In vitro demonstration of an echogenic emulsion: relationship of lipid particle size to echo detection.

To prove that protein-lipid emulsions can be echogenic, we made two lipid-in-water emulsions. The first emulsion was composed of lipid micelles approximately 10 microns in diameter. The second emulsion was composed of micelles approximately 100 microns in diameter. The first emulsion was anechoic; the second emulsion was echogenic. These results are consistent with the physical laws governing the scatter of ultrasound and demonstrate that collagen containing connective tissue is not necessary for echoes. In addition, these data support the hypothesis that the wide differences in echogenicity of fatty tissues is due to the differences in the thickness of their connective tissue stromata.