Development and Implementation of a PIN-Diode Controlled, Quadrature-Enhanced, Double-Tuned RF Coil for Sodium MRI

Ha, Yonghyun; Choi, C.; Shah, N. Jon

doi:10.1109/tmi.2017.2786466

Cited by 11 publications

(7 citation statements)

References 35 publications

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“…In general, a coil benchmarking may have to be carried out when a coil is newly developed [53], [54], [55] or when the performance of a double-tuned or MR-PET hybrid coil is compared against its counterpart single-tuned or singlemodality coil [56], [57]. In this study, we built three coils with different coil types and geometries, and each coil was built to focus on the coverage of a different target.…”

Section: Discussionmentioning

confidence: 99%

Project-Oriented RF Coil Comparison and Optimization for Preclinical, Single-Voxel MR Spectroscopy of the Rat Visual Cortex at 9.4 T

et al. 2023

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As one of the most important cortical structures in the brain, the visual cortex plays a primary role in processing visual data. Observing the metabolic changes in this region using single-voxel MR spectroscopy (MRS) can provide a plethora of information on the disease stage and progress in vivo. For single-voxel MRS experiments, a target voxel is always chosen and specifically investigated. The volume of the voxel must be sufficiently small to avoid any interference from adjacent areas but large enough to maximise its signal-to-noise ratio (SNR). Of the factors used to improve SNR, e.g. enlarging voxel size or increasing the number of signal averaging, the optimisation of the RF coil can contribute significantly to the SNR improvement. In this work, we compared and optimised RF coils which include a circularly-polarised (CP) high-pass birdcage coil and two CP surface coils with different dimensions. The coils were particularly designed for the entire rat head, brain and the target region (visual cortex), respectively. The performance of these coils was evaluated based on the project-specific purpose of investigating metabolite concentration changes in the visual cortex of the in vivo rat brain, assessed by means of single-voxel MRS at 9.4 T. In the SNR comparison, the values obtained using the optimised small loop coil were found to be approximately 5 and 1.35 times higher than those using the birdcage volume head coil and the medium-sized loop coil, respectively. In other words, using the optimised coil rather than, for example, the birdcage coil allows the acquisition to be completed more quickly by a factor of 25 times. In conclusion, by using the optimised setup, we can i) benefit either from reduced measurement time or in the acquisition of high-quality MR images or ii) obtain spectra with a minimum quantification error.

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Section: Discussionmentioning

confidence: 99%

Project-Oriented RF Coil Comparison and Optimization for Preclinical, Single-Voxel MR Spectroscopy of the Rat Visual Cortex at 9.4 T

et al. 2023

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“…This suggests that the optimisation of tuning and matching in all the nuclei of interest using, e.g., the dual-frequency matching networks, may not be required in order to improve the quality of multinuclear MR imaging and spectroscopy. Investigating other approaches introduced in double-tuned coils, e.g., using PIN-diodes [25,26] or LCC trap circuits [27,28] would also be useful, as these might provide less degradation in the coil sensitivity. It would also be of interest to explore whether the matching networks for coils operating at close frequencies (e.g., 1 H/ 19 F or 13 C/ 23 Na) or at other frequencies that are far apart from 1 H (e.g., 17 O or 39 K) are affected in a similar way.…”

Section: Discussionmentioning

confidence: 99%

Design and Comparison of Different Types of Dual-Frequency Matching Networks Used in Double-Tuned Coils for Multinuclear Magnetic Resonance Imaging and Spectroscopy

et al. 2022

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Multi-resonant RF coils are often used in multinuclear MR imaging and/or spectroscopy experiments, and a large variety of strategies for multi-tuning coils exist. However, designing a multi-tuned coil with good performance is challenging, and improvements in sensitivity are always desirable -particularly on the X-nucleus coil due to the intrinsically lower MR sensitivity of non-proton nuclei. In this work, various dual-frequency matching networks in double-tuned coils are compared, and their effect on the coil performance is investigated. Four different dual-frequency matching networks were designed and constructed with frequency-splitting or -blocking traps, which enable exploration of both proton-1 ( 1 H) and sodium-23 ( 23 Na) nuclei. Two single-frequency matching networks were also built without any additional lossy components as a reference, and their matchings were set to either the 1 H or the 23 Na frequency. The initial evaluation was conducted on the bench using a network analyser to examine the scattering (S)-parameters and quality factors of the connected RF coils. The performance of the attached matching networks was then further evaluated by measuring the corresponding signal-to-noise ratio (SNR) based on images obtained at a 7 T clinical MRI scanner. It was found that even though the tuning and matching conditions were nearly impeccable in the S-parameters, the actual 1 H SNR decreased significantly due to the inserted traps, whereas the SNRs of the 23 Na frequency were nearly maintained with the added traps and the losses were much less. The dual-frequency matching networks create additional sensitivity loss, which is dependent on the actual implementation of the matching circuit. This is in agreement with previously reported results associated with the evaluation of inserted double-tuning traps for RF coils.

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“…The volume coil and the RF encoding array are geometrically decoupled because the former has a B 1 +-field oriented in the x-direction and the latter in the y-direction. Each element in the array was designed to passively switch between the off-resonance frequency (870kHz), and the on-resonance frequency (1MHz) [ 45 , 46 ]. Two non-magnetic cross-diodes were integrated in the tuning and impedance matching circuits such that low power RF signals would drive the coils in 1MHz Rx-only mode, and high power RF pulses would switch the coils to 870kHz Tx-only mode.…”

Section: Methodsmentioning

confidence: 99%

Magnetic resonance imaging using a nonuniform Bo (NuBo) field-cycling magnet

Selvaganesan

Wan

et al. 2023

PLoS ONE

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Magnetic resonance imaging (MRI) is a powerful noninvasive diagnostic tool with superior soft tissue contrast. However, access to MRI is limited since current systems depend on homogeneous, high field strength main magnets (B0-fields), with strong switchable gradients which are expensive to install and maintain. In this work we propose a new approach to MRI where imaging is performed in an inhomogeneous field using radiofrequency spatial encoding, thereby eliminating the need for uniform B0-fields and conventional cylindrical gradient coils. The proposed technology uses an innovative data acquisition and reconstruction approach by integrating developments in field cycling, parallel imaging and non-Fourier based algebraic reconstruction. The scanner uses field cycling to image in an inhomogeneous B0-field; in this way magnetization is maximized during the high field polarization phase, and B0 inhomogeneity effects are minimized by using a low field during image acquisition. In addition to presenting the concept, this work provides experimental verification of a long-lived spin echo signal, spatially varying resolution, as well as both simulated and experimental 2D images. Our initial design creates an open MR system that can be installed in a patient examination table for body imaging (e.g., breast or liver) or built into a wall for weighted-spine imaging. The proposed system introduces a new class of inexpensive, open, silent MRIs that could be housed in doctor’s offices much like ultrasound is today, making MRI more widely accessible.

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Development and Implementation of a PIN-Diode Controlled, Quadrature-Enhanced, Double-Tuned RF Coil for Sodium MRI

Cited by 11 publications

References 35 publications

Project-Oriented RF Coil Comparison and Optimization for Preclinical, Single-Voxel MR Spectroscopy of the Rat Visual Cortex at 9.4 T

Project-Oriented RF Coil Comparison and Optimization for Preclinical, Single-Voxel MR Spectroscopy of the Rat Visual Cortex at 9.4 T

Design and Comparison of Different Types of Dual-Frequency Matching Networks Used in Double-Tuned Coils for Multinuclear Magnetic Resonance Imaging and Spectroscopy

Magnetic resonance imaging using a nonuniform Bo (NuBo) field-cycling magnet

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