Three-dimensional transcranial ultrasound imaging of microbubble clouds using a sparse hemispherical array.

Area of Science:

• Neurosurgery
• Biomedical Engineering
• Acoustic Imaging

Background:

• Focused ultrasound (FUS) interventions in the brain show promise but require spatial monitoring of microbubble interactions.
• Current technologies lack the ability to spatially monitor microbubble activity, hindering safe clinical translation.
• Passive acoustic mapping offers a potential solution for monitoring microbubble emissions and bioeffects.

Purpose of the Study:

• To develop and evaluate a system for passive acoustic monitoring of microbubble activity during transcranial FUS treatments.
• To integrate a receiver array with an existing FUS therapy array for simultaneous treatment delivery and monitoring.
• To assess the system's feasibility for real-time imaging of bubble clouds and cavitation dynamics.

Main Methods:

• Integration of a hemispherical receiver array with a transcranial FUS therapy array.
• Construction and characterization of a 128-element receiver array.
• Feasibility testing using ex vivo human skull and in vivo experiments to map bubble emissions.

Main Results:

• The system successfully monitored bubble emissions, including single bubble events, through ex vivo human skull.
• Achieved lateral resolution of 1.25-2 mm and axial resolution of 2-3.5 mm.
• Demonstrated mapping of bubble activity at pressures below the blood-brain barrier disruption threshold in vivo.

Conclusions:

• The developed system provides a feasible method for imaging microbubble activity during cavitation-mediated FUS brain treatments.
• This technology is critical for enhancing the safety and efficacy of FUS interventions.
• The system's resolution is comparable to MRI-based temperature monitoring, offering valuable real-time feedback.