Reflection matrix approach for quantitative imaging of scattering media

TL;DR

This paper introduces a matrix-based wave imaging method that uses virtual transducers to map and analyze scattering media, providing new quantitative imaging capabilities applicable across wave physics.

Contribution

The paper presents a novel reflection matrix approach that enables detailed spatial mapping and characterization of wave propagation and scattering in media, including in vivo human imaging.

Findings

Effective local focusing criterion for image quality assessment

High-resolution spatial mapping of multiple scattering

Successful demonstration in phantom and in vivo human abdomen

Abstract

We present a physically intuitive matrix approach for wave imaging and characterization in scattering media. The experimental proof-of-concept is performed with ultrasonic waves, but this approach can be applied to any field of wave physics for which multi-element technology is available. The concept is that focused beamforming enables the synthesis, in transmit and receive, of an array of virtual transducers which map the entire medium to be imaged. The inter-element responses of this virtual array form a focused reflection matrix from which spatial maps of various characteristics of the propagating wave can be retrieved. Here we demonstrate: (i) a local focusing criterion that enables the image quality and the wave velocity to be evaluated everywhere inside the medium, including in random speckle, and (ii) an highly resolved spatial mapping of the prevalence of multiple scattering, which constitutes a new and unique contrast for ultrasonic imaging. The approach is demonstrated for a controllable phantom system, and for in vivo imaging of the human abdomen. More generally, this matrix approach opens an original and powerful route for quantitative imaging in wave physics.