＜正＞Speed of Sound is different in various breast tissues（such as glands,fat,tumors,etc）.Reconstruction of spee...
Yang YANG Minhua LU Tianfu WANG Siping CHEN 1 Department of Biomedical Engineering,Shenzhen University,Guangdong 518060 2 Shenzhen Key laboratory of Biomedical Engineering,Shenzhen,Guangdong 518060
The interaction between microbubble and elastic microvessel wall has been hypothesized to be important in the mechanisms of therapeutic ultrasound applications.In this study,a 2D axisymmetric finite element numerical model is established to study the interaction between elastic microvessel wall and oscillating microbubble in low frequency ultrasound field using fluid solid interaction method.The numerical results show that the bubble oscillation induces the vessel wall dilation and depression.The von Mises stress distribution over the microvessel wall is heterogeneous and the maximum value of the midpoint on the inner vessel wall could reach 0.23 MPa and 1.32 MPa under PNP 0.2 MPa and 0.5 MPa,respectively.When the bubble collapses,the circumferential stress decreases rapidly and the transmural pressure increases dramatically.Noticeably,the circumferential stress becomes compressive with the maximum magnitude 1.83 MPa under PNP 0.5 MPa,larger than the maximum tension value.It is possible that the rapid compression stress during bubble collapse plays important role in mechanical effect on microvessel wall endothelial lining disruption.
肝纤维化是在肝细胞发生广泛变性和坏死基础上产生肝内纤维结缔组织异常增生的病理过程,是慢性乙肝发展的重要病理特征以及肝硬化发生的必经环节,无创性准确分期肝纤维化程度是近年研究热点。近年来无创性分期肝纤维化的诊断指标主要包含了血生化指标、影像学指标、弹性成像指标:其中谷草转氨酶/血小板比值(aspartate aminotransferase to platelet ratio index,APRI)和Forns指数作为血生化指标的代表已经应用于临床无创性诊断肝纤维化。声辐射力脉冲成像(Acoustic radiation force impulse,ARFI)与Fibroscan作为弹性成像技术的代表,是一项通过测量肝组织弹性、硬度等生物力学参数来反映肝脏纤维化程度的新技术,具有简单易行、可重复性强、结果量化等特点。
