Quantitative sodium MRI of the human kidneys at 7T – Before, during and after water load via sliding window evaluation

23Na-MRI is a non-invasive tool for the in-vivo quantification of the tissue sodium concentration (TSC); however, it suffers from low in-vivo signals and short relaxation times. High magnetic field strengths, dedicated hardware and pulse sequences as well as various correction methods contribute to obtaining reliable TSCs. In the presented work we employ a custom-built coil and reference vial setup and perform T1, B1+ and B1- corrections that were validated in phantom measurements. We use a sliding window reconstruction for the quantitative 23Na-images to investigate the changes in the TSC before, during and after a water load in two healthy volunteers.