Nikolai I. Avdievich¹, Georgiy Solomakha², Loreen Ruhm¹, Anton V Nikulin^1,3, Arthur Magill⁴, and Klaus Scheffler^1,3
1High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, ²Physics and Engineering, ITMO University, St. Petersburg, Russian Federation, ³Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany, ⁴Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany

In spite of great benefits of 7T MRI, its further clinical development is associated with difficulties in designing RF coils. Recently, we developed a novel type of dipole antennas, a folded-end dipole. In this work we evaluated an 8-element transceiver folded-end dipole array for 7T human head imaging. The array provided ~20% higher Tx-efficiency and significantly better whole-brain coverage than that of a widely-used commercial array. In addition, we evaluated passive dipoles for decoupling the proposed array. In contrast to the common unfolded dipole array, the passive dipoles produce practically no destructive interference with the RF field of the array.

Ria Forner¹, Ingmar Voogt², Bart Steensma³, Kyungmin Nam³, Mark Gosselink³, Debra Rivera⁴, William T Clarke^5,6, Aidin Alihaghnejad², Arjan Hendriks³, and Dennis Klomp^1
1UMC Utrecht, Utrecht, Netherlands, ²Wavetronica B.V., Utrecht, Netherlands, ³University Medical Center Utrecht, Utrecht, Netherlands, ⁴Eindhoven University of Technology, Eindhoven, Netherlands, ⁵Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield, United Kingdom, ⁶Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom

A novel coil design with a 31P birdcage and a 1H dipole array is presented for the purpose of fMRS applications.  This design allows for free line-of-sight for fMRI and fMRS visual stimulation via mirrors and despite a lower fill-factor performs comparably to a smaller dual-tuned birdcage. The matching of both frequencies is adequate for a range of human head circumferences from 52cm through 57cm. The 31P birdcage performance is not significantly degraded by presence of 1H dipoles when compared to a conventional birdcage dual-tuning strategy with Foster networks.

Jabrane Karkouri*¹, Ria Forner*², Martijn Lunenburg³, Ettore Flavio Meliadò³, Catalina Arteaga³, Alexander Raaijmakers^4,5, Christopher T. Rodgers†¹, and Dennis Klomp†^4
1University of Cambridge, Cambridge, United Kingdom, ²Radiology, UMC Utrecht, Utrecht, Netherlands, ³Tesla Dynamic Coils, Zaltbommel, Netherlands, ⁴UMC Utrecht, Utrecht, Netherlands, ⁵Biomedical engineering, Eindhoven University of Technology, Utrecht, Netherlands

We present a novel dual dipole coil concept for 7T ³¹P metabolic imaging in the body.

We constructed an array of 8x stacked ¹H/ ³¹P dipoles, evaluating their performance by bench measurements, EM modelling, phantom experiments and in vivo scans in human liver. Parameters such as coupling, transmission efficiency and SAR are compared to those of a whole-body ³¹P birdcage coil.

Shajan Gunamony^1,2 and David Feinberg^3
1Imaging Centre of Excellence, University of Glasgow, Glasgow, United Kingdom, ²MR CoilTech Limited, Glasgow, United Kingdom, ³Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States

The NextGen 7T scanner is equipped with a high-performance head gradient insert and hence the radial space available on the patient table for radiofrequency (RF) coils is limited. In addition to a large visual field to support fMRI studies, a split-top receive array on a sliding mechanism is desirable for improved patient comfort. We have developed a novel 8-channel transmit 64-channel receive 7T head coil and implemented a sliding mechanism to operate within the limited space in the head gradient insert. In this abstract, we present the overall coil design, transmit array performance and preliminary phantom results.

D Rangaprakash¹, Bastien Guerin¹, Jason P Stockmann¹, Markus W May², Nibardo Lopez Rios³, Kyle M Gilbert⁴, Yulin Chang⁵, Lawrence L Wald^1,6, Julien Cohen-Adad^3,7,8, Boris Keil^1,2, and Robert L Barry^1,6
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, ²Institute of Medical Physics and Radiation Protection, University of Applied Sciences Mittelhessen, Giessen, Germany, ³NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada, ⁴Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, ON, Canada, ⁵Siemens Medical Solutions USA Inc., Malvern, PA, United States, ⁶Harvard-Massachusetts Institute of Technology Division of Health Sciences & Technology, Cambridge, MA, United States, ⁷Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montreal, QC, Canada, ⁸Mila – Quebec AI Institute, Montreal, QC, Canada

Several neurological diseases affect both the brain and spinal cord. 7T MRI enables better imaging of the narrow cord as well as single-subject prediction using fMRI. However, concurrent brain-cord 7T imaging requires a coil with good SNR and acceleration capabilities in both head and neck, which has been unavailable. To overcome this, we performed flip-angle, SNR, g-factor and tSNR characterization of a custom-built 16Tx/64Rx head/neck radiofrequency coil. We also compared it against a custom-built 8Tx/20Rx cervical spine coil as well as a commercial 8Tx/32Rx brain coil. This hardware will pave the way for concurrent brain-cord 7T MRI in the future.

Sadri Guler^1,2, Giovanni Costa³, Vincent Boer², Maarten Paulides³, Peter Baltus³, Esben Petersen^1,2, and Irena Zivkovic^3
1Section for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Copenhagen, Denmark, ²Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen, Denmark, ³Electrical Engineering Department, Technical University of Eindhoven, Eindhoven, Netherlands

The shielded-coaxial-cable (SCC) coils have been proposed recently as highly decoupled elements per se. The SCC coils are not very sensitive to bending, elongation and various degrees of overlapping. We experimentally investigated the central SNR when the SCC coils are placed in three different arrangements on a cylindrical object. The highest central SNR (more than 30% higher than in the other two arrangements) was obtained when the coils were elongated and adjacent to each other. This arrangement is important when the ROI is located deep inside the field of view, such in c-spine spinal cord or deep brain imaging.   

Paul-François Gapais^1,2, Saadou Almokdad², Michel Luong³, Eric Giacomini², Elodie Georget¹, and Alexis Amadon^2
1Multiwave Imaging SAS, Marseille, France, ²Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France, ³CEA, IRFU, Université Paris-Saclay, Gif-sur-Yvette, France

With the increasing number of elements in receive arrays, the need to accurately predict coil performance is crucial. Decoupling is usually performed with low-input impedance preamplifier decoupling. Recently, new schematics have been proposed that rely on high-input impedance preamplifiers. A simulation method is proposed here to evaluate preamplifier decoupling performance in this context on a 2-layer array at 7T. Results show a strong influence on the thermal SNR according to the impedance presented by the preamplifier to the coil output. The higher this impedance the higher the SNR, but practical implementation need a trade-off between high impedance and noise-matching.