Proposed Coil System Research Articles

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

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.

Design of Self-Shielded Uniform Magnetic Field Coil via Modified Pigeon-Inspired Optimization in Miniature Atomic Sensors

This article presents a modified pigeon-inspired optimization method for designing self-shielded uniform magnetic field coils that offers an innovation in miniature atomic sensors. The proposed coil system consists of circular coil pairs distributed on two coaxial cylinder surfaces, which can provide a highly uniform magnetic field at the coil center and rapidly attenuate the external field. This design is transformed into a nonlinear objective optimization problem with constraints, so that the coil geometric parameters can be obtained by the proposed algorithm, instead of solving closed-form equations by pure numerical method. Parallel competition and hierarchical search strategy are firstly introduced to accelerate the convergence speed and avoid falling into the local optimal value. Comparative experiments of several algorithms demonstrate the accuracy, effectiveness, convergence stability of the proposed method. Compared with traditional design methods, this method can automatically find the optimal parameters of the coil according to any constraints. Theoretical contrast shows that compared with the Lee-Whiting coil, the uniformity of proposed coil is improved by about 2 to 3 orders of magnitude and has a significant self-shielded effect. This work is beneficial to the miniaturization of atomic sensors.

A 32-channel coil system for MR vessel wall imaging of intracranial and extracranial arteries at 3T

PurposeTo develop a RF coil system for joint imaging of intracranial and extracranial arterial vessel wall at 3T. Materials and methodThe coil system consists of a 24-channel head coil combined with an 8-channel carotid coil. It is compared with a standard coil configuration (12-channel head coil+4-channel neck coil+8-channel carotid coil) for SNR and g-factors in phantoms and healthy volunteers. The clinical relevance of the proposed coil system is also evaluated in patients. ResultsIn phantom experiments, the SNR of the proposed coil system is 53% higher than the maximum SNR of the standard coil configuration at the center of the phantom which usually corresponds to the intracranial region of the head. The g-factors of the proposed coil system in the sagittal plane are lower than the standard coil configuration (by 10.8% and 26.6% for R=2 and 4 respectively) in the same experiment. In healthy volunteer experiments, 55% of the pixels have SNR above 100 for the proposed coil system, which is 33% more than that of the standard coil configuration. The maximum g-factors in the standard configuration are higher than those from the new coil design by 12% at R=2 and up to 36% at R=4 in the sagittal plane. In patients, in-vivo intracranial and extracranial arterial wall images at an isotropic spatial resolution of 0.6mm can be acquired using the proposed coil system. Plaques are well depicted from the images. ConclusionsThe performance of the proposed coil set is superior to the standard coil configuration, providing high SNR, low g-factor and good spatial coverage needed for simultaneous high resolution imaging of intracranial and extracranial arterial walls. Images acquired in 7.6min using the proposed coil system can achieve an isotropic spatial resolution of 0.6mm and can be used to depict plaques on the intracranial and extracranial arterial walls in patients.

A Reconfigurable Resonant Coil for Range Adaptation Wireless Power Transfer

To widen the range of a magnetically coupled wireless power transfer system, we propose a novel reconfigurable resonant coil. This device consists of a series of subcoils that use switches to control the number of turned-on subcoils. With this design, both the coupling coefficient between coils and the quality factor of the proposed coil can be dynamically tuned when the distance between the transmit and receive coils changes. Thus, the proposed coil system increases the efficient power transfer range compared to a conventional resonant system. In this work, we replace the first coil in a four-coil system with the proposed coil. This coil uses six switches to change the number of series subcoils from six to one as the distance between the transmit and receive coils increases. A theoretical analysis demonstrates how to properly design and configure the proposed coil. Experimental results show the range at which the system achieves 70% efficiency or higher increases by 120% compared to the conventional system without the proposed method. The proposed system keeps high efficiency when the load varies from 40 to ${\hbox{300}}~\Omega$ .

A Proposed Coil System for the Improved Realization of the Absolute Ampere.

In order to resolve the discrepancies which presently exist between the directly measured values of the absolute or SI ampere and the calculated values obtained indirectly from other fundamental physical constant determinations, one must design an absolute ampere experiment which will produce a result with an uncertainty of one half part per million or less. A new approach recently proposed by Kibble promises such sub-ppm accuracy. Presented here is the design and evaluation of a coil system which will fulfill the requirements of this new approach.