Echocardiography is a widely-used noninvasive diagnostic technique that is extremely valuable in evaluating patients with suspected heart disease. As routinely used, this technique utilizes a single ultrasound transducer that can be oriented so that the ultra-sound beam is directed through a specific region of the heart. With this method, rapidly moving structures can be easily visualized. The spatial orientation of cardiac structures, however, is more difficult to evaluate, a limitation that is particularly important when evaluating congenital heart disease where normal anatomic relations cannot be relied upon. In order to overcome this difficulty, several systems have been developed to image a larger region of the heart. These systems can be grouped into a) real-time systems (1-3); i.e., those that allow visualization of heart motion while it actually is occurring and b) non-real time systems (4,5); i.e., those that require multiple consecutive heart beats in order to construct images of the heart.
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