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 gamma_mean(t), allowing regularized values of the ratio to be estimated. The predefined value gamma_mean(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.