Modified phased tracking method for measurement of change in thickness of arterial wall

In this study, the change in thickness of the arterial wall caused by the heartbeat was measured by the phased tracking method [IEEE Trans. UFFC. 43 (1996) 791] for noninvasive assessment of the regional elasticity of the arterial wall. In the phased tracking method, the change in thickness of the arterial wall is obtained from the difference between displacements of two points set along an ultrasonic beam. The displacement during the pulse repetition interval is determined by the phase of the complex correlation between the quadrature modulated ultrasonic waves. For suppressing noise components, the complex correlation function is spatially averaged in the region, which corresponds to the ultrasonic wavelength. However, spatial averaging of displacements is not desirable for measurement of the change in thickness, because the change in thickness is caused by the spatial inhomogeneity of displacements. In this paper, the phased tracking method was modified for direct estimation of the change in thickness without spatial averaging of displacements.