Real-time velocimetry for evaluation of change in thickness of arterial wall

We previously developed a new method, namely, the phased tracking method, f or accurately tracking the movement of the heart wall and arterial wall bas ed on both the phase and magnitude of the demodulated signals to determine the instantaneous position of an object. By this method, the local change i n wall thickness during one heartbeat can be determined. We have now develo ped a real-time system for measuring change in thickness of the myocardium and arterial wall. In this system, four highspeed digital signal processing (DSP) chips are employed for obtaining the initially developed method in r eal time. The tracking results for both sides of the wall are superimposed on the M (motion)-mode image in the workstation, and the thickness changes of the arterial wall are displayed in real time. Using this system, reporte d herein, velocity signals of the arterial wall with amplitudes less than s everal micrometers can be successfully detected in real time with sufficien t reproducibility. The elasticity of the arterial wall is evaluated by refe rring to the blood pressure. In in vivo experiments, the rapid response of the change in wall thickness of the carotid artery to the dose of nitroglyc erine (NTG) is evaluated for a young healthy subject and a young smoker. Th is new real-time system offers potential for quantitative diagnosis of earl y-stage atherosclerosis by the transient evaluation of the rapid response o f the cardiovascular system to physiological stress. (C) 2000 Elsevier Scie nce B.V. All rights reserved.