中文摘要：

基于Church—Hoff模型从理论上研究了具有有限厚度的单个包膜微气泡在超声辐射下的非线性振动情况．分别研究了膜壳黏弹性对微气泡径向振动、基频成分和谐波成分的影响．径向振动峰值、功率谱基波和谐波的幅值都随着膜壳剪切模量以0．1MPa的间隔从0～10MPa逐渐增大而增大，随着剪切黏性以0．01 Pa·S的间隔从0～1 Pa·S逐渐增大而减小．次谐波和超谐波成分幅值波动范围大于基波和二次谐波成分，即微气泡膜壳黏弹性对次谐波和基波信号的影响大于对基波和二次谐波的成分影响．这就使得调整微气泡膜壳黏弹性至合适的数值以制备得到具有较好的次谐波和超谐波成像的微气泡这一潜在方法成为可能．最后，任选取基波和谐波成分都较为显著的4对黏弹性处以示说明，其剪切黏性和剪切模量分别为：0．39Pa·S和3．9MPa；0．39Pa·S和6．6MPa；0．39Pa·S和8．6MPa；0．42Pa·S和6．6MPa．

英文摘要：

Based on the Church-Hoff model, the nonlinear oscillations of a single encapsulated microbubble with a finite thickness shell are theoretically studied. The effects of viscoelasticity on radial oscillations and the fundamental and harmonic components are researched. The peaks of radial oscillations and magnitudes of power spectra of the fundamental and harmonic components all increase gradually with the shear modulus of shell varying from 0 to 10 MPa by an interval of 0. 1 MPa at the same shear viscosity, while they decrease as the shear viscosity increases from 0 to 1 Pa · s by an interval of 0. 01 Pa · s at the same shear modulus. The fluctuation ranges of subharmonic and ultraharmonic signals are much larger than both the fundamental and second harmonic components. It means that the effect of viscoelasticity on the subharmonic and ultraharmonic signals is greater than that on the fundamental and second harmonic components. So adjusting the viscoelasticity of the shell is a potential method to obtain a perfect microbubble contrast agent used for the subharmonic and ultraharmonic imaging. Four points with significant fundamental and harmonic components are chosen as an example： a shear viscosity of 0. 39 Pa · s with shear modulus of 3.9, 6. 6, and 8.6 MPa, respectively; a shear modulus of 6.6 MPa with a shear viscosity of 0.42 Pa · s.