IMPROVEMENT IN ENDOCARDIAL BORDER DELINEATION USING TISSUE HARMONIC IMAGING

Background and Methods: For years, tissue has been, assumed to be a li near medium in diagnostic ultrasound applications; thus, no backscatte red signals in the second harmonic band are expected in, harmonic imag ing without the injection of a contrast agent. However, it has been sh own, that a useful tissue image is formed even without a contrast agen t. The aim of this study teas to evaluate whether this tissue harmonic image provided improved visualization of endocardial borders. Fifty-s ix adult patients with various heart diseases were investigated using conventional two-dimensional echocardiography and tissue harmonic imag ing. In 30 of these patients, the left ventricular endocardial borders were well defined in, the standard parasternal and apical views using conventional two-dimensional echocardiography. In the remaining 26 pa tients, delineation of endocardial borders was not possible in, at lea st two segments. The equipment used was an ATL HDI-3000 diagnostic sys tem equipped with harmonic imaging. Results: In all 56 patients, the m yocardium and valves could be imaged with tissue harmonic imaging. Har monic recordings were sharper and contained fewer clutter artifacts th an conventional recordings. Most striking was the enhancement of left ventricular endocardial borders. In the 26 patients with incomplete de lineation of left ventricular endocardial borders, wall motion could b e evaluated in 290 of 312 (93%) segments with tissue harmonic imaging compared with only 168 of 312 (54%) segments with conventional echocar diography (P < 0.001). Conclusions: Tissue harmonic imaging improves i mage quality and can be used to enhance the definition of left ventric ular endocardial borders. These findings can be explained by the nonli near propagation of ultrasound within the tissue, which results in dis tortion of the transmitted signal and, thus, harmonic generation.