Effect of coil size on transcranial magnetic stimulation (TMS) focality

Bagherzadeh, Hedyeh; Choa, Fow-Sen

doi:10.1117/12.2524503

Cited by 5 publications

(4 citation statements)

References 10 publications

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“…Various TMS coil geometries have been adopted along with additional methods for field divergence improvement [19][20][21][22][23][24][25]. To optimize the TMS coil's electric field distribution, theoretical analysis based on analytical models [26][27][28][29] or numerical simulations using either finite element method (FEM) or finite difference method [30][31][32][33][34][35][36][37] have been implemented along with additional physical and experimental verifications [38][39][40] and rodent experiments [41][42][43]. The coil performance is generally governed by a depth¬-spread tradeoff [25].…”

Section: Introductionmentioning

confidence: 99%

Angle-tuned coils: attractive building blocks for TMS with improved depth-spread performance

et al. 2022

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Objective: A novel angle-tuned ring coil is proposed for improving the depth-spread performance of Transcranial Magnetic Stimulation (TMS) coils and serve as the building blocks for high-performance composite coils and multisite TMS systems Approach: Improving depth-spread performance by reducing field divergence through creating a more elliptical emitted field distribution from the coil. To accomplish that, instead of enriching the Fourier components along the planarized (x-y) directions, which requires different arrays to occupy large brain surface areas, we worked along the radial (z) direction by using tilted coil angles and stacking coil numbers to reduce the divergence of the emitted near field without occupying large head surface areas. The emitted electric field distributions were theoretically simulated in spherical and real human head models to analyze the depth-spread performance of proposed coils and compare with existing figure-8 coils. The results were then experimentally validated with field probes and in-vivo animal tests. Main Results: The proposed "angle-tuning" concept improves the depth-spread performance of individual coils with a significantly smaller footprint than existing and proposed coils. For composite structures, using the proposed coils as basic building blocks simplifies the design and manufacturing process and helps accomplish a leading depth-spread performance. In addition, the footprint of the proposed system is intrinsically small, making them suitable for multisite stimulations of inter and intra-hemispheric brain regions with an improved spread and less electric field divergence. Significance: Few brain functions are operated by isolated single brain regions but rather by coordinated networks involving multiple brain regions. Simultaneous or sequential multisite stimulations may provide tools for mechanistic studies of brain functions and the treatment of neuropsychiatric disorders. The proposed AT coil goes beyond the traditional depth-spread tradeoff rule of TMS coils, which provides the possibility of building new composite structures and new multisite TMS tools.

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Section: Introductionmentioning

confidence: 99%

Angle-tuned coils: attractive building blocks for TMS with improved depth-spread performance

et al. 2022

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“…Several previous works have been focused on introducing new coils with improved depth-focality performance and reduced spot size. These were done through analytical models or numerical simulations using either the finite element method (FEM) or finite difference method (FDM) [15,[18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

“…Several studies reported the designs of rodent-specific TMS coils [ 23 , 27 , 28 ]. In general, these coils either stimulate a large portion of the rodent brain or the induced field is too weak to reach suprathreshold brain stimulation, as Bagherzadeh and Choa [ 21 ] pointed out. High permeability materials can enhance magnetic field strength and have been applied to design TMS coils for humans [ 29 , 30 ].…”

Section: Introductionmentioning

confidence: 99%

High-Performance Magnetic-core Coils for Targeted Rodent Brain Stimulations

Bagherzadeh

Meng

et al. 2022

BME Front

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Objective and Impact Statement. There is a need to develop rodent coils capable of targeted brain stimulation for treating neuropsychiatric disorders and understanding brain mechanisms. We describe a novel rodent coil design to improve the focality for targeted stimulations in small rodent brains. Introduction. Transcranial magnetic stimulation (TMS) is becoming increasingly important for treating neuropsychiatric disorders and understanding brain mechanisms. Preclinical studies permit invasive manipulations and are essential for the mechanistic understanding of TMS effects and explorations of therapeutic outcomes in disease models. However, existing TMS tools lack focality for targeted stimulations. Notably, there has been limited fundamental research on developing coils capable of focal stimulation at deep brain regions on small animals like rodents. Methods. In this study, ferromagnetic cores are added to a novel angle-tuned coil design to enhance the coil performance regarding penetration depth and focality. Numerical simulations and experimental electric field measurements were conducted to optimize the coil design. Results. The proposed coil system demonstrated a significantly smaller stimulation spot size and enhanced electric field decay rate in comparison to existing coils. Adding the ferromagnetic core reduces the energy requirements up to 60% for rodent brain stimulation. The simulated results are validated with experimental measurements and demonstration of suprathreshold rodent limb excitation through targeted motor cortex activation. Conclusion. The newly developed coils are suitable tools for focal stimulations of the rodent brain due to their smaller stimulation spot size and improved electric field decay rate.

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“…A variety of TMS coil geometries have been adopted along with additional methods for field divergence improvement [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] . To optimize the design of TMS coil's electric field distribution, theoretical analysis based on analytical models 12,[29][30][31][32] or numerical simulations using either finite element method (FEM) or finite difference method (FDM) [33][34][35][36][37][38][39][40][41][42] have been implemented along with additional physical and experimental verifications [43][44][45] . In general, the coil performance is governed by a depth-spread tradeoff 27 .…”

Section: Introductionmentioning

confidence: 99%

Angle-Tuned TMS Coils: Building Blocks for Brain Stimulation with Improved Depth-Spread Performance

Bagherzadeh

Meng

Deng

et al. 2021

Preprint

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Objective: A novel angle-tuned ring coil is proposed for improving the depth-spread performance of Transcranial Magnetic Stimulation (TMS) coils and serve as the building blocks for high-performance composite coils and multisite TMS systems. Approach: Improving depth-spread performance by reducing field divergence through creating a more elliptical emitted field distribution from the coil. To accomplish that, instead of enriching the Fourier components along the planarized (x-y) directions, which requires different arrays to occupy large brain surface areas, we worked along the radial (z) direction by using tilted coil angles and stacking coil numbers to reduce the divergence of the emitted near field without occupying large head surface areas. The emitted electric field distributions were theoretically simulated in spherical and real human head models to analyze the depth-spread performance of proposed coils and compare with existing figure-8 coils. The results were then experimentally validated with field probes and in-vivo animal tests. Main Results: The proposed "angle-tuning" concept improves the depth-spread performance of individual coils with a significantly smaller footprint than existing and proposed coils. For composite structures, using the proposed coils as basic building blocks simplifies the design and manufacturing process and helps accomplish a leading depth-spread performance. In addition, the footprint of the proposed system is intrinsically small, making them suitable for multisite stimulations of inter and intra-hemispheric brain regions with an improved spread and less electric field divergence. Significance: Few brain functions are operated by isolated single brain regions but rather by coordinated networks involving multiple brain regions. Simultaneous or sequential multisite stimulations may provide tools for mechanistic studies of brain functions and the treatment of neuropsychiatric disorders. The proposed AT coil goes beyond the traditional depth-spread tradeoff rule of TMS coils, which provides the possibility of building new composite structures and new multisite TMS tools.

show abstract

Effect of coil size on transcranial magnetic stimulation (TMS) focality

Cited by 5 publications

References 10 publications

Angle-tuned coils: attractive building blocks for TMS with improved depth-spread performance

Angle-tuned coils: attractive building blocks for TMS with improved depth-spread performance

High-Performance Magnetic-core Coils for Targeted Rodent Brain Stimulations

Angle-Tuned TMS Coils: Building Blocks for Brain Stimulation with Improved Depth-Spread Performance

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