Computer methods for myocardial contrast two-dimensional echocardiography

Two computer-aided videodensitometric methods that may be used in conjunction with two-dimensional contrast echocardiography were examined to quantify the time course of echographic opacification in the myocardium after experimental injections of contrast agents (hand-agitated Renografin-saline and sonicated sorbitol 70% solutions) into the left main coronary artery. Echographic studies of myocardial cross sections were digitized with an image processing computer using a 128 X 128 resolution matrix. Both stop frame and continuous cycle modes of acquisition were performed. A set of computer programs was developed to extract and analyze time-intensity curves from the digitized images. These included cardiac outline delineation, segmental division, regional intensity computation and exponential curve analysis. The stop frame method was applied to experimental studies in 17 closed chest dogs during control states and after coronary occlusions. Significant differences were found in the decay half-lives of echo intensity between normal (24 +/- 8 seconds) and acutely ischemic (293 +/- 165 seconds; p less than 0.001) myocardium for the Renografin-saline solution. Interobserver reproducibility of the measured half-lives was r = 0.91 and standard error of the estimate = 5 seconds. The continuous cycle method of analysis was examined in five closed chest dogs (with up to six injections per dog), applying the sonicated sorbitol 70% solution in only the control state. The mean half-life was 4.2 +/- 1.1 seconds. These computer-based videodensitometric methods might be applied to a wide variety of experimental studies in two-dimensional contrast echocardiography that attempt to quantify myocardial perfusion and function.