Acoustic hologram-enabled simultaneous multi-target blood-brain barrier opening (AH-SiMBO).

Focused ultrasound-induced blood-brain barrier (BBB) opening enables targeted brain drug delivery. However, achieving simultaneous multi-target BBB opening across various depths and regions remains challenging and cost-prohibitive. Here we address these challenges by employing encoded acoustic holograms combined with a single-element plane-wave transducer to generate precise focused acoustic fields. The holograms designed using an iterative angular spectrum approach and fabricated via 3D printing produce single or multiple foci at different depths and regions, which are confirmed by simulations and hydrophone-based measurements. Beam steering capability is demonstrated and further validated in vivo. We design a hologram with less than 10% variation in amplitude across different foci and successfully achieve biplane multi-target ( ≥3) BBB opening in the bilateral hippocampus and medial septum of mice in a single sonication session with no adverse effects. This innovative acoustic holographic approach for simultaneous multi-target BBB opening is time-efficient and cost-effective, presenting broad potential applications in brain drug delivery and neuromodulation.

Introduction

Purpose Drug delivery with BBB opening

Study Objective To develop and validate an encoded acoustic hologram method coupled with a single-element plane-wave transducer for simultaneous multi-target, multi-plane blood-brain barrier opening in mice.

Animal model / Human subject Mus musculus (mouse), C57BL/6, 6–10 weeks old, male

Disease model Healthy

MRI or image guidance method Stereotactic frame (ear and bite bars) with targeting referenced to cranial bregma and lambda landmarks

Targeted brain region(s) Bilateral Hippocampus And Medial Septum

Cargo name and characteristics Evans Blue (EB) dye — small-molecule, albumin-binding dye used as tracer to confirm BBB opening (2%, 3.33 mL kg−1, i.v.); Gadoteric acid — gadolinium-based MRI contrast agent (small-molecule Gd chelate, 0.1 mol L−1, i.v.)

Route of administration intravenous

Outcomes and Safety

Summary of Outcomes Acoustic-hologram–guided focused ultrasound produced simultaneous biplane multi-target BBB opening in mice (bilateral hippocampus and medial septum) confirmed by contrast-enhanced MRI and Evans Blue leakage, with no histological evidence of edema, hemorrhage, cell damage, or inflammation. Successful acoustic conditions included holograms with focal lengths of ~10, 20, and 30 mm (with effective beam steering via axial translations 5–20 mm and rotations ≤9° maintaining focal shape), amplitude-modulated multi-focus designs with ≤10% inter-focal pressure variation, and sonication at derated peak negative pressures ≈0.28–0.33 MPa (Isppa ~5.6 W·cm⁻2, Ispta ~56 mW·cm⁻2).

Safety-related matter The authors report no adverse effects — histological analyses (H&E, Iba1, TUNEL) and T2-weighted MRI showed no edema, hemorrhage, cellular damage, or inflammation after AH-SiMBO, and the applied acoustic intensities were well below FDA safety limits.

Brain Region

Ultrasound Parameters

Ultrasound instrument Single-element plane-wave transducer TP1.5P30NF (Guangzhou Doppler Electronic Technologies, Guangzhou, China); transducer aperture/diameter: None

FUS Frequency 1.5 MHz

FUS Pressure 0.35 MPa, 0.37 MPa, 0.41 MPa

FUS Mode pulsed

Pulse duration 10 ms

Duration of a single FUS session 2 minutes (120 s)

Focal Characteristics Focal depth: None; Focal length: None; Aperture size: None

Treatment frequency single

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