Three‐dimensional ultrasound image registration and shear elastic modulus reconstruction

It is widely recognized that tissue pathologies often change biomechanical properties. For instance, neoplastic tissue is typically highly vascularized, contains abnormal concentrations of extracellular proteins (i.e., collagen, proteoglycans) and has a high interstitial fluid pressure compared to most normal tissues. The aim of this work is to develop and evaluate an ultrasound technique to quantitatively measure and image the mechanical properties of soft tissues in three dimensions. The intended application of our work is in the detection and diagnosis of breast cancer and other soft tissue pathologies. The specific goal of this project is the accurate measurement of the elastic shear modulus distribution of a tissue‐mimicking ultrasound phantom, using a 3‐D ultrasound imaging system. This requires the design and characterization of algorithms to provide three‐dimensional motion estimates from ultrasound images and to solve the three‐dimensional inverse problem to recover shear elastic modulus. Modulus images, reconstructed using our algorithms, are presented and compared to values determined by independent mechanical testing. The effect of the boundary conditions and regularization methods on the reconstructed modulus images and the uniqueness of the solution is also discussed.