Correlation between the characteristics of acceleration and visco elasticity of artery wall under pulsatile flow conditions (physical meaning of I* as a parameter of progressive behaviors of atherosclerosis and arteriosclerosis).

Previously, I* parameter has been proposed to diagnose noninvasively the progressive degree of atherosclerosis which is considered to concern the discrimination of the progressive degree of visco elasticity of blood vessel wall. However, the detailed physical meaning of this parameter has not yet been clarified. In this paper, the theoretical analysis and experiments were conducted and the detailed physical meaning of I* parameter was clarified. The following results were obtained. I* parameter was found to well correlate with the progressive degree of visco elasticity of blood vessel wall characterized by the Ith* parameter derived based on the analysis of visco elasticity in this paper. That is, I* was found to have the physical meaning of representing the progressive degree of visco elasticity of blood vessel wall. On the basis of this results, using clinical data, two dimensional representation between the progressive degree of visco elasticity of blood vessel wall by I* and the decrease in the rigidity of blood vessel wall by PWV was found to be useful to conduct much more detailed diagnosis of atherosclerosis.

Frequency response of blood vessel wall with atherosclerosis and aneurysm.

This research was conducted to investigate frequency response of blood vessel wall. The principal frequency of blood vessel wall, f1 was found to decrease with progression of atherosclerosis and irregularity of the vibration trajectory of blood vessel wall was found to increase. When an aneurysm appeared, a new vibration wave was found to appear in the high frequency region, f2. When the aneurysm wall has enough strength, intensity of high frequency wave was found to increase. However, it decreases with decrease in the strength of aneurysm wall. The visco-elastic deterioration of blood vessel wall was found to well correlate with the changing characteristics of f1. A two-dimensional representation of f1 and f2 was conducted which tracks the progression of atherosclerosis and aneurysm. It will enable us to diagnose the introduction period of operation of blood vessel wall of atherosclerosis with an aneurysm.