剪切波成像中剪切波速度变化规律 注：研究生论坛稿件

超声辐射力可激励组织产生单色波,其剪切波的传播速度与组织的剪切粘弹性是密切相关。目前通过剪切波速度反演各向同性剪切模量的研究,均是基于各向同性介质中剪切波传播速度恒定这一假设。研究表明,各向同性介质中剪切波的传播速度在剪切方向上并不恒定,不同的检测位置测得的速度不同,它与检测位置点当前的振动相位相关。剪切波的传播速度在剪切方向上呈现近似于正弦的变化规律。研究还表明,这种变化主要是由局部密度随着振动传播变化所引起的,并给出了剪切波传播速度以及局部密度变化的修正公式。为证明剪切波速度修正的必要性,将由未经修正的剪切波速度所得的剪切模量,与经过修正的剪切波速度所得的剪切模量进行了比较,误差下降了10%。

Law of Shear wave speed in Shear Wave Imaging

Radiation force from ultrasound has been used to excite monochromatic waves in tissues.The shear wave propagation speed is related to the shear elasticity and shear viscosity of the tissue.In previous researches,the thinking that shear wave propagation speed is a constant in isotropic media was widely used to estimate the viscoelastic modulus.Nevertheless,the present work shows that shear wave propagation speed in isotropic media follows the fact that it’s not a constant but regularly vary with vibration phase of measuring point in shear direction,which appears sinusoidal change approximately with phase.It is shown that the variance of shear wave propagation speed is mainly caused by the change of local density with time.The modified formulas of shear wave propagation speed and density are presented.Finally,shear elasticity modulus is deduced respectively with constant speed and modified,which demonstrates the essential of modification and the error of shear elasticity modulus fall by more than 10%.