Feasibility of Ultrasonic Heating through Skull Phantom Using Single-element Transducer

Area of Science:

• Neurosurgery
• Biomedical Engineering
• Acoustic Physics

Background:

• Transcranial focused ultrasound (FUS) enables noninvasive neurosurgery.
• This study evaluates single-element transducers at 0.4 and 1.1 MHz.
• Three-dimensional (3D) printed thermoplastic skull phantoms were utilized.

Purpose of the Study:

• To assess the heating capability of focused ultrasound transducers through realistic skull phantoms.
• To determine the efficacy of different frequencies (0.4 MHz and 1.1 MHz) for trans-skull energy delivery.
• To evaluate the potential of 3D printed skull phantoms for preclinical FUS research.

Main Methods:

• 3D printed thermoplastic skull phantoms were created from patient CT scans.
• An in-house agar-based gel mimicked brain tissue.
• Transmission-through attenuation measurements guided material selection.
• Thermometry at the focal spot was performed using thermocouples during sonication through water and phantoms.

Main Results:

• The 0.4 MHz transducer reduced focal temperature change to <20% of free-field levels.
• The 1.1 MHz transducer showed minimal to no focal temperature change.
• The 0.4 MHz transducer demonstrated better, though inefficient, trans-skull transmission.

Conclusions:

• Single-element transducers are insufficient for effective trans-skull FUS due to high skull attenuation.
• Correction techniques, such as those used with phased arrays, are necessary to overcome energy losses.
• The developed 3D printed phantom is a valuable, cost-effective tool for preclinical trans-skull FUS studies.