First In-vivo Demonstration of Hologram-assisted Bilateral Blood-Brain Barrier Opening in Non-Human-Primates

Focused ultrasound (FUS) and microbubbles facilitate blood-brain barrier opening (BBBO) non-invasively, transiently and safely, enabling targeted drug delivery into the brain. However, state-of-the-art approaches have not shown the feasibility of simultaneous multifocal BBBO. In this study, we demonstrate for the first time the simultaneous, bilateral BBBO in non-human-primates (NHP) using acoustic holograms in two configurations: targeting caudate and putamen structures. We used a simple and low-cost system composed of a single-element FUS transducer and a 3D-printed hologram, guided by neuronavigation, with a robotic arm. The advantages of holograms are: 1) skull, muscle and brain aberration correction, 2) multiple and highly-localized BBBO with a single sonication, and 3) target-independent positioning of the transducer, defining a promising alternative for time- and cost-efficient therapeutic systems for neurological diseases. Holograms were designed using the k-space method by time-reversal techniques. MRI scans were used for the target and trajectory selection, while CT scans provided the maps for the acoustic properties of skull, muscle and brain. For the BBBO procedure, a robotic arm was used for the transducer positioning allowing positioning errors below 0.1 mm and 0.1 ⁰, and 0.5-0.6-MPa 513-kHz FUS was applied for 4 minutes in conjunction with microbubbles. For BBBO assessment, T1-MRI Post-FUS was acquired. Contrast-enhanced T1-MRI showed bilateral gadolinium extravasation, observing BBBO at both caudate or putamen structures. For the caudate configuration, both BBBO locations were separated by 13.13 mm with a volume of 91.81 mm
³
, compared to the simulated separation of 9.40 mm with a volume of 124.52 mm
³
. For the putamen configuration, both BBBO locations were separated by 21.74 mm with a volume of 145.38 mm
³
, compared to a simulated separation of 22.32 mm with a volume of 156.42 mm
³
. No radiological damage was observed. This study demonstrates for the first time the feasibility and safety of hologram-assisted neuronavigation-guided-FUS for simultaneous bilateral BBBO in NHP.