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An edge detection algorithm used in conjunction with digitized two-dimensional echocardiograms was applied to validate computerized two-dimensional echocardiographic (2DE) quantitation of cross-sectional areas of canine left ventricular chambers. Images were enhanced by space-time smoothing and dynamic range expansion, after which automatic edge detection was performed by convolving a Laplacian operator with the enhanced image. In an in vitro study of 29 myocardial slabs, computer-derived 2DE measurements of short-axis sections of the left ventricle were compared with manually derived 2DE data and validated against direct measurements of intraluminal areas of myocardial slabs. Correlations of both manually and computer-derived 2D echocardiograms vs direct measurements were equally satisfactory (r = .95 for both). Computer-derived measurements of perimeters tended to underestimate actual perimeters of the endocardial outlines of left ventricular sections. In 13 closed-chest anesthetized dogs, manually and computer-derived left ventricular short-axis areas measured by 2DE techniques showed a good correlation at both end-diastole (r = .91) and end-systole (r = .92). Left ventricular volumes reconstructed from 2DE images were compared with angiographically determined volumes. The computer-enhanced 2DE method correlated against angiography, with r = .93 for end-diastolic and r = .93 for end-systolic volumes. Left ventricular volume correlations between manually and computer-derived 2D echocardiograms were satisfactory, with r = .87 for end-diastole and r = .87 for end systole. We conclude that computerized enhancement and edge detection of 2D echocardiograms obtained in dogs provided accurate analysis of actual left ventricular cross-sectional areas and left ventricular volumes.
Zwehl et al. (Tue,) studied this question.