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Assessment of the arterial pulse wave velocity (PWV) has long been an area of interest in physiology, and ultrasound has long been used to provide measurements for such assessments. Recently, new signal processing approaches for ultrasound data have emerged. However, these methods suffer from inaccuracies due to pulse wave reflections, which are always present and can strongly bias the PWV estimates away from the true velocity. Recently the authors (Hoctor et al. (2004)) showed that pulse wave velocity estimation from several ultrasound measurements taken along a short uniform arterial segment is equivalent to the broadband directional of arrival problem with coherent multipath found in radar and sonar. This tutorial paper reviews the physiological and ultrasound-systems aspects of the PWV estimation problem, and examines its relationship to the direction-of-arrival estimation problem. The paper also demonstrates why nonlinear, high-resolution methods are needed and outlines the application of several such estimators to the problem. |
