An ultrasound based method for measuring multiple velocity components in opaque macro and micro flows

We report here on the development of an ultrasound-based particle image velocimetry (PIV) system for measurement of multiple velocity components in opaque flows. The method takes advantage of the non-linear backscatter characteristics of small (1 - 5 mu) gas-filled microbubbles used as markers of flow trajectories. PIV algorithms, modified for use with ultrasound data, are applied to calculate the local velocity vector. Preliminary data from in vitro and in vivo studies are presented. The method should be useful for a variety of fluid diagnostics applications where optical access (as is required for conventional PIV techniques) is not available. This. includes biomedical imaging and MEMS micro-fluidic applications.