Dynamic sonoelastography—Making the impossible, possible

Abstract

Sonoelastography refers to the use of ultrasound to image the viscoelastic properties of soft tissues. Although a number of techniques have emerged, most are qualitative and static in nature. The availability of dynamic quantitative methods could open a new field of functional imaging for the study of biomechanics. We have developed an approach using 2D speckle tracking and finite element-based elastic modulus reconstruction. The speckle tracking method uses a deformable mesh with nodes assigned to points with a high feature content. The tissue is harmonically excited at a frequency of less than 100 Hz and vibration vectors are obtained at the nodes of the mesh. Young’s modulus is then obtained within a series of small regions of interest using an iterative forward estimation approach. In each region, a finite element algorithm is used to predict the internal displacements from the measured motion on the boundary. A sum squared difference operator is used to estimate the associated error, from which an improved Young’s modulus is obtained for use in the next iteration. Results from simulations and from measurements in soft tissue phantoms and in human muscle will be presented. Limitations of the technique will be discussed along with potential solutions.