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 ofsmall motion and deformation of biological tissue is described. In thedisplacement estimation based on the phase change of echoes, the displacementestimates are biased when the center frequency of the RF echochanges. Such an apparent change in the center frequency could be causedby the interference of echoes from scatterers. To reduce the influence ofthe center frequency variation on the estimation of motion and deformation,an error correcting function, which does not require the assumptionthat the center frequency distributions in 2 different frames are the same,was introduced. As a result, the proposed method provides better strainestimates in comparison with conventional phase-sensitive correlationmethods. This monograph also shows examples of applications of this method tomeasurement of small motion and deformation of biological tissues. Thismethod can be applied to measurement of elasticity of dynamic tissues,such as the artery. Also, elastic properties of static tissues can be also measuredby combining with actuation using the acoustic radiation force.