WO2007021194A1 - Estimation de parametres de diffuseurs acoustiques dans un objet - Google Patents

Estimation de parametres de diffuseurs acoustiques dans un objet Download PDF

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Publication number
WO2007021194A1
WO2007021194A1 PCT/NO2005/000295 NO2005000295W WO2007021194A1 WO 2007021194 A1 WO2007021194 A1 WO 2007021194A1 NO 2005000295 W NO2005000295 W NO 2005000295W WO 2007021194 A1 WO2007021194 A1 WO 2007021194A1
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WO
WIPO (PCT)
Prior art keywords
region
observation
acoustic
scatterers
array
Prior art date
Application number
PCT/NO2005/000295
Other languages
English (en)
Inventor
Bjørn A.J. ANGELSEN
Tonni F. Johansen
Original Assignee
Angelsen Bjoern A J
Johansen Tonni F
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Angelsen Bjoern A J, Johansen Tonni F filed Critical Angelsen Bjoern A J
Priority to PCT/NO2005/000295 priority Critical patent/WO2007021194A1/fr
Publication of WO2007021194A1 publication Critical patent/WO2007021194A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
    • G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
    • G01S15/8909—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using a static transducer configuration
    • G01S15/8915—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using a static transducer configuration using a transducer array
    • G01S15/8927—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using a static transducer configuration using a transducer array using simultaneously or sequentially two or more subarrays or subapertures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
    • G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
    • G01S15/8909—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using a static transducer configuration
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
    • G01S7/5205—Means for monitoring or calibrating

Definitions

  • the invention presents methods and instrumentation for estimation of frequency dependent acoustic scatterer parameters in an object with elimination of the influence of the accumulative absorption in the object on these scatterers.
  • the present invention relates to characterization of acoustic scatterers in an object.
  • the methods and instrumentation have applications to wide range of acoustic imaging situations, like geologic imaging of structures around oil wells, and SONAR imaging of fish and the sea bed, with particular reference to ultrasound imaging of scatterers in biological tissue.
  • the method eliminates the effect of unknown acoustic absorption between the transducer and the scatterers, and produces local scattering parameters in the object and their frequency dependence.
  • Acoustic back scatter imaging is a widely used imaging modality for diagnosis of many diseases of humans and animals, nondestructive testing of materials, acoustic imaging of geologic structures, and SONAR imaging offish and other objects and the sea bed.
  • the method is used mainly to visualize object structures, object velocities, movements, and shear elasticity of the object, and there is a further need for improved characterization of the scattering oobject structures with dimensions below the resolution in the structural image.
  • K is an amplitude parameter
  • f is the acoustic frequency
  • e ⁇ 2a(s)f represents acoustic absorption
  • a(s) is the integral of the absorption coefficient for the whole propagation distance s of the signal along transmit and the receive beams.
  • ⁇ is the relative deviation in the bulk compressibility and ⁇ is the relative deviation in the mass density between the scatterer and the surrounding medium
  • V s is the scatterer volume
  • the scatterer dimensions approaches or becomes larger than ⁇ (for example as ⁇ is reduced with higher frequencies)
  • ⁇ t and ⁇ tr one can get destructive interference that reduces the scattered power in certain directions, or constructive interference that increases the scattered power in other directions.
  • the invention provides methods on how one can use this angular variation to characterize the scatterers.
  • IVUS intravascular imaging
  • carotid plaque we have typically z ⁇ 2.5 cm
  • liver disorders we have typically z ⁇ 7cm.
  • the influence of absorption on the frequency variation of the scattered intensity can be neglected when the scatterer dimension approaches or gets larger than the wavelength, which is 50 - 80 ⁇ m for these frequencies.
  • the frequency variation of the scattered intensity can contain some information for scatterers with dimensions approaching ⁇ 50 ⁇ m.
  • the image depth is inversely proportional to the frequency.
  • the acoustic absorption will then play an important role in the frequency dependency of the back scattered intensity.
  • the wave length at 100 MHz is ⁇ 15 ⁇ m, and by reducing the effect of absorption on the frequency variation of the scattered intensity, one is able to extract information on scatterers down to ⁇ 2 ⁇ m dimension.
  • the present invention provides methods for characterizing the scatterers in acoustic imaging that strongly reduces the effect of absorption attenuation of the waves in the characterization, and makes it possible to eliminate the effect of frequency dependent absorption in the transmit path of the acoustic pulse, and obtain frequency dependent scattering parameters from local regions in the tissue. It is furthermore possible to obtain information of scattering anisotropy in such regions, that can provide information about fiber direction in fibrous and muscular tissue, as well as degree of fibroses. Moreover, by comparing acoustic angular scattering with back scattering, one is able to derive anisotropic properties of the scattering cross section from a local region, that can give information about fibrous structures in the tissue.
  • the method provides new acoustic parameters for characterization and contrast enhancement of tissue structures in acoustic imaging, like tumor structures, ischemia of a myocardial wall, and plaque composition in vascular atheroma. It can be used with many arrangements of acoustic transducers, particularly switched linear or curvilinear arrays.
  • the essence of the invention is to use scattered signals either from multiple regions where one region is used as a reference, or multiple scattering directions, creating own reference signals from the same scattering region, so that the absorption attenuation of the acoustic wave is eliminated from the estimated parameters, and directional scattering information can be acheived.
  • Figure 1 shows an example embodiment according to the invention of two transducers arranged so that the scattering parameters of the tissue in the overlap region of the transducers beams can be investigated.
  • Figure 2 shows example embodiments according to the invention where a switched linear array is used to realize two transducer apertures, which are arranged so that the scattering parameters of the tissue in the overlap region of the apertures beams can be investigated.
  • Figure 3 illustrates how the scattering from a vessel atheroma with scatterers comparable to or larger than the wavelength can be investigated using a linear array.
  • Figure 4 shows imaging of anisotropic structures of a vascular plaque combined with two dimensional backscatter imaging.
  • FIG. 1 shows two acoustic transducers 101 and 102 that are connected to an acoustic instrument 100 that allows selectable transmission of acoustic pulses on each transducer, with selectable reception of the scattered signal on each transducer, independent of the transducer selected for transmission.
  • the transducers can be directed at an angle towards each other, where ⁇ t represents the direction of the transmit beam and ⁇ tr is the angle between the transmit beam and the receive beam.
  • Beam 1 Beam 1
  • Beam 2 Beam 2
  • the beams intercept in a region labeled 105 in Figure 1.
  • the angle between Beam 1 and Beam 2 is indicated as ⁇ 12 in Figure 1.
  • a first method for reduction of the effect of frequency absorption according to the invention is to combine the scattered signal from an observation region with the scattered signal from reference scatterers with known frequency variation of the scattering cross section, and located in a neighboring reference region with close to the same absorption attenuation of the signals as for the scatterers to be characterized in the observation region.
  • This is obtained by using the same transmit and receive beams for the reference and the observation regions, where the reference region is so close to the observation region that the signals from the two regions have practically the same absorption attenuation.
  • Such a situation can for example be obtained with backscatter imaging with the same beams, where the reference and observation regions have neighboring depths. Similar situations can also be obtained with angular scattering by adjusting the beam directions.
  • Example reference scatterers can be the erythrocytes in blood, where for characterization of arterial wall plaque one would use the signal scattered from the blood close to the plaque as reference. For other situations (like the liver) one would find the blood vessels close to the area of interest as reference, or use other reference scatterers in the neighborhood of the region of interest. In such situations one can do back scatter imaging and use the same beam directions for the transmit and the receive beams. This will create a reference signal for back scatter imaging obtained from Eq.(l) as
  • H ref ( ⁇ - ⁇ ) 2 for the parameters of the reference scatterers with back scattered imaging
  • H ref represents the frequency variation of the back scatterers for the reference scatterers.
  • H re f 1.
  • the backscattered signal from blood is often masked in close to stationary reverberation noise.
  • the scatterers also move and the backscattered signal from blood can be retrieved from the stationary noise by collecting back scattered signal from several pulses in substantially the same beam direction and perform high pass filtering of the signal along the pulse number coordinate.
  • a small variation of the beam direction between the pulses can be accepted, as for example with continuous, mechanical scanning of the beam direction.
  • Ultrasound contrast agent micro bubbles can also conveniently be used as reference scatterers, both in visible blood vessels, and within the capillary vessels.
  • the reference signal from the contrast agent bubbles can be separated from the signal from surrounding tissue by several known methods, such as harmonic imaging, pulse inversion imaging, and manipulation of the scattering properties by a low frequency pulse.
  • Other reference scatterers can be identifiable cells, like normal liver cells, or fat cells in atheroma.
  • the back scattered intensity from the scatterers in the observation region to be characterized can be approximated as S sca , ⁇
  • a second method according to the invention is to use angular scattering with two beams as illustrated in FIG. 1- 4. First transmitting on Transducer 1 101 and receiving the back scattered signal at a depth range along the beam corresponding to the cross over region 105 between the two beams, one receives a back scattered signal power on Transducer 1 and Transducer 2 102 as
  • a 1 contains the one-way power attenuation along Beam 1 103 from Transducer 1 101 to the scattering region 105
  • a 2 contains the one-way power attenuation along the Beam 2 104 from Transducer 2 102 to the scattering region 105. Transmitting at Transducer 2 102 one gets scattered signal power from the overlap region 105 as
  • (11) is independent of the cumulative power absorption along Beam 1 103 and Beam 2 104.
  • the frequency variation of the ratios ⁇ a contains information on the scatterer size, and ⁇ a will also contain information on the degree of anisotropy of the scatterers in the overlap region 103.
  • the shape of the scatterers influences the scattering cross section so that the H's in Eq.(l 1) are different from unity. This influences the frequency variation of ⁇ a , and ⁇ a becomes dependent on the direction of the incident and the receive beams.
  • ⁇ a For unidirectional fibrous scatterers, like collagene or muscle fibers, one can get large ⁇ a when the angle of Beam 1 to the fiber direction is similar to the angle of Beam 2 to the fiber direction. The value of ⁇ a then also increases above 0.3.
  • the instrument is designed for free selection of the transmit apertures, where the Figure by way of example illustrates two transmit/receive apertures, Aperture 1 as 201 and Aperture 2 as 202, where one by time delay of the element signals steers the direction of the Beam 1 203 from Aperture 1 and the direction of Beam 2 204 from Aperture 2, so that we get an overlap region 205 between the beams.
  • Aperture 1 As 201 and Aperture 2 as 202, where one by time delay of the element signals steers the direction of the Beam 1 203 from Aperture 1 and the direction of Beam 2 204 from Aperture 2, so that we get an overlap region 205 between the beams.
  • ⁇ a as defined in Eq.(ll).
  • the linear array allows common lateral scanning of Beam 1 and Beam 2 that enables spatial imaging of ⁇ a , as illustrated in FIG.
  • curving the array into a curvilinear array would also allow the same type of operation. Maintaining the distance between Aperture 1 and Aperture 2 and scanning the beams laterally with a fixed direction angle of the beams, one obtains a spatial image of ⁇ a at a fixed beam overlap depth. This overlap depth can be varied by varying the distance between Aperture 1 and Aperture 2, with constant direction angles of the beams. The angles between the beams can also be varied for more details of the anisotropic scattering.
  • the two-dimensional back scatter image will indicate the location of the plaque, and one can hence use the back scatter image to limit the spatial region that is actual for interrogation or observation of anisotropic scattering structures by the methods presented above, hence reducing the time of interrogation and the possibility of using multiple directions of the transmit beam with adequate frame rate of the anisotropic scattering imaging.
  • FIG. 4 illustrates a method for at least semi-automatic observation of anisotropic scattering structures of unknown direction in relation to the transducer array.
  • the Figure shows a linear array 404, and an anisotropic scattering structure 410.
  • a pulsed beam 403 is emitted from the aperture 401 of the array, and the scattered wave is picked up by an array element or group of array elements 402, for several positions along the array.
  • the received signal power as a function of receive element position is monitored at a time interval after the pulse transmission that selects a particular depth along the transmitted beam.
  • An anisotropic scattering structure like 410 will back-scatter the main energy in a particular direction ⁇ tr indicated by the scattering diagram 411.
  • the angle ⁇ tr between the transmit and the receive beam directions is determined by specular scattering.
  • the middle direction between the incident beam direction and the peak scattered energy is then normal to the anisotropy direction of the scatterers.
  • This scattering diagram produces a variation of the power in the received signal along the element position, indicated as 412 in FIG. 4, where the spread of this variation is determined by the correlation length of the scatterers in the anisotropy direction.
  • a peaked variation of the scattering power along the element position like at 413 indicates an anisotropic scattering structure at the particular depth, the anisotropy direction of the scattering structures, and also scatterer dimensions in the anisotropy direction.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Acoustics & Sound (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)

Abstract

L'invention concerne des procédés et des instruments d'estimation de paramètres de diffuseurs acoustiques dépendants de la fréquence dans un objet avec élimination de l'influence de l'absorption cumulative sur ces diffuseurs dans l'objet.
PCT/NO2005/000295 2005-08-17 2005-08-17 Estimation de parametres de diffuseurs acoustiques dans un objet WO2007021194A1 (fr)

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Application Number Priority Date Filing Date Title
PCT/NO2005/000295 WO2007021194A1 (fr) 2005-08-17 2005-08-17 Estimation de parametres de diffuseurs acoustiques dans un objet

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Application Number Priority Date Filing Date Title
PCT/NO2005/000295 WO2007021194A1 (fr) 2005-08-17 2005-08-17 Estimation de parametres de diffuseurs acoustiques dans un objet

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009056857A1 (fr) * 2007-10-31 2009-05-07 Imperial Innovations Limited Correction d'atténuation lors de l'imagerie d'un agent de contraste par ultrasons
CN113359137A (zh) * 2021-05-06 2021-09-07 上海交通大学 基于周期结构声散射共振特征的水中目标声标识方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0343969A2 (fr) * 1988-05-26 1989-11-29 Fujitsu Limited Dispositif diagnostique à ultrason
EP0349321A1 (fr) * 1988-06-30 1990-01-03 Hewlett-Packard Company Méthode et dispositif pour déterminer quantitativement la valeur absolue de rayonnement rétrodiffusé
EP0383288A1 (fr) * 1989-02-16 1990-08-22 Fujitsu Limited Appareil diagnostique à ultrasons pour caractériser un tissu par analyse de rayonnement rétrodiffusé

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0343969A2 (fr) * 1988-05-26 1989-11-29 Fujitsu Limited Dispositif diagnostique à ultrason
EP0349321A1 (fr) * 1988-06-30 1990-01-03 Hewlett-Packard Company Méthode et dispositif pour déterminer quantitativement la valeur absolue de rayonnement rétrodiffusé
EP0383288A1 (fr) * 1989-02-16 1990-08-22 Fujitsu Limited Appareil diagnostique à ultrasons pour caractériser un tissu par analyse de rayonnement rétrodiffusé

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Title
J. M. EVANS , R. SKIDMORE , N. P. LUCKMAN AND P. N. T. WELLS: "A new approach to the noninvasive measurement of cardiac output using an annular array doppler technique?I. Theoretical considerations and ultrasonic fields", ULTRASOUND IN MEDICINE & BIOLOGY, vol. 15, no. 3, 1989, Elsevier USA, pages 169 - 178, XP002371886 *
LU Z F ET AL: "A METHOD FOR ESTIMATING AN OVERLYING LAYER CORRECTION IN QUANTITATIVE ULTRASOUND IMAGING", ULTRASONIC IMAGING, DYNAMEDIA INC., SILVER SPRING, MD, US, vol. 17, no. 4, 1 October 1995 (1995-10-01), pages 269 - 290, XP000589900, ISSN: 0161-7346 *
MARUVADA S ET AL: "High-frequency backscatter and attenuation measurements of selected bovine tissues between 10 and 30 MHz", ULTRASOUND IN MEDICINE AND BIOLOGY, NEW YORK, NY, US, vol. 26, no. 6, July 2000 (2000-07-01), pages 1043 - 1049, XP004295638, ISSN: 0301-5629 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009056857A1 (fr) * 2007-10-31 2009-05-07 Imperial Innovations Limited Correction d'atténuation lors de l'imagerie d'un agent de contraste par ultrasons
CN113359137A (zh) * 2021-05-06 2021-09-07 上海交通大学 基于周期结构声散射共振特征的水中目标声标识方法
CN113359137B (zh) * 2021-05-06 2022-03-08 上海交通大学 基于周期结构声散射共振特征的水中目标声标识方法

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