Abstract
BackgroundThe analysis of abdominal sounds can help to diagnose gastro-intestinal diseases. Sounds originating from the stomach and the intestine, the so-called bowel sounds, occur in various forms. They are described as loose successions or clusters of rather sudden bursts. Realistic recordings of abdominal sounds are contaminated with noise and artifacts from which the bowel sounds must be differentiated.MethodsThe proposed intrinsic mode function-fractal dimension (IMF-FD) filtering utilizes the property of the multivariate empirical mode decomposition (MEMD) to behave as a series of band pass filters. The MEMD decomposes the abdominal signal into its different frequency components. The resulting intrinsic mode functions (IMFs) are modulated in amplitude and frequency where transient sonic events occur. Based on the complexity of the IMFs, measured by their fractal dimension (FD) in sliding windows, the information-carrying IMFs are selected. The filtered signal is formed as the superposition of all selected IMFs. The IMF-FD filter not only enhances the non-linear components of the original signal but also segments them from the rest. Another important aspect of this work is that typical artifacts that occur in the same frequency range as bowel sounds can be subsequently eliminated by heuristic rules.ConclusionsThe method is tested on a realistic, contaminated data set with promising performance: close to 100% of the manually labeled bowel sounds are identified.
Highlights
Classical diagnosis of gastrointestinal disorders is uncomfortable for the patient, timeconsuming for the medical staff, and expensive for the health care system
This paper proposes a data driven filtering method that enhances bowel sounds by removing noise and typical artifacts
Qualitative comparison of intrinsic mode functions (IMFs)‐fractal dimension (FD) filter and wavelet‐based methods The training examples were only moderately contaminated by background noise
Summary
Classical diagnosis of gastrointestinal disorders is uncomfortable for the patient, timeconsuming for the medical staff, and expensive for the health care system. Diagnosing gastrointestinal disorders based on manual auscultation is time-consuming and prone to error [2] This increases the health care expenditure and prolongs the discomfort for the patients. Sounds originating from the stomach and the intestine, the so-called bowel sounds, occur in various forms. They are described as loose successions or clusters of rather sudden bursts. A more recent study confirmed that only 0.5% of the signal’s power spectrum density occurs at frequencies above 1000 Hz [13]. The same study revealed that the largest part of the power spectrum density of abdominal sounds is located between 100 Hz and 500 Hz [13]
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