A CLINICAL SYSTEM FOR NON-INVASIVE BLOOD-BRAIN BARRIER OPENING USING A NEURONAVIGATION-GUIDED SINGLE-ELEMENT FOCUSED ULTRASOUND TRANSDUCER

Focused ultrasound (FUS)-mediated blood-brain barrier (BBB) opening is currently being investigated in clinical trials. Here, we describe a portable clinical system with a therapeutic transducer suitable for humans, which eliminates the need for in-line magnetic resonance imaging (MRI) guidance. A neuronavigation-guided 0.25-MHz single-element FUS transducer was developed for non-invasive clinical BBB opening. Numerical simulations and experiments were performed to determine the characteristics of the FUS beam within a human skull. We also validated the feasibility of BBB opening obtained with this system in two non-human primates using U.S. Food and Drug Administration (FDA)-approved treatment parameters. Ultrasound propagation through a human skull fragment caused 44.4 +/- 1% pressure attenuation at a normal incidence angle, while the focal size decreased by 3.3 +/- 1.4% and 3.9 +/- 1.8% along the lateral and axial dimension, respectively. Measured lateral and axial shifts were 0.5 +/- 0.4 mm and 2.1 +/- 1.1 mm, while simulated shifts were 0.1 +/- 0.2 mm and 6.1 +/- 2.4 mm, respectively. A 1.5-MHz passive cavitation detector transcranially detected cavitation signals of Definity microbubbles flowing through a vessel-mimicking phantom. T-1-weighted MRI confirmed a 153 +/- 5.5 mm(3) BBB opening in two non-human primates at a mechanical index of 0.4, using Definity microbubbles at the FDA-approved dose for imaging applications, without edema or hemorrhage. In conclusion, we developed a portable system for non-invasive BBB opening in humans, which can be achieved at clinically relevant ultrasound exposures without the need for in-line MRI guidance. The proposed FUS system may accelerate the adoption of non-invasive FUS-mediated therapies due to its fast application, low cost and portability. (C) 2019 World Federation for Ultrasound in Medicine & Biology. All rights reserved.