Recent Progress in Birdcage RF Coil Technology for MRI System

Ahmad, S.; Kim, Young Cheol; Choi, Ick Chang; Kim, Hyun Deok

doi:10.3390/diagnostics10121017

Cited by 22 publications

(14 citation statements)

References 103 publications

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“…The increased intensity of magnetic field will allow the acquisition of anatomical and functional information at high resolution. Among the various practical designs of RF coils used for NMR imaging and EUHF MRI, birdcage RF coils are widely used, with applications ranging from low-field MRI systems to ultra-high-end MRI systems [76][77][78][79][80][81][82][83][84][85][86][87][88][89][90]. Recently, BC RF coils have been actively used in clinical applications [8,83,84] and pre-clinical animal experimental studies [85,86].…”

Section: Resultsmentioning

confidence: 99%

A Preliminary Study for Reference RF Coil at 11.7 T MRI: Based on Electromagnetic Field Simulation of Hybrid-BC RF Coil According to Diameter and Length at 3.0, 7.0 and 11.7 T

Seo

Chung

2022

Sensors

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Magnetic resonance imaging (MRI) systems must undergo quantitative evaluation through daily and periodic performance assessments. In general, the reference or standard radiofrequency (RF) coils for these performance assessments of 1.5 to 7.0 T MRI systems have been low-pass-type birdcage (LP-BC) RF coils. However, LP-BC RF coils are inappropriate for use as reference RF coils because of their relatively lower magnetic field (B1-field) sensitivity than other types of BC RF coils, especially in ultrahigh-field (UHF) MRI systems above 3.0 T. Herein, we propose a hybrid-type BC (Hybrid-BC) RF coil as a reference RF coil with improved B1-field sensitivity in UHF MRI system and applied it to an 11.7 T MRI system. An electromagnetic field (EM-field) analysis on the Hybrid-BC RF coil was performed to provide the proper dimensions for its use as a reference RF coil. Commercial finite difference time-domain program was used in EM-field simulation, and home-made analysis programs were used in analysis. The optimal specifications of the proposed Hybrid-BC RF coils for them to qualify as reference RF coils are proposed based on their B1+-field sensitivity under unnormalized conditions, as well as by considering their B1+-field uniformity and RF safety under normalized conditions.

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Section: Resultsmentioning

confidence: 99%

A Preliminary Study for Reference RF Coil at 11.7 T MRI: Based on Electromagnetic Field Simulation of Hybrid-BC RF Coil According to Diameter and Length at 3.0, 7.0 and 11.7 T

Seo

Chung

2022

Sensors

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“…Here G x , G y and G z are constants (one unit of 𝐵 ⃗ field per centimeter). The fitting error was assessed by (5). Six array coils that include closed-surface arrays and open-surface arrays were compared (Table 3).…”

Section: B Comparison Of Flat Array and Composite Array In Accuracy And Power Efficiency For Generating Linear Magnetic Field (Constant Gmentioning

confidence: 99%

Limitations of Surface Current Model of Magnetic Field and a Remedy

Seo

Wang

2022

IEEE Access

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It is well known that any realistic static magnetic field in a source-free volume can be generated by electric currents on a surface enclosing the volume. The magnetic field generated by surface currents is equivalent to that from magnetic dipoles distributed on the surface and along the surface normal directions. We demonstrate the limitations of the surface current model for instrumentation, and show vertical current loops corresponding to magnetic dipoles along the surface tangent directions may be employed to mitigate these limitations. We consider loop coil elements distributed on a cylindrical surface. A closed-surface array has loops on the entire surface, and an open-surface array does not have loops on the surface of both ends. A coil array may contain only flat elements (each loop is inside the cylindrical surface) or composite elements consisting of three orthogonal loops (one flat loop and two vertical loops) instead of just one flat loop at the location of each element. With computer simulations, the array coils were tested for generating the spatial field pattern of a vertical loop or a linear field gradient. The simulations showed that ( 1) an open-surface composite loop array produces less errors than a similar flat loop array in generating linear field patterns; the percentage root mean square error (RMSE) of the composite coil loops was 8.46 %, compared with 21.5 % of the similar flat loops; (2) A composite loop array consumes less power than a corresponding flat array. For the open-surface array with similar number of loops, the power consumption of the composite loop array was 73.9 vs. the flat loop array with 184 (arbitrary power units).

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“…Although there is plenty of work dealing with birdcage resonators for MRI [8], their application in plasma process-ing is not examined profoundly yet. There is the work of Ph.…”

Section: Introductionmentioning

confidence: 99%

Design and Fabrication of Birdcage Resonators for Low-pressure Plasma Excitation

Jurik¹,

Stary²,

Drexler³

2023

RADIOENGINEERING

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This paper presents a design, analysis and optimization of birdcage resonators employed in a novel radiofrequency plasma source. Three resonators were simulated and fabricated. The resonators differ in their design and in the different materials of used dielectric -polyimide and polytetrafluorethylene (PTFE). The resonance frequency of fabricated samples possesses a maximal error of 2.2% compared to the simulated values. The performance in plasma excitation is related to the electrical parameters, while the best performing resonator (PTFE-based) exhibits the maximum real impedance of 644.3 Ω at the resonance frequency and the 799.5 V/m electric field strength. This resonator shows the best power efficiency in a plasma ignition experiment. The resonator ignited the discharge at ca. 1 Pa of ambient air atmosphere with only 0.34 W of input radiofrequency power.

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Recent Progress in Birdcage RF Coil Technology for MRI System

Cited by 22 publications

References 103 publications

A Preliminary Study for Reference RF Coil at 11.7 T MRI: Based on Electromagnetic Field Simulation of Hybrid-BC RF Coil According to Diameter and Length at 3.0, 7.0 and 11.7 T

A Preliminary Study for Reference RF Coil at 11.7 T MRI: Based on Electromagnetic Field Simulation of Hybrid-BC RF Coil According to Diameter and Length at 3.0, 7.0 and 11.7 T

Limitations of Surface Current Model of Magnetic Field and a Remedy

Design and Fabrication of Birdcage Resonators for Low-pressure Plasma Excitation

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