Simulation of elastic wave scattering in living tissue at the cellular level

Abstract

Elastic wave scattering in biological tissue has been simulated at the cellular level by incorporating a first-order approximation of the cell structure and multiple scattering between cells. The cells were modeled with a concentric spherical shell-core structure embedded in a medium, with the core, shell, and medium representing the cell nucleus, the cell cytoplasm, and the extracellular matrix, respectively. Using vector multipole expansions and boundary conditions, scattering solutions were derived for a single cell with either solid or fluid properties for each of the cell components. Multiple scattering between cells was simulated using addition theorems to translate the multipole fields from cell to cell and using an iterative process to refine the scattering solutions. Backscattering simulations of single cells demonstrated that changes in the nuclear diameter had the greatest effect on the frequency spectra as compared to changes in cell size, density, and shear modulus. Wave field images and spectra from clusters of up to several hundred cells were also simulated, and they exhibited phenomena such as wave field enhancement at the cell membrane and nuclear envelope due to the scattering processes. Relevant applications for these models include ultrasonic tissue characterization and ultrasound-mediated gene transfection and drug delivery.