A finite element model to study the effect of tissue anisotropy on<i>ex vivo</i>arterial shear wave elastography measurements

Shcherbakova, Darya; Debusschere, Nic; Caenen, Annette; Iannaccone, Francesco; Pernot, Mathieu; Swillens, Abigaïl; Segers, Patrick

doi:10.1088/1361-6560/aa7125

Cited by 8 publications

(6 citation statements)

References 55 publications

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“…The shear wave velocity is directly related to the elastic properties of the tissue, such as, the shear and Young's modulus. Although clinical SWE is commonly applied to soft tissues with isotropic elastic properties, such as the liver or the breast, the feasibility of SWE to non-invasively characterize tissue anisotropy was also shown in vivo in skeletal muscles (Gennisson et al 2010), arteries (Shcherbakova et al 2017) and in the myocardium (Couade et al 2011, Lee et al 2012. SWE can indeed quantify the shear wave velocities parallel (i.e.…”

Section: Introductionmentioning

confidence: 99%

3D elastic tensor imaging in weakly transversely isotropic soft tissues

et al. 2018

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We present herein 3D elastic tensor imaging (3D ETI), an ultrasound-based volumetric imaging technique to provide quantitative volumetric mapping of tissue elastic properties in weakly elastic anistropic media. The technique relies on (1) 4D ultrafast shear wave elastography (SWE) at very high volume rate (e.g. > 8000 Hz, depending only on the imaging depth), (2) a volumetric estimation of shear wave velocity using the eikonal equation and (3) a generalized 3D elastic tensor-based approach. 3D ETI was first evaluated using numerical simulations in homogeneous isotropic and transverse isotropic media. Results showed that 3D ETI can accurately assess tissue stiffness and tissue anisotropy in weakly transversely isotropic media (elastic fractional anisotropy coefficient < 0.34). Experimental feasibility was shown in vitro in a transverse isotropic phantom. Quantification of the elastic properties by 3D ETI was in good agreement with 2D SWE results performed at different orientations using a clinical ultrafast ultrasound scanner. 3D ETI has the potential to provide a volumetric quantitative map of tissue elastic properties in weakly transversely isotropic soft tissues within less than 20 ms of acquisition for the entire imaged volume.

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Section: Introductionmentioning

confidence: 99%

3D elastic tensor imaging in weakly transversely isotropic soft tissues

et al. 2018

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“…When they are under compression (I 4s < 1 or I 4f < 1), their contribution is zero, as myocytes nor collagen fibers support compression. The material constants for the deviatoric part of the strain energy function were derived from healthy porcine myocardium as reported in Gao et al (2015), whereas the density ρ and parameter D were derived from our previous work (Shcherbakova et al 2017, Caenen et al 2017b. Parameter D is chosen to ensure (quasi)-incompressibility of the tissue.…”

Section: Materials Modelmentioning

confidence: 99%

“…It was originally proposed and validated by Palmeri et al (2005) for bulky isotropic elastic media. This approach has later been adapted and further validated for other geometries and material models, such as an isotropic low-viscous ventricle (Caenen et al 2017b) and an arterial slab (Shcherbakova et al 2017). To the best of our knowledge, our study is the first to study SWE in a FEM model that makes use of the orthotropic HO material law (Holzapfel and Ogden 2009) in combination with mechanical loading.…”

Section: Combining An Orthotropic Materials Law With Swe-modelingmentioning

confidence: 99%

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Anin silicoframework to analyze the anisotropic shear wave mechanics in cardiac shear wave elastography

et al. 2018

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Shear wave elastography (SWE) is a potential tool to non-invasively assess cardiac muscle stiffness. This study focused on the effect of the orthotropic material properties and mechanical loading on the performance of cardiac SWE, as it is known that these factors contribute to complex 3D anisotropic shear wave propagation. To investigate the specific impact of these complexities, we constructed a finite element model with an orthotropic material law subjected to different uniaxial stretches to simulate SWE in the stressed cardiac wall. Group and phase speed were analyzed in function of tissue thickness and virtual probe rotation angle. Tissue stretching increased the group and phase speed of the simulated shear wave, especially in the direction of the muscle fiber. As the model provided access to the true fiber orientation and material properties, we assessed the accuracy of two fiber orientation extraction methods based on SWE. We found a higher accuracy (but lower robustness) when extracting fiber orientations based on the location of maximal shear wave speed instead of the angle of the major axis of the ellipsoidal group speed surface. Both methods had a comparable performance for the center region of the cardiac wall, and performed less well towards the edges. Lastly, we also assessed the (theoretical) impact of pathology on shear wave physics and characterization in the model. It was found that SWE was able to detect changes in fiber orientation and material characteristics, potentially associated with cardiac pathologies such as myocardial fibrosis. Furthermore, the model showed clearly altered shear wave patterns for the fibrotic myocardium compared to the healthy myocardium, which forms an initial but promising outcome of this modeling study.

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“…However, application of dynamic elastography to tissues with aligned fibrous structure resulting in local transverse isotropic mechanical properties, such as can be found in striated skeletal and cardiac muscle as well as brain white matter, may benefit from analysis that takes into consideration anisotropy of the tissue. Recognizing this, many groups have pioneered research in this direction over the past few decades, using US-based elastography, 9,[12][13][14][15][16][17][18][19] as well as magnetic resonance (MR) based elastography. [20][21][22][23][24][25][26][27][28][29][30][31][32] Many of these studies have tried to tackle the associated inversion problem.…”

Section: A Background and Motivationmentioning

confidence: 99%

Analytical solution for converging elliptic shear wave in a bounded transverse isotropic viscoelastic material with nonhomogeneous outer boundary

Guidetti

Royston

2018

The Journal of the Acoustical Society of America

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Dynamic elastography methods—based on optical, ultrasonic, or magnetic resonance imaging—are being developed for quantitatively mapping the shear viscoelastic properties of biological tissues, which are often altered by disease and injury. These diagnostic imaging methods involve analysis of shear wave motion in order to estimate or reconstruct the tissue's shear viscoelastic properties. Most reconstruction methods to date have assumed isotropic tissue properties. However, application to tissues like skeletal muscle and brain white matter with aligned fibrous structure resulting in local transverse isotropic mechanical properties would benefit from analysis that takes into consideration anisotropy. A theoretical approach is developed for the elliptic shear wave pattern observed in transverse isotropic materials subjected to axisymmetric excitation creating radially converging shear waves normal to the fiber axis. This approach, utilizing Mathieu functions, is enabled via a transformation to an elliptic coordinate system with isotropic properties and a ratio of minor and major axes matching the ratio of shear wavelengths perpendicular and parallel to the plane of isotropy in the transverse isotropic material. The approach is validated via numerical finite element analysis case studies. This strategy of coordinate transformation to equivalent isotropic systems could aid in analysis of other anisotropic tissue structures.

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A finite element model to study the effect of tissue anisotropy onex vivoarterial shear wave elastography measurements

Cited by 8 publications

References 55 publications

3D elastic tensor imaging in weakly transversely isotropic soft tissues

3D elastic tensor imaging in weakly transversely isotropic soft tissues

Anin silicoframework to analyze the anisotropic shear wave mechanics in cardiac shear wave elastography

Analytical solution for converging elliptic shear wave in a bounded transverse isotropic viscoelastic material with nonhomogeneous outer boundary

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