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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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Related in: MedlinePlus

Imaging and FEA strain values. Average strain values and standard deviations from five regions of interest at the top (A) and sides (B) of the arterial wall under physiologic pressure and pressure equalization, as determined by high-resolution ultrasound imaging with speckle tracking (US) and finite-element analysis models with surrounding tissue (FEA1) and without surrounding tissue (FEA2).
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Figure 6: Imaging and FEA strain values. Average strain values and standard deviations from five regions of interest at the top (A) and sides (B) of the arterial wall under physiologic pressure and pressure equalization, as determined by high-resolution ultrasound imaging with speckle tracking (US) and finite-element analysis models with surrounding tissue (FEA1) and without surrounding tissue (FEA2).

Mentions: Average strain differences and standard deviations (SDs) of n = 5 regions of interest obtained from the FEA artery models for both physiologic pressure and equalized pressure are shown in Table 2, where they are compared with the ultrasound imaging results. FEA and imaging results are also compared in Figures 6(a) and 6(b) for the regions of interest at the top and sides, respectively, of the arterial wall. Under physiologic pressure, the average strain at the top and bottom of the arterial wall in the model with surrounding tissue (FEA1) was -9%, compared to -11% in the model without surrounding tissue (FEA2). The difference in average strain values at the sides was 13% vs. 17% in the models with and without surrounding tissue, respectively. Under pressure equalization, however, the differences in average strain values between the two models were considerably greater: -20% vs. -60% in the models with and without surrounding tissue, respectively, at the top and bottom regions of interest; and 16% vs. 91% in the models with and without surrounding tissue, respectively, at the sides of the arterial wall.


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)

Imaging and FEA strain values. Average strain values and standard deviations from five regions of interest at the top (A) and sides (B) of the arterial wall under physiologic pressure and pressure equalization, as determined by high-resolution ultrasound imaging with speckle tracking (US) and finite-element analysis models with surrounding tissue (FEA1) and without surrounding tissue (FEA2).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Imaging and FEA strain values. Average strain values and standard deviations from five regions of interest at the top (A) and sides (B) of the arterial wall under physiologic pressure and pressure equalization, as determined by high-resolution ultrasound imaging with speckle tracking (US) and finite-element analysis models with surrounding tissue (FEA1) and without surrounding tissue (FEA2).
Mentions: Average strain differences and standard deviations (SDs) of n = 5 regions of interest obtained from the FEA artery models for both physiologic pressure and equalized pressure are shown in Table 2, where they are compared with the ultrasound imaging results. FEA and imaging results are also compared in Figures 6(a) and 6(b) for the regions of interest at the top and sides, respectively, of the arterial wall. Under physiologic pressure, the average strain at the top and bottom of the arterial wall in the model with surrounding tissue (FEA1) was -9%, compared to -11% in the model without surrounding tissue (FEA2). The difference in average strain values at the sides was 13% vs. 17% in the models with and without surrounding tissue, respectively. Under pressure equalization, however, the differences in average strain values between the two models were considerably greater: -20% vs. -60% in the models with and without surrounding tissue, respectively, at the top and bottom regions of interest; and 16% vs. 91% in the models with and without surrounding tissue, respectively, at the sides of the arterial wall.

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