Application of Direction of Arrival for Slow Wave Propagation in Isolated Duodenum

Document Type : Original Article

Authors

1 Military Technical College, Cairo, Egypt.

2 Systems and Biomedical Engineering Dept., Cairo University; Egypt.

Abstract

The technique of multiple simultaneous recordings from a large number of extracellular electrodes (>100) is currently used in the study of normal and abnormal electrical conduction in the heart and the genesis of cardiac arrhythmias. To investigate whether such a system could also be applied in gastrointestinal electrophysiology, several studies were performed with this technique on segments of isolated rabbit duodenum. A multiple electrode assembly consisting of 240 silver wires was positioned on the serosal surface of the duodenum and the recorded signals were, after suitable processing, stored. Thereafter, analysis of all simultaneously recorded slow waves during a selected period of time was performed to reconstruct the pattern of conduction in the duodenum. The first method based on isochrine contours shows considerable pattern through which the pacemaker(s) location(s) would be determined as well as the main direction of propagation. Its output results are sensitive to signal conversion and quantization error and it will show noticeable error if signal-to-noise ratio increases. Moreover, it assumes the homogenous characteristic of the tissue. On the other hand, the second method based on Multiple Signal Classification (MUSIC) technique overcomes the sources of errors mentioned with the first method. It gives the spatial variation of Direction of Arrival (DOA) which is confirmed with the inhomogenity of the tissue.This property is very helpful to follow up the variation of conduction velocity over the sample.

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