RCBU Seminar

Abstract

Elastography is a term that generally describes techniques used to determine mechanical properties of tissue based on its response to an applied force. Spatially Modulated Ultrasound Radiation Force (SMURF) Imaging is a novel elastographic technique that has been developed in the McAleavey Ultrasound Lab at the University of Rochester. SMURF Imaging involves applying a spatially modulated intensity beam to a region of interest. The shear wave generated by the force, due to the transfer of momentum to the tissue, is shaped by the intensity pattern. This means that the wavelength of the induced shear wave is known, and so, the shear wave speed, and thus, the shear modulus (measure of stiffness), can be estimated using motion tracking techniques and cross-correlation algorithms. SMURF imaging has the combined advantages of being fast, safe, inexpensive, quantitative, and easy to employ using standard clinical equipment.

According to the World Health Organization, chronic liver diseases, such as viral hepatitis C, affect millions of individuals worldwide. The Center for Disease Control and the National Institute of Diabetes and Digestive and Kidney Diseases, report that thousands of individuals die from chronic liver diseases every year in the United States alone. Chronic liver diseases result in liver fibrosis, which is a non-specific inflammatory response of injured liver cells. It is characterized by a disorganized, over-synthesis of fibrous tissue (collagen), which leads to a diffuse stiffening of the organ. Over time, this response affects the structure, microcirculation, and function of the liver.

Various studies have shown that there is a correlation between the degree of fibrosis (fibrosis stage), as assessed by biopsy, and the stiffening of the liver tissue. This suggests that the progression of liver fibrosis could potentially be assessed via the measurement of liver stiffness, rather than by repeated biopsies. Since the rate of progression of fibrosis varies from one individual to the next, there is a need for a safe, inexpensive, and quantitative way to monitor patients (as often as needed) that are flagged as being at risk for liver fibrosis.

The proposed work aims to develop the use of SMURF imaging as a way to diagnose and monitor the progression of liver fibrosis. The first two aims address the optimization of, and the challenges faced by, the SMURF technique for an in-vivo application. The third aim will demonstrate SMURFs capabilities in an animal model of liver fibrosis, while the fourth aim is a feasibility study in humans.