Distortion matrix approach for ultrasound imaging of random scattering media

TL;DR

This paper introduces a novel full-field wave imaging method using a distortion matrix to achieve diffraction-limited resolution in inhomogeneous media, outperforming traditional adaptive focusing especially in random scattering environments.

Contribution

The paper presents a new distortion matrix approach for wave imaging that effectively compensates for aberrations in complex media, applicable across various wave-based imaging modalities.

Findings

Successful experimental validation on tissue-mimicking phantom

Effective in vivo imaging of human soft tissues

Outperforms traditional adaptive focusing in random scattering media

Abstract

Focusing waves inside inhomogeneous media is a fundamental problem for imaging. Spatial variations of wave velocity can strongly distort propagating wavefronts and degrade image quality. Adaptive focusing can compensate for such aberration, but is only effective over a restricted field of view. Here, we introduce a full-field approach to wave imaging based on the concept of the distortion matrix. This operator essentially connects any focal point inside the medium with the distortion that a wavefront, emitted from that point, experiences due to heterogeneities. A time-reversal analysis of the distortion matrix enables the estimation of the transmission matrix that links each sensor and image voxel. Phase aberrations can then be unscrambled for any point, providing a full-field image of the medium with diffraction-limited resolution. Importantly, this process is particularly efficient in random scattering media, where traditional approaches such as adaptive focusing fail. Here, we first present an experimental proof-of-concept on a tissue mimicking phantom, and then apply the method to in vivo imaging of human soft tissues. While introduced here in the context of acoustics, this approach can also be extended to optical microscopy, radar or seismic imaging.