Mechanism of synchronized change in ultrasonic integrated backscatter across human heart wall

Ultrasonic integrated backscatter (IB) from the heart wall, which has been employed for quantitative tissue characterization of the myocardium, is known to have cyclic variation-a decrease in systole and an increase in diastole. In the present study, by tracking the measurement position of the myocardium and compensating for the movement due to the heartbeat, IB and its temporal variation were obtained from the same site with a high temporal resolution of 1.73 ms. In an in vivo study on a healthy subject, the temporal variation of IB values homogeneously changed across the heart wall, especially during the slow filling and the atrial systole phases. This new finding shows that the IB value reflects a small movement of the myocardium of about 5mm/s. Thus, the proposed measurement has a potential for quantitative and accurate evaluation of the contraction and relaxation of the myocardium.