A multi-frequency sparse hemispherical ultrasound phased array for microbubble-mediated transcranial therapy and...

Area of Science:

• Biomedical Engineering
• Acoustic Physics
• Neuroscience

Background:

• Focused ultrasound (FUS) phased arrays offer non-invasive brain therapy but often lack frequency versatility for monitoring.
• Multi-frequency capabilities can enhance FUS by allowing variable focal sizes and spectral analysis for imaging.

Purpose of the Study:

• To develop and evaluate a three-frequency sparse hemispherical ultrasound phased array for microbubble-mediated transcranial therapy and simultaneous cavitation mapping.
• To assess the array's electronic beam steering, focal characteristics, and imaging capabilities for brain applications.

Main Methods:

• Construction of a three-frequency (306, 612, 1224 kHz) phased array with a 128-transducer module hemispherical design.
• Evaluation of electronic beam steering, focal size (FWHM), dual-frequency excitation, and multi-foci sonication capabilities.
• Passive acoustic mapping of microbubble clouds and harmonic imaging through the intact skull; in vivo validation in a rat model.

Main Results:

• The array demonstrated effective electronic beam steering and variable focal sizes (0.9-3.1 mm lateral FWHM) at different frequencies.
• Passive acoustic mapping achieved a point spread function FWHM of 0.8-3.5 mm (lateral) and 1.7-11.7 mm (axial).
• The system enabled half and second harmonic imaging through the skull and successfully induced blood-brain barrier opening with cavitation mapping in vivo.

Conclusions:

• The developed multi-frequency FUS phased array provides enhanced versatility for non-invasive brain therapy and monitoring.
• This tool facilitates investigation into optimal non-thermal FUS brain therapy strategies with concurrent microbubble cavitation monitoring.
• The ability to perform multi-frequency imaging and therapy simultaneously opens new avenues for complex FUS applications.