A patient‐friendly 16‐channel transmit/64‐channel receive coil array for combined head–neck MRI at 7 Tesla

May, Markus W; Hansen, Sam‐Luca J. D.; Mahmutović, Mirsad; Scholz, Alina; Kutscha, Nicolas; Guérin, Bastien; Stockmann, Jason P.; Barry, Robert; Kazemivalipour, Ehsan; Gumbrecht, Rene; Kimmlingen, Ralph; Adriany, Markus; Chang, Yulin V.; Triantafyllou, Christina; Knake, Susanne; Wald, Lawrence L.; Keil, Boris

doi:10.1002/mrm.29288

Cited by 17 publications

(37 citation statements)

References 41 publications

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“…Previously, multiple research groups demonstrated that a two-row combination of 16 loops (2 x 8) can be well decoupled 2,9,11 and provide a robust design for 3D RF shimming 9 of a whole human brain at 7 T. This approach has been previously used for designing both Tx-only 7-T volume coils (arrays) combined with smaller tight-fit multichannel Rx-arrays, that is, a so-called Tx-only/Rx-only (ToRo) setup, [13][14][15] and transceiver (TxRx) arrays, 9,16,17 in which all elements are used in both transmission and reception. Examples of 7-T ToRo human head arrays with 64 Rx-loops, 18,19 96 Rx-loops, 20 and potentially 128 Rx-loops, 21 have been reported.…”

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confidence: 99%

Double‐row dipole/loop combined array for human whole brain imaging at 7 T

et al. 2022

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Important issues in designing radiofrequency (RF) coils for human head imaging at ultra-high field (UHF; ≥7 T) are the inhomogeneity and longitudinal coverage (along the magnet axis) of the transmit (Tx) RF field. Both the homogeneity and coverage produced by Tx volume coils can be improved by means of three-dimensional (3D) RF shimming, which requires the use of multirow Tx-arrays. In addition, according to recent findings of the ultimate intrinsic signal-to-noise ratio (UISNR) theory, the loop-only receive (Rx) arrays do not provide optimal SNR near the brain center at UHF. The latter can be obtained by combining complementary conductive structures carrying different current patterns (e.g., loops and dipole antennas). In this work, we developed, constructed, and evaluated a novel 32-element hybrid array design for human head imaging at 7 T. The array consists of 16 transceiver loops placed in two rows circumscribing the head and 16 folded-end Rx-only dipoles positioned in the centers of loops. By placing all elements in a single layer, we increased RF power deposition into the tissue and, thus, preserved the Tx-efficiency. Using this hybrid design also simplifies the coil structure by minimizing the total number of array elements. The array demonstrated whole brain coverage, 3D RF shimming capability, and high SNR. It provided $15% higher SNR near the brain center and, depending on the RF shim mode, from 20% to 40% higher Tx-efficiency than a common commercial head array coil.central SNR improvement, folded-end dipole, human head imaging, hybrid array design, ultrahigh field MRI, whole brain coverage | INTRODUCTIONIn two decades since ultra-high field (UHF; ≥7 T) MRI scanners became available to the research community, they have provided evidence of the indisputable benefits of UHF MR imaging, including substantial increases of signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Further

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confidence: 99%

Double‐row dipole/loop combined array for human whole brain imaging at 7 T

et al. 2022

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“…Testing of this coil showed excellent performance over an extended range beyond the cervical spine including the occipital and upper thoracic regions when compared to other coils 5,6 . The Tx and Rx coils are integrated into a single housing equipped with hinges that allow it to be easily opened and closed to expedite the placement of the subject.…”

Section: Discussionmentioning

confidence: 91%

“…The SNR declines in the upper part of the studied region, which comprises most of the brain, but useful values were registered in the occipital region. Comparison to other coils (head and head-neck) with more channels demonstrated that 20 receive loops, with convenient dimensions and placement, were sufficient to obtain higher SNR along the spinal cord 5 . Average g-factors obtained during the same study over an axial plane positioned at level C3 of the cervical spine showed similar values for all coils up to acceleration factors (R) of 4, while reductions of 27% (0.67/0.49) and 22% (0.63/0.49), respectively, were observed for R=6.…”

Section: Comparison With Other Coilsmentioning

confidence: 97%

“…Overall, spine coil transceiver archetypes can be classified based upon the anatomical region to which they are tailored: head-neck, cervical spine, thoracic, and lumbar. Head-neck coils [3][4][5] , as well as cervical spine coils 2,6 , are typically conformed to the complex shape of these sections of anatomy-the focal coverage produces higher transmit efficiency and receive sensitivity.…”

Section: Introductionmentioning

confidence: 99%

“…Local transmit coils can reduce this difficulty by placing the coil in close proximity to the subject. This has been accomplished with two-channel coils 7,[35][36][37] and array coils 2,5,8,20,[38][39][40] . To additionally leverage the capability of array coils to improve transmit uniformity through RF shimming or spatially selective pulses, an 8-channel transverse electromagnetic (TEM) coil 17 and a 16-channel meandered stripline coil 41 were developed for torso imaging, including the lower spinal cord.…”

Section: Introductionmentioning

confidence: 99%

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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

Rios

Gilbert

Papp

et al. 2023

Preprint

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The quality of cervical spinal cord images can be improved by the use of tailored radiofrequency coil solutions for ultra-high field imaging; however, very few commercial and research 7 Tesla radiofrequency coils currently exist for the spinal cord, and in particular those with parallel transmit 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 8 dipoles to ensure high homogeneity over this large region of the spinal cord. The Rx portion is made of 20 semi-adaptable 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 being tight fitting to ensure high sensitivity. We demonstrate RF shimming capabilities to optimize B1+ uniformity, power efficiency and/or specific absorption rate (SAR) efficiency. B1+ homogeneity, SNR and g-factor was 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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A 128‐channel receive array for cortical brain imaging at 7 T

Gruber

Stockmann

Mareyam

et al. 2023

Magnetic Resonance in Med

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PurposeA 128‐channel receive‐only array for brain imaging at 7 T was simulated, designed, constructed, and tested within a high‐performance head gradient designed for high‐resolution functional imaging.MethodsThe coil used a tight‐fitting helmet geometry populated with 128 loop elements and preamplifiers to fit into a 39 cm diameter space inside a built‐in gradient. The signal‐to‐noise ratio (SNR) and parallel imaging performance (1/g) were measured in vivo and simulated using electromagnetic modeling. The histogram of 1/g factors was analyzed to assess the range of performance. The array's performance was compared to the industry‐standard 32‐channel receive array and a 64‐channel research array.ResultsIt was possible to construct the 128‐channel array with body noise–dominated loops producing an average noise correlation of 5.4%. Measurements showed increased sensitivity compared with the 32‐channel and 64‐channel array through a combination of higher intrinsic SNR and g‐factor improvements. For unaccelerated imaging, the 128‐channel array showed SNR gains of 17.6% and 9.3% compared to the 32‐channel and 64‐channel array, respectively, at the center of the brain and 42% and 18% higher SNR in the peripheral brain regions including the cortex. For R = 5 accelerated imaging, these gains were 44.2% and 24.3% at the brain center and 86.7% and 48.7% in the cortex. The 1/g‐factor histograms show both an improved mean and a tighter distribution by increasing the channel count, with both effects becoming more pronounced at higher accelerations.ConclusionThe experimental results confirm that increasing the channel count to 128 channels is beneficial for 7T brain imaging, both for increasing SNR in peripheral brain regions and for accelerated imaging.

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A patient‐friendly 16‐channel transmit/64‐channel receive coil array for combined head–neck MRI at 7 Tesla

Cited by 17 publications

References 41 publications

Double‐row dipole/loop combined array for human whole brain imaging at 7 T

Double‐row dipole/loop combined array for human whole brain imaging at 7 T

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

A 128‐channel receive array for cortical brain imaging at 7 T

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