The effect of ultrasound frame rate on perfluorocarbon-exposed sonicated dextrose albumin microbubble size and concentration when insonifying at different flow rates, transducer frequencies, and acoustic outputs

The purpose of this article was to compare the effects of 1 and 30 Hz frame rates on perfluorocarbon-exposed sonicated dextrose albumin microbubble size and concentration in a flow cell containing either saline or blood at 37 degrees C. Microbubble size and concentration of perfluorocarbon-exposed sonicated dextrose albumin were measured after insonation at different acoustic outputs, transducer frequencies, and flow rates with the use of the two different frame rates and compared with no ultrasound exposure. At 2.0 MHz insonation frequency, microbubble concentration was significantly reduced with the use of a 30 Hz frame rate and peak negative pressures of 1.1 megaPascal (mPa). This destruction did not occur when using a lower acoustic output, a 1 Hz frame rate, or when flow rate was increased to 100 cc/min. One-hertz frame rates at 2.0 MHz resulted in a significantly larger mean microbubble size than 30 Hz or no ultrasound in both saline and blood, which was in part due to selective destruction of smaller microbubbles. These findings indicate that 30 Hx frame rates destroy perfluorocarbon-exposed sonicated dextrose albumin microbubbles only at higher diagnostic acoustic outputs. A 1 Hz frame rate prevents this destruction, especially destruction of larger (>5.0 mu m) microbubbles.