Theoretical Analysis and Design of an Innovative Coil Structure for Transcranial Magnetic Stimulation

Abstract

Previous research showed that pulsed functional magnetic stimulation can activate brain tissue with optimum intensity and frequency. Conventional stimulation coils are always set as a figure-8 type or Helmholtz. However, the magnetic fields generated by these coils are uniform around the target, and their magnetic stimulation performance still needs improvement. In this paper, a novel type of stimulation coil is proposed to shrink the irritative zone and strengthen the stimulation intensity. Furthermore, the electromagnetic field distribution is calculated and measured. Based on numerical simulations, the proposed coil is compared to traditional coil types. Moreover, the influential factors, such as the diameter and the intersection angle, are also analyzed. It was demonstrated that the proposed coil has a better performance in comparison with the figure-8 coil. Thus, this work suggests a new way to design stimulation coils for transcranial magnetic stimulation.

Devices and Technology in Transcranial Magnetic Stimulation: A Systematic Review

“…This can be improved by incorporating additional passive shielding materials with certain shapes close to the focalization zone [ 44 ]. The use of a double upward–downward butterfly coil has proven to produce larger focality compared with the FoE coil under similar conditions [ 69 ]. Applications of this new coil range from the same mentioned for the FoE coils (FBM, MEP, rehabilitation, etc.)…”

“…The necessity of validated therapy strategies that are fully effective for deep-brain TMS should encourage designers to propose further developments in this specific area. Coils with improved focality have been the objective of certain groups with promising results [ 69 , 100 ]; however, more emphasis on coil optimization should permit much better focality with smaller lateral lobes for FBM and MEP applications [ 44 ].…”

“…There are important aspects to consider when analyzing the modeling paradigms for TMS, for example, the required computer capabilities, the use of more reliable 3D modeling software based on medical images, and the required spatial/temporal resolutions of the final model. Current strategies propose optimization techniques for certain coils in order to provide increased focality with larger field intensities [ 69 ] by using geometry variations [ 98 ] and coils shielding (RQ5) [ 44 , 100 ]. The current most used approach for 3D modeling is based on the finite element method [ 43 , 53 , 88 ], which consumes large amounts of computational resources.…”