A Review on the RF Coil Designs and Trends for Ultra High Field Magnetic Resonance Imaging

Hernández, Daniel; Kim, Kyoung Nam

doi:10.13104/imri.2020.24.3.95

Cited by 32 publications

(19 citation statements)

References 88 publications

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“…Using the geometric parameters used in this work, we estimated that less than 0.1 𝜇𝜇W of heat is deposited to the sample if B1 = 10 𝜇𝜇T is applied with 10% duty cycle. Even when normalized to the small mass of the sample, this corresponds to a SAR of less than 0.2 W/kg, an order of magnitude lower than typical SAR values in human scans [20]. Based on this, we believe that the temperature of the ex-vivo sample can be easily regulated in scans using the proposed coil.…”

Section: Discussionmentioning

confidence: 82%

“…To achieve this, the inductance 𝐿𝐿 of the coil and the sensitivity to the sample's MR signal need to increase while maintaining a homogeneous B1 + and high filling factor. In a multiturn design, as in a solenoid, the coil's 𝐿𝐿 is proportional to the square of the number of turns (𝑛𝑛), and the MR signal induced in the coil increases in proportion to 𝑛𝑛 [13,[20][21][22]. However, when 𝑛𝑛 increases, the cross-section of each conductor decreases because multiple turns must be manufactured within a fixed surface; in addition, the conductor length increases in proportion to n [23].…”

Section: A Theory Of Mtpimentioning

confidence: 99%

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Multiturn Planar Inductor for the Improvement of Signal-to-Noise Ratio Response in Magnetic Resonance Microscopy

et al. 2022

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In this study, we propose a novel, multiturn histology coil for microscopic magnetic resonance (MR) imaging of histological tissue slices with substantially higher signal-to-noise-ratio (SNR) outcomes compared with previously developed coils. We performed electromagnetic simulations of the proposed coils and acquired MR images from a gelatin phantom and a rat brain slice with the implemented coils. The performances of the coils were evaluated by comparing the measured and simulated radio-frequency transmission (B1 + ) fields in a flip-angle map form, and with low flip-angle gradient echo images to calculate the SNR increase as a function of the number of turns (n) of the coils. This study was performed on a 3 T MR imaging system. The proposed coil with n = 7 achieved SNR greater than 3.5 times that of a single-turn coil while preserving the highly uniform B1 + field across the imaging region. The proposed method provides new possibilities for high-resolution MR imaging of microscopic tissue samples for biomedical applications.INDEX TERMS magnetic resonance imaging (MRI), microscopy, signal-to-noise ratio (SNR), radiofrequency (RF), Multiturn planar inductor (MTPI)

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Section: Discussionmentioning

confidence: 82%

Section: A Theory Of Mtpimentioning

confidence: 99%

Multiturn Planar Inductor for the Improvement of Signal-to-Noise Ratio Response in Magnetic Resonance Microscopy

et al. 2022

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“…To increase the SNR under a given magnetic field, the development of radiofrequency (RF) coil technology, such as a multichannel phased-array coil, is also important. The sensitivity of the MR signal can be increased by optimizing the transmission and reception of the RF coil system [ 22 ]. The multichannel transmission/reception RF coil facilitates the reduction of the acquisition time by combining various recently introduced data sampling strategies, including compressed sensing technology.…”

Section: Mri-pet Fusion Imagingmentioning

confidence: 99%

Future Prospects of Positron Emission Tomography–Magnetic Resonance Imaging Hybrid Systems and Applications in Psychiatric Disorders

Son

Kim

et al. 2022

Pharmaceuticals

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A positron emission tomography (PET)–magnetic resonance imaging (MRI) hybrid system has been developed to improve the accuracy of molecular imaging with structural imaging. However, the mismatch in spatial resolution between the two systems hinders the use of the hybrid system. As the magnetic field of the MRI increased up to 7.0 tesla in the commercial system, the performance of the MRI system largely improved. Several technical attempts in terms of the detector and the software used with the PET were made to improve the performance. As a result, the high resolution of the PET–MRI fusion system enables quantitation of metabolism and molecular information in the small substructures of the brainstem, hippocampus, and thalamus. Many studies on psychiatric disorders, which are difficult to diagnose with medical imaging, have been accomplished using various radioligands, but only a few studies have been conducted using the PET–MRI fusion system. To increase the clinical usefulness of medical imaging in psychiatric disorders, a high-resolution PET–MRI fusion system can play a key role by providing important information on both molecular and structural aspects in the fine structures of the brain. The development of high-resolution PET–MR systems and their potential roles in clinical studies of psychiatric disorders were reviewed as prospective views in future diagnostics.

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“…Several RF transmissions and receptors [15][16][17] have been proposed to address the occurrence of eld non-uniformity. The use of high frequencies allows the application of antennas such as microstrips [18,19], dipoles [20,21], and monopoles [22], because the sizes of these devices, as determined by the wavelength, are acceptable and practical for use inside an MRI scanner within this frequency range.…”

Section: Introductionmentioning

confidence: 99%

Effects of Non-symmetrical Current Distribution Controlled by Capacitor Placement in Loop Coils at 300 MHz MRI

Hernández

Kim

Jeong

et al. 2022

Preprint

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In this work, we present a study on the effects of the non-symmetric electrical design of radiofrequency (RF) coils for magnetic resonance imaging (MRI) operating at ultra-high frequency (UHF). A typical loop coil used in MRI consists of symmetrically distributed capacitors along the coil; this design is able to produce uniform current distributions inside the coil. However, in UHF conditions, the magnetic flux density (|B1|) field produced by this setup may exhibit field distortion, requiring a method of controlling the field distribution and improving the field intensity of the circular loop coil. The control mechanism investigated in this study is based on the position of the tuning capacitor in the circular coil. We performed comparisons against a reference coil that is based on a circular coil with four symmetrically distributed tuning capacitors. We performed electromagnetic (EM) simulations and MRI at 7 T to determine the effects of variations in the position of the capacitor and confirmed that unbalanced current distributions were created.

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A Review on the RF Coil Designs and Trends for Ultra High Field Magnetic Resonance Imaging

Cited by 32 publications

References 88 publications

Multiturn Planar Inductor for the Improvement of Signal-to-Noise Ratio Response in Magnetic Resonance Microscopy

Multiturn Planar Inductor for the Improvement of Signal-to-Noise Ratio Response in Magnetic Resonance Microscopy

Future Prospects of Positron Emission Tomography–Magnetic Resonance Imaging Hybrid Systems and Applications in Psychiatric Disorders

Effects of Non-symmetrical Current Distribution Controlled by Capacitor Placement in Loop Coils at 300 MHz MRI

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