Feature extraction in two-dimensional short-axis echocardiographic images

An automatic method for identification of the center point of the left ventricle of the myocardium during systole in two-dimensional short-axis echocardiographic images is described. This method, based on the use of large matched filters, identifies a single fixed center point during systole by locating three key features: the epicardial border along the posterior wall, the epicardial border along the anterior wall, and the endocardial border along the anterior wall. Thus it provides a first step toward the long-term goal of automatic recognition of all the endocardial and epicardial borders. An index (or normalized output value) associated with the filter used to approximate the epicardial boundary along the posterior wall provides an indication of the quality of the image and a reliability measurement of the estimate. When this method was tested on 207 image sequences, 18 images were identified by this index (applied to the end diastolic frame) as unsuitable for processing. In the remaining 189 image sequences, 173 of the automatically defined center points were judged to be in good agreement with estimates made on the end diastolic frame by an independent expert observer. Thus only 16 automatically defined centers were judged to be in poor agreement. Comparisons of the computer and expert-observer estimates were also made for the three key border locations.