Diagnostic ultrasound induces membrane damage in phagocytic cells loaded with contrast agent in vitro

Ultrasound contrast-agent gas bodies can be taken up from the circulation by phagocytic cells, which make these cells likely targets for bioeffects of diagnostic ultrasound. A mouse macrophage cell line was cultured in monolayer on the inside of one window of a disc-shaped exposure chamber. After incubation with contrast agent for 15 min, the monolayer was rinsed to remove un-attached gas bodies. The chamber was filled with saline plus fluorescent Dextran and closed with a second window. A clinical scanner provided ultrasound exposure of the chamber in a water bath. Exposures were made in B scan mode, color Doppler imaging mode and power Doppler mode for 1 min. After exposure the chamber was opened, rinsed and stained with trypan blue. A field of view of a fluorescence microscope was scored for sonoporation (fluorescent cells) and cell lysis (blue stained cells). No significant effect was seen for exposure without contrast agent. With contrast agent, statistically significant sonoporation was induced by all the modes either for transmission through a water path or through a tissue-mimicking phantom. Cell lysis was significant for all modes for the water path, but not for the phantom. These results suggest that a risk of cell membrane bioeffects in phagocytic cells may exist for contrast-aided diagnostic ultrasound.