Simulation and analysis of three-dimensional echo decorrelation imaging

Abstract

A numerical model for pulse-echo ultrasound imaging [Mast, JASA 128:EL99-EL104, 2010] is extended to three-dimensional (3D) imaging of linear, weakly scattering continuum media by matrix array transducers. In this model, beam patterns for steered transmit and receive subapertures, calculated analytically under the Fresnel approximation, are combined with a 3D numerical tissue model to yield beamformed scan lines in a rectilinear or pyramidal configuration. Simulated scan lines are processed to yield both volumetric B-mode images and echo decorrelation images, comprising spatial maps of the normalized decorrelation between sequential pulse-echo image volumes. A method is demonstrated for construction and scan conversion of quantitative 3D echo decorrelation images such that, as for 2D echo decorrelation imaging [Hooi et al., JASA 137:585-597, 2015], the mapped echo decorrelation consistently estimates the local decoherence spectrum of the tissue reflectivity. Simulated 3D echo decorrelation images of random media are shown to accurately estimate known decoherence distributions that simulate heating effects in thermal ablation. Effects of factors including transducer frequency, scan configuration, and simulated lesion size on accuracy of decoherence estimates are tested. Applications to 3D monitoring of radiofrequency and microwave ablation are discussed.