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Thursday, Jan 16, 2014

11:30 AM12:30 PM Gavett 312

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BME PhD Proposal Seminar: Jonathan Langdon

Single Tracking Location Acoustic Radiation Force Viscosity Estimation

Professor Stephen McAleavey, Ph.D.


Single Tracking Location Acoustic Radiation Force Impulse (STL-ARFI) imaging is a method for determining the elastic properties of various materials. The measurement is accomplished by comparing the arrival time difference of two consecutive shear waves, generated by acoustic radiation force and applied at two spatially varied locations. A linear elastic model is then assumed to arrive at an estimate of the materials stiffness. However, biological tissues are viscoelastic. It was previously shown that the single tracking location configuration confers the advantage of a lower estimator variance compared with multiple tracking locations. We hypothesize that this advantage is equally applicable to viscoelastic materials. However, an understanding of how viscosity affects the STL-ARFI measurement must be developed to prove this hypothesis. In this work, the effect of viscosity on the STL-ARFI stiffness estimate is determined and modeled. Next, alternative post-processing techniques that allow for the measurement of viscosity and stiffness are developed. These new methods are collectively referred to as STL-ARFI Viscosity Estimation (STL-VE) and have been implemented in real-time using Graphics Processing Units (GPUs). The task of validating the technique remains and we propose accomplishing this by comparison with a similar multiple tracking location technique known as Shearwave Dispersion Ultrasound Vibrometry (SDUV). Finally, the applicability of the STL-VE technique to liver fibrosis monitoring will be demonstrated using a rat model.