8-channel Tx dipole and 20-channel Rx loop coil array for MRI of the cervical spinal cord at 7 Tesla

Rios, Nibardo Lopez; Gilbert, Kyle M.; Papp, Daniel S.; Cereza, Gaspard; Foias, Alexandru; Rangaprakash, D.; May, Markus W; Guérin, Bastien; Wald, Lawrence L.; Keil, Boris; Stockmann, Jason P.; Barry, Robert; Cohen‐Adad, Julien

doi:10.1101/2023.02.08.527664

Cited by 4 publications

(4 citation statements)

References 64 publications

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“…This premise was demonstrated with HIC elements in this work, but other types of coil elements such as those printed on circuit boards could conceivably be used. There has been recent interest in developing transmit/receiver neck arrays for spine imaging at 7 Tesla (Zhao et al 2014, Rios et al 2023; the conformal concepts and design from the FACE may also be applicable for the arrangement of receiver elements at 7 Tesla. An alternative approach is to replace copper-based elements with liquid metal conductors that can stretch for even higher flexibility (Port et al 2020).…”

Section: Discussionmentioning

confidence: 99%

Flexible array coil for cervical and extraspinal (FACE) MRI at 3.0 Tesla

Abel,

Tan,

Lunenburg

et al. 2023

Phys. Med. Biol.

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Objective. High-resolution MRI of the cervical spine (c-spine) and extraspinal neck region requires close-fitting receiver coils to maximize the signal-to-noise ratio (SNR). Conventional, rigid C-spine receiver coils do not adequately contour to the neck to accommodate varying body shapes, resulting in suboptimal SNR. Recent innovations in flexible surface coil array designs may provide three-dimensional (3D) bendability and conformability to optimize SNR, while improving capabilities for higher acceleration factors. Approach. This work describes the design, implementation, and preliminary in vivo testing of a novel, conformal 23-channel receive-only flexible array for cervical and extraspinal (FACE) MRI at 3-Tesla (T), with use of high-impedance elements to enhance the coil’s flexibility. Coil performance was tested by assessing SNR and geometry factors (g-factors) in a phantom compared to a conventional 21-channel head-neck-unit (HNU). In vivo imaging was performed in healthy human volunteers and patients using high-resolution c-spine and neck MRI protocols at 3T, including MR neurography (MRN). Main results. Mean SNR with the FACE was 141%–161% higher at left, right, and posterior off-isocenter positions and 4% higher at the isocenter of the phantom compared to the HNU. Parallel imaging performance was comparable for an acceleration factor (R) = 2 × 2 between the two coils, but improved for R = 3 × 3 with mean g-factors ranging from 1.46–2.15 with the FACE compared to 2.36–3.62 obtained with the HNU. Preliminary human volunteer and patient testing confirmed that equivalent or superior image quality could be obtained for evaluation of osseous and soft tissue structures of the cervical region with the FACE. Significance. A conformal and highly flexible cervical array with high-impedance coil elements can potentially enable higher-resolution imaging for cervical imaging.

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Section: Discussionmentioning

confidence: 99%

Flexible array coil for cervical and extraspinal (FACE) MRI at 3.0 Tesla

Abel,

Tan,

Lunenburg

et al. 2023

Phys. Med. Biol.

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“…We used a computer‐aided design tool (Autodesk, AutoCAD, version 2018, San Francisco, CA, USA) to design a close‐fitting inner coil former. As a reference for this process, we utilized a three‐dimensional (3D) average head model created by a procedure described in an earlier work 55 . The basic structure of the resulting former was a complex surface that slightly reduced the typical curvature of the cervical spine during scans, while leaving additional space for padding.…”

Section: Methodsmentioning

confidence: 99%

An 8‐channel Tx dipole and 20‐channel Rx loop coil array for MRI of the cervical spinal cord at 7 Tesla

et al. 2023

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The quality of cervical spinal cord images can be improved by the use of tailored radiofrequency (RF) coil solutions for ultrahigh field imaging; however, very few commercial and research 7‐T RF coils currently exist for the spinal cord, and in particular, those with parallel transmission (pTx) capabilities. This work presents the design, testing, and validation of a pTx/Rx coil for the human neck and cervical/upper thoracic spinal cord. The pTx portion is composed of eight dipoles to ensure high homogeneity over this large region of the spinal cord. The Rx portion is made up of twenty semiadaptable overlapping loops to produce high signal‐to‐noise ratio (SNR) across the patient population. The coil housing is designed to facilitate patient positioning and comfort, while also being tight fitting to ensure high sensitivity. We demonstrate RF shimming capabilities to optimize B1+ uniformity, power efficiency, and/or specific absorption rate efficiency. B1+ homogeneity, SNR, and g‐factor were evaluated in adult volunteers and demonstrated excellent performance from the occipital lobe down to the T4‐T5 level. We compared the proposed coil with two state‐of‐the‐art head and head/neck coils, confirming its superiority in the cervical and upper thoracic regions of the spinal cord. This coil solution therefore provides a convincing platform for producing the high image quality necessary for clinical and research scanning of the upper spinal cord.

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“…What: B1 static shimming Where: Brain Imaging Centre, Montreal Neurological Institute, Canada (7T Siemens Terra) Coil: 8 Tx/20 Rx channel custom DC coil 34 Structure: Spinal cord Sequence: Pre‐saturated TurboFLASH B1 mapping …”

Section: Methodsmentioning

confidence: 99%

Shimming toolbox: An open‐source software toolbox for B0 and B1 shimming in MRI

D'Astous

Cereza

Papp

et al. 2022

Magnetic Resonance in Med

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Purpose: Introduce Shimming Toolbox (https://shimming-toolbox.org), an open-source software package for prototyping new methods and performing static, dynamic, and real-time B0 shimming as well as B1 shimming experiments. Methods: Shimming Toolbox features various field mapping techniques, manual and automatic masking for the brain and spinal cord, B0 and B1 shimming capabilities accessible through a user-friendly graphical user interface. Validation of Shimming Toolbox was demonstrated in three scenarios: (i) B0 dynamic shimming in the brain at 7T using custom AC/DC coils, (ii) B0 real-time shimming in the spinal cord at 3T, and (iii) B1 static shimming in the spinal cord at 7T. Results: The B0 dynamic shimming of the brain at 7T took about 10 min to perform. It showed a 47% reduction in the standard deviation of the B0 field, associated with noticeable improvements in geometric distortions in EPI images. Real-time dynamic xyz-shimming in the spinal cord took about 5 min and showed a 30% reduction in the standard deviation of the signal distribution. B1 static shimming experiments in the spinal cord took about 10 min to perform and showed a 40% reduction in the coefficient of variation of the B1 field. Conclusion: Shimming Toolbox provides an open-source platform where researchers can collaborate, prototype and conveniently test B0 and B1 shimming experiments. Future versions will include additional field map preprocessing techniques, optimization algorithms, and compatibility across multiple MRI manufacturers.

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8-channel Tx dipole and 20-channel Rx loop coil array for MRI of the cervical spinal cord at 7 Tesla

Cited by 4 publications

References 64 publications

Flexible array coil for cervical and extraspinal (FACE) MRI at 3.0 Tesla

Flexible array coil for cervical and extraspinal (FACE) MRI at 3.0 Tesla

An 8‐channel Tx dipole and 20‐channel Rx loop coil array for MRI of the cervical spinal cord at 7 Tesla

Shimming toolbox: An open‐source software toolbox for B0 and B1 shimming in MRI

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