Abstract
Useful ultrasound contrast enhancement has been obtained using liquid emulsion contrast agents developed in our laboratory [Evaluation of liquid perflourocarbon nanoparticles as a blood pool contrast agent utilizing power Doppler harmonic imaging, IEEE Ultrason. Symp. 00CH37121, 1931–1934 (2000)]. While the physical basis for enhancement is unknown, it is reproducible, in vivo and in vitro. It is hypothesized that microbubble formation is not a significant factor in the acoustic behavior of these contrast agents; attenuation and backscatter (measured in a water bath at 37<th>°C) are uneffected by changes in hydrostatic pressure (from −50 to 200 mm Hg), acoustic pressure (0.038–3.0 MPa), and show no evidence of scattering agent destruction with ultrasound exposure time (2–80 s). The microbubble agent attenuation coefficient exhibits a single peak between 1 and 2 MHz. The exact peak location, height and width vary significantly with experimental conditions. In contrast, the emulsion does not exhibit any of these effects, which makes it appear very unlikely that microbubble formation through perflourocarbon phase conversion contributes in a measurable manner to the acoustic properties of the liquid perflourocarbon nanoparticle contrast agent over the range of experimental parameters in this study. [Work supported in part by HL-59865, N01-C0-07013-32.]
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