Effect of ultrasound on the viability of SAS cells. (A) SAS cell suspension was exposed to ultrasound in the presence or absence of microbubbles. Cells were incubated in 96-well plates for 48 h and cell viability was measured by MTT assay. The duty cycle and exposure time were fixed to 10% and 20 sec and output intensity was changed from 0.5 to 2.0 W/cm2, according to Sonitron intensity dial settings. (B) The output intensity and exposure time were fixed to 0.5 W/cm2 and 20 sec and duty cycle output was changed from 5 to 50%. (C) The output intensity and duty cycle were fixed to 0.5 W/cm2 and 10% and exposure time was changed from 10 to 40 sec. The values were divided by that of the control and the percentage was calculated. Data are means ± SDs of three determinations. *P < 0.05 vs. control.