Use of pulse repetition frequency to augment acoustic droplet vaporization in vivo

Tumor infarction shows promise as a cancer treatment. Gas embolotherapy tries to achieve this by locally occluding blood vessels supplying tumors using bubbles resulting from vaporization of liquid droplets. Sufficient occlusion may be necessary in order to starve tumors to death. The purpose of this study is to increase vaporization of droplets in vivo by changing the pulse repetition frequency (PRF) in order to improve the therapy. One milliliter of a solution containing 3 x 107 lipid-coated perfluorocarbon droplets was injected through the tail vein of a rat at a rate of 0.1 mL/min. Acoustic droplet vaporization (ADV) was induced in the feeder vessel of the exposed cremaster muscle using a focused, 7.5 MHz transducer and 3 MPa rarefactional pressure. A pulse length of 1μs was used, while the PRF was varied from 10 to 1000 Hz. Recordings of ADV showed substantial vaporization in both arterial and venous sides at higher PRFs. Vessel rupture and RBC extravasation were also observed. In other instances, bl...