Simulation of ultrasonic propagation through abdominal wall

Abstract

Ultrasonic pulse propagation through the human abdominal wall is simulated using a model for two‐dimensional propagation through anatomically realistic tissue cross sections. The time‐domain wave equation for a medium of variable sound speed and density is discretized and solved as a set of coupled finite‐difference equations. The finite‐difference algorithm used is a two‐step MacCormack scheme that is fourth‐order accurate in space and second‐order accurate in time. The inhomogeneous tissue of the abdominal wall is represented by two‐dimensional matrices of sound speed and density values. These values are determined by mapping scanned images of abdominal wall cross sections that have been stained to identify connective tissue, muscle, and fat, each of which is assumed to have a constant sound speed and density. The computational configuration is chosen to simulate the experimental wave‐front distortion measurements of Hinkelman et al. [ 530–541 (1994)]. Qualitative agreement is found between those measurements and the results of the present computations. Visualization of calculated sound fields is used to illustrate the salient characteristics of ultrasonic wave‐front distortion in vivo.