Flexible TMS coil for reducing inter-individual variabilities in clinical use

摘要

Transcranial Magnetic Stimulation (TMS) is a painless and noninvasive procedure for treating neurological and psychiatric brain disorders. Coils matched with the target curvatures exhibit optimized properties. However, patients have different head topologies, which makes it difficult for a rigid coil to fit all patients. In this study, we developed a rubber-like flexible coil that can be shaped into different geometries according to the target curvatures, greatly reducing the challenges of inter-individual variabilities in clinical use, and investigated the influence of bending on the electromagnetic and mechanical characterization of this coil. The magnetic field distribution was calculated based on the Ampere's law with Maxwell's addition. The coil efficiency, was simulated using custom-made software based on scalar potential finite difference (SPFD) methods. We measured the magnetic flux induced by our prototype with a search coil. The induced Lorentz force of the coil was calculated based on Ampere's force law, and measured with a pressure sensor. Fatigue analysis was carried out with ANSYS both on external bending force and Lorentz force. The results show the eddy current density induced by the flexible coil is significantly stronger than the figure-8 coil and butterfly coil in most cases. And human hand bending force (less than 1 k N) and pressure (～0.1 MPa) caused by the Lorentz force lead to a sufficiently long coil lifetime.