Method and system for ultrasonic characterization of a medium

Patent metadata

Field	Value
Publication number	US-12529682-B2
Application number	US-202118024934-A
Country	US
Kind code	B2
Filing date	Sep 14, 2021
Priority date	Sep 15, 2020
Publication date	Jan 20, 2026
Grant date	Jan 20, 2026

Abstract

Method for ultrasonic characterization of a medium, comprising a step of generating a series of incident ultrasonic waves, a step of generating an experimental reflection matrix R ui (t) defined between the emission basis (i) as input and a reception basis (u) as output, a step of 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 . A method for ultrasonic characterization of a medium in order to carry out a local spectral analysis in the medium, the method comprising:
a step of generating a series of incident ultrasonic waves in an area of said medium, by means of an array of transducers, said series of incident ultrasonic waves being an emission basis (i); and a step of generating an experimental reflection matrix R ui (t) defined between the emission basis i as input and a reception basis u as output; a step of determining a focused reflection matrix RFoc(r, δt) which comprises responses of the medium between an input virtual transducer of spatial position r in and an output virtual transducer of spatial position r out , the input and output virtual transducers being superimposed at the same spatial position r, with r in =r out =r, and the responses of the output virtual transducer 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 ), a step of determining a frequency matrix RFreq t (r, ω) which is a temporal Fourier transform of each cell of the focused reflection matrix RFoc(r, δt), this temporal Fourier transform being:
RFreq t ( r ,ω)= TF t [RFoc( r,δt )]

where
TF t is the temporal Fourier transform, and
ω is a pulse with ω=2πf, f being the frequency corresponding to said pulse.

2 . The method according to claim 1 , further comprising a filtering step during which a frequency filtering of the cells of said frequency matrix is carried out.

3 . The method according to claim 2 , wherein the filtering extracts harmonic components of a fundamental frequency of the incident ultrasonic waves.

4 . The method according to claim 1 , further comprising a step of determining an average spectrum at depth S(z, ω), determined by an average of at least part of the spectra of the frequency matrix at a predetermined depth z in the medium.

5 . The method according to claim 4 , wherein a first average spectrum is determined at a first depth of the medium, a second average spectrum is determined at a second depth of the medium, and the first average spectrum and second average spectrum are compared in order to deduce an attenuation value of the medium.

6 . The method according to claim 1 , further comprising a step of determining the spectral correlation width δω(r) for the point of spatial position r, by calculating the full width at half maximum of the autocorrelation of each spectrum of the frequency matrix RFreq r (r, ω), by the following formula:

δω
⁡
(
r
)

=

FWHM
(

1
Δω

⁢

∫

ω
-

ω
+

RFreq
t

(

r
,
ω

)

⁢

RFreq
t
*

(

r
,

ω
+

d
⁢
ω

)

⁢
d
⁢
ω

where
FWHM is the function for calculating the full width at half maximum
( )* is the complex conjugate function,
ω − and ω + are the bounding pulses, Δω is the interval between the bounding pulses.

7 . The method according to claim 6 , further comprising a step of determining at least one spectral correlation image, said at least one spectral correlation image being obtained by determining the spectral correlation widths δω(r) for a plurality of points of the medium each corresponding to a point of the medium of spatial position r.

8 . The method according claim 1 , wherein:
generating an experimental reflection matrix R ui (t) comprises:
generating a first experimental reflection matrix R 1 ui (t) based on echoes from first incident waves,
generating a second experimental reflection matrix R 1 ui (t) based on echoes from second incident waves, and
determining a focused reflection matrix RFoc(r, δt) comprises:
determining a first focused reflection matrix RFoc 1 ( r , δt) based on the first experimental reflection matrix,
determining a second focused reflection matrix RFoc 2 ( r , δt) based on the second experimental reflection matrix, and
determining the focused reflection matrix RFoc(r, δt) by combining the signals from first focused reflection matrix and signals from the second focused reflection matrix for removing therein the linear component of the medium,
determining a frequency matrix RFreq t (r, ω) comprises:
determining a first frequency matrix RFreq 1 t (r, ω) being a temporal Fourier transform of each cell of the first focused reflection matrix RFoc 1 ( r , δt),
determining a second frequency matrix RFreq 2 t (r, ω) being a temporal Fourier transform of each cell of the second focused reflection matrix RFoc 2 ( r , δt).

9 . The method according to claim 8 , further comprising:
comparing at least one value of the first frequency matrix being obtained at a spatial position r and a pulse ω to a value of the second frequency matrix being obtained at the same spatial position r and the same pulse ω, and determining a non-linearity characteristic of the medium for that spatial position and that pulse on the basis of said comparison.

10 . The method according to claim 9 , further comprising:
comparing at least one value of the first frequency matrix being obtained at a spatial position r and a pulse ω to a value of the second frequency matrix being obtained at the same spatial position r and the same pulse ω, and determining nature of the medium at the spatial position r based on said non-linearity characteristic, by comparing said non-linearity characteristic to predetermined characteristics recorded in a library.

11 . The method according to claim 1 , wherein, in the step of determining the focused reflection matrix:
the calculation of the responses of the input virtual transducer 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 to create an input focal spot at spati

Assignees

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

Inventors

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

Classifications

• G01N2291/015

  Attenuation, scattering · CPC title

• G01N29/46 Primary

  by spectral analysis, e.g. Fourier analysis {or wavelet analysis (spectral signal processing per se G06F17/14)} · CPC title

• G01N2291/106

  one or more transducer arrays · CPC title

• G10K11/346

  using phase variation · CPC title

• A61B8/08

  Clinical applications (A61B8/02, A61B8/04, A61B8/06 take precedence) · CPC title