Experimental Study Of High-resolution Ultrasound Imaging Of The Phase Angle Between Circumferential Stress And Wall Shear Stress

Cardiovascular disease (CVD) is the leading cause of death, thus new methods are urgent to be developed for early diagnosis of CVD. Wall shear stress (WSS) and circumferential stress (CS) are greatly out-of-phase or asynchronous at sites that are prone to atherosclerosis and intimal hyperplasia. The angle between WSS and CS was designated as stress phase angle (SPA). SPA not only modulates cardiovascular function, but also is a powerful criterion for early diagnosis of CVD. However, the quantitative measurement of SPA has not been reported. Thus, this project proposes a high-resolution ultrasound imaging method to accurately measure SPA, researching the change of SPA with vascular elasticity. In this paper, a vitro pipe flow (polyvinyl alcohol hydrogel phantom and a silicone tube vascular phantom) and a live animal experiments are carried out to study the evolution of the stress phase angle with the change of vascular wall elasticity. This study provides a new means of early diagnosis of cardiovascular diseases.This thesis can be detailed as:Firstly, the calculation method about SPA and the effect of vascular morphology and elasticity on SPA are studied; Secondly, a high-resolution ultrasound imaging method is proposed to simultaneous accurate obtain the curve about the change of CS and WSS with the cardiac cycle, measuring SPA; Thirdly, flow and elastic vessel phantoms are prepared, and a fluid circulation system is constructed, making the vessel phantom under pulsatile diastole and systole like real human vessel; Fourthly, the role of SPA in the detection and localization of vascular lesions is researched by in vitro and in vivo experiments using a high-resolution ultrasound imaging system.The results of experiments show that the negative stress phase angle and the shear stress increase and the strain of the diameter decreases with the increasing of elastic modulus. The results are according to the theory of arteriosclerosis and identified the role of stress phase angle in the detection and localization of vascular lesions.