A recent innovation by the proposing researchers in medical ultrasound has made it possible to detect microcirculatory blood flow, in which a special contrast agent is injected, and a previously ignored component of backscattered echo is analyzed. In Phase I, the applicants described a demonstration that this system could be easily implemented into existing ultrasound scanner technology, and has the potential to be used for image enhancement. In Phase II, the applicants proposed to exploit this enhancement and use it to quantify blood perfusing in living tissues. Specifically, the applicants proposed to correlate the contrast agent characteristics to new signal processing techniques, and to test these algorithms on both in vitro and in vivo systems, In addition, they would endeavor to improve the second harmonic image quality of the HP Sonos 100 seen in the Phase I feasibility study. Finally, they proposed to perform a limited number of preliminary clinical trails.