Quantification of flow using ultrasound and microbubbles: a disruption replenishment model based on physical principles.

With contrast agents, ultrasound can make hemodynamic measurements in microvascular networks with the technique of disruption replenishment. In its current form, the method suffers from poor reproducibility and accuracy, largely due to the inappropriate use of a mono-exponential model for fitting the time replenishment data. In reality, the time-intensity replenishment curve reflects the hemodynamics and morphology of the vascular system being measured, the ultrasound field distribution and microbubble properties. Here, we introduce an analytic replenishment model that attempts to account for these parameters and compare its performance to the established model in a flow phantom. Specifically, the proposed model 1) incorporates the hemodynamic properties of the flow system (velocity distribution and vascular cross section), 2) includes the elevation and axial plane pressure distributions and 3) accounts for the distinct high and low MI disruption and detection boundaries. Compared to the currently accepted mono-exponential model, the presented model shows better agreement in both the quality of the fit and estimation of velocity (~5-10% vs. 20% error) for the same flow and acoustic conditions