Measurement of Phantom Viscoelasticity with Supersonic Shear Imaging and Its Application in Accessing Hemodynamics of Carotid Artery

• Main Authors: Wei-Chieh Yang, 楊偉杰
• Other Authors: 郭柏齡
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/41570318688512850700

碩士 === 國立臺灣大學 === 生醫電子與資訊學研究所 === 101 === Clinically, cerebral blood flow(CBF) is an important indicator for the prevention and curation of cerebral vascular accident(CVA) which is a major cause of death worldwide. Since cerebral blood flow is provided by carotid artery, one possible monitoring method of CBF is to measure the pressure on the neck surface. Theoretically, blood flow can be estimated from the surface pressure using Navier-Stokes equation and pressure transfer function derived by Lame problem. The derived transfer function considers only purely elastic material which is different from the viscoelastic human tissues. Therefore viscoelasticity estimation might help us correct and improve the accuracy of this mechanical model. Estimation of viscoelasticity is used in diagnosis of pathologic tissues like breast cancer or liver fibrosis recently. In this thesis, Superesonic shear imaging(SSI) method is used to estimate viscoelasticity because of its advantages of real-time, noninvasive and quantitative mapping. Phantoms with different materials are prepared for estimation. Our results have obtained quantitative elasticity mapping and qualitative viscosity information. Two dimensional viscoelasticity mapping for inhomogeneous phantom is reconstructed and can show the difference between inclusion and background phantoms. As for validation of new monitoring approach''s theory, because it gives access to verify pressure transfer function by displacement transfer function from the derivation of pressure transfer function. We measure flow velocity and material displacements of a vessel wall phantom based on Doppler ultrasound. The flow velocity computed by Doppler is considered to be the real velocity value and compared with the velocity evaluated by Navier-Stokes equation. Experimental data of displacements fit well to theoretic transfer function curve. Waveforms between true and estimated flow velocity show similarity except some distortion due to approximation of implementation method and parameters. These validation results show the potential to let us monitor the carotid flow by this approach.