This study was performed to investigate the two-dimensional unprocessed radiofrequency (rf) ultrasonic backscatter from myocardium throughout the cardiac cycle. Eleven mongrel dogs underwent left lateral thoracotomy and had two-dimensional echocardiographic studies performed using a 5 MHz transducer. Regions of interest, selected to encompass a portion of the myocardium, were transported at 33 ms intervals to a host computer and disc. Results show a reproducible cyclic variation in backscatter power throughout the cardiac cycle for the anterior wall. The backscatter power was highest during diastolic relaxation and lowest during systolic contraction. The average change was 4.5 dB.
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