Abstract
Recently, magnetocardiography (MCG) has attracted increasing attention as a non-invasive and non-contact technique for detecting electrocardioelectric functions. However, the severe background noise makes it difficult to extract information. Variational Mode Decomposition (VMD), which is an entirely non-recursive model, is used to decompose the non-stationary signal into the intrinsic mode functions (IMFs). Traditional VMD algorithms cannot control the bandwidth of each IMF, whose quadratic penalty lacks adaptivity. As a result, baseline drift noise is still present or medical information is lost. In this paper, to overcome the unadaptable quadratic penalty problem, an improved VMD model via correlation coefficient and new update formulas are proposed to decompose MCG signals. To improve the denoising precision, this algorithm is combined with the interval threshold algorithm. First, the correlation coefficient is calculated, to determine quadratic penalty, in order to extract the first IMF made up of baseline drift. Then, the new update formulas derived from the variance that describes the noise level are used, to perform decomposition on the rest signal. Finally, the Interval thresholding algorithm is performed on each IMF. Theoretical analysis and experimental results show that this algorithm can effectively improve the output signal-to-noise ratio and has superior performance.
Highlights
In recent years, the research on signal processing, modeling, imaging theory, and methods related to bio-electromagnetism has become a hot topic
In the expression of the traditional EMD and EEMD methods, the intrinsic mode functions (IMFs) is defined as a function where the difference between the number of zeros and poles does not exceed one [24]
To overcome the unadaptable quadratic penalty problem, we propose an improved Variational Mode Decomposition (VMD) method with correlation coefficient and new update formulas
Summary
The research on signal processing, modeling, imaging theory, and methods related to bio-electromagnetism has become a hot topic. The relationship between heart function and heart disease is studied by researching the characteristics of magnetic field strength changes at different locations; this type of study can be called interdisciplinary basic research Such measurements are conducted in order to detect small magnetic field signals in the presence of large background noise [6,7]. Decomposition (EMD) [12,13] is one of the decomposition methods of signal denoising, and is widely used to decompose a signal into different modes recursively. Based on the definition of intrinsic mode functions (IMF), a new adaptive decomposition method called Variational Mode Decomposition (VMD) [19] has been proposed. Proposed using the VMD method to denoise ECG signals.
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