On the imaging of slip boundaries using 3D elastography

Slip elastography is a new branch of elastography which incorporates shear strain imaging and force estimation, with a view to detecting and characterizing slip boundaries between tumors and their surroundings. This paper introduces the principles of slip elastography. It is hypothesized that apparent shear strains may arise due to shear motion across a slip boundary. This is investigated through FEM simulation and phantom experiments. It was found that axial shear strain across a tumor boundary is greater when it may slip freely against the surrounding material compared to when it is adhered. Additional indicators of slip motion were found: discontinuous gradients in displacement data at the tumor boundary; high axial strain surrounding the tumor, as a result of high local spatial gradients in displacement at the tumor boundary; inhomogeneous distribution axial strain within the tumor; axial shear strain contrast inside the tumor. In the future, these indicators will be used to help locate slip boundaries in the scan plane.