Graphical user interface (GUI) for semi-automated M-Mode data analysis.

The GUI visualizes eight cardiac cycles at a time (A) while allowing the user to examine the entire series of data via a slider (bottom). Canny filter parameters (top-right) can be tuned to detect the inner diameter of the vessel from M-Mode images. ECG (B) and inner diameter (C) data are digitized, then R peaks in the ECG time series are identified and used to delimit individual cardiac cycles (red vertical lines in the image, red open dots in the time series). Individual cardiac cycles showing poor tracking or breathing artifacts can be deleted by selecting the “Delete Cycles” button and then clicking anywhere within the area of the cardiac cycle to be discarded. The remaining data can be ensemble averaged to obtain the mean inner diameter waveform over the mean cardiac cycle (D). In the case of poor quality data, the user can specify a few selected cardiac cycles to be considered by selecting the “Select & Average Cycles” button.