Centre-specific multichannel electrogastrographic testing utilizing wavelet-based decomposition

Abstract

Although the principles of electrogastrography (EGG) have been known for years, the clinical utility of EGG has not been clearly demonstrated, and EGG recording and analysis techniques have not been fully standardized. The aim of this study was to develop a multichannel EGG technique for detecting abnormal gastric motility using an EGG database specifically designed for a particular testing centre, maximizing the sensitivity and the specificity of the test. Eight healthy volunteers formed a reference group to which 4 study groups (17 gastro-oesophageal reflux disease (GORD) patients, 7 functional dyspepsia patients, 8 post-fundoplication patients and 12 healthy volunteers) were compared. Eight-channel EGG was recorded in the postprandial and fasting states for 30 min each. The recorded signals were wavelet compressed and the resulting error (per cent root mean square difference (PRD)) after the compression was utilized to compare the study groups to the reference group. A threshold in the number of channels with significantly different PRD values was introduced. Sensitivity (SE), specificity (SP) and correct classification rate (CC) of the test in recognizing each clinical condition in the study groups for several channel thresholds and compressions were calculated, and were maximized. Increasing the compression and channel threshold levels improved the specificity, but decreased the sensitivity of the multichannel EGG test. An optimal combination region was identified based on a centre-specific adjustment of the channel threshold and the wavelet compression. The achieved maximum sensitivity, specificity and correct classification for this region in our test centre were as follows: GORD--SE 82.4%, SP 83.3%, CC 82.8%; functional dyspepsia--SE 100%, SP 75%, CC 84.2%; post-fundoplication--SE 75.0%, SP 83.3%, CC 80.0%. The utilization of a wavelet-based decomposition technique to process multichannel EGG signals can be a very effective method for enhancing the clinical utility of EGG, provided it is specifically developed for a given testing centre.

Methods for measurement of gastric motility

“…The patient needs to be in a comfortable reclining position or at a 45°angle in a quiet room throughout the study to prevent movement artifact that could be erroneously diagnosed as dysrhythmia. Multichannel recordings may enhance the information obtained with cutaneous EGG, such as the identification of slow-wave coupling (70,123,142).…”

Wavelet analysis of an electrogastrogram database

“…Hubka et al proposed an independent component analysis for denoising that have a good performance, but recordings where made with subcutaneous electrodes so further comparative analysis of this database is recommended [6]. Minchev et al proposed an analysis of threshold of the channels and compression ratio using wavelets as parameters that determinate the efficiency of the multichannel recordings for further analysis [7], as in the previous case, once the classic parameters were used for testing this database, there are several techniques that have to be proved.…”

Detection of patients with functional dyspepsia using wavelet transform applied to their electrogastrogram

“…Attempts to systematically extract EGG characteristics for their subsequent classification using WT have generated adequate results in other gastric diseases (10,12). In many cases, a multichannel EGG was necessary to obtain the signals (13,14).…”

“…Since traditional Fourier analysis uses block processing, which produces undesired averaging effects in the spectra, special processing techniques have been developed based on adaptive and mobile media models, and more recently on the wavelet transform (WT) (12,14). The WT stands out because it avoids the problems of segmenting the signal by using windows based on functions that can be completely scaled and modulated.…”

“…For FD classification, Tchervensky et al (14) used the compression ability of the WT to evaluate abnormal frequencies.…”