Development of Focused Transcranial Magnetic Stimulation for Rodents by Copper-Array Shields

Area of Science:

• Neuroscience
• Biomedical Engineering
• Physics

Background:

• Transcranial magnetic stimulation (TMS) is a prevalent noninvasive brain stimulation technique used for diagnosing and treating neurological conditions like stroke and neuropathic pain.
• Current TMS devices lack the ability to deliver a focused electric field to specific, deep brain penetration depths, limiting their therapeutic efficacy for disorders originating in these areas.

Purpose of the Study:

• To develop a novel magnetic shield for achieving noninvasive, focused transcranial magnetic stimulation (TMS) for deep brain targets.
• To overcome the limitations of existing TMS technology in delivering precise electric fields to targeted depths.

Main Methods:

• A magnetic shield composed of multi-layered copper ring arrays was designed and simulated.
• The shield utilizes induced currents to generate counter magnetic fields, focusing the TMS.
• A two-pole stimulator system was experimentally set up and verified with device simulations and transient magnetic field probe measurements.

Main Results:

• The magnetic shield successfully achieved magnetic focusing without significant loss of throughput.
• Experimental measurements confirmed a tightly focused spot with a diameter smaller than 5mm.
• The designed shield demonstrated the capability to produce a focused field distribution with enhanced strength at a depth of 7.5mm, suitable for targeting deep brain structures.

Conclusions:

• The developed magnetic shield represents a significant advancement in noninvasive brain stimulation technology.
• This focused TMS approach can effectively target deep and critical regions of the brain, potentially improving treatment outcomes for various neurological disorders.
• The geometric design of the copper ring arrays is crucial for achieving precise focal spot characteristics and effective field enhancement at desired depths.