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Arterial elasticity imaging: comparison of finite-element analysis models with high-resolution ultrasound speckle tracking.

Park DW, Richards MS, Rubin JM, Hamilton J, Kruger GH, Weitzel WF - Cardiovasc Ultrasound (2010)

Bottom Line: The nonlinear mechanical properties of internal organs and tissues may be measured with unparalleled precision using ultrasound imaging with phase-sensitive speckle tracking.The many potential applications of this important noninvasive diagnostic approach include measurement of arterial stiffness, which is associated with numerous major disease processes.Use of the pressure equalization technique during imaging resulted in average strain values of 26% and 18% at the top and sides, respectively, compared to 5% and 2%, at the top and sides, respectively, under physiologic pressure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA.

ABSTRACT

Background: The nonlinear mechanical properties of internal organs and tissues may be measured with unparalleled precision using ultrasound imaging with phase-sensitive speckle tracking. The many potential applications of this important noninvasive diagnostic approach include measurement of arterial stiffness, which is associated with numerous major disease processes. The accuracy of previous ultrasound measurements of arterial stiffness and vascular elasticity has been limited by the relatively low strain of nonlinear structures under normal physiologic pressure and the measurement assumption that the effect of the surrounding tissue modulus might be ignored in both physiologic and pressure equalized conditions.

Methods: This study performed high-resolution ultrasound imaging of the brachial artery in a healthy adult subject under normal physiologic pressure and the use of external pressure (pressure equalization) to increase strain. These ultrasound results were compared to measurements of arterial strain as determined by finite-element analysis models with and without a surrounding tissue, which was represented by homogenous material with fixed elastic modulus.

Results: Use of the pressure equalization technique during imaging resulted in average strain values of 26% and 18% at the top and sides, respectively, compared to 5% and 2%, at the top and sides, respectively, under physiologic pressure. In the artery model that included surrounding tissue, strain was 19% and 16% under pressure equalization versus 9% and 13% at the top and sides, respectively, under physiologic pressure. The model without surrounding tissue had slightly higher levels of strain under physiologic pressure compared to the other model, but the resulting strain values under pressure equalization were > 60% and did not correspond to experimental values.

Conclusions: Since pressure equalization may increase the dynamic range of strain imaging, the effect of the surrounding tissue on strain should be incorporated into models of arterial strain, particularly when the pressure equalization technique is used.

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FEA model. Finite-element analysis (FEA) model of artery and surrounding tissue, including dimensions.
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Figure 2: FEA model. Finite-element analysis (FEA) model of artery and surrounding tissue, including dimensions.

Mentions: FEA of the artery models with and without surrounding tissue was performed using ABAQUS software (Simulia, Providence, Rhode Island), version 6.4, and the Young's moduli obtained in the microelastometer experiment. The axial strain was analyzed under conditions simulating both physiologic pressure and pressure equalization. A simplified model of the brachial artery and its surrounding tissue was designed (Fig. 2). For the FEA model, the quadratic-dominated element shape was used. Dimensions were determined on the basis of the ultrasound B-mode image, and boundary conditions were based on the ultrasound experiment. We assumed the volume of the surrounding tissue to be much larger than that of the artery. Thus, the boundary conditions for surrounding tissue included a fixed bottom and sides that were free to move vertically but not horizontally (horizontally symmetric conditions). Two-dimensional mesh was designed to analyze this model. Volume change of the tissue was assumed to be negligible and thus the Poisson's ratio was regarded as 0.5.


Arterial elasticity imaging: comparison of finite-element analysis models with high-resolution ultrasound speckle tracking.

Park DW, Richards MS, Rubin JM, Hamilton J, Kruger GH, Weitzel WF - Cardiovasc Ultrasound (2010)

FEA model. Finite-element analysis (FEA) model of artery and surrounding tissue, including dimensions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2908573&req=5

Figure 2: FEA model. Finite-element analysis (FEA) model of artery and surrounding tissue, including dimensions.
Mentions: FEA of the artery models with and without surrounding tissue was performed using ABAQUS software (Simulia, Providence, Rhode Island), version 6.4, and the Young's moduli obtained in the microelastometer experiment. The axial strain was analyzed under conditions simulating both physiologic pressure and pressure equalization. A simplified model of the brachial artery and its surrounding tissue was designed (Fig. 2). For the FEA model, the quadratic-dominated element shape was used. Dimensions were determined on the basis of the ultrasound B-mode image, and boundary conditions were based on the ultrasound experiment. We assumed the volume of the surrounding tissue to be much larger than that of the artery. Thus, the boundary conditions for surrounding tissue included a fixed bottom and sides that were free to move vertically but not horizontally (horizontally symmetric conditions). Two-dimensional mesh was designed to analyze this model. Volume change of the tissue was assumed to be negligible and thus the Poisson's ratio was regarded as 0.5.

Bottom Line: The nonlinear mechanical properties of internal organs and tissues may be measured with unparalleled precision using ultrasound imaging with phase-sensitive speckle tracking.The many potential applications of this important noninvasive diagnostic approach include measurement of arterial stiffness, which is associated with numerous major disease processes.Use of the pressure equalization technique during imaging resulted in average strain values of 26% and 18% at the top and sides, respectively, compared to 5% and 2%, at the top and sides, respectively, under physiologic pressure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA.

ABSTRACT

Background: The nonlinear mechanical properties of internal organs and tissues may be measured with unparalleled precision using ultrasound imaging with phase-sensitive speckle tracking. The many potential applications of this important noninvasive diagnostic approach include measurement of arterial stiffness, which is associated with numerous major disease processes. The accuracy of previous ultrasound measurements of arterial stiffness and vascular elasticity has been limited by the relatively low strain of nonlinear structures under normal physiologic pressure and the measurement assumption that the effect of the surrounding tissue modulus might be ignored in both physiologic and pressure equalized conditions.

Methods: This study performed high-resolution ultrasound imaging of the brachial artery in a healthy adult subject under normal physiologic pressure and the use of external pressure (pressure equalization) to increase strain. These ultrasound results were compared to measurements of arterial strain as determined by finite-element analysis models with and without a surrounding tissue, which was represented by homogenous material with fixed elastic modulus.

Results: Use of the pressure equalization technique during imaging resulted in average strain values of 26% and 18% at the top and sides, respectively, compared to 5% and 2%, at the top and sides, respectively, under physiologic pressure. In the artery model that included surrounding tissue, strain was 19% and 16% under pressure equalization versus 9% and 13% at the top and sides, respectively, under physiologic pressure. The model without surrounding tissue had slightly higher levels of strain under physiologic pressure compared to the other model, but the resulting strain values under pressure equalization were > 60% and did not correspond to experimental values.

Conclusions: Since pressure equalization may increase the dynamic range of strain imaging, the effect of the surrounding tissue on strain should be incorporated into models of arterial strain, particularly when the pressure equalization technique is used.

Show MeSH
Related in: MedlinePlus