T. Douglas Mast
Laura M. Hinkelman
Robert C. Waag
Dept. of Elec. Eng., Univ. of Rochester, Rochester, NY 14627
Victor W. Sparrow
Penn State Univ., University Park, PA 16802
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. [