Computational models of aberration in ultrasound breast imaging.

Abstract

Two methods are proposed for simulation of distributed aberration. One method models aberration as a superposition of five parallel time‐shift screens with 8–11 irregularly shaped strongly scattering inclusions. The second method employs an anatomically realistic three‐dimensional model of breast anatomy that includes lobular ducts, periductal and intralobular loose fibrous tissue, interlobular dense fibrous tissue, Cooper's ligaments, fat, and skin. Simulations of two‐dimensional linear ultrasound propagation in the two model media and digitized breast tissue specimens were performed using a first‐order k‐space ultrasound simulator [Tabei et al., J. Acoust. Soc. Am. 111, 53–63 (2002)]. The initial field was a planar pulse wavefront with a 7.5‐MHz center frequency and a 5‐MHz −6‐dB bandwidth. Propagation was computed over 25‐mm paths. Both of the proposed models reproduce two characteristics of aberration observed in simulations using digitized breast specimens that are not included in conventional aberration models: non‐Gaussian first‐order statistics of arrival‐time fluctuations and sharp changes in root‐mean‐square arrival‐time fluctuation as a function of propagation distance. The two models, respectively, represent a relatively simple and a detailed approach in simulating realistic challenging aberration for in‐silico testing of adaptive focusing techniques. [Research supported by an NSERC Discovery Grant.]