Computational Methods for Simulating Ultrasonic Scattering in Soft Tissue

The direct scattering problem of pulsed ultrasound in spatially inhomogeneous dispersive tissue is investigated with emphasis on computer simulation techniques. The motivation for this is that model images synthesized from known system and tissue parameters may be useful in designing and testing algorithms for ultrasonic tissue characterization. In this context the scattering process is fundamental to forming sonograms commonly used for medical diagnosis, and simulation of the scattered field is the most computationally demanding step in forming realistic models of sonograms. Some potential problems and trade-offs associated with the implementation of large-scale simulations are discussed, including constraints on the choice of spatial and temporal sampling increments, spatial aliasing, numerical dispersion, and wrap-around error. An example of transient scattering is presented using a spectral approach applied to an integral formulation for the scattered field.