First in-vivo Demonstration of Bilateral Blood-Brain Barrier Opening Using Acoustic Holograms in Mice

Focused ultrasound (FUS) with microbubbles allows for non-invasive targeted drug delivery into the central nervous system (CNS) by temporally and locally disrupting the blood-brain barrier (BBB). However, current FUS technologies are not able to simultaneously target several brain structures. In this work, we open the BBB in two regions in a murine brain using a single-element transducer with a coupled 3D-printed holographic lens, which is designed to simultaneously create two symmetric foci in anesthetized mice in vivo. The proposed approach shows many advantages: (1) simple and low-cost; (2) correction of aberrations due to skull and water cone; and (3) multiple BBB opening (BBBO) locations with only one sonication, becoming a time- and cost-effective therapeutic system for neurological diseases. For the in-vivo experiment, contrast-enhanced, T1-weighted MRI scan was conducted following BBBO, showing gadolinium extravasation at two symmetric focal spots. The two BBBO regions were separated by 3.0 ±0.7 mm ( n=5 mice) compared to 5.3 mm in full-wave simulations. This work shows the capability of bifocal ultrasound generation in separate animals using a unique μCT scan. A bilateral BBBO was achieved with a single sonication using a holographic lens in mice, thus improving the efficiency and defining a new approach for several neurodegenerative diseases targeting symmetric brain structures, e.g. hippocampus, putamen or caudate. This study demonstrates the feasibility of hologram-assisted BBBO for targeted drug delivery in the CNS in symmetric regions in separate hemispheres.