Twin Coil Design Considerations for Depth and Focality in Transcranial Magnetic Stimulation

This paper conducts a comprehensive analysis on the impact of the coil size and the opening angle of twin coils on the stimulation depth and the focality. The finite-element method is utilized to analyze the head-model-inside distributions of the electric field induced by twin coils with various diameters and opening angles. The depth and focality of the electric field are quantified based on the simulation results. It shows that the depth can reach to optimal value by adjusting opening angle. Meanwhile, increasing twin coil size can improve both the depth and the focality. In addition, the experimental results are also given to further validate the conclusion drawn from the computational simulation results. The presented results show significant meanings for researchers and clinicians to design or configure the optimal twin coil for the transcranial magnetic stimulation systems.