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This paper proposes the combined use of Finite Element Modeling (FEM) and Equivalent Circuit Modeling (ECM) to describe the nonlinear electromechanical and acoustic behavior of a CMUT in an integrated circuit simulation environment. CMUT ECM lumped parameters are computed by FEM simulations. The proposed method is implemented in LTSpice, and validated by comparing ECM and FEM static, small-signal harmonic, and large-signal transient simulation results. The model was then applied to the performance assessment of the CMUT coupled to a realistic integrated transceiver configuration by computing TX efficiency and noise figure. The proposed approach allows accurate large-signal analysis of CMUTs interfaced to ultrasound front-end circuits by considering non-ideal characteristics of the system, such as the pulser nonlinearities.

The twinkling sign in B-flow imaging (BFI-TS) has been reported in the literature to increase both specificity and sensitivity compared to the traditional gray-scale imaging. Unfortunately, there has been no conclusive study on the mechanism of this effect. In the study presented here, a comparative test on phantoms is introduced, where the variance of a phase estimator is used to quantify the motion amplitude. The statistical inference is employed later to find the dominate factor for the twinkling sign, which is proven by computer simulation. Through the analysis, it is confirmed that the tissue viscoelasticity is closely coupled with the twinkling sign. Moreover, the acoustic radiation force caused by tissue attenuation is found to be the trigger of the twinkling sign. Based on these findings, the BFI-TS is interpreted as a tissue movement triggering vibration of microcalcifications particle.