Acoustic emission as a measure of exposure of suspended cells in vitro.

Cell viability, survival, and growth of C1300 mouse neuroblastoma cells were assayed by trypan blue dye exclusion, clonogenesis, and culturing, respectively, after exposure in suspension to therapeutic levels of ultrasound (1 MHz; continuous wave; spatial peak intensity 0.9, 1.7, and 2.6 W/cm2; 5 min at 37 degrees C). Acoustic emission from the cavitating cell suspensions was recorded as the rms value of the half-harmonic and noise components combined. Cell viability and survival appeared better correlated with acoustic emission than with spatial peak intensity, implying that acoustic emission may provide a more direct measure of insult to the cells in a cavitating field than the incident intensity. Biological assay results of growth were well correlated with spatial peak intensity but not with acoustic emission levels, which seems to imply that for this end point incident intensity is a more directly interacting parameter than cavitational activity, provided however that the latter is present. Further refinement of the technique for measuring acoustic emission from cell suspensions should permit separate measurements of the half-harmonic and noise components. When thus refined, it may provide the means to demonstrate cavitational action without resorting to additional experiments to suppress cavitation.