Biology subjects

Bagherzadeh, H.

Publications and source records attributed to Bagherzadeh, H..

2 recordsLinked to original sources

bioRxiv2021

Angle-Tuned Coils: Enabling Building Blocks for High Performance and Multisite TMS Systems

Coordinated whole-brain neural dynamics are essential for proper control of the functionality of different brain systems. Multisite simultaneous or sequential stimulations may provide tools for mechanistic studies of brain functions and the treatment of neuropsychiatric disorders. Conventional circular and figure-8 Transcranial Magnetic Stimulation (TMS) coils occupy a large footprint, and it is difficult to reach desired multiple stimulation locations with close proximity for comprehensive multisite stimulations. These conventional coils, limited by the depth-spread tradeoff rule, also lack the required focality for targeted stimulations. In this work, we propose and demonstrate angle-tuned TMS (AT) coils with an intrinsically reduced footprint with their geometric arrangements of stacking and angle tuning. The stimulation depth can be adjusted with the coil stacking number, and the field spread can be reduced by increasing the tilted wire-wrapping angle of the coils. With either smaller or larger diameter coils than a standard commercial figure-8 coil, we show, theoretically and experimentally, improved field decay rate and field intensity, and the reduced field spread spot size at different stimulation depths. These results indicate that the proposed novel coil establishes a better depth-spread tradeoff curve than the conventional circular and figure-8 coils. This coil design has a simple and single element structure and provides a promising solution for an improved multisite brain stimulation performance and serves as the building block of more complex coils for further depth-spread improvements.

neuroscience↗

bioRxiv2019

Angle-tuned Coil: A Focal Spot-size Adjustable Transcranial Magnetic Stimulator

BackgroundConventional transcranial magnetic stimulation (TMS) coils are limited by the depth-focality tradeoff rule and the emission field intensity from coils with either small or large apertures will diverge quickly at less than one aperture diameter distance away from the coil. To utilize a better depth-focality tradeoff rule and accomplish deep and focused stimulation, a new approach needs to be employed.\n\nObjectivesWe report a new TMS coil design that can deliver deep and spot size adjustable stimulation to deep brain regions.\n\nMethodsIn our design, we introduce a magnetic core at the center of a coil to help confine the magnetic field and prevent leakage. We further tilted the wire wrapping angle of the coil to break its ring symmetry and accomplish tunable focusing by adjusting the tilting angle.\n\nResultsBy comparing the electric field decay curves of five types of coils, our results concluded the proposed novel method to improve the coils depth-focality profile. Both theoretical calculations and experimental data collectively demonstrated that by using a larger tilting angle, we were able to accomplish a more tightly focused stimulation at any distance away from the coil.\n\nConclusionEnlarging the tilting angle of the coil wire wrapping and applying magnetic core significantly improved the spatial resolution of the field without inducing considerable effect on field decay speed. Our novel TMS coil design plots a new curve in the depth-focality profile with better performance than the existing conventional coil designs in the tradeoff rule.

bioengineering↗