Simultaneous multiparameter visco-acoustic full waveform inversion for breast ultrasound imaging.

Full waveform inversion (FWI) is widely regarded as a promising advanced imaging technique in medical ultrasound imaging. However, further improvements are still required in forward modeling and inversion strategies, particularly concerning medium attenuation properties. Accurate modeling of the attenuation parameter Q is crucial for distinguishing tissue characteristics. To address this, this study proposes a multiparameter FWI approach based on simultaneous inversion strategy. Different from conventional acoustic FWI, a visco-acoustic wave equation is formulated using the Kolsky-Futterman (K-F) model, explicitly incorporating the Q factor into the complex slowness term, thus precisely describing acoustic wave attenuation behavior in forward simulations. In response to the issue of ill-posedness arising from coupling between velocity and Q parameters in multiparameter inversion, two inversion strategies, hierarchical inversion and simultaneous inversion, are designed and compared. In addition, the Minimum Gradient Support (MGS) regularization function is incorporated as an extra model constraint term alongside the traditional data misfit term to enhance structural reconstruction within the model. Quantitative experiments conducted on single-tumor models demonstrate that simultaneous inversion exhibits superior convergence and inversion accuracy, effectively suppressing parameter crosstalk. Further verifications performed on multiple-tumor and strongly attenuated calcification models indicate the adaptability and robustness of the proposed method in achieving high-precision joint reconstruction of velocity and Q distributions within complex tissue structures, facilitating accurate differentiation of tissue characteristics.