Shear wave velocity imaging using transient electrode perturbation: A phantom study

A new shear wave velocity imaging technique to monitor radiofrequency and microwave ablation procedures is presented, coined electrode vibration elastography. A piezoelectric actuator is attached to the ablation needle and is transiently vibrated to generate shear waves that are tracked at high frame rates. The time-to-peak algorithm is used to reconstruct the shear wave velocity and thereby the shear modulus variations. The feasibility of this approach is demonstrated in phantoms mimicking fully ablated (phantom 1) and partially ablated (phantom 2) regions. Shear wave velocity estimates in phantom 1 were within 7% of mechanical measurements and within 17% in phantom 2. Good boundary delineation was observed in both phantoms. No significant differences in ellipsoid area estimates between shear wave velocity and B-mode images were present in phantom 1. Shear wave velocity area estimates were significantly higher than B-mode area estimates in phantom 2. Electrode vibration elastography shows promise as an imaging modality that provides ablation boundary delineation and quantitative information during ablation procedures.