FDTD SIMULATIONS FOR ULTRASOUND PROPAGATION IN A 2-D BREAST MODEL

To increase the survival rates of patients with breast cancer, an ultr asound imaging system must detect tumors when they are small, with a d iameter of 5 mm or less. This requires an understanding of how propaga tion of ultrasound energy is affected by the complex structure of the breast. Tn this paper, a Finite-Difference Time-Domain (FDTD) method i s developed to simulate ultrasound propagation in a two-dimensional mo del of the human breast. The FDTD simulations make it possible to bett er understand the behavior of an ultrasound signal in the breast. For example, here the simulations are used to investigate the effect of fa t lobes adjacent to the skin layer in a simple breast model. Experimen tal work performed at the University of Pennsylvania has shown that st rong refraction caused by the fat lobes results in nulls in the forwar d transmitted field. This result was duplicated with the FDTD simulati ons, and it was shown that the effect of refraction is clearly evident for energy exiting the breast. The existence of strong refraction has a significant impact on ultrasound imaging since it implies that an i maging method based on a weak scattering assumption is unlikely to wor k well. (C) 1996 Academic Press, Inc.