Real-time measurements of local myocardium motion and arterial wall thickening

We have already developed a new method, namely, the phased tracking method, to track the movement of the heart wall and arterial wall accurately based on both the phase and magnitude of the demodulated signals to determine th e instantaneous position of an object. This method has been realized by an off-line measurement system, which cannot be applied to transient evaluatio n of rapid response of the cardiovascular system to physiological stress. I n this paper, therefore, a real-time system to measure change in the thickn ess of the myocardium and the arterial wall is presented. In this system, a n analytic signal from standard ultrasonic diagnostic equipment is analogue -to-digital (A/D) converted at a sampling frequency of 1 MHz. By pipelining and parallel processing using four highspeed digital signal processing (DS P) chips, the method just described is realized in real time. The tracking results for both sides of the heart and/or arterial wall are superimposed o n the M (motion)-mode image in the work station (WS), and the thickness cha nges of the heart and/or arterial wall are also displayed and digital-to-an alogue (D/A) converted in real time. From the regional change in thickness of the heart wall, spatial distribution of myocardial motility and contract ility can be evaluated. For the arterial wall, its local elasticity can be evaluated by referring to the blood pressure. In in vivo experiments, the r apid response of the change in wall thickness of the carotid artery to the dose of the nitroglycerine (NTG) is evaluated. This new real-time system of fers potential for quantitative diagnosis of myocardial motility, early sta ge atherosclerosis, and the transient evaluation of the rapid response of t he cardiovascular system to physiological stress.