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Accurate, Reliable and Optimized functional MAgnetic resonance imaging at unprecedented field strength for unique exploration of the human brain

Periodic Reporting for period 1 - AROMA (Accurate, Reliable and Optimized functional MAgnetic resonance imaging at unprecedented field strength for unique exploration of the human brain)

Reporting period: 2021-01-01 to 2021-12-31

The objectives of the project are to overcome the fundamental obstacles to leverage the potential of a unique whole-body 11.7 Tesla MRI scanner located at CEA (France). With greater magnetic fields however come greater challenges. The nature of the problems compared to lower field magnets is not new, but they are amplified. As a result, they require innovative actions to fetch and exploit the boost of signal to noise ratio delivered by the field. The vocation of the instrument is to provide non invasice means to explore the human brain with unprecedented details, i.e. its cognitive functions and associated pathologies. Zooming on the brain or acquiring data with boosted sensitivty could thereby provide knowledge hardly accessible with other modalities. The novel solutions developed in the AROMA project, although they are centered around the 11.7T problems, should have implications for lower field strengh MRI available in the clinic.
The radiofrequency coil used in MR exams is of paramount importance to excite the water magnetization and collect signal to reconstruct images. In this context, the partner in Glasgow in collaboration with CEA has performed many electromagnetic simulations to tune different parameters to narrow down the optimal design. After one year, the coil design layout is complete. In the meantime, CEA has coordinated the project, continued the commissioning of the 11.7T MRI instrument, developed an MR thermometry method to measure non invasively the temperature rise induced by RF pulses and has boosted parallel transmission performance at 7T (while still minimizing the impact on the workflow). A lot of work also has been performed with DZNE and the University of Maastricht to program anatomical and fMRI sequences readily applicable at 11.7T once authorization to scan volunteers at that field strength is obtained. ETH has continued exploring different motion compensation techniques using different methodologies: field sensors, RF trackers and 3D navigators. Skope has designed, produced and tested their first clip on camera at 11.7T. It has already turned to be an invaluable tool for troubleshooting the scanner. They have also supported the entire consortium in their applications (Gradient Impulse Response Function measurements, k-space trajectory monitoring and MR thermometry). The first images acquired at 11.7T on a pumpkin were released Oct 7th 2021, after nearly 20 years of research and development. The project thus has benefitted from great media exposure with interviews for newspapers, radio and national TV.
It is too early to evaluate experimentally the performance of the RF coil. But with two other 11.7T MRI scanners (NIH USA and South Korea), the University of Glasgow will have a unique first experience at that field strength and will likely participate in other, comparable, projects. The development of the Pasteur package by CEA and DZNE, with universal pulses, on the software platform of the 7T Siemens Terra also could have implications for clinical routine at 7T. The sequences indeed allow solving to a great extent the RF field inhomogeneity problem in the brain, with zero time penalty for the user and no expertise required. It could be a game changer to leverage the potential of 7T scanners in the clinic. The package is available to the community under a C2P agreement. The tools resulting from ERC proof of concept and FET Open grants, obtaining CE marking for parallel transmission at 7T towards the commercialization of the technology could be the subject of an EIC transition call for proposals... Some of the anatomical sequences programmed by DZNE furthermore yield impressive spatiotemporal resolution (e.g. 1:15 min for 0.7 mm isotropic resolution using segmented 3D-EPI). Motion correction is also of paramount importance and to date there is no perfect solution. The developments carried out by ETH could lead to solutions of interest to the industrials who could benefit from them in their applications at lower fields. Finally, the MR thermometry results published by CEA and Skope present the first strong evidence that there could be more heat dissipation in the brain than the theoretical models suggest. It is the first time that the small temperature rises induced by RF fields in MRI could be measured with such precision and accuracy, non invasively, in the human brain and in normal conditions. Such technology thereby could be of use to verify the safety limits used in the mobile phone industry, where the specific absorption rate (SAR) metric remains also the norm for simplicity. Last but not least, the troubleshooting of the scanner demonstrated with the Skope technology has turned already invaluable for experimental devices. After dissemination on the subject, the company should benefit from additional exposure and may sensitize the industrials about the importance of these measurements.
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