Cross-plane shear wave elastography for viscoelasticity imaging

OBJECTIVE: Shear wave elastography (SWE) is widely used for elasticity imaging, but conventional implementations remain confined to two-dimensional (2D) measurement planes and lack sensitivity to viscosity, an emerging biomarker linking shear wave dissipation and disease progression. The objective of this work is to extend SWE for viscoelasticity imaging beyond the measurement plane through methodological and acquisition-based advances. APPROACH: We introduce a cross-plane acquisition strategy in which multiple measurement planes are recorded per acoustic radiation force (ARF) push to capture dissipation across planes. We perform imaging using recently developed full-waveform inversion (FWI), enhanced with an H1 regularization scheme that stabilizes reconstructions by penalizing spurious oscillations. The method is validated using synthetic datasets generated using a reduced-dimension proof-of-concept model focused on out-of-plane sensitivity under varying inclusion geometries, contrasts, and noise levels. Reconstructions were performed using a multiresolution sequential inversion framework that progressively refines elasticity (G) and viscosity (eta). MAIN RESULTS: The cross-plane strategy significantly improved the recovery of viscosity distributions by capturing dissipative behavior between measurement planes, while H1 regularization enhanced stability and suppressed noise-induced artifacts without over smoothing. Elasticity maps remained consistent across all cases, whereas viscosity reconstructions exhibited improved boundary fidelity and reduced ambiguity compared with single-plane configurations. SIGNIFICANCE: These findings demonstrate the feasibility of reconstructing viscoelastic properties beyond the measurement plane using cross-plane SWE. The proposed framework establishes a pathway toward true volumetric (3D) viscoelastic imaging using standard 2D ultrasound acquisitions.