TY - GEN
T1 - Characterization of transverse isotropy in compressed tissue mimicking phantoms
AU - Urban, Matthew W.
AU - Kinnick, Randall R.
AU - Zhang, Xiaoming
AU - Greenleaf, James F.
N1 - Publisher Copyright:
© 2014 IEEE.
PY - 2014/10/20
Y1 - 2014/10/20
N2 - Tissues such as skeletal muscle and kidneys have well-defined structure that affects the measurements of mechanical properties. As an approach to characterize the material properties of these tissues, different groups have assumed that they are transversely isotropic (TI) and measure the shear wave velocity as it varies with angle with respect to the structural architecture of the organ. To refine measurements in these organs, it is desirable to have tissue mimicking phantoms that exhibit similar anisotropic characteristics. Some approaches involve embedding fibers into a material matrix. However, if a homogeneous solid is under compression due to a static stress, an acoustoelastic effect can manifest which makes the measured wave velocities change with the compression stress. We propose to exploit this characteristic to demonstrate that stressed tissue mimicking phantoms can be characterized as a TI material. We tested four gelatin phantoms made with different concentrations of gelatin. Stress was applied by the weight of a water container centered on top of a plate on top of the phantom. A linear array transducer and a V-1 Verasonics system (Verasonics, Inc., Redmond, WA) were used to induce and measure shear waves in the phantoms. The shear wave motion was measured using a compound plane wave imaging technique and applying autocorrelation to the received in-phase/quadrature data. The shear wave velocity, c, was estimated using a Radon transform method. The transducer was mounted on a rotating stage so measurements were made every 10° over a range of 0-360°, where the stress is applied along 0-180° direction. The shear moduli were estimated. A TI model was fit to the data and the fractional anisotropy was evaluated. This approach can be used to explore many configurations of transverse isotropy with the same phantom, simply by applying stress to the tissue mimicking phantom.
AB - Tissues such as skeletal muscle and kidneys have well-defined structure that affects the measurements of mechanical properties. As an approach to characterize the material properties of these tissues, different groups have assumed that they are transversely isotropic (TI) and measure the shear wave velocity as it varies with angle with respect to the structural architecture of the organ. To refine measurements in these organs, it is desirable to have tissue mimicking phantoms that exhibit similar anisotropic characteristics. Some approaches involve embedding fibers into a material matrix. However, if a homogeneous solid is under compression due to a static stress, an acoustoelastic effect can manifest which makes the measured wave velocities change with the compression stress. We propose to exploit this characteristic to demonstrate that stressed tissue mimicking phantoms can be characterized as a TI material. We tested four gelatin phantoms made with different concentrations of gelatin. Stress was applied by the weight of a water container centered on top of a plate on top of the phantom. A linear array transducer and a V-1 Verasonics system (Verasonics, Inc., Redmond, WA) were used to induce and measure shear waves in the phantoms. The shear wave motion was measured using a compound plane wave imaging technique and applying autocorrelation to the received in-phase/quadrature data. The shear wave velocity, c, was estimated using a Radon transform method. The transducer was mounted on a rotating stage so measurements were made every 10° over a range of 0-360°, where the stress is applied along 0-180° direction. The shear moduli were estimated. A TI model was fit to the data and the fractional anisotropy was evaluated. This approach can be used to explore many configurations of transverse isotropy with the same phantom, simply by applying stress to the tissue mimicking phantom.
KW - acoustoelasticity
KW - shear wave
KW - stress
KW - transverse isotropy
UR - http://www.scopus.com/inward/record.url?scp=84910090989&partnerID=8YFLogxK
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U2 - 10.1109/ULTSYM.2014.0455
DO - 10.1109/ULTSYM.2014.0455
M3 - Conference contribution
AN - SCOPUS:84910090989
T3 - IEEE International Ultrasonics Symposium, IUS
SP - 1834
EP - 1837
BT - IEEE International Ultrasonics Symposium, IUS
PB - IEEE Computer Society
T2 - 2014 IEEE International Ultrasonics Symposium, IUS 2014
Y2 - 3 September 2014 through 6 September 2014
ER -