Design of transcranial magnetic stimulation coils with optimal trade-off between depth, focality, and energy

Gomez, Luis J.; Goetz, Stefan M.; Peterchev, Angel V.

doi:10.1088/1741-2552/aac967

Cited by 86 publications

(57 citation statements)

References 47 publications

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“…This circuit characterization lays the groundwork for understanding how unilateral perturbations may contribute to changes observed in humans using noninvasive imaging techniques. For example, if the phenomenon we describe is involved in beneficial recovery, interventions such as rTMS can be designed to speed up or otherwise enhance recovery by targeting deeper cortical layers (36). Understanding the circuit level changes may enhance our ability to aid patients’ recovery from stroke or amputation by providing a guide for more specific, targeted interventions.…”

Section: Discussionmentioning

confidence: 99%

Interhemispheric plasticity is mediated by maximal potentiation of callosal inputs

Petrus

Saar

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Central or peripheral injury causes reorganization of the brain’s connections and functions. A striking change observed after unilateral stroke or amputation is a recruitment of bilateral cortical responses to sensation or movement of the unaffected peripheral area. The mechanisms underlying this phenomenon are described in a mouse model of unilateral whisker deprivation. Stimulation of intact whiskers yields a bilateral blood-oxygen-level−dependent fMRI response in somatosensory barrel cortex. Whole-cell electrophysiology demonstrated that the intact barrel cortex selectively strengthens callosal synapses to layer 5 neurons in the deprived cortex. These synapses have larger AMPA receptor- and NMDA receptor-mediated events. These factors contribute to a maximally potentiated callosal synapse. This potentiation occludes long-term potentiation, which could be rescued, to some extent, with prior long-term depression induction. Excitability and excitation/inhibition balance were altered in a manner consistent with cell-specific callosal changes and support a shift in the overall state of the cortex. This is a demonstration of a cell-specific, synaptic mechanism underlying interhemispheric cortical reorganization.

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Section: Discussionmentioning

confidence: 99%

Interhemispheric plasticity is mediated by maximal potentiation of callosal inputs

Petrus

Saar

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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“…The target region, most commonly the DLPFC for depression, is the area of cortex where the induced electrical field is maximal, and successful targeting depends on accurate surface placement of the TMS coil and coil geometry. One of the greatest challenges in targeting derives from a fundamental property of coil design: greater depth, achieved by larger dimensions of a coil, results in a less focal electrical field [ 46 •]. While the figure-8 coil design, the most commonly used coil in clinical TMS, significantly improved focality, the so-called depth-focality trade-off remains an important limitation with depth of stimulation around 2–3 cm [ 47 ].…”

Section: Technical Aspects Of Tmsmentioning

confidence: 99%

Repetitive Transcranial Magnetic Stimulation for Treatment-Resistant Depression: Recent Critical Advances in Patient Care

Cosmo

Zandvakili

Petrosino

et al. 2021

Curr Treat Options Psych

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Purpose Transcranial magnetic stimulation (TMS) is an evidence-based treatment for pharmacoresistant major depressive disorder (MDD). In the last decade, the field has seen significant advances in the understanding and use of this new technology. This review aims to describe the large, randomized controlled studies leading to the modern use of rTMS for MDD. It also includes a special section briefly discussing the use of these technologies during the COVID-19 pandemic. Recent findings Several new approaches and technologies are emerging in this field, including novel approaches to reduce treatment time and potentially yield new approaches to optimize and maximize clinical outcomes. Of these, theta burst TMS now has evidence indicating it is non-inferior to standard TMS and provides significant advantages in administration. Recent studies also indicate that neuroimaging and related approaches may be able to improve TMS targeting methods and potentially identify those patients most likely to respond to stimulation. Summary While new data is promising, significant research remains to be done to individualize and optimize TMS procedures. Emerging new approaches, such as accelerated TMS and advanced targeting methods, require additional replication and demonstration of real-world clinical utility. Cautious administration of TMS during the pandemic is possible with careful attention to safety procedures.

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“…(In SimNIBS v2.0 this mesh was updated with one having nearly doubled resolution; however, we employed the lower-resolution version since it enables more barycentric refinements while maintaining computational tractability.) The mesh consisted of five homogenous compartments including white/gray matter (WM/GM), CSF, skull, and skin with conductivity of 0.126, 0.276, 1.65, 0.01 and 0.465 S/m, respectively [52]. Starting from the SimNIBS v1.0 example mesh, we generated refined meshes, each time by subdividing each tetrahedron of the earlier mesh into eight equal sized tetrahedrons using the GMSH 'refine by splitting' option [50].…”

Section: Head Modelingmentioning

confidence: 99%

Conditions for numerically accurate TMS electric field simulation

2020

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Background: Computational simulations of the E-field induced by transcranial magnetic stimulation (TMS) are increasingly used to understand its mechanisms and to inform its administration. However, characterization of the accuracy of the simulation methods and the factors that affect it is lacking. Objective: To ensure the accuracy of TMS E-field simulations, we systematically quantify their numerical error and provide guidelines for their setup. Method: We benchmark the accuracy of computational approaches that are commonly used for TMS Efield simulations, including the finite element method (FEM) with and without superconvergent patch recovery (SPR), boundary element method (BEM), finite difference method (FDM), and coil modeling methods. Results: To achieve cortical E-field error levels below 2%, the commonly used FDM and 1st order FEM require meshes with an average edge length below 0.4 mm, 1st order SPR-FEM requires edge lengths below 0.8 mm, and BEM and 2nd (or higher) order FEM require edge lengths below 2.9 mm. Coil models employing magnetic and current dipoles require at least 200 and 3000 dipoles, respectively. For thick solid-conductor coils and frequencies above 3 kHz, winding eddy currents may have to be modeled. Conclusion: BEM, FDM, and FEM all converge to the same solution. Compared to the common FDM and 1st order FEM approaches, BEM and 2nd (or higher) order FEM require significantly lower mesh densities to achieve the same error level. In some cases, coil winding eddy-currents must be modeled. Both electric current dipole and magnetic dipole models of the coil current can be accurate with sufficiently fine discretization.

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Design of transcranial magnetic stimulation coils with optimal trade-off between depth, focality, and energy

Cited by 86 publications

References 47 publications

Interhemispheric plasticity is mediated by maximal potentiation of callosal inputs

Interhemispheric plasticity is mediated by maximal potentiation of callosal inputs

Repetitive Transcranial Magnetic Stimulation for Treatment-Resistant Depression: Recent Critical Advances in Patient Care

Conditions for numerically accurate TMS electric field simulation

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