Fluorocarbon droplets as next generation contrast agents - their behavior under 1–3 MHz ultrasound

Our study on fluorocarbon droplets revealed that the sensitivity of mixed-component fluorocarbon droplets to ultrasound differs with ultrasound frequency at the frequency range of 1-3 MHz. In the perfluoropentane droplets, fluorocarbon with higher boiling point is added in the droplets´ core structure and ultrasonic and thermal threshold to induce phase change are compared. For all cases, adding the higher boiling point fluorocarbon increased the temperature threshold required for the phase change. The composition of the fluorocarbon droplet changed the ultrasound intensity threshold for the phase change, which corresponded with results of our previous studies done at higher frequencies. However, at 1 and 2 MHz, the amount of added higher boiling point fluorocarbon did not affect the ultrasound intensity threshold. Also, the highest magnitude of ultrasound intensity was required for a frequency of 3 MHz. For applications with lower frequency ultrasound, thermal mechanism plays a less significant role in inducing microbubbles.