Comparison of Reverberant Shear Wave Speed Estimators in Non-Ideal Fields

Reverberant shear wave elastography (RSWE) enables tissue stiffness estimation but implementations can be limited by non-ideal wave fields and directional artifacts. This study compares two robust shear wave speed (SWS) estimators: Angular Integration Autocorrelation (AIA) and Regularized Total Variation Phase Gradient (PG-TV) - across five experimental setups using three heterogeneous custom-made gelatin phantoms, a calibrated breast phantom, and ex vivo liver tissue, with vibrations from 100-900 Hz applied using 1-5 mini shakers. Results show that AIA consistently achieved an average lower error across setups (27.1%) compared to PG-TV (38.2%), providing greater robustness to noise and directional bias, particularly in background regions at higher frequencies. Nevertheless, PG-TV provided greater CNR overall, with an average of 2.78 vs. 2.11 from the AIA estimator, showing sharper boundaries, especially in heterogeneous media. Both estimators showed reduced performance at low frequencies due to standing waves. Notably, increasing the number of actuators did not guarantee improved estimations. Results suggest that AIA and PG-TV offer complementary strengths and highlight the need for adaptive metrics to assess field diffusivity and estimator reliability.