Time Steps Expandable Inverse Model for Ultrasound Shear Wave Elastography Imaging.

Aim: Ultrasound shear wave elastography (USWE) is a noninvasive imaging technique developed in the last two decades for clinical diagnosis. Commercialized tools of USWE perform imaging by measuring tissue elasticity. Consequently, pathological diagnosis can be ineffective owing to a lack of viscosity. Accurately imaging complete viscoelasticity is challenging for USWE because it induces high underdetermination level of the inverse problem. We seek to develop a time steps expandable inverse model to facilitate viscoelasticity imaging for USWE. Materials and Methods: Tissue displacements induced by ultrasound shear waves are simulated by an in-house forward model. Then, the time steps expandable inverse model is used as a regularization method for USWE imaging. Results: By applying the proposed time steps expandable inverse model, our numerical results demonstrate that the underdetermination level of the system can be reduced, and USWE is able to image complete viscoelasticity. Conclusions: The proposed inverse model enables USWE to image complete viscoelasticity. It possesses advantages to reduce memory storage and to accelerate computational speed during inversion. The proposed model is helpful to enable wider clinical diagnosis for the state-of-the-art USWE technology.