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The arterial walls become less flexible as individuals age or due to specific diseases. This leads to the heart pressure wave being less dampened, potentially damaging the sensitive tissues of organs such as the brain and kidneys. Additionally, the pressure wave reflected from the arterial branches combines with the primary wave from the heart, leading to hypertension. The traditional method of assessing arterial wall stiffness involves measuring the times when pressure maxima occur in the carotid and femoral arteries. This approach utilizes the Moen-Korteweg equation to calculate the average arterial stiffness between these points. However, accurately determining the distance and average diameter of the arteries between these points introduces challenging measurement errors.
The paper presents an innovative technique to determine the local stiffness of the carotid artery by measuring its diameter changes with an ultrasound scanner and blood pressure using an applanation tonometer. Using these noninvasive techniques, an equivalent Young's modulus, representing the arterial wall stiffness, is calculated through a Kalman filter.
Two vessel deformation models are applied: an analytical model of a linearly elastic cylinder under internal pressure and a numerical model utilizing a neo-Hookian constitutive law. The Dual Extended Kalman Filter is used, wherein the first phase filters the measured pressure, which is then used in the Extended Kalman Filter to determine Young's modulus of the artery wall. Both the analytical and numerical models yielded close results.
