Ultrasonic Measurement of Change in Elasticity due to Endothelium Dependent Relaxation Response by Accurate Detection of Artery-Wall Boundary

Abstract

Ross hypothesized that an endothelial dysfunction is considered to be an initial step in atherosclerosis. Endothelial cells, which release nitric oxide (NO) in response to shear stress from blood flow, have a function of relaxing smooth muscle in the media of the arterial wall. For the assessment of the endothelial function, there is a conventional method in which the change in the diameter of the brachial artery caused by flow-mediated dilation (FMD) is measured with ultrasound. However, despite the fact that the collagen-rich hard adventitia does not respond to NO, the conventional method measures the change in diameter depending on the mechanical property of the entire wall including the adventitia. Therefore, we developed a method of measuring the change in the thickness and the elasticity of the brachial artery during a cardiac cycle using the phased tracking method for the evaluation of the mechanical property of only the intima-media region. In this study, the initial positions of echoes from the lumen-intima and media-adventitia boundaries are determined using complex template matching to accurately estimate the minute change in the thickness and the elasticity of the brachial and radial arteries. The ambiguity in the determination of such boundaries was eliminated using complex template matching, and the change in elasticity measured by the proposed method was larger than the change in inner diameter obtained by the conventional method.

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

“…The impaired NO on peripheral blood vessels in the hypertensive state is well-documented [35]. Accordingly, as claimed previously, the radial artery (as used in the ULPAS measurements), rather than larger arteries, is suitable for examining the vascular state including endothelial function and that evaluation of peripheral arterial stiffness can thus result in an early diagnosis of atherosclerotic processes [17,18,36]. Taken together, these findings may support the results that indicate that ULPAS is more obviously correlated to SBP and CRP than to IMT and CAVI.…”

“…There are, however, no radial-artery-related clinical data available for this method. Furthermore, although endothelial dysfunction has been implicated in the pathology of large-and medium-sized arteries in HT and DM [15,16], a smaller artery may show a greater correlation with endothelium-dependent vasodilation than a larger-sized artery [17,18]. Examination using the radial artery is thus expected to more clearly reflect endothelial function.…”

Flow-Mediated Change in Viscoelastic Property of Radial Arterial Wall Measured by 22 MHz Ultrasound

“…4) For a more sensitive and regional evaluation, we developed a method of directly measuring the change in the elasticity of the intima-media region due to FMD. 5) We propose a method for the evaluation of FMD, which was previously applied to the measurement of the radial artery. There is an inversely proportional relationship between the percent change in inner diameter due to FMD and that in the inner diameter of the artery at rest because the flow velocity, which affects the shear stress, is inversely proportional to the square of the inner diameter when the pressure and flow volume are constant.…”

A new approach to automatic continuous artery diameter measurement

“…The a priori knowledge about the image features and its content is exploited in this approach. Kaneko et al [8] developed a method of measuring the change in the thickness and the elasticity of the brachial artery during a cardiac cycle using the so-called phased tracking method for the evaluation of the mechanical property of only the intima media region. Our approach is based on profile plot analysis and active contour method.…”