Validation and SAR evaluation of a 16-channel 1H/23Na dipole/loop array for 7T MRI

Motivation: 7T MRI enables 23Na MRI due to enhanced sensitivity. Combined with proton imaging, functional and anatomical information can be acquired to characterise brain status. Goal(s): Establishing safe RF power limits for an in-house built 1H/23Na loop/dipole array for subsequent in-vivo experiments. Approach: Phantom MR results at 7T and electromagnetic simulations were compared to evaluate consistency between experiments and simulations. Human models were simulated to demonstrate SAR10g levels for different patients. Results: Simulated and experimental B1+fields showed high correlation for individual magnitudes and phases. Worst-case SAR10g for human models all remain within safety limits, demonstrating the clinical potential of our proposed coil. Impact: Towards in-vivo RF coil use, we validated simulated RF models of the coil at 23Na/1H frequencies using measured B1+field magnitude and phase maps. Safe RF power limits can therefore be established for research coils to proceed to in-vivo experiments.