Ultrasonic Methods for Measurement of Small Motion and Deformation of Biological Tissues for Assessment of Viscoelasticity

In this monograph, an accurate ultrasonic method for measurement of
small motion and deformation of biological tissue is described. In the
displacement estimation based on the phase change of echoes, the displacement
estimates are biased when the center frequency of the RF echo
changes. Such an apparent change in the center frequency could be caused
by the interference of echoes from scatterers. To reduce the influence of
the center frequency variation on the estimation of motion and deformation,
an error correcting function, which does not require the assumption
that the center frequency distributions in 2 different frames are the same,
was introduced. As a result, the proposed method provides better strain
estimates in comparison with conventional phase-sensitive correlation
methods.
This monograph also shows examples of applications of this method to
measurement of small motion and deformation of biological tissues. This
method can be applied to measurement of elasticity of dynamic tissues,
such as the artery. Also, elastic properties of static tissues can be also measured
by combining with actuation using the acoustic radiation force.