Millimeter spatial resolution in vivo sodium MRI of the human eye at 7 T using a dedicated radiofrequency transceiver array

1H imaging is concerned with contrast generation among anatomically distinct soft tissues. X‐nuclei imaging, on the other hand, aims to reveal the underlying changes in the physiological processes on a cellular level. Advanced clinical MR hardware systems improved 1H image quality and simultaneously enabled X‐nuclei imaging. Adaptation of 1H methods and optimization of both sequence design and postprocessing protocols launched X‐nuclei imaging past feasibility studies and into clinical studies. This review outlines the current state of X‐nuclei MRI, with the focus on 23Na, 35Cl, 39K, and 17O. Currently, various aspects of technical challenges limit the possibilities of clinical X‐nuclei MRI applications. To address these challenges, quintessential physical and technical concepts behind different applications are presented, and the advantages and drawbacks are delineated. The working process for methods such as quantification and multiquantum imaging is shown step‐by‐step. Clinical examples are provided to underline the potential value of X‐nuclei imaging in multifaceted areas of application. In conclusion, the scope of the latest technical advance is outlined, and suggestions to overcome the most fundamental hurdles on the way into clinical routine by leveraging the full potential of X‐nuclei imaging are presented. Level of Evidence: 1 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2020;51:355–376.

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“… and Fig. , respectively. State‐of‐the‐art coils for 35 Cl, 17 O, and 39 K imaging are transmit‐and‐receive birdcage coils.…”

Section: Current State and Technical Challengesmentioning

confidence: 94%

“…Different Na setups have been reviewed for applications in the head, the heart, and in the body . The latest developments in RF coils for X‐nuclei imaging focus on setups comprising multiple transmit‐and‐receive coils, especially for 23 Na MRI . Exemplary images in the abdomen and the eyes are shown in Fig.…”

Section: Current State and Technical Challengesmentioning

confidence: 99%

X‐nuclei imaging: Current state, technical challenges, and future directions

Kleimaier

Malzacher

et al. 2019

Magnetic Resonance Imaging

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“…Given the intrinsic sensitivity gains achievable at higher magnetic field strengths, 23 Na MRI at B 0 = 7.0 Tesla (T) is conceptually appealing. Recognizing this opportunity, a number of RF coil setups have been implemented at 7.0 T for 23 Na MRI of the brain, eye, lung and abdomen, and musculoskeletal system . The literature reveals a single original report for 23 Na MRI of the kidney at 7.0 T .…”

Section: Introductionmentioning

confidence: 99%

Cardiorenal sodium MRI at 7.0 Tesla using a 4/4 channel ¹H/²³Na radiofrequency antenna array

Boehmert

Kuehne²,

Waiczies³

et al. 2019

Magnetic Resonance in Med

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Purpose Cardiorenal syndrome describes disorders of the heart and the kidneys in which a dysfunction of 1 organ induces a dysfunction in the other. This work describes the design, evaluation, and application of a 4/4‐channel hydrogen‐1/sodium (1H/23Na) RF array tailored for cardiorenal MRI at 7.0 Tesla (T) for a better physiometabolic understanding of cardiorenal syndrome. Methods The dual‐frequency RF array is composed of a planar posterior section and a modestly curved anterior section, each section consisting of 2 loop elements tailored for 23Na MR and 2 loopole‐type elements customized for 1H MR. Numerical electromagnetic field and specific absorption rate simulations were carried out. Transmission field (B1+) uniformity was optimized and benchmarked against electromagnetic field simulations. An in vivo feasibility study was performed. Results The proposed array exhibits sufficient RF characteristics, B1+ homogeneity, and penetration depth to perform 23Na MRI of the heart and kidney at 7.0 T. The mean B1+ field for sodium in the heart is 7.7 ± 0.8 µT/√kW and in the kidney is 6.9 ± 2.3 µT/√kW. The suitability of the RF array for 23Na MRI was demonstrated in healthy subjects (acquisition time for 23Na MRI: 18 min; nominal isotropic spatial resolution: 5 mm [kidney] and 6 mm [heart]). Conclusion This work provides encouragement for further explorations into densely packed multichannel transceiver arrays tailored for 23Na MRI of the heart and kidney. Equipped with this technology, the ability to probe sodium concentration in the heart and kidney in vivo using 23Na MRI stands to make a critical contribution to deciphering the complex interactions between both organs.

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“…Red arrows in Fig. 1 represent discrete ports (16) used for the electromagnetic field simulations: impedance value = 50 Ω (for S-parameter), voltage amplitude = 1 V, and current value = 1 A. Two stimulation ports were set on one end-ring and these ports were used to send the electric signals to the coil with the phase shift = 90° in the EMC simulations.…”

Section: Radiofrequency Coil Designmentioning

confidence: 99%

“…In the CST Studio, each element of the coil circuit was tuned to the resonance frequency of 300 MHz and matched to the impedance of 50 Ω. Failure to properly tune and match the coil may result in noisy images with poor contrast in the experiments [16,17]. In our study, we used a manual tuner for changing values of capacitors.…”

Section: Electrical Circuit Modelmentioning

confidence: 99%

Electromagnetic simulation of low-pass birdcage coil

Mańko

2019

MATEC Web Conf.

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Magnetic resonance imaging (MRI) is a widely used non-invasive imaging modality that provides a variety of high-resolution soft-tissue contrast and functional information. The development of imaging technique employing the phenomenon of nuclear magnetic resonance is focused on obtaining the best possible tissue contrast, maximisation of ratio defined by signal-to-noise-ratio (SNR) and improving the image quality. SNR can be improved by the use of contrast agents and higher-field scanners, however these are better RF coils that often provide more significant gains. Using full-wave analysis and design tools becomes especially important when the coil dimensions approach a significant fraction of a wavelength. In this paper, modelling of RF coil is presented by using special-purpose software for electromagnetic simulations. The methodology of the research assumes making numerical calculations of RF coil. The presented approach of a design of radiofrequency (RF) coils for MRI scanners using lumped circuit modelling based techniques begins to fail at high frequencies, and therefore more accurate models based on the electromagnetic field calculations must be used. This paper presents simple simulations of the electric and magnetic field in LP birdcage coil.

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Millimeter spatial resolution in vivo sodium MRI of the human eye at 7 T using a dedicated radiofrequency transceiver array

Cited by 7 publications

References 48 publications

X‐nuclei imaging: Current state, technical challenges, and future directions

X‐nuclei imaging: Current state, technical challenges, and future directions

Cardiorenal sodium MRI at 7.0 Tesla using a 4/4 channel ¹H/²³Na radiofrequency antenna array

Electromagnetic simulation of low-pass birdcage coil

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Millimeter spatial resolution in vivo sodium MRI of the human eye at 7 T using a dedicated radiofrequency transceiver array

Cited by 7 publications

References 48 publications

X‐nuclei imaging: Current state, technical challenges, and future directions

X‐nuclei imaging: Current state, technical challenges, and future directions

Cardiorenal sodium MRI at 7.0 Tesla using a 4/4 channel 1H/23Na radiofrequency antenna array

Electromagnetic simulation of low-pass birdcage coil

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Cardiorenal sodium MRI at 7.0 Tesla using a 4/4 channel ¹H/²³Na radiofrequency antenna array