Ultrasound Elastography

Example of elastography on a tissue mimicking phantom

(a) Elastogram showing a hard inclusion

(b) Standard B-mode ultrasound image that does not depict the inclusion

Ultrasound Elastography is a new field in which the mechanical properties – usually elasticity and viscosity – are measured using ultrasound. These parameters cannot normally be measured by standard medical imaging techniques. Just as a doctor will palpitate a breast to feel for stiff lumps while looking for breast cancer, elasticity (stiffness) images can be used to locate and identify malignant tissues.

Elastography requires the application of an excitation force to induce motion in the tissue. The motion of the tissue can then be captured by the imaging system and the pattern of the motion can be used to estimate the mechanical parameters. With an ultrasound imaging system, typically only the motion along the propagation axis of the sound wave is measured with high accuracy. However, when a force is applied to a body, the resulting motion is in three dimensions. In my work I try to improve the measurement capability of ultrasound methods by using multiple transducers to measure motion from different angles. More in depth discussion can be found in the following sections.