A Path-Based Model for Aberration Correction in Ultrasound Imaging

Abstract

Pulse-Echo Ultrasound Imaging suffers from several sources of image degradation. In clinical conditions, superficial layers made of different tissues (e.g. skin, fat or muscles) create aberrations that can severely deteriorate image quality. To correct such aberrations, the majority of existing methods use either phase screens or speed of sound maps. However, a technique that is both accurate in real-world scenarios and compatible with near-real time imaging is lacking. Indeed phase screens are too simplistic to be physically accurate and speed of sound maps are computationally costly to estimate. We propose a new model of aberrations driven by the paths followed by ultrasound waves in the aberrating layer. With this new representation, we formulate an optimization problem in which a coherence factor is maximized with respect to a grid of aberrating paths. This problem is solved via a gradient ascent algorithm with variable splitting, in which all necessary gradients are expressed analytically. Using simulations of aberrating layers, we show that the proposed method can correct strong aberrations (i.e. of several periods) and outperforms a state-of-the-art technique based on speed of sound maps. Using in vivo experiments, we demonstrate that the proposed method is able to correct real aberrations in a few seconds which represents a major step forward towards a broader use of aberration correction methods.