Finite element analysis of radiation force induced tissue motion with experimental validation

An ultrasonic radiation force-based method for remote palpation of tissue is investigated. The use of radiation force to image tissue stiffness has been proposed by several researchers. In this paper, the potential for using a diagnostic ultrasound system to both apply radiation force and track the resulting tissue displacements is investigated using Finite Element Methods (FEM), and the results are compared with experimental results. Remote palpation is accomplished by interspersing high intensity pushing beams with low intensity tracking beams. This generates localized radiation forces which can be applied throughout the tissue, with the resulting displacement patterns determined using correlation techniques. An area that is stiffer than the surrounding medium distributes the force, resulting in larger regions of displacement, and smaller maximum displacements. The resulting displacement maps provide information as to the location and size of regions of increased stiffness. The authors have developed an FEM model that predicts displacements resulting from acoustic radiation force fields generated by diagnostic transducers in various complex media. They perform a parametric analysis of varying tissue and acoustic beam characteristics on radiation force induced tissue displacements. Displacements are on the order of microns, with considerable differences in displacement patterns in the presence and absence of a lesion (or stiff inclusion). Initial experimental results are presented that support the findings in the model.