Estimation of mechanical properties of arteries and soft tubes using shear wave speeds

Arterial elasticity has gained importance in the past few decades as a predictor of cardiovascular diseases and mortality. We propose a noninvasive technique using ultrasound radiation force and measurement of shear wave speed to calculate the mechanical properties of soft tubes and arteries noninvasively. To validate the technique we made three urethane tubes with different Young´s moduli, tested the tubes and used the measured tube wall´s shear wave speed and the modified Moens-Korteweg equation to estimate the Young´s moduli. Samples of the same material were mechanically tested to compare the results from our technique. Excised carotid arteries from a pig were used to study the applicability of our method in soft tissues. Both the tubes and the arteries were embedded in gelatin to simulate the soft tissue surrounding the arteries, and pressurized using a column of water. The results from the tubes were in very good agreement with the mechanical testing, and the shear wave speed did not seem to change very much with change in transmural pressure. On the other hand, the excised arteries showed an increase in shear wave velocity with pressure and an increase in the Young´s modulus. The technique we present here showed to be in good agreement with mechanical testing which gives us confidence to think that it can be applied in the study of arteries in vivo. Efforts towards implementing this technique in a clinical scanner are underway.