Noninvasive Measurement of Brachial Wall Mechanics During Flow-Mediated Vasodilation Using 2D Ultrasound Strain Tensor Imaging

Atherosclerosis has become one of the contributing factors of cardiovascular diseases. Endothelial dysfunction is considered a key factor in the development of atherosclerosis [1]. Flow-mediated vasodilatation (FMD) measurement in brachial and other conduit arteries has become a common method to asses the endothelial function in vivo [2]. Fluid shear-stress increases due to blood flow increases, thus stimulating endothelial cell production and release of nitric oxide, a potent endogenous vasodilator. The mechanical behavior of the arterial wall during vasodilatation is considered an indication for endothelial health. In FMD measurement, the endothelium-dependent variation in arterial diameter in response to reactive ischemia-induced hyperemia is measured by comparing the luminal diameter of the brachial artery before and after the ischemia of the forearm induced by pressurizing a cuff [3]. Ultrasound imaging modalities has been widely used in the FMD analysis as a noninvasive low-cost tool, which can be used to track the arterial diameter change with time. Most of the FMD measurements in the literature are based on tracing the vessel wall boundary manually. Since this process is time consuming and may introduce human errors, automatic measurement techniques have been implemented [3,4]. These techniques utilize image processing algorithms to identify the edges of arterial walls, and then calculate the relative displacement change with time.