Left ventricular volume determination using colour superpositioning of contrast echocardiograms

Abstract

Objective: To delineate the endocardium, selective colouring of contrast regions in left ventricular contrast echocardiograms was performed using digital image processing. Methods: Volume determinations were performed in end-diastolic and end-systolic frames before and after the injection of contrast agent into the left ventricle and were compared to cineventriculograms in 30 patients by two independent investigators. Results: The mean end-diastolic volume measured was 114 ± 44 ml in the native, 235 ± 79 ml in the contrast, 175 ± 70 ml in the color-superimposed (observer 1), and 187 ± 79 ml in the cineventriculographic images. Thus, native echocardiograms underestimated angiographic volumes by 39%, contrast echocardiographic pictures overestimated angiographic volumes by 26%, and color-superimposed pictures underestimated angiographic volumes by 6%. The mean end-systolic volume measured was 61 ± 34 ml in the native, 126 ± 51 ml in the contrast, 88 ± 47 in the color-superimposed (observer 1) and 93 ± 53 in the cineventriculographic images. Ejection fractions were identical in the color-superimposed and angiographic images. In a two-factor cross classified analysis of variance the factor methodology showed significant differences for end-diastolic (P = 0.0001) and end-systolic volumes (P = 0.0001) and the ejection fraction (P = 0.0003), while the factor observer did not show significant differences (P = 0.046, 0.70 and 0.0435). Inter-observer variability was significantly lower for end-diastolic, end-systolic volumes and the ejection fraction (P = 0.0060, 0.0006 and 0.0001, F-test) in the color-superimposed images when compared to native echocardiographic images. Conclusion: Color superpositioning of contrast echocardiograms allows improved volume determination due to better left ventricular endocardial delineation.