Computational Study Toward Deep Transcranial Magnetic Stimulation Using Coaxial Circular Coils.

Area of Science:

• Neuroscience
• Biomedical Engineering
• Medical Physics

Background:

• Transcranial magnetic stimulation (TMS) traditionally targets superficial brain regions.
• Deep brain stimulation is crucial for treating various neurological and psychiatric disorders.
• Current TMS coil designs face limitations in effectively stimulating deeper brain structures.

Purpose of the Study:

• To explore the potential of coaxial circular coils for deep brain stimulation.
• To investigate methods for increasing electrical field penetration depth in the brain.
• To reduce electrical fields in superficial cortical regions during deep brain stimulation.

Main Methods:

• Application of Halo coil, Halo-circular assembly (HCA) coil, and Halo coil with two circular coils (HTC coil) on a 36-tissue head model.
• Utilizing a 3-D impedance method to compute magnetic flux density and induced electric fields.
• Analysis of field distributions under different current flow conditions in the coils.

Main Results:

• The HCA coil increased field penetration depth but reduced focality.
• The HTC coil, with opposing currents in adjacent coils, generated overthreshold electric fields in deep brain regions.
• The HTC coil produced subthreshold fields in superficial cortical areas, indicating targeted deep stimulation.

Conclusions:

• The HTC coil offers a flexible platform for deep brain stimulation by adjusting coil parameters and currents.
• It achieves a favorable ratio of deep region field to shallow area field.
• The HTC coil shows promise as a new tool for deep transcranial magnetic stimulation in research and clinical applications for brain disorders.