Coil Design Research Articles

Flexible in-cavity MRI receiving coil for ultra-high-resolution imaging of the pituitary gland.

The objective of this study was the preclinical design and construction of a flexible intrasphenoid coil aiming for submillimeter resolution of the human pituitary gland. Sphenoid sinus measurements determined coil design constraints for use in > 95% of adult patients. Temperature safety parameters were tested. The 2-cm-diameter coil prototype was positioned in the sphenoid sinus of cadaveric human heads utilizing the transnasal endoscopic approach that is used clinically. Signal-to-noise ratio (SNR) was estimated for the transnasal coil prototype compared with a standard clinical head coil. One cadaveric pituitary gland was explanted and histologically examined for correlation to the imaging findings. With the coil positioned directly atop the sella turcica at a 0° angle of the B0 static field, the craniocaudal distance (21.2 ± 0.8 mm) was the limiting constraint. Phantom experiments showed no detectable change in temperature at two sites over 15 minutes. The flexible coil was placed transnasally in cadaveric specimens using an endoscopic approach. The image quality was subjectively superior at higher spatial resolutions relative to that with the commercial 20-channel head coil. An average 17-fold increase in the SNR was achieved within the pituitary gland. Subtle findings visualized only with the transnasal coil had potential pathological correlation with immunohistochemical findings. A transnasal radiofrequency coil feasibly provides a 17-fold boost in the SNR at 3 T. The ability to safely improve the quality of pituitary imaging may be helpful in the identification and subsequent resection of small functional pituitary lesions.

Improving Efficiency of a Wireless Power Transfer (WPT) System by Increasing Coil-Width

Abstract: Efficiency of a wireless power transfer (WPT) system depends on the resonance components and mutual inductance between primary and secondary coils of the transformer. Therefore, design of coils of a transformer is very crucial in WPT system as primary and secondary coils of the WPT transformer are separated by a large air gap. Due to large air gap between primary and secondary coils, coupling coefficient in a WPT system is very low compared to conventional transformer. Therefore, efficiency of the system is very low. In this paper, it is discussed that efficiency of a wireless power transfer (WPT) system can be enhanced by increasing its coil-width.

Numerical study on the transport current distribution in the multi-layer CORC coil

The conductor on round core (CORC) cable has attracted increasing attention due to its strong and high-efficient current carrying capacity. It is considered as one of ideal candidate cables for manufacturing nuclear fusion magncets. Under the circumstance, the transport current distribution of the coils wound by CORC cables has significant impacts on the operating performance of nuclear fusion magnets. Considering the difficulty in experimental tests, numerical model is an effective way to illustrate transport current distribution of the multi-layer CORC coil and provide further insights into its working performance. Therefore, in this work, A 3D finite element model based on the H formulation is proposed to simulate a single-turn and multi-layer CORC coil. The validity of the model has been verified by experimental results. Based on the proposed model, the transport current distribution of the multi-layer straight CORC cable and the multi-layer CORC coil is compared and discussed. In addition, the current density distribution on the superconducting tapes of the multi-layer CORC coil is also investigated. This work can provide an important reference for the design and practical application of multi-layer CORC coils.

Optimization Design of DC Electromagnet Coil Considering the Power Consumption and Cost

Electromagnet coil is mainly composed of enameled wire which wound on the coil skeleton, and the function is to convert the electrical signal into a magnetic signal, which is a very important electric‐magnetic conversion element. When designing the electromagnet coil, usually only the total winding turns and winding inner diameter can be calculated, and the specific design parameters such as the diameter of copper wire, paint layer thickness, and winding turns of each layer can only be selected through experience, indicating that the design method should be improved. In addition, the unreasonable design parameters will seriously affect the power consumption and cost of coil, so it is highly necessary to improve the optimization design method. In order to solve the above problems, an optimization design method for DC electromagnet coil is proposed in this paper. This method simultaneously takes into account both power consumption and manufacturing cost, and can achieve the optimal matching of design parameters. In this paper, the structure of electromagnet coil is introduced, and the theoretical calculation model of resistance is improved first. Then, according to the expected requirements of electromagnet coil for steady current, the optimization design method is proposed and the optimal design parameters are obtained. Finally, the effectiveness of the proposed optimization design method is verified by the test platform of electromagnet coil. The results show that the electromagnet coil designed by the optimization design method fully meets the expected requirements. The relevant research results can provide reference for the optimization design of electromagnet coil, which has a certain engineering practical value. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Effect of MR head coil geometry on deep-learning-based MR image reconstruction.

To investigate whether parallel imaging-imposed geometric coil constraints can be relaxed when using a deep learning (DL)-based image reconstruction method as opposed to a traditional non-DL method. Traditional and DL-based MR image reconstruction approaches operate in fundamentally different ways: Traditional methods solve a system of equations derived from the image data whereas DL methods use data/target pairs to learn a generalizable reconstruction model. Two sets of head coil profiles were evaluated: (1) 8-channel and (2) 32-channel geometries. A DL model was compared to conjugate gradient SENSE (CG-SENSE) and L1-wavelet compressed sensing (CS) through quantitative metrics and visual assessment as coil overlap was increased. Results were generally consistent between experiments. As coil overlap increased, there was a significant (p < 0.001) decrease in performance in most cases for all methods. The decrease was most pronounced for CG-SENSE, and the DL models significantly outperformed (p < 0.001) their non-DL counterparts in all scenarios. CS showed improved robustness to coil overlap and signal-to-noise ratio (SNR) versus CG-SENSE, but had quantitatively and visually poorer reconstructions characterized by blurriness as compared to DL. DL showed virtually no change in performance across SNR and very small changes across coil overlap. The DL image reconstruction method produced images that were robust to coil overlap and of higher quality than CG-SENSE and CS. This suggests that geometric coil design constraints can be relaxed when using DL reconstruction methods.

Design and measurement of three-dimensional uniform-field coils based on swarm intelligence algorithms under ferromagnetic boundaries

Combination systems of high permeability magnetic shields and coils are widely used in fields such as the magnetic field standard metrology and the zero magnetic room construction. To solve the problem that the magnetic field of uniform-field coils under the ferromagnetic boundary of magnetic shields is difficult to design precisely and the uniformity is difficult to improve, three-dimensional uniform field coils are designed based on the magnetic field model of coils under the ferromagnetic boundary using the target-field method (TFM), and the weight coefficient vectors determining the coils’ structure are optimized using intelligent optimization algorithms, which improves the uniformity of the magnetic field in the target region by 2 orders of magnitude through whale optimization algorithm (WOA). Then, the radial WOA-TFMUFY coil and the axial WOA-TFMUFZ coil are designed considering sidewall optical holes, and their magnetic field distribution is analyzed and verified under different permeabilities and axial opening sizes of the shield. Compared to the traditional saddle coil and Lee-whiting coil, the maximum magnetic field non-uniformity in the target uniform field region is reduced by 82.2 % and 92.8 % for the WOA-TFMUFY coil and WOA-TFMUFZ coil. The maximum relative errors between the measured magnetic field generated by the designed coils and the finite element method (FEM) simulation results are no higher than 2.2%. This novel method can provide more precise and uniform magnetic field metrology standard elements.

Energy Efficient and Adaptive Design for Wireless Power Transfer in Electric Vehicles

Wireless power transfer (WPT) has the potential to revolutionise global transportation and to catalyse the rise of the market for electric vehicles (EVs) by providing a compelling alternative to the conventional ways of charging that involve the use of cables. Nevertheless, coil misalignment, which is caused by the behaviours of drivers who park their vehicles, is a substantial challenge since it has a detrimental impact on power transfer efficiency (PTE). This work presents a unique coil design that is coupled with adaptive hardware in order to improve power transfer efficiency (PTE) in magnetic resonant coupling waste power transfer (WPT) systems and reduce the impacts of coil misalignment, which is a significant impediment that is preventing the broad implementation of WPT for electric vehicles (EVs). Simulation with ADS was used to validate the effectiveness of the new design, which exhibited a high degree of congruence with the theoretical analysis. In addition, receiver and transmitter circuitry that was specifically constructed for the purpose of simulating real-world vehicle and parking bay settings was utilised. This allowed for the collecting of PTE data in a controlled environment that was on a smaller scale. Experiments showed that there was a significant thirty percent improvement in the power transfer efficiency (PTE) at the centre of the coil array, and an astonishing ninety percent improvement was recorded when the array was misaligned by three quarters of its radius. When compared to single coil designs that serve as benchmarks, the suggested new coil array displays improved property transfer efficiency (PTE).

Enhanced beam extraction system at the U-120M cyclotron

Since its commissioning in 1977, the U-120M cyclotron was initially equipped with a single pair of harmonic coils aimed at optimizing beam quality at lower accelerating radii. In 2022, a significant upgrade introduced a second pair of harmonic coils, positioned at a radius of approximately 50 cm, aligning with the outermost beam orbit. This addition is essential for the efficient extraction of positively accelerated ions and serves as the basis for the newly developed extraction system, which, unlike the original fully electrostatic system, consists of electrostatic deflectors and magnetic channels. This paper describes the design and installation of new harmonic coils in the accelerator vacuum chamber and presents a new extraction system using precession and linear integer resonance methods. Basic properties of these two extraction methods are given and finally, an evaluation of their advantages and limitations concerning their possible use in the cyclotron and an estimation of the efficiency of the new extraction system is made.

Multi-objective design optimization of electromagnetic coil for effective actuation of magnetic endocapsule devices

Magnetic actuation with cylindrical electromagnetic coils is an upcoming technology due to its straightforward design and adaptability for magnetic endocapsule control in the gastrointestinal tract. This paper presents a mathematical model for characterizing the magnetic field generated by cylindrical electromagnetic coils and optimizing design parameters tailored for a typical 6.50-gram magnetic endocapsule. This paper adopted a dual-set parallel cylindrical electromagnetic coil configuration. The cylindrical electromagnetic coil design was conceptualized as a multi-objective optimization problem, which concerns geometrical parameters and copper winding usage, resolved through the amalgamation of a genetic algorithm and a Pareto optimal methodology. The optimal design produces an actuation force of 132.20 mN for a 6.50-gram magnetic endocapsule, and the results are validated with finite element simulations. The adopted and optimized system configuration has a average motion resolution of 2.7 mm and an average motion velocity of 162 mm/min.

Design and Modelling of an Induction Heating Coil to Investigate the Thermal Response of Magnetic Nanoparticles for Hyperthermia Applications

Magnetic Field Hyperthermia is a technique where tumours are treated through an increase in local temperature upon exposure to alternating magnetic fields (AMFs) that are mediated by magnetic nano-particles (MNPs). In an AMF, these particles heat-up and kill the cells. The relationship between an AMF and the heating-rate is complex, leading to confusion when comparing data for different MNP and AMF conditions. This work allows for the thermal-response to be monitored at multiple AMF amplitudes while keeping other parameters constant. An induction-heating coil was designed based on a Zero-Voltage-Zero-Current (ZVZC) resonant circuit. The coil operates at 93 kHz with a variable DC drive-voltage (12–30 V). NEC4 software was used to model the magnetic field distribution, and MNPs were synthesised by the coprecipitation method. The magnetic field was found to be uniform at the centre of the coil and ranged from 1 kAm−1 to 12 kAm−1, depending on the DC drive-voltage. The MNPs were found to have a specific absorption rate (SAR) of 1.37 Wg−1[Fe] and 6.13 Wg−1[Fe] at 93 kHz and 2.1 kAm−1 and 12.6 kAm−1, respectively. The measured SAR value was found to be directly proportional to the product of the frequency and field-strength (SARα f Ho). This leads to the recommendation that, when comparing data from various groups, the SAR value should be normalized following this relationship and not using the more common relationship based on the square of the field intensity (SARα f Ho2).

420 Decrease in Post-Coiling Aneurysm Recanalization With Regular Aspirin Use

INTRODUCTION: Endovascular coiling has remained an efficacious mechanism for aneurysm treatment. While continued biomechanical advancements in coil design have led to improved aneurysm embolization rates (1), aneurysm recanalization is estimated to remain between 21-33% (2, 3, 4). Post-occlusion, cerebral aneurysm sac growth has been identified as one of the driving components of aneurysm recurrence (2, 5). Recently, antiplatelet agents such as aspirin (ASA) have been shown to be significantly associated with decreased aneurysm growth and rupture (6, 7, 8). METHODS: All aneurysms treated by a single surgeon over 10 years (n = 2236) were screened for adherence to inclusion criteria. The primary endpoint was follow-up more than 12 months from the original intervention. Of 525 treated with coils only, 109 patients reported regular ASA use (defined as = 3x/ week, irrespective of dose). No significant demographic differences were identified between patients with regular ASA use and those without. While there were no significant differences in aneurysm size, location, or history of rupture, there was an increased presence of daughter sacs in patients without regular ASA. Rates of aneurysm recanalization, defined as a change of Raymond-Roy occlusion classification =1, were compared between ASA-treated and non-ASA-treated groups. RESULTS: Of the 109 coiled aneurysms with concomitant regular ASA use, only 9.2% underwent recanalization compared to 23.6% in patients without regular ASA use (P = 0.001, OR = 0.33, 95% CI = 0.15–0.66). Furthermore, when specifically considering cases of recanalization that only demonstrated sac growth, 5.5% occurred with regular ASA use compared to 18% without (P = 0.001, OR = 0.26, 95% CI = 0.09–0.63). CONCLUSIONS: ASA use significantly decreased the odds of post-coiling aneurysm sac growth and recanalization 12 months post-original intervention when compared to those without regular ASA use.

A Search Coil Design Method of PMSM for Detection of Inter-Turn Short-Circuit Fault

Fault diagnosis systems based on search coils are widely used for detecting the inter-turn short-circuit (ITSC) fault, which is one of the most common electrical faults in electrical machines. Although various search coil structures have been proposed, there is not a systematic method proposed for the design of search coils. In addition, there is not a quantitative evaluation standard to evaluate the performances of search coils in each aspect, making it difficult to judge whether the proposed search coil structure is the optimal one. In this paper, the reliability, sensitivity and positioning ability of search coils are derived and evaluated by four defined characteristic indexes. And based on these four characteristic indexes, a systematic search coil design method based on the mutual inductance matrix is also proposed. With the proposed design method, the optimal search coil structures for different permanent magnet synchronous machines (PMSMs) are designed and optimized. It is found that the search coils designed by the proposed method have good performance in reliability, sensitivity and positioning ability. The performances of designed search coils are validated by the finite element analysis (FEA) and experiment.

Efficient coil design for transcranial magnetic stimulation using computational tools

Efficient coil design for transcranial magnetic stimulation using computational tools

Feasibility analysis of wireless power delivery to implanted sensors of XLIF patients

Abstract The paper aims to aid in developing a monitoring system for surgery patients who have undergone lumbar interbody fusion (LIF). The present body of work functions as a comprehensive analysis of relevant available literature along with our investigation regarding techniques for power delivery; both energy harvesting and wireless power transfer (WPT) alike. In addition, biological considerations are taken into account as they strongly influence the design and testing methodology of an implanted medical device (IMD). This study proposes using inductive coupling as a power delivery method. This was chosen due to the robust nature of the technology, with the IMD being deeply situated and encased in bone and tissue. Three types of receiver coil architectures were explored and designed around the geometry of a polyether ether ketone (PEEK) Extreme lateral interbody fusion (XLIF) Nuvasive Coroent XL interbody cage. With the use of off-the-shelf components, functionality was only attainable for the V3 coil design featured with 0.4 mm wire windings around horizontal and vertical beams present on the implant. The secondary coil was resonantly tuned and optimized for a 141 kHz working frequency. At a 100 mm coupling distance, it was demonstrated that a power delivery load (PDL) of 3.94 mA was able to be induced resulting in a power output of 7.21 mW. The recorded PDLs are capable of powering a high pressure P122 sensor, EFM8BB52 microcontroller, and Ultra-wideband (UWB) data telemetry link, and demonstrate the feasibility of this WPT technique for in vivo monitoring of bone fusion post XLIF surgery.

Enhanced Domino Wireless Power Transfer for Transmission Line Monitoring: Overcoming External Metal Object Interference and Optimizing Coil Design

Enhanced Domino Wireless Power Transfer for Transmission Line Monitoring: Overcoming External Metal Object Interference and Optimizing Coil Design

Use of nonlinear pulsed magnetic fields for spatial encoding in magnetic resonance imaging

This study examines the use of nonlinear magnetic field coils for spatial encoding in magnetic resonance imaging. Existing theories on imaging with such coils share a complex reconstruction process that originates from a suboptimal signal interpretation in the spatial-frequency domain (k-space). In this study, a new solution to this problem is proposed, namely a two-step reconstruction process, in which in the first step, the image signal is converted into a frequency spectrum, and in the second step, the spectrum, which represents the distorted image, is geometrically and intensity corrected to obtain an undistorted image. This theory has been verified by numerical simulations and experimentally using a straight wire as a coil model for an extremely nonlinear magnetic field. The results of this study facilitate the use of simple encoding coil designs that can feature low inductance, allowing for much faster switching times and higher magnetic field gradients.

Optimal Design of Relay Coil Inductance to Improve Transmission Efficiency of Four-Coil Magnetic Resonance Wireless Power Transmission Systems

Magnetic resonance wireless power transmission consists of a source coil and relay coil (transmission coil (Tx-coil), receiving coil (Rx-coil)). The relay coil is designed with windings and a series capacitor, which are resonant with the input voltage frequency. Magnetic resonant wireless power transmission by a relay coil enables the transmission of power from a few centimeters to several meters. Recently, research has been conducted on the shape and material of each coil to increase the transmission distance. However, limitations remain with respect to increasing the transmission distance. Specifically, the optimization of the electrical characteristics of the relay coil is necessary to increase the transmission distance and improve efficiency. In this study, we configured the inductance of the relay coil to be approximately 95 μH, 270 μH, and 630 μH. Accordingly, we designed the series capacitors to have the same resonant frequency and analyzed the transmission characteristics of each relay coil. We confirmed that as the inductance increased, the transmission efficiency increased by up to 10%. The relay coil was designed to have an inductance of approximately three to six times that of the source coil (load coil). Thus, the optimal design of the relay coil is believed to be the most efficient and economical coil design.

Theoretical Impedance Calculation Method for Air‐Core Coils

Coils are designed to have impedance characteristics appropriate for any use of the sensors, analog circuits and so on. The impedance characteristics of a coil depends on the coil shape and used materials, and these factors make coil design difficult. Therefore, we proposed a convenient method to obtain the impedance characteristics of a coil by theoretical calculation of the inductance, resistance, and capacitance. The difference between the calculated and measured values was within 15%, which demonstrated the usefulness of the proposed method. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Dual-Channel Transverse Fields Radiofrequency Coils for 1.5 T Magnetic Resonance Imaging.

This theoretical study presents the design and analytical/numerical optimization of novel dual-channel transverse fields radiofrequency (RF) surface coils for 1.5 T Magnetic Resonance Imaging (MRI). The research explores a planar setup with two channels on a row with aligned spatial orientation of the RF coils, aiming to solve a common design drawback of single-channel transverse field RF coils: the reduced Field Of View (FOV) along the direction of the RF field. A significant challenge in this design is the efficient decoupling of two sets of transverse field RF coils to prevent mutual interference. Our modeling approach integrates thin wire theoretical modeling, magnetostatic computation for strip conductor coils, and their full-wave electromagnetic simulation. Key findings at 64 MHz demonstrate that strategic geometric placement among the two-channel RF coil and the introduction of geometrical asymmetry in the design of the individual RF coils does minimize the mutual inductance, paving the way for effective dual-channel MRI applications. This decoupling approach allows to enhance the FOV, providing a theoretical framework for the development of optimized dual-channel transverse field RF coil configurations. The current design was validated with full-wave numerical study at 64 MHz (1H, 1.5 T), has the potential to be extended at lower or higher frequencies, and the presence of lossy samples needs to be considered in the latter case.

Optimal design of wireless power transfer coils for biomedical implants using machine learning and meta-heuristic algorithms

Optimal design of wireless power transfer coils for biomedical implants using machine learning and meta-heuristic algorithms