Changes in myocardial backscatter throughout the cardiac cycle.

This investigation was performed to identify and quantify systematic variations of myocardial ultrasonic backscatter throughout the cardiac cycle. Using a broadband 5 MHz focused transducer coupled to the epicardial surface of the left ventricle in dogs, backscatter measurements were obtained from each of 7 intervals (windows) of 34 milliseconds duration evenly distributed throughout the cardiac cycle and referenced to backscatter from a steel reflector. Values of integrated backscatter obtained demonstrated a consistent and reproducible pattern throughout the cardiac cycle characterized by elevated values at end-diastole and significantly lower values at end-systole. The average maximum difference was 3.5 dB.