Method and system for non-invasively characterizing a heterogeneous medium using ultrasound

Patent metadata

Field	Value
Publication number	US-12257103-B2
Application number	US-202017631929-A
Country	US
Kind code	B2
Filing date	Jul 31, 2020
Priority date	Aug 2, 2019
Publication date	Mar 25, 2025
Grant date	Mar 25, 2025

Abstract

Method for non-invasively characterizing a heterogeneous medium using ultrasound, comprising a step of generating a series of incident ultrasonic waves, a step of recording an experimental reflection matrix R ui (t) defined between the input emission basis (i) and an output reception basis (u), a step of determining a response REP(r,Δr) of the medium between an input virtual transducer (TV in ) calculated based on an input focusing of the experimental reflection matrix that creates an input focal spot around a first point (P 1 ), and an output virtual transducer (TV out ) calculated based on an output focusing of the experimental reflection matrix that creates an output focal spot around a second point (P 2 ), said response being expressed as a function of a central point (PC) of spatial position (r) in the medium located midway between the first and second points (P 1 , P 2 ).

First claim

The invention claimed is:

1. Method for non-invasive ultrasound characterization of a heterogeneous medium, the method comprising:
generating a series of incident ultrasonic waves in a region of the heterogeneous medium, generated by a transducer array, said series of incident ultrasonic waves constituting an input emission basis (i);
recording an experimental reflection matrix R ui (t) defined between the input emission basis (i) and an output reception basis (u);
determining a response REP(r,Δr) of the medium between an input virtual transducer (TV in ) of spatial position r in calculated based on an input focusing of the experimental reflection matrix corresponding to an input focal spot around a first point (P 1 ) and an output virtual transducer (TV out ) of spatial position r out calculated based on an output focusing of the experimental reflection matrix corresponding to an output focal spot around a second point (P 2 ),
said response REP(r,Δr) being expressed as a function of a central point (PC) of spatial position r in the medium and as a function of a distance coordinate Δr from said central point,
said central point (PC) being located midway between the first and second points (P 1 , P 2 ) such that r=(r out +r in )/2 and such that Δr=(r out −r in )/2, and
said central point being the origin of a measurement axis (AXm) passing through said first and second points (P 1 , P 2 ), said measurement axis (AXm) forming an angle β relative to a first axis (X) of the medium, and
the first point (P 1 ) being at the distance coordinate +Δr on the measurement axis (AXm), and the second point (P 2 ) being at an opposite distance coordinate −Δr on the measurement axis (AXm).

2. Method according to claim 1 , wherein, in determining the response REP(r,Δr), the input focusing of the experimental reflection matrix uses an outward time-of-flight of the waves between the input emission basis and the input virtual transducer, and the output focusing uses a return time-of-flight of the waves between the output virtual transducer and the output reception basis.

3. Method according to claim 1 , wherein the response REP(r,Δr) of the medium is calculated by the following formula:

REP
⁡
(

r
,

Δ
⁢
r

)

=

1

N

i
⁢
n

⁢

N

o
⁢
u
⁢
t

⁢

∑

i

i
⁢
n

∑

u

o
⁢
u
⁢
t

R

u
⁢
i

(

u
out

,

i
in

,

τ
⁡
(

r
in

,

r
out

,

u
out

,

i

i
⁢
n

)

)

in which
N in is the number of elements of the input emission basis,
N out is the number of elements of the output reception basis,
R ui (t) is the experimental reflection matrix, in which R ui (u out , i in , τ(r in , r out , u out , i in )) is the element of the experimental reflection matrix R ui (t) recorded by transducer u out consecutive to emission i in at time τ,
τ is a time which is the sum of the outward time-of-flight τ in of the ultrasonic wave between the input emission basis (i) and the first point (P 1 ) and the return time-of-flight Tout of the ultrasonic wave between the second point (P 2 ) and the output reception basis (u), as explained by the following formula:
τ( r in ,r out ,u out ,i in )=τ in ( r in ,i in )+τ out ( r out ,u out ).

4. Method according to claim 1 , further comprising:
determining a response profile PR(δr) which is a plurality of responses REP(r,Δr) calculated for a plurality of values of the distance coordinate Δr and for the central point (PC), and for the measurement axis (AX m ), corresponding to the angle β, δr being the distance of the second point from the central point, wherein the value of said distance being such that Δr=u β ·u β , u β being a unit vector in the direction of the measurement axis AX m defined by the angle β.

5. Method according to claim 4 , further comprising:
determining the resolution w(r) of the central point (PC) based on a modulus of the response profile PR(δr), in which the resolution w(r) is a width of a peak of said modulus of the response profile PR(δr), centered around a distance being null (δr=0).

6. Method according to claim 5 , wherein the width of the peak is estimated at a height which is a portion of a maximum height of said peak, said portion being half the maximum height of the peak.

7. Method according to claim 5 , further comprising:
determining a focusing criterion F(r) of the central point (PC) based on a resolution w(r) and a theoretical resolution w 0 (r), said theoretical resolution w 0 (r) being determined based on the input emission basis (i) and the output reception basis (u).

8. Method according to claim 7 , further comprising:
calculating the focusing criterion

Assignees

• Supersonic Imagine
• Centre National De La Rech Scientifique—Cnrs
• Ecole Superieure Physique & Chimie Ind Ville De Paris
• Centre Nat Rech Scient

Inventors

• Lambert William
• Aubry Alexandre
• Fink Mathias
• Cobus Laura

Classifications

• G01S15/88

  Sonar systems specially adapted for specific applications (seismic or acoustic prospecting or detecting G01V1/00) · CPC title

• A61B8/5207

  involving processing of raw data to produce diagnostic data, e.g. for generating an image · CPC title

• A61B8/4488 Primary

  the transducer being a phased array · CPC title

• G01N2291/106

  one or more transducer arrays · CPC title

• G01N2291/02491

  Materials with nonlinear acoustic properties · CPC title