1984 Volume 25 Issue 1 Pages 31-43
A new practical method of computer digital image processing of two-dimensional echocardiograms was developed for the quantification of the left ventricular regional contractility.
Short axis, cross-sectional images of the left ventricle at the levels of the mitral valve, papillary muscle and apex were recorded by a phased array sector scanner. The echo data recorded on video tape were transfered to a minicomputer through the interface circuits and digitized and processed automatically. Automatic edge detection of the endocardial and epicardial walls was performed by applying sequential steps, including smoothing, dynamic thresholding, region growing and filling small holes. The rationale for edge detection depended upon the assumptions that the abrupt changes of the gray levels occurred at the boundaries and that the points with the maximum gradient values are boundaries of the left ventricular wall. Best-fit contours of endocardial and epicardial edges were drawn by fitting a spline.
The short axis cross-sectional left ventricular wall at each level was divided into eight segments, with the center of gravity of end-diastolic left ventricular cavity and the axis connecting this with the posterior end of the right side of the septum being used as the reference point and line. The segmental hemiaxis, area and wall thickness were measured every 33 msec from end-diastole during the cardiac cycle and the systolic percent changes were calculated automatically by a computer. Regional contractility of the left ventricle was evaluated by systolic percent changes of the segmental hemiaxis, area and wall thickness.
The measured values in a patient with dilated cardiomyopathy were lower than those of a normal subject, probably reflecting myocardial damage of the left ventricle. Although there are some points to be improved, including a better system for transferring echo data to the computer and the evaluation of the validity of this fixed reference system, it is likely that computer analysis of the short axis cross-sectional echocardiogram of the left ventricle will be useful in a clinical setting.
