Ferromagnetic Components in TMS Coils for Depth and Surface Control
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Solution Overview
Problem
Transcranial magnetic stimulation (TMS) devices face challenges in achieving targeted brain stimulation with minimal side effects due to high surface stimulation and uneven current distribution, leading to undesirable stimulation of untargeted brain regions.
Innovation Solution
Incorporating ferromagnetic components with TMS devices to modify the magnetic field characteristics, reducing surface stimulation intensity and improving penetration depth while maintaining or increasing the intensity in the target brain area, and redistributing return currents to minimize side effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a rapidly changing magnetic field is applied to stimulate neurons at depth, then treatment depth is improved, but surface stimulation intensity increases causing side effects
Solution Approach 1:
A ferromagnetic component is introduced as an intermediary element between the treatment coil and the target brain tissue. This component modifies the magnetic field distribution by concentrating flux lines toward the target area while shielding surface regions, thereby enabling deep penetration without excessive surface stimulation
Solution Approach 2:
The magnetic field distribution is made non-uniform through the ferromagnetic component, creating different field characteristics in different spatial zones: high intensity and focality at the target depth, and reduced intensity at surface regions, thus addressing the harmful surface stimulation locally
2Measurement precision
If the magnetic field is concentrated to improve focality, then treatment precision is improved, but penetration depth decreases
Solution Approach 1:
The ferromagnetic component extends the field interaction into a third spatial dimension by creating a vertically oriented flux concentration path through the scalp and skull layers to the target cortex, allowing focality and penetration depth to be optimized simultaneously through spatial field shaping
3Quantity of substance
If return currents are spread over a wide surface area, then current distribution is improved, but return current concentration increases leading to higher side effects
Solution Approach 1:
The ferromagnetic component acts as a flux mediator that redirects return current paths away from sensitive surface regions and toward less sensitive areas, reducing the harmful effects while maintaining overall current distribution
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The use of ferromagnetic components in TMS devices enhances the magnetic field's focus and penetration depth, reducing side effects by spreading return currents and maintaining or improving treatment efficiency, thus providing more targeted and effective brain stimulation.
Implementation Method 1
TMS devices may include one or more treatment coils and one or more ferromagnetic components that are configured to be disposed proximate to corresponding ones of the one or more treatment coils
Implementation Method 2
TMS typically uses a rapidly changing (e.g., pulsed) magnetic field to induce a current in a nerve cell
Data Source
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Figure 1B
Figure 2A
AI summary
A TMS device may include treatment coils and ferromagnetic components that are configured to be disposed proximate to corresponding ones of the treatment coils. The treatment coils and ferromagnetic components of the TMS device may cooperatively generate a magnetic field that exhibits one or more characteristics that differ from those of a magnetic field that is generated by the treatment coils alone. For example, the magnetic field may exhibit lower induced electrical stimulation intensity in the cranial nerves, while substantially maintaining a penetration depth into the subject's brain. In another example, the magnetic field may exhibit increased penetration depth into the subject's brain, while substantially maintaining induced electrical stimulation intensity in the cranial nerves. The TMS device may be configured to be adjustable and/or reconfigurable, for instance with respect to the anatomy of a subject (e.g., to the shape of the subject's head).