Diagnostic ultrasound-induced membrane damage in phagocytic cells loaded with contrast agent and its relation to Doppler-mode images.

Cell membrane damage induced by diagnostic ultrasound exposure with contrast agent was examined and related to the display of stimulated acoustical emission in Doppler images. Monolayers of mouse macrophage-like cells were cultured on the inside of one window of an exposure chamber. The monolayers were incubated with 5% Optison (Mallinckrodt, Inc., St. Louis, MO) for 15 minutes then rinsed to remove unattached gas bodies. A Spectra Plus scanner (Diasonics GE Medical Systems, Inc., Cincinnati, OH) in B-scan or Doppler-imaging modes exposed the chamber 3.5 cm away in a 37 degrees C water bath. The cells were scored either for uptake of fluorescent Dextran (sonoporation), or for trypan blue dye exclusion (cell death). No significant effect was seen for exposure in any mode without a contrast agent. Significant effects with contrast agent included 5.8% (2.3% standard deviation, SD) fluorescent cells and 33.4% (7.7% SD) trypan blue-stained cells in Doppler-imaging modes, compared to 0.0% and 2.2% (1.7% SD), respectively, in sham exposures. Frames of the power Doppler image were analyzed for pixel brightness to quantify the brief flash in the Doppler window. Although both membrane damage and the flash brightness increased with increasing pressure amplitude, there did not appear to be a direct correlation between the two phenomena.