over a part of a surface of the system using a plurality of sensors and a data acquisition unit,(b) determining positions of the sensors,(c) reducing measurement noise in the collected signals by applying a spatial pre-filtering,(d) reducing volume conduction distortion in the collected signals by using a spatial threshold filter which uses simultaneously both the collected signals and surface differentials of the collected signals, and(e) displaying simultaneously the processed signals in one of the time domain and space domain, together with the collected signals and the surface differentials of the collected signals.
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Abstract
An instrument and method for measuring, analyzing and visualizing electrical activities in a biological system, comprising a plurality of sensors for detecting signals over a part of a surface of the biological system, a data acquisition unit for collecting the signals and for time-domain pre-processing, a positioning device for determining positions of the sensors, an estimator for determining surface differentials of the collected signals, a spatial pre-filter for reducing measurement noise in the collected signals, a spatial threshold filter for reducing volume conduction distortion, and a unit for displaying the processed signals in one of the time domain and space domain, together with the collected signals and the surface differentials of the collected signals. The collected biosignals over the scalp are also deconvolved to estimate the electrical activity over the brain surface.
67 Citations
16 Claims
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1. A method of measuring, analyzing and visualizing electrical activities in a system comprising the steps of:
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(a) collecting signals over a part of a surface of the system using a plurality of sensors and a data acquisition unit, (b) determining positions of the sensors, (c) reducing measurement noise in the collected signals by applying a spatial pre-filtering, (d) reducing volume conduction distortion in the collected signals by using a spatial threshold filter which uses simultaneously both the collected signals and surface differentials of the collected signals, and (e) displaying simultaneously the processed signals in one of the time domain and space domain, together with the collected signals and the surface differentials of the collected signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
- 9. The method of claim 1 wherein the surface differentials are the surface Laplacian and the surface Laplacian of the surface Laplacian, wherein the following threshold filtering
- space="preserve" listing-type="equation">h(I)=S(I)*L(I)*LL(I)
is performed, where h(I), S(I), L(I), and LL(I) refer to the processed signal, the collected signal, the surface Laplacian of said signal, and the surface Laplacian of the surface Laplacian of said signal, at the location I;
the notion "*" refers to multiplication operation in the space domain of the signals at each position I;
where the following pre-filtering is performed to S, L, and LL, ##EQU4## wherein a local mean μ and
variance σ
2 of the signals around each position (i, j) in the space domain are estimated at positions i=1, 2, . . . , N1 and j=1, 2, . . . , N2;
S, F represent the processed and before-processed signals at a position (i, j);
ν
2 refers to the variance of noise.
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10. The method of claim 1 further including a step of determining the surface Laplacian of the signals using one of a local Laplacian estimation algorithm, global Laplacian estimation algorithm, spline Laplacian estimation algorithm, and non-spline Laplacian estimation algorithm.
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11. The method of claim 1 wherein the biosignals are collected by a cardiac catheter.
- 12. An apparatus for measuring, analyzing and visualizing electrical activities in a biological system, comprising a plurality of sensors for detecting signals over a part of a surface of the biological system, means for collecting the detected signals, means for determining positions of the sensors, means for determining surface differentials of the collected signals, means for reducing measurement noise in the collected signals by applying a spatial pre-filtering, means for reducing volume conduction distortion in the collected signals based on both the collected signals and the surface differentials in the space domain, and means for displaying the processed signals in one of the time domain and space domain, together with the collected signals and the surface differentials of the collected signals.
Specification