Optimal Magnetic Coil Shape Design for Neural Stimulation
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Solution Overview
Problem
Current magnetic stimulation coils are limited in their ability to design optimal shapes that can efficiently induce a desired electric field at specific locations within a patient without interfering with neighboring areas, and they do not consider tissue conductivity heterogeneity, making it difficult to control stimulation effectively at multiple locations.
Innovation Solution
The method uses Lagrange multipliers to determine an optimal magnetic coil shape by modeling electrical properties of the stimulation location and surrounding tissues, identifying constraints, and calculating electromagnetic effects from current elements with varying orientations to ensure global optimality and efficient stimulation at multiple locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional optimization studies assume a general (round or elliptical) shape of the optimal coil and alter limited parameters, then the optimization process is simplified, but there is no guarantee that the coil design found is globally optimal
Solution Approach 1:
The patent transforms the coil design problem from assuming a general shape with limited parameters to determining the optimal shape by calculating the orientation of current elements at multiple locations. This involves changing the parameters from simple geometric dimensions to complex spatial orientations determined through optimization algorithms, thereby achieving globally optimal coil designs rather than locally optimal solutions based on assumed shapes.
2Device complexity
If traditional magnetic stimulation coils are designed without considering tissue conductivity heterogeneity, then the design process is simplified, but the ability to control stimulation at multiple locations is limited
Solution Approach 1:
The patent applies local quality by considering the heterogeneity of tissue conductivity at different locations within the patient's body. The optimization algorithm calculates the orientation of current elements based on the specific conductivity properties of tissues at each location, allowing the coil design to adapt to local tissue characteristics and achieve effective stimulation at multiple distinct locations with different conductivity profiles.
3Measurement precision
If a coil design aims to induce a desired electric field at a specified stimulation location, then stimulation control at that location is improved, but the ability to stimulate multiple locations simultaneously is reduced
Solution Approach 1:
The patent achieves multi-functionality by designing a coil that can simultaneously induce desired electric fields at multiple stimulation locations. The optimization algorithm determines the orientation of current elements to satisfy multiple constraints concurrently, enabling the single coil design to perform multiple stimulation functions at different locations rather than requiring separate coils for each location.
4Reliability
If the orientation of current elements is optimized to satisfy constraints at stimulation locations, then stimulation effectiveness is improved, but the computational complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the continuous coil into multiple discrete current element locations. The optimization algorithm then determines the orientation of current elements at each discrete location independently based on the constraints at stimulation locations. This segmentation transforms the complex continuous optimization problem into a series of manageable discrete optimization steps, reducing computational complexity while maintaining stimulation effectiveness.
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
This approach allows for the design of a globally optimal magnetic coil that can simultaneously stimulate multiple locations with precise control over the electric field, minimizing root mean square di/dt values and ensuring physical realizability, thereby enhancing the effectiveness and safety of magnetic stimulation.
Implementation Method 1
passing a time varying current through a coil. As known to those skilled in the art, the time varying current creates a time varying magnetic field in the area near the coil. By placing the coil near or in contact with a patient, the time varying magnetic field passes through at least a portion of the patient. The time varying magnetic field induces an electrical field which in turn causes an electrical current (or eddy current) within the patient.
Implementation Method 2
The eddy current interacts with and is capable of stimulating the patient's neural tissue. For example, if the electrical field has a large negative gradient of sufficient duration, it can cause nerve fibers in the patient to depolarize and initiate an action potential. If the electrical field has a large positive gradient, it can cause nerve fibers to hyperpolarize, and may even be able to block action potential propagation.
Data Source
AI summary
A method of determining an optimal coil shape for use in magnetic stimulation includes identifying a stimulation location and a constraint at the stimulation location. A first electromagnetic effect at the stimulation location is determined. The first electromagnetic effect is induced by a first electrical quantity assigned to a first current element at a first current element location with a first orientation. A second electromagnetic effect at the stimulation location is also determined. The second electromagnetic effect is induced by a second electrical quantity assigned to a second current element at the first current element location with a second orientation. Based on the first electromagnetic effect and the second electromagnetic effect, an optimal orientation of a current element at the first current element location is determined. The optimal orientation is such that the constraint is satisfied. Repeating the process at a plurality of locations yields the optimal coil shape.