Abstract
This paper presents the analysis of multi-channel electrogastrographic (EGG) signals using the continuous wavelet transform based on the fast Fourier transform (CWTFT). The EGG analysis was based on the determination of the several signal parameters such as dominant frequency (DF), dominant power (DP) and index of normogastria (NI). The use of continuous wavelet transform (CWT) allows for better visible localization of the frequency components in the analyzed signals, than commonly used short-time Fourier transform (STFT). Such an analysis is possible by means of a variable width window, which corresponds to the scale time of observation (analysis). Wavelet analysis allows using long time windows when we need more precise low-frequency information, and shorter when we need high frequency information. Since the classic CWT transform requires considerable computing power and time, especially while applying it to the analysis of long signals, the authors used the CWT analysis based on the fast Fourier transform (FFT). The CWT was obtained using properties of the circular convolution to improve the speed of calculation. This method allows to obtain results for relatively long records of EGG in a fairly short time, much faster than using the classical methods based on running spectrum analysis (RSA). In this study authors indicate the possibility of a parametric analysis of EGG signals using continuous wavelet transform which is the completely new solution. The results obtained with the described method are shown in the example of an analysis of four-channel EGG recordings, performed for a non-caloric meal.
Highlights
Electrogastrography is a research method designed for noninvasive assessment of gastric slow wave propagation [1,2,3,4].One or multichannel EGG signals are obtained from the disposable electrodes, appropriately arranged on the surface of the abdomen of the patient’s stomach [5,6,7]
These values were obtained based on the analysis of the CWTFT coefficients
Thanks to fast Fourier transform (FFT) applying in the continuous wavelet transform (CWT) algorithm computation, the results for relatively long records of EGG
Summary
One or multichannel EGG signals are obtained from the disposable electrodes, appropriately arranged on the surface of the abdomen of the patient’s stomach [5,6,7]. It is assumed that the frequency range of EGG signal is from 0.015 to 0.15 Hz and the amplitude of it is about 100–400 μV [6, 8]. EGG examination takes about 2 h and consists of three parts: the first one - preprandial, usually no longer than 30 min, it is a stage before a meal (person under investigation should be fasted). The second part takes about 5 to 15 min, including time when the person accepts a standardized meal, and the third part - postprandial, about 60–120 min, when the meal is digested. The standard of a meal depends on the examining center. Most frequently three types of meals are used: noncaloric meal e.g., 400 ml water, liquid meal e.g., 250 ml of yogurt and the caloric meal, e.g., pancake with jam prepared according to a well-defined recipe [9, 10]
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