Angle-tuned coils: attractive building blocks for TMS with improved depth-spread performance.

Area of Science:

• Biomedical Engineering
• Neuroscience
• Medical Physics

Background:

• Transcranial magnetic stimulation (TMS) coils traditionally face a depth-spread tradeoff, limiting their effectiveness.
• Existing TMS coil designs often require large head surface areas, hindering applications like multisite stimulation.
• Developing novel coil geometries is crucial for improving TMS performance and expanding its therapeutic and research applications.

Purpose of the Study:

• To introduce a novel angle-tuned ring coil (AT coil) designed to enhance the depth-spread performance of TMS.
• To utilize the AT coil as a building block for high-performance composite coils and multisite TMS systems.
• To overcome the limitations of traditional TMS coils regarding footprint and the depth-spread tradeoff.

Main Methods:

• Theoretical simulation of emitted electric field distributions in spherical and human head models.
• Analysis of depth-spread performance for the proposed angle-tuned coils compared to existing figure-8 coils.
• Experimental validation using field probes and in-vivo animal tests.

Main Results:

• The angle-tuning concept significantly improves coil depth-spread performance with a smaller footprint.
• Composite structures built with AT coils demonstrate leading performance and simplified design/manufacturing.
• The intrinsically small footprint of AT coil systems is ideal for multisite brain stimulation with reduced electric field divergence.

Conclusions:

• The proposed AT coil design offers superior depth-spread performance and a reduced footprint compared to conventional TMS coils.
• AT coils serve as effective building blocks for advanced composite coils and multisite TMS systems.
• This innovation facilitates mechanistic studies of brain networks and novel treatments for neuropsychiatric disorders by enabling precise, multi-region brain stimulation.