P3E-3 Finite Element Modeling of Ultrasound Scattering by Spherical Objects and Cells

It has been shown that high-frequency ultrasound (20 MHz-60 MHz) can be used to detect structural and physical changes in tissues and cell ensembles during cell death. However, the changes observed are not well understood. Recent theoretical models treating the cell as a homogeneous sphere did not show good agreement with experimental data. We have recently developed a finite element model of wave propagation through inhomogeneous spherical structures (COMSOL Multiphysics, COMSOL Inc., Burlington, MA) to solve the problem of high-frequency acoustic scattering from cells. We will discuss the improvement to our previous model by using a second-order boundary condition. The improved model predicts scattering by a homogeneous sphere with a 2% average accuracy when compared to the Faran model. Applications of the model to ultrasound scattering by two types of objects that represent biological cells will be presented. In both applications the cell is a sphere (representing the nucleus) surrounded by a spherical shell (representing the cytoplasm). The cytoplasm has either an elastic property with a stiffness less than that of the nucleus, or is fluid, having similar physical properties to water. The deformations of an air-filled microbubble subject to various acoustic wave frequencies will also be presented. Finally, the significance of this work on the prediction of ultrasound backscatter from cells, and on ultrasound tissue characterization techniques will be discussed