12A-6 A Method for the Regularized Estimation of Contrast Agent Concentration in Small Animal Contrast-Enhanced Ultrasound Studies

The aim of this paper was to propose a robust method for estimating contrast agent attenuation in vivo in small animal studies from contrast-enhanced ultrasound images acquired in fundamental mode. A model of sound propagation was previously presented to take into account the presence of ultrasound contrast agent in the tissue. This model was solved by considering the microbubble backscatter-to-attenuation ratio gamma(k,t) constant on each A-line of an image. In this paper, an improvement of the model solving is proposed. At each time t, the microbubble backscatter-to-attenuation ratio gamma(k, t) is constrained to be homogeneous on the whole field of view around a predefined value gammamean(t), allowing regularized values of the ratio to be estimated. The predefined value gammamean(t) is estimated using an iterative process, starting from the value provided by the first approach. To test this new approach, twelve murine renal perfusion studies are considered. A large recovery of the signal in the deep regions is observed. Compared with the initial method, a higher signal-to-noise ratio is found. Moreover, the process is more robust.