Non-invasive write · writes
Focused-ultrasound blood-brain barrier opening is image-guided sonication at low acoustic pressure, delivered together with injected gas-filled microbubbles. The sound makes the microbubbles in the capillaries expand and contract, and the resulting mechanical forces open the blood-brain barrier in the targeted region for a limited time, without open surgery; that opening is what it writes. What it reads is not brain activity: acoustic cavitation feedback and MR-derived temperature during sonication, patient feedback, and afterwards gadolinium-enhanced MRI as a surrogate for barrier permeability.
Focused-ultrasound blood-brain barrier opening is image-guided sonication at low acoustic pressure delivered with injected gas-filled microbubbles. The sound makes the microbubbles in the capillaries expand and contract (stable cavitation); the resulting mechanical forces open the barrier in the targeted region without open surgery. The opening is transient, reversible and repeatable; in a human brain-tumour study, post-sonication enhancement of the target region resolved by 24 hours. A reviewed pressure window of 0.4 to 1.2 MPa opened the barrier safely; higher pressures can trigger damaging inertial cavitation. In one MR-guided patient study, power rose in 5% steps until hydrophones detected sub-harmonic acoustic feedback, with MR thermometry and patient feedback monitored during sonication. In a 220 kHz trial, power rose until an accumulated cavitation dose of 0.4 to 0.65 was reached, and sonication stopped when inertial cavitation was confirmed. Both verified the opening afterwards with gadolinium-enhanced MRI, a surrogate for barrier permeability.
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