Space-time-frequency analysis of the scattered acoustic wave field from elastic shells recorded by bistatic sonar systems.

2009 ◽  
Vol 126 (4) ◽  
pp. 2207
Author(s):  
Karim G. Sabra ◽  
Shaun D. Anderson
Keyword(s):  
Acoustic Wave ◽  
Wave Field ◽  
Frequency Analysis ◽  
Space Time ◽  
Elastic Shells ◽  
Time Frequency Analysis ◽  
Time Frequency ◽  
Sonar Systems

scholarly journals Ultrasound shear wave elastography: numerical modeling and time-frequency analysis with an application in HIFU thermal lesion detection

2021 ◽  
Author(s):  
Pooya Sobhe Bidari
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Shear Wave ◽  
Frequency Analysis ◽  
Acoustic Wave Propagation ◽  
Thermal Lesion ◽  
Time Frequency Analysis ◽  
Time Frequency ◽  
Thermal Lesions ◽  
Viscoelastic Parameters

In this work, a new numerical framework is proposed and implemented to simulate acoustic wave propagation in 3D viscoelastic heterogeneous media. The framework is based on the elastodynamic wave equation in which a 3D second-order time-domain perfectly matched layer (PML) formulation is developed to model unbounded media. The numerical framework is discretized by a finite difference formulation and its stability analysis is discussed. The proposed numerical method is capable of simulating 3D shear and longitudinal acoustic waves for arbitrary source geometries and excitations, together with arbitrary initial and boundary conditions. After validation of the framework, it was used to simulate the propagation of ultrasound shear wave in high intensity focused ultrasound (HIFU) induced thermal lesions located within soft tissue. The parameters in these simulations were obtained from standard double-indentation measurements of the viscoelastic parameters of normal and thermally coagulated chicken breast tissue samples. A HIFU system was used to induce thermal lesions in tissue. In this study, a new elastography procedure was also introduced to differentiate between the normal and HIFU induced thermal lesions. This method is based on time-frequency analysis of shear wave propagation within the tissue. In the proposed method, the Wigner-Ville distribution has been used as a time-frequency analytical technique to detect the location of shear wave propagating within the tissue, and to estimate the shear speed of the wave as well as its center frequency and attenuation coefficient. This method was applied to the acoustic wave propagation simulation results of the HIFU thermal lesion. It was finally used to estimate the local viscoelastic parameters of the medium. It was demonstrated that the proposed method is capable of differentiating the thermal lesions from the normal tissue based on their viscoelastic parameters.

Space-time visualization of vibration of a ribbed cylinder

2000 ◽  
Vol 214 (10) ◽  
pp. 1259-1271 ◽  
Author(s):  
J Woodhouse ◽  
J Power
Keyword(s):  
Frequency Analysis ◽  
Cross Sections ◽  
Vibration Analysis ◽  
Experimental Approach ◽  
Space Time ◽  
Theoretical Modelling ◽  
Time Frequency Analysis ◽  
Time Frequency ◽  
Vibrational Response ◽  
Engineering Vibration

Data from an axial array of sensors along a ribbed cylindrical structure may be analysed to allow the evolving vibrational response to impulsive driving to be plotted as a function of space and time. The process is carried out separately in a series of frequency bands, by first carrying out a time-frequency analysis at each position. Aspects of the behaviour not previously discussed are highlighted by this analysis. These aspects are discussed in the light of a previously published theoretical model [1]. Since reflections from the cylinder's ends also play a role here, it has been necessary to develop further theoretical modelling to interpret the measurements. The new experimental approach, which is described here as the method of ‘space-time cross-sections', has scope for application to other problems involving structure-borne vibration. This illustrates the power of time-frequency analysis and its extensions for engineering vibration analysis.

scholarly journals Ultrasound shear wave elastography: numerical modeling and time-frequency analysis with an application in HIFU thermal lesion detection

2021 ◽  
Author(s):  
Pooya Sobhe Bidari
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Shear Wave ◽  
Frequency Analysis ◽  
Acoustic Wave Propagation ◽  
Thermal Lesion ◽  
Time Frequency Analysis ◽  
Time Frequency ◽  
Thermal Lesions ◽  
Viscoelastic Parameters

In this work, a new numerical framework is proposed and implemented to simulate acoustic wave propagation in 3D viscoelastic heterogeneous media. The framework is based on the elastodynamic wave equation in which a 3D second-order time-domain perfectly matched layer (PML) formulation is developed to model unbounded media. The numerical framework is discretized by a finite difference formulation and its stability analysis is discussed. The proposed numerical method is capable of simulating 3D shear and longitudinal acoustic waves for arbitrary source geometries and excitations, together with arbitrary initial and boundary conditions. After validation of the framework, it was used to simulate the propagation of ultrasound shear wave in high intensity focused ultrasound (HIFU) induced thermal lesions located within soft tissue. The parameters in these simulations were obtained from standard double-indentation measurements of the viscoelastic parameters of normal and thermally coagulated chicken breast tissue samples. A HIFU system was used to induce thermal lesions in tissue. In this study, a new elastography procedure was also introduced to differentiate between the normal and HIFU induced thermal lesions. This method is based on time-frequency analysis of shear wave propagation within the tissue. In the proposed method, the Wigner-Ville distribution has been used as a time-frequency analytical technique to detect the location of shear wave propagating within the tissue, and to estimate the shear speed of the wave as well as its center frequency and attenuation coefficient. This method was applied to the acoustic wave propagation simulation results of the HIFU thermal lesion. It was finally used to estimate the local viscoelastic parameters of the medium. It was demonstrated that the proposed method is capable of differentiating the thermal lesions from the normal tissue based on their viscoelastic parameters.

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