In vivo human head MRI at 10.5T: a radiofrequency safety study and preliminary imaging results
Embargo Lift Date: 2020-11-21
Moortele, P. -F.
Magnetic Resonance in Medicine
International Society for Magnetic Resonance in Medicine
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Purpose: The purpose of this study is to safely acquire the first human head images at 10.5T.Methods: To ensure safety of subjects, we validated the electromagnetic simula-tion model of our coil. We obtained quantitative agreement between simulated and experimental B+1 and specific absorption rate (SAR). Using the validated coil model, we calculated radiofrequency power levels to safely image human subjects. We con-ducted all experiments and imaging sessions in a controlled radiofrequency safety lab and the whole-body 10.5T scanner in the Center for Magnetic Resonance Research.Results: Quantitative agreement between the simulated and experimental results was obtained including S-parameters, B+1 maps, and SAR. We calculated peak 10 g average SAR using 4 different realistic human body models for a quadrature excita-tion and demonstrated that the peak 10 g SAR variation between subjects was less than 30%. We calculated safe power limits based on this set and used those limits to acquire T2- and T∗2-weighted images of human subjects at 10.5T.Conclusions: In this study, we acquired the first in vivo human head images at 10.5T using an 8-channel transmit/receive coil. We implemented and expanded a previ-ously proposed workflow to validate the electromagnetic simulation model of the 8-channel transmit/receive coil. Using the validated coil model, we calculated radi-ofrequency power levels to safely image human subjects.