Characteristics of Focused Ultrasound Mediated Blood-Brain Barrier Opening in Magnetic Resonance Images.

The blood-brain barrier (BBB) is an obstacle for molecules to pass through from blood to the brain. Focused ultrasound is a new method which temporarily opens the BBB, which makes pharmaceutical delivery or removal of neurodegenerative proteins possible. This study was demonstrated to review our BBB opening procedure with magnetic resonance guided images and find specific patterns in the BBB opening. In this study, we reviewed the procedures and results of two clinical studies on BBB opening using focused ultrasound regarding its safety and clinical efficacy. Magnetic resonance images were also reviewed to discover any specific findings. Two clinical trials showed clinical benefits. All clinical trials demonstrated safe BBB opening, with no specific side effects. Magnetic resonance imaging showed temporary T1 contrast enhancement in the sonication area, verifying the BBB opening. Several low-signal intensity spots were observed in the T2 susceptibility-weighted angiography images, which were also reversible and temporary. Although these spots can be considered as microbleeding, evidence suggests these are not ordinary microbleeding but an indicator for adequate BBB opening. Magnetic resonance images proved safe and efficient BBB opening in humans, using focused ultrasound.

Introduction

Purpose Drug delivery with BBB opening

Study Objective To review focused ultrasound–mediated blood–brain barrier opening procedures using MRI guidance and identify characteristic MRI patterns associated with BBB opening.

Animal model / Human subject Homo sapiens (human), strain: N/A, age: None, sex: None

MRI or image guidance method Magnetic resonance imaging (MR-guided)

Outcomes and Safety

Summary of Outcomes MR‑guided low‑intensity focused ultrasound (MRgFUS) safely and reversibly opened the blood–brain barrier in humans, producing transient T1 contrast enhancement and occasional reversible low‑signal SWAN spots, with clinical benefits including tumor size reduction/stabilization in GBM and reduced Aβ deposition with transient cognitive improvements in AD and no procedure‑related neurological complications. Successful parameters reported were MRgFUS low‑intensity sonications delivered as small 1 cm3 focal targets (GBM) and larger bilateral frontal lobe coverage (mean 21.1±2.7 cm3) with repeated sessions; higher sonication energy produced more SWAN susceptibility spots but most were reversible.

Duration of biological effect 15 months

Safety-related matter All clinical trials reported safe, transient BBB opening with no procedure-related neurological complications or adverse events such as intracerebral hemorrhage, edema, infarction, or systemic/neurological worsening. Transient MRI findings (T1 contrast enhancement and reversible low-signal SWAN spots possibly reflecting minor/temporary blood pooling or microleakage) were observed, and patients reported only discomfort/pain from stereotactic frame fixation and hair shaving.

Brain Region

Visualization unavailable

Ultrasound Parameters

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

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