SWAVE Imaging of Placental Elasticity and Viscosity: Proof of Concept.

The placenta is the interface between the fetus and the mother and is vital for fetal development. Ultrasound elastography provides a non-invasive way to examine in vivo the stiffness of the placenta; increased stiffness has previously been linked to fetal growth restriction. This study used a previously developed dynamic elastography method, called shear wave absolute vibro-elastography, to study 61 post-delivery clinically normal placentas. The shear wave speeds in the placenta were recorded under five different low-frequency mechanical excitations. The elasticity and viscosity were estimated through rheological modeling. The shear wave speeds at excitation frequencies of 60, 80, 90, 100 and 120 Hz were measured to be 1.23 ± 0.44, 1.67 ± 0.76, 1.74 ± 0.72, 1.80 ± 0.78 and 2.25 ± 0.80 m/s. The shear wave speed values we obtained are consistent with previous studies. In addition, our multi-frequency acquisition approach enables us to provide viscosity estimates that have not been previously reported.