GREENLEAF James F.

James GREENLEAF

Mayo Clinic, USA

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Abstract−Viscoelastic properties of the myocardium may be altered by disease. Quantification of these properties may aid with evaluation of the health of the heart. We have developed Lamb wave dispersion ultrasound vibrometry （LDUV, which uses wave velocity dispersion to measure the underlying viscoelastic material properties of soft tissue with plate-like geometries. In eight pigs we tested this method in an open-chest preparation. Harmonic propagating mechanical waves in the myocardial wall were created with a mechanical actuator. The resulting motion was tracked using a high frame rate acquisition sequence, typically 2500 Hz. Wave propagation velocities were measured over the 50-400 Hz frequency range in 50 Hz increments. Data were acquired over several cardiac cycles. The viscoelastic, anti-symmetric Lamb wave model was fit to the data for estimates of the shear elasticity, and viscosity, as defined by the Kelvin-Voigt rheological model. We report wave velocity measurements and use Lamb wave theory to estimate the variation of viscoelastic moduli of the myocardial walls in vivo throughout the cardiac cycle.


Summary of phase velocity dispersion for diastole and systole for all eight animals. The values represent the mean and standard deviations from eight animals.