Real-Time 3D Ultrafast Shear Wave Absolute Vibro-Elastography

3D ultrasound elastography has the potential to be a fast and accurate approach for estimating tissue shear modulus from the wave equation. One of the drawbacks of 3D imaging is the long data acquisition time which reduces practicality and can introduce artifacts from unwanted tissue motion such as from breathing. This paper presents a novel imaging technique for real-time 3D data collection with a volume rate of 2000 volumes/s and total acquisition time of 0.05 s. Plane wave imaging is used with Shear Wave Absolute Vibro-Elastography (S-WAVE) where an external mechanical vibration source generates multi-frequency shear waves in tissue. A matrix array transducer is used to collect volumes of radio frequency (RF) data. Axial, lateral and elevational displacements are then estimated over 3D volumes. The curl of the displacements is used in a local frequency estimation technique to estimate elasticity in the acquired volumes. The S-WAVE excitation frequency is substantially extended up to 500 Hz by using a high volume rate imaging. Therefore, the method can be applied on a wide range of applications such as prostate, breast, liver, and thyroid elastography. Results on liver fibrosis phantoms using several excitation frequencies are presented and compared with the manufacturer elasticity values for validation. The estimated elasticities by the proposed method fall within the manufacturer's elasticity range for all frequencies.