Method and system for ultrasonic characterization of a medium

Patent metadata

Field	Value
Publication number	US-12153131-B2
Application number	US-202117472983-A
Country	US
Kind code	B2
Filing date	Sep 13, 2021
Priority date	Sep 15, 2020
Publication date	Nov 26, 2024
Grant date	Nov 26, 2024

Abstract

Method for ultrasonic characterization of a medium, including generating a series of incident ultrasonic waves, generating an experimental reflection matrix R ui (t) defined between the emission basis (i) as input and a reception basis (u) as output, and determining a focused reflection matrix RFoc(r in , r out , δt) of the medium between an input virtual transducer (TV in ) calculated based on a focusing as input to the experimental reflection matrix and an output virtual transducer (TV out ) calculated based on a focusing as output from the experimental reflection matrix, the responses of the output virtual transducer (TV out ) being obtained at a time instant that is shifted by an additional delay δt relative to a time instant of the responses of the input virtual transducer (TV in ).

First claim

The invention claimed is:

1. Method for ultrasonic characterization of a medium, in order to determine a temporal and local characterization of an ultrasonic focusing, the method comprising:
generating a series of incident ultrasonic waves (US in ) in an area of said medium, by means of an array ( 10 ) of transducers ( 11 ), said series of incident ultrasonic waves being an emission basis (i);
generating an experimental reflection matrix R ui (t) defined between the emission basis (i) as input and a reception basis (u) as output; and
determining a focused reflection matrix RFoc(r in , r out , δt) which comprises responses of the medium between an input virtual transducer (TV in ) of spatial position r in and an output virtual transducer (TV out ) of spatial position r out , the responses of the output virtual transducer (TV out ) being obtained at a time instant that is shifted by an additional delay δt relative to a time instant of the responses of the input virtual transducer (TV in ).

2. Method according to claim 1 , further comprising determining at least one propagation image between an input virtual transducer (TV in ) and a plurality of output virtual transducers (TV out ), the output virtual transducers being located at spatial positions r out around the input virtual transducer (TV in ) of spatial position r in , said at least one propagation image being determined from the focused reflection matrix RFoc(r in , r out , δt) for a predetermined additional delay δt, this propagation image including a representation of the wave propagation between these virtual transducers, and at a time instant equal to the additional delay.

3. Method according to claim 2 , wherein an ultrasonic wave propagation film is constructed by determining a plurality of propagation images for a plurality of additional temporally successive delays St obtained within an additional delay interval.

4. Method according to claim 3 , wherein the additional delay interval is an interval that is symmetrical around the zero value and of amplitude δt max .

5. Method according to claim 3 , further comprising processing a linear combination of a set of propagation films, each propagation film being obtained between an input virtual transducer (TV in ) of different spatial position r in , and selected output virtual transducers (TV out ) of spatial position r out such that r out =δr out +r in , with δr out being predefined and identical for all propagation films of the set, and the selected input virtual transducers being close to each other, in order to obtain a coherent wave propagation film corresponding to a reference input virtual transducer (TV in,ref ) and for the same additional delays δt.

6. Method according to claim 5 , wherein the linear combination is determined by calculating the singular value decomposition (SVD) of the set of propagation films in order to obtain a singular vector (V 1 ) associated with the singular value of greatest absolute value of the singular value decomposition, this singular vector (V 1 ) then being the coherent wave propagation film corresponding to said reference input virtual transducer (TV in,ref ) and for the same additional delays δt.

7. Method according to claim 6 , wherein calculation of the singular value decomposition (SVD) is carried out by constructing a concatenated focused reflection matrix (RFoc′) in which the rows of this concatenated focused reflection matrix are the selected input virtual transducers, and the columns of this concatenated focused reflection matrix are the propagation films for these selected input virtual transducers.

8. Method according to claim 1 , further comprising determining a wavefront image for an input virtual transducer (TV in ) and for an additional delay interval, said wavefront image being determined based on:
the focused reflection matrix RFoc(r in , r out , δt) and
a ballistic propagation relation of the type δt(Δr out )=−sign(Δz out )·|Δr out |fc 0 , which makes it possible to extract values from the focused reflection matrix in order to construct the wavefront image, and where:
δt is the additional delay,
c 0 is the speed of sound in the medium,
|Δr out | is the modulus of the vector between the input virtual transducer (TV in ) and the output virtual transducer (TV out ), with Δr out =r out −r in ,
Δz out is the component along a depth axis Z of the spatial position vector Δr out .

9. Method according to claim 5 , further comprising determining a wavefront image for an input virtual transducer (TV in ) or for a reference input virtual transducer (TV in,ref ) and for an additional delay interval, the wavefront image being respectively determined based on:
images from the propagation film or from the coherent wave propagation film that is calculated by singular decomposition of a set of propagation films, and
a ballistic propagation relation of the type δt(Δr out )=−sign(Δx out )·|Δr out |/c 0 which makes it possible to extract values from each of said images of the films in order to construct the wavefront image.

10. Method according to claim 1 , wherein, in determining the focused reflection matrix:
the calculation of the responses of the input virtual transducer (TV in ) corresponds to a focusing process at input based on the experimental reflection matrix R ui (t) which uses an outward time-of-flight of the waves between the emission basis and the input virtual transducer (TV in ) to create an input focal spot at spatial position r in ,
the calculation of the responses of the output virtual transducer (TV out ) corresponds to a focusing process at output based on the experimental reflection matrix R ui (t) which uses a return time-of-flight of the waves between the output virtual transducer (TV out ) and the transducers of the reception basis u, to create an output focal spot at spatial position r out , and
the additional delay δt being a time lag added to the outward and return times-of-flight during the focusing processes.

11. Method according to claim 1 , wherein the focused reflection matrix is calculated by the following formula:

RFoc
⁡

(

r
in

,

r
out

,

δ
⁢

⁢
t

)

=

1

N

i
⁢
n

⁢

N

o
⁢
u
⁢
t

⁢

∑

i

i
⁢
n

Assignees

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

Inventors

• Lambert William
• Aubry Alexandre
• Fink Mathias
• Frappart Thomas

Classifications

• G01S7/52036

  using analysis of echo signal for target characterisation · CPC title

• G01S7/52049

  using correction of medium-induced phase aberration · CPC title

• G01S15/8915 Primary

  using a transducer array · CPC title

• A61B8/52

  Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves · CPC title

• G01S15/006

  Theoretical aspects · CPC title