Magn Reson Med. 2019;1–9. wileyonlinelibrary.com/journal/mrm | 1 © 2019 International Society for Magnetic Resonance in Medicine Received: 23 November 2018 | Revised: 2 April 2019 | Accepted: 7 April 2019 DOI: 10.1002/mrm.27787 NOTE Correlation of quantitative conductivity mapping and total tissue sodium concentration at 3T/4T Yupeng Liao 1 | Nazim Lechea 1 | Arthur W. Magill 1 | Wieland A. Worthoff 1 | Vincent Gras 1 | N. Jon Shah 1,2,3,4,5 1 Institute of Neuroscience and Medicine (INM‐4), Forschungszentrum Jülich, Jülich, Germany 2 Institute of Neuroscience and Medicine (INM‐11), JARA, Forschungszentrum Jülich, Jülich, Germany 3 JARA‐BRAIN‐Translational Medicine, Aachen, Germany 4 Department of Neurology, RWTH Aachen University, Aachen, Germany 5 Monash Biomedical Imaging, School of Psychology, Monash University, Melbourne, Australia Correspondence N. Jon Shah, Institute of Neuroscience and Medicine, Medical Imaging Physics (INM‐4), Forschungszentrum Jülich GmbH, Wilhelm‐Johnen‐Straße 52425 Jülich, Germany. Email: n.j.shah@fz-juelich.de Present Address Arthur W. Magill, Medical Physics in Radiology, German Cancer Research Centre (DKFZ), Heidelberg, Germany Vincent Gras, UNIRS, Institut d’Imagerie Biomédicale, Neurospin, CEA Saclay, Gif‐ sur‐Yvette, France Nazim Lechea, PAREXEL International GmbH, Berlin, Germany Funding information China Scholarship Council (20126090020). Purpose: To investigate the correlation between electrical conductivity and sodium concentration, both measured in vivo, in the human brain. Methods: Conductivity measurements were performed on samples with different sodium (Na + ) and agarose concentrations using a dielectric probe, and the corre- lation between conductivity and Na + content was evaluated. Subsequently, brain conductivity and total Na + content maps were measured in 8 healthy subjects using phase‐based MREPT and sodium MRI, respectively. After co‐registration and spatial normalization to the 1 mm 152 MNI brain atlas, the relationship between conduc- tivity and tissue sodium concentration (TSC) was examined within different brain regions. Results: The conductivities of agarose gels increased linearly with NaCl concentra- tion, while remaining almost independent of agarose content. When measured in healthy subjects, conductivities showed positive correlation with total tissue sodium concentration (R = 0.39, P < 0.005). The same trend was found in gray matter (R = 0.36, P < 0.005) and in white matter (R = 0.28, P < 0.05). Conclusion: Tissue conductivity shows a positive correlation with total sodium con- centration. Conductivity might serve as a novel technique to visualize the total tissue electrolyte concentration, although refinements in the consideration of e.g., tissue water content, would be necessary to improve the quantitative value. KEYWORDS electrical conductivity, magnetic resonance electrical properties tomography (MREPT), sodium MRI, sodium quantification, tissue sodium concentration (TSC) 1 | INTRODUCTION Conductivity is a fundamental property of tissue that char- acterizes its capability to conduct electrical current when external electromagnetic fields are applied. Mapping conductivity can potentially serve as a biomarker, indicating tissue health. 1-3 For example, compared to normal tissue, a typical conductivity elevation of 10–30% was found in tumor tissues, whereas in certain types of malignant breast carci- noma, an increment of over 200% was reported. 4,5 Moreover,