Browsing by Author "Yang, Yihong"
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Item Angle-Tuned Coil: A Focality-Adjustable Transcranial Magnetic Stimulator(Springer, 2022-11-29) Meng, Qinglei; Bagherzadeh, Hedyeh; Hong, Elliot; Yang, Yihong; Lu, Hanbing; Choa, Fow-SenTranscranial magnetic stimulation (TMS) has been approved by the Food and Drug Administration (FDA) for treatment-resistant major depression [1] and ObsessiveCompulsive Disorder [2]. Its therapeutic effects in other psychiatric and neurological disorders, including drug addiction, are emerging [3, 4]. From both clinical and basic neuroscience perspectives, there has been a strong demand for stimulation tools that can reach deep brain regions with small size targeted stimulations. For example, decades of neuroimaging studies have identifed malfunction of dorsal anterior cingulate cortex, insular and amygdala in a range of psychiatric disorders. These structures are 4 cm or more below the scalp. Unfortunately, with current technologies, the stimulation targets are limited to superfcial brain regions, or otherwise wide brain areas are stimulated when a deep brain structure is targeted.Item Angle-Tuned Coils: Attractive Building Blocks for TMS with Improved Depth-Spread Performance(IOP, 2022-05-04) Bagherzadeh, Hedyeh; Meng, Qinglei; Deng, Zhi-De; Lu, Hanbing; Hong, Elliott; Yang, Yihong; Choa, Fow-SenObjective. 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.Item High-Performance Magnetic-core Coils for Targeted Rodent Brain Stimulations(Science Partner Journals, 2022-03-07) Bagherzadeh, Hedyeh; Meng, Qinglei; Lu, Hanbing; Hong, Elliott; Yang, Yihong; Choa, Fow-SenObjective 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.