title: Multiple scattering of ultrasound in weakly inhomogeneous media: application to human soft tissues.
abstract: Waves scattered by a weakly inhomogeneous random medium contain a predominant single-scattering contribution as well as a multiple-scattering contribution which is usually neglected, especially for imaging purposes. A method based on random matrix theory is proposed to separate the single- and multiple-scattering contributions. The experimental setup uses an array of sources/receivers placed in front of the medium. The impulse responses between every couple of transducers are measured and form a matrix. Single-scattering contributions are shown to exhibit a deterministic coherence along the antidiagonals of the array response matrix, whatever the distribution of inhomogeneities. This property is taken advantage of to discriminate single- from multiple-scattered waves. This allows one to evaluate the absorption losses and the scattering losses separately, by comparing the multiple-scattering intensity with a radiative transfer model. Moreover, the relative contribution of multiple scattering in the backscattered wave can be estimated, which serves as a validity test for the Born approximation. Experimental results are presented with ultrasonic waves in the megahertz range, on a synthetic sample (agar-gelatine gel) as well as on breast tissues. Interestingly, the multiple-scattering contribution is found to be far from negligible in the breast around 4.3 MHz.
authors.affiliation: Institut Langevin, ESPCI ParisTech, CNRS UMR 7587, Université Denis Diderot (Paris VII), 10 rue Vauquelin, 75005 Paris, France. alexandre.aubry@espci.fr
authors.forename: Alexandre
authors.initials: A
authors.lastname: Aubry
authors.forename: Arnaud
authors.initials: A
authors.lastname: Derode
mesh_terms: D000042:Absorption; D000362:Agar; D005260:Female; D005780:Gelatin; D006801:Humans; D008954:Models, Biological; D009038:Motion; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D014159:Transducers; D014465:Ultrasonics / Q000295:instrumentation; D016217:Ultrasonography, Mammary / Q000295:instrumentation
chemical_list: D005780:Gelatin; D000362:Agar