Disruption of the blood-brain barrier (BBB) may be transiently achieved via high-frequency focused spherical ultrasound in the presence of microbubbles. In this experimental animal study, we sought to determine whether focal reversible opening of the BBB may be achieved using low-frequency (i.e., 20-30 kHz) planar ultrasonic waves. In the presence of microbubbles, we were able to obtain BBB opening using non-focused ultrasound irradiation with a frequency as low as 28 kHz. We also achieved a tight regulation of the ultrasound patterns by using a mechanical scanning device equipped with a pinhole. Histologic examination of the brains supported the feasibility of our system. The areas of BBB disruption obtained with this method were large enough to cover a typical circumscribed cerebral tumor mass. The inherent advantages of our BBB opening method include an improved portability, the possibility to obtain fairly wide areas of BBB opening and a low incidence of hemorrhagic complications. In addition, our system has the potential to reduce the need for image guidance for treating superficial brain lesions.
2010 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.