Abstract:

The use of finite-difference time-domain (FDTD) computer simulations for wave equation calculations has deep roots in the electromagnetic pulse propagation literature, where many of the modern techniques were developed. Results are presented from high-resolution simulations of the linear acoustic wave equation in inhomogeneous media with absorbing boundary conditions. The results address the focusing behavior of sparse ultrasonic arrays under various propagation conditions. Focal spot attributes and size are investigated in the presence of inhomogeneities, time-varying media, and multiple scatterers. Comparison with known benchmarks, such as the diffraction limit, show that useful results can be obtained using FDTD calculations in medical applications, for example, where the frequencies and scales allow full-sized simulations in major organs. [Work supported by the Office of Naval Research.]