Erosion of artificial endothelia in vitro by pulsed ultrasound: Acoustic pressure, frequency, membrane orientation and microbubble contrast agent dependence

The erosion of cells from fibroblast monolayers simulating the vascular end othelium by 20 ms pulses of ultrasound at 500 Hz PRF was studied in relatio n to the peak negative acoustic pressure (P-; 0.0-2.5 MPa), ultrasound (US) frequency (1.0, 2.1 or 3.5 MHz), orientation of the monolayer (Le., simula ting the sites of ultrasound entry/exit from a blood vessel) and the presen ce or absence of a microbubble contrast agent (3 Vol% Albunex(R)). The a pr iori hypotheses were that erosion of the monolayers would: 1. arise due to insonation treatment, 2. arise as a consequence of cavitation activity and, thus, increase with increasing P- at constant frequency, and decrease with increasing frequency at constant P-, 3. be significantly increased by the presence of a microbubble contrast agent, and 4. have a weak dependence on monolayer orientation. The data support these hypotheses. Under the most se vere exposure conditions used, most of the affected cells appeared to have been lysed; however, a substantial number of viable cells were dislodged fr om the monolayer surface. (C) 1999 World Federation for Ultrasound in Medic ine & Biology.