Quantitative laser Doppler anemometry measurements of the shear-stresses exerted on ultrasonic microbubbles attached to surfaces under physiological flow conditions

Ultrasonic contrast agents are currently being developed to target and attach to specific sites of interest within the body. This paper presents microbubbles which have been developed and can be attached to agar surfaces. They have been successfully imaged with high frequency intravascular ultrasound at 40 MHz. A flow chamber has been developed for imaging attached microbubbles under flow conditions. To determine the shear stresses the microbubbles were subjected to in the flow chamber, and to investigate the shear stresses the microbubbles can withstand, laser Doppler anemometry (LDA) was used to determine the flow profile within the chamber. The shear stresses at 80, 90 and 100 ml min/sup -1/ were found. It is hoped to improve the resolution of the profiles obtained from LDA and to investigate increased flow rates and shear stresses.