Real-Time Monitoring of Shear Wave Traveling in Liver Tissue In Vivo

Real-time imaging of tissue dynamic response caused by internal or external stress forces acting across a living tissue is promising for improving diagnostic quality and accuracy of clinical palpation as an “ultrasonic visualized palpation”. Thus we have investigated a real-time imaging system of local tissue displacement along an ultrasonic beam scanned across the living tissue, which realized straightforward but tissue-oriented physiological and dynamic color imaging on a conventional B-mode screen. System performance is fairly supported by a flexible design of a digital signal processor for real-time local cross correlation between successive two-dimensional complex speckle echo frames. Propagation of shear waves raised by external stress in a tissue phantom was clearly observed, so that real-time observation of shear wave traveling across a physiological liver tissue locally stressed by heartbeats was studied. As a result, we could confirm the characteristic shear wave propagation pattern by internal stress synchronous with heartbeat.