Sensitivity enhancement of traveling wave MRI using free local resonators: an experimental demonstration

Zhang, Xiaoliang

doi:10.21037/qims.2017.02.10

Cited by 6 publications

(8 citation statements)

References 23 publications

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“…The B 1 − field is significantly improved in the presence of wireless coils, especially at the surface area near the wireless coil. The reason is that the wireless coil acts as a secondary coil and locally enhances the B 1 − field, which is also consistent with the results in previous work 3–5,21–23 . Compared with the single‐loop wireless coil, the stacked wireless coil exhibited further B 1 − efficiency and SNR improvement up to 28% at the center.…”

Section: Resultssupporting

confidence: 90%

“…The reason is that the wireless coil acts as a secondary coil and locally enhances the B 1 À field, which is also consistent with the results in previous work. [3][4][5][21][22][23] Compared with the single-loop wireless coil, the stacked wireless coil exhibited further B 1 À efficiency and SNR improvement up to 28% at the center. The stacked wireless coil exhibited a lower SNR than a same-sized single-loop wired coil (no power loss from the body coil), which is an acceptable penalty (18% surface SNR decrease and 7% central SNR decrease compared with the wired coil) for the stacked wireless coil, considering its obvious benefits of simple structure and low cost.…”

Section: Coil Fabrication and Mr Experimentsmentioning

confidence: 99%

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Low‐cost inductively coupled stacked wireless RF coil for MRI at 3 T

2022

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Inductively coupled RF coils are an inexpensive and simple method to realize wireless RF coils in MRI. They are low cost and can greatly ease the MR scan setup and improve patient comfort, since they do not require bulky components such as cables, baluns, preamplifiers, and connectors. Previous works have typically used single-layer loops as wireless coils. In this work, we present a novel wireless coil, where two loops are stacked and decoupled with a shared capacitor. We found that such a stacked structure could increase the coil efficiency and SNR. Compared with the single-layer wireless coil, both electromagnetic simulation and MR experiment results demonstrate that the stacked wireless coil has a considerable SNR improvement of approximately 35%.

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Section: Resultssupporting

confidence: 90%

Section: Coil Fabrication and Mr Experimentsmentioning

confidence: 99%

Low‐cost inductively coupled stacked wireless RF coil for MRI at 3 T

2022

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“…Another method is to introduce additional materials into the magnet bore, such as metamaterials [11] and dielectric fillings with specific geometry and permittivity [12,13]. An alternative simple method proposed recently is to place local resonators around the subject [14-16]. The local resonators are tuned to the proton Larmor frequency and have no connections to the MR scanner, so we refer to them as passive elements in this study.…”

Section: Introductionmentioning

confidence: 99%

“…The local resonators are tuned to the proton Larmor frequency and have no connections to the MR scanner, so we refer to them as passive elements in this study. The feasibility of this approach has been demonstrated in previous work using a single small loop [14-16], where traveling-wave efficiency was improved by at least 10-fold.…”

Section: Introductionmentioning

confidence: 99%

Improved traveling-wave efficiency in 7 T human MRI using passive local loop and dipole arrays

Yan

Zhang

Gore

et al. 2017

Magnetic Resonance Imaging

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Traveling-wave MRI, which uses relatively small and simple RF antennae, has robust matching performance and capability for large field-of-view (FOV) imaging. However, the power efficiency of traveling-wave MRI is much lower than conventional methods, which limits its application. One simple approach to improve the power efficiency is to place passive resonators around the subject being imaged. The feasibility of this approach has been demonstrated in previous works using a single small resonant loop. In this work, we aim to explore how much the improvements can be maintained in human imaging using an array design, and whether electric dipoles can be used as local elements. First, a series of electromagnetic (EM) simulations were performed on a human model. Then RF coils were constructed and the simulation results using the best setup for head imaging were validated in MR experiments. By using the passive local loop and transverse dipole arrays, respectively, the transmit efficiency (B1+) of traveling-wave MRI can be improved by 3-fold in the brain and 2-fold in the knee. The types of passive elements (loops or dipoles) should be carefully chosen for brain or knee imaging to maximize the improvement, and the enhancement depends on the local body configuration.

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“…Our work, hence, focuses on enhancing the detection sensitivity of deep-lying structures during MR imaging, with a flexibility to extend the sensitivelydetected region. Our approach has benefited from the fact that the localized coil placed in the vicinity of the regions-of-interest (ROIs) has better sensitivity with a significant increase in signal-to-noise ratio (SNR) [3]. But instead of using wire connectors [4], [5] for signal transmission, this method uses the novel Wireless Amplified Nuclear MR Detector (WAND) [6]- [8], thus removing the constraints imposed by physical links used for signal propagation.…”

Section: Introductionmentioning

confidence: 99%

Signal Sensitivity Enhancement of High-Spatial-Resolution MR Imaging With a Concatenated Cylindrical Parametric RF-Resonator

2019

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Phased array MRI coils can increase sensitivity of superficial tissues owing to their proximity to the detection region. Deep-lying tissues, on the other hand, do not benefit to the same degree. Here we investigate the use of a localized cylindrically symmetric quadruple frequency resonator concatenated with a double frequency resonator to increase the longitudinal field-of-view (FOV) without compromising the spatial-resolution and detection sensitivity. These concatenated array coils work on the principle of a parametric amplification to provide wireless amplification of the locally detected NMR signal prior to inductively coupling the coil to an external pick-up loop with connection to the system receiver. When both the detectors are activated together, the effective range of both overlay to create a larger FOV enabling better identification of detectable regions. Furthermore, the in-vivo test of the concatenated detector provides a worst-case 5-fold SNR gain in regions separated from the cylindrical surface larger than its own diameter. This proposed approach of concatenated detector realization can be individually activated and manipulated to enlarge the sensitivity-enhanced region without sacrificing their individual performance. Compared to double frequency detectors, quadruple frequency detectors offer more flexibility in the choice of detector dimension, enabling multi-element concatenation over an extended FOV.

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Sensitivity enhancement of traveling wave MRI using free local resonators: an experimental demonstration

Abstract: The proposed free local resonator technique is able to enhance the MR sensitivity and acquisition efficiency of traveling wave MR at ultrahigh fields . This method can be a simple solution to alleviating low sensitivity problem of traveling wave MRI.

Cited by 6 publications

References 23 publications

Low‐cost inductively coupled stacked wireless RF coil for MRI at 3 T

Low‐cost inductively coupled stacked wireless RF coil for MRI at 3 T

Improved traveling-wave efficiency in 7 T human MRI using passive local loop and dipole arrays

Signal Sensitivity Enhancement of High-Spatial-Resolution MR Imaging With a Concatenated Cylindrical Parametric RF-Resonator

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