Design of a Dynamic Transcranial Magnetic Stimulation Coil System

Abstract

To study the brain activity at the whole-head range, transcranial magnetic stimulation (TMS) researchers need to investigate brain activity over the whole head at multiple locations. In the past, this has been accomplished with multiple single TMS coils that achieve quasi whole-head array stimulation. However, these designs have low resolution and are difficult to position and control over the skull. In this study, we propose a new dynamic whole-head TMS mesh coil system. This system was constructed using several sagittal and coronal directional wires. Using both simulation and real experimental data, we show that by varying the current direction and strength of each wire, this new coil system can form both circular coils or figure-eight coils that have the same features as traditional TMS coils. Further, our new system is superior to current coil systems because stimulation parameters such as size, type, location, and timing of stimulation can be dynamically controlled within a single experiment.

Consensus Recommendations for the Clinical Application of Repetitive Transcranial Magnetic Stimulation (rTMS) in the Treatment of Depression

“…The effect size for the FDA-cleared * protocols with rTMS as monotherapy was in the medium range, but there is potential to improve efficacy. Evidence for potential improvements has emerged in studies that optimized rTMS pulse and train parameters, 29 developed new coils, 30 and combined therapy paradigms (eg, coupled rTMS with psychotherapy and/or pharmacotherapy). 31 However, these approaches are investigational at present.…”

Devices and Technology in Transcranial Magnetic Stimulation: A Systematic Review

“…The use of multichannel excitation systems was a logical step after the proposal of coil arrays [ 82 ] and meshed configurations [ 83 ]. Most of these applications are composed of N independent stimulators synchronized by a common digital controller [ 84 ].…”

“…This mesh can be driven using a multi-channel system that would inject the electrical current into individual wires to form a customized shape of excitation, including the shape of classical circular and FoE coils. Although this development produces the equivalent effect of different types of coils [ 83 ], it is still under research because of the technical difficulties associated with a multichannel stimulator capable of driving this configuration. Having multiple coils placed very close to each other produces mutual inductances that modify the design parameters and may affect the operation of the excitation circuit [ 85 ].…”

The development and modelling of devices and paradigms for transcranial magnetic stimulation

“…Wang, Chen, Guo, & Wang, 2005). Alternatively, Ge et al use a grid of vertical and horizontal lines mapped onto a head instead of loops (Ge, Wang, Tang, Xiao, & Wu, 2012). A ring current can be generated by controlling the current of two vertical and two horizontal lines appropriately.…”