Neuronavigation-Guided Focused Ultrasound-Induced Blood- Brain Barrier Opening: A Preliminary Study in Swine

BACKGROUND AND PURPOSE: FUS-induced BBB opening is a promising technique for noninvasive and local delivery of drugs into the brain. Here we propose the novel use of a neuronavigation system to guide the FUS-induced BBB opening procedure and investigate its feasibility in vivo in large animals. MATERIALS AND METHODS: We developed an interface between the neuronavigator and FUS to allow guidance of the focal energy produced by the FUS transducer. The systemwas tested in 29 swine bymore than 40 sonication procedures and evaluated byMR imaging. Gd-DTPA concentrationwas quantitated in vivo byMR imaging R1 relaxometry and comparedwith ICP-OES assay. Brain histology after FUS exposure was investigated using H&E and TUNEL staining. RESULTS: Neuronavigation could successfully guide the focal beam, with precision comparable to neurosurgical stereotactic procedures (2.3 0.9 mm). A FUS pressure of 0.43 MPa resulted in consistent BBB opening. Neuronavigation-guided BBB opening increased Gd-DTPA deposition by up to 1.83 mmol/L (a 140 % increase). MR relaxometry demonstrated high correlation with ICP-OES measurements (r2 0.822), suggesting that Gd-DTPA deposition can be directly measured by imaging. CONCLUSIONS: Neuronavigation provides sufficient precision for guiding FUS to temporally and locally open the BBB. Gd-DTPA depo-sition in the brain can be quantified by MR relaxometry, providing a potential tool for the in vivo quantification of therapeutic agents in CNS disease treatment