Coil optimisation for transcranial magnetic stimulation in realistic head geometry

Area of Science:

• Neuroscience
• Biomedical Engineering
• Medical Physics

Background:

• Transcranial Magnetic Stimulation (TMS) enables non-invasive cortical stimulation.
• High current and voltage are necessary for TMS pulse intensity, limiting repetition rates and causing coil heating.
• Existing TMS coils face limitations due to thermal constraints and energy inefficiency.

Purpose of the Study:

• To develop methods for optimizing, designing, and manufacturing energy-efficient TMS coils.
• To create coils suitable for realistic head geometries and arbitrary shapes.
• To enhance the overall efficiency of TMS devices.

Main Methods:

• Derived a semi-analytical integration scheme for magnetic field energy computation.
• Utilized a boundary element method to compute induced electric fields.
• Optimized TMS coil design for focal stimulation and introduced a manufacturing method using Litz wire and a custom coil former.

Main Results:

• Designed, manufactured, and validated an optimized TMS coil.
• Simulations showed the new coil requires less than half the power of a commercial figure-of-eight coil.
• Achieved resting motor threshold with reduced capacitor voltage and peak current, indicating higher efficiency.

Conclusions:

• The developed method enables the design of practical TMS coils with significantly higher efficiency than conventional designs.
• This advancement can lead to more effective and potentially less resource-intensive TMS therapies.
• Optimized coil design and manufacturing offer a pathway to improved TMS system performance.