23Na-MRI and EPT: Are Sodium Concentration and Electrical Conductivity at 298 MHz (7T) Related?

Astrid L.H.M.W. van Lier¹, Paul W. de Bruin², Sebastian A. Aussenhofer³, Peter R. Luijten¹, Jan J.W. Lagendijk¹, Cornelis A.T. van den Berg¹, Andrew G. Webb³

The electrical conductivity at the Larmor frequency can be measured with electrical properties tomography (EPT). It is assumed that the conductivity at RF frequencies (>100 MHz) is not affected by impaired ion mobility (e.g. by cell membranes), but only by ion concentration. Comparing EPT-based conductivity maps and ²³Na-MR images offers the possibility to investigate this hypothesis in vivo. Based on the graphical analysis of residuals, it is concluded that the conductivity of healthy brain tissue at 298 MHz can be described using a model derived for saline solutions. This might enable direct extraction of sodium concentrations from electrical conductivity images.