Abstract
Transcranial Magnetic Stimulation (TMS) is a technique for neuromodulation that can be used as a non-invasive therapy for various neurological disorders. In TMS, a time varying magnetic field generated from an electromagnetic coil placed on the scalp is used to induce an electric field inside the brain. TMS coil geometry plays an important role in determining the focality and depth of penetration of the induced electric field responsible for stimulation. Clinicians and basic scientists are interested in stimulating a localized area of the brain, while minimizing the stimulation of surrounding neural networks. In this paper, a novel coil has been proposed, namely Quadruple Butterfly Coil (QBC) with an improved focality over the commercial Figure-8 coil. Finite element simulations were conducted with both the QBC and the conventional Figure-8 coil. The two coil’s stimulation profiles were assessed with 50 anatomically realistic MRI derived head models. The coils were positioned on the vertex and the scalp over the dorsolateral prefrontal cortex to stimulate the brain. Computer modeling of the coils has been done to determine the parameters of interest-volume of stimulation, maximum electric field, location of maximum electric field and area of stimulation across all 50 head models for both coils.
Highlights
Transcranial Magnetic Stimulation (TMS) is a technique for neuromodulation which has therapeutic effect for neurological disorders such as major depressive disorder, traumatic brain injury (TBI), Parkinson’s disease (PD), and post-traumatic stress disorder (PTSD).[1,2,3,4,5] The time varying magnetic field generated from a TMS coil will induce an electric field and cause depolarization of neurons
The ability to modulate the activity of neural networks noninvasively and relatively painlessly allows researchers to explore brain stimulation as a tool to treat disease with much more ease than previous neuromodulation techniques such as deep brain stimulation (DBS) and electroconvulsive therapy (ECT) have allowed
Results from the Figure-8 coil were included in this paper for the purposes of comparison, since this coil has been widely used in TMS literature and is able to provide a reference for the results from the new Quadruple Butterfly Coil (QBC).[19,20]
Summary
Transcranial Magnetic Stimulation (TMS) is a technique for neuromodulation which has therapeutic effect for neurological disorders such as major depressive disorder, traumatic brain injury (TBI), Parkinson’s disease (PD), and post-traumatic stress disorder (PTSD).[1,2,3,4,5] The time varying magnetic field generated from a TMS coil will induce an electric field and cause depolarization of neurons. Any development of TMS coils that allow for stimulation beyond the resolution of Figure-8 coils will give researchers more opportunities to stimulate specific neural circuits that are identified to be important in neurological disorders. A new coil design namely, Quadruple Butterfly Coil (QBC) has been developed with the main purpose of allowing researchers a finer resolution for stimulation. This new coil aims to decrease the stimulation volume over the cortex and not to achieve deeper brain stimulation as highlighted in previous work.[12] The focality term used in this paper refers to the decrease in volume of stimulation due to the QBC when compared with the Figure-8 coil. These coils were positioned on the vertex of the head and on the area of the scalp over the dorsolateral prefrontal cortex
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