Ultrasonic Measurement of Transient Change in Stress–Strain Property of Radial Arterial Wall Caused by Endothelium-Dependent Vasodilation

Abstract

The endothelial dysfunction is considered to be an initial step of atherosclerosis. Additionally, it was reported that the smooth muscle, which constructs the media of the artery, changes its characteristics owing to atherosclerosis. Therefore, it is essential to develop a method for assessing the regional endothelial function and mechanical property of the arterial wall. There is a conventional technique of measuring the transient change in the diameter of the brachial artery caused by flow-mediated dilation (FMD) after the release of avascularization. For more sensitive and regional evaluation, we developed a method of measuring the change in the elasticity of the radial artery due to FMD. In this study, the transient change in the mechanical property of the arterial wall was further revealed by measuring the stress-strain relationship during each heartbeat. The minute change in the thickness (strain) of the radial arterial wall during a cardiac cycle was measured by the phased tracking method, together with the waveform of blood pressure which was continuously measured with a sphygmometer at the radial artery. The transient change in stress-strain relationship during a cardiac cycle was obtained from the measured changes in wall thickness and blood pressure to show the transient change in instantaneous viscoelasticity. From the in vivo experimental results, the stress-strain relationship shows the hysteresis loop. The slope of the loop decreased owing to FMD, which shows that the elastic modulus decreased, and the increasing area of the loop depends on the ratio of the loss modulus (depends on viscosity) to the elastic modulus when the Voigt model is assumed. These results show a potential of the proposed method for the thorough analysis of the transient change in viscoelasticity due to FMD.

Relationship between upper limb peripheral artery stiffness using the radial artery and atherosclerotic parameters

“…Recently, a noninvasive transcutaneous ultrasonic technology that utilizes the ''phased tracking method'' was developed in order to evaluate atherosclerotic formation based on the compositional features of the artery wall [9][10][11][12]. This method allows the detection of minute changes in the thickness of the layers of the arterial wall by subtracting the displacements of two points set along an ultrasonic beam during a single heartbeat.…”

“…When we use a system based on this technology, the elasticity distribution is seen as the mean elastic modulus [9]. This method has already been used for detecting regional changes in the arterial wall [9] and to assess endothelial function in combination with the flow-mediated dilation test [12]. Higher carotid artery elasticity in smokers as compared with nonsmokers has also been suggested [13].…”

Introduction of measurement techniques in ultrasonic electronics: Basic principles and recent trends

“…Scattering [359][360][361][362][363][364] Ultrasonic transducers (piezoelectric effect) and its attachments [375][376][377][378][379][380][381] Acoustic field measurement and control [382][383][384][385][386] Blood flow measurement [394][395][396][397] Tissue characterization Velocity [125][126][127][128][129][130][131][132][133][134][406][407][408]420,422) Displacement 409,413,425) Thickness 399,418) Viscoelasticity 398,[401][402][403][404][405][410]…”

Blood flow stream line imaging by direct visualization of echo trajectories

“…In relation to the shear stress acting on the arterial wall, it has been reported that the artery dilates when blood flow increases because endothelial cells produce nitric oxide, which relaxes smooth muscle in the media, in response to the shear stress due to blood flow. Therefore, the endothelial function can be evaluated by measuring the dilation of the artery or the change in the mechanical property of the wall [3], [4], [5].…”