Na-23 Magnetic Resonance Imaging of Tissue Sodium

Hypertension is linked to disturbed total-body sodium (Na+) regulation; however, measuring Na+ disposition in the body is difficult. We implemented Na-23 magnetic resonance spectroscopy (Na-23-MR) and imaging technique (Na-23-MRI) at 9.4T for animals and 3T for humans to quantify Na+ content in skeletal muscle and skin. We compared Na-23-MRI data with actual tissue Na+ content measured by chemical analysis in animal and human tissue. We then quantified tissue Na+ content in normal humans and in patients with primary aldosteronism. We found a 29% increase in muscle Na+ content in patients with aldosteronism compared with normal women and men. This tissue Na+ was mobilized after successful treatment without accompanying weight loss. We suggest that, after further refinements, this tool could facilitate understanding the relationships between Na+ accumulation and hypertension. Furthermore, with additional technical advances, a future clinical use may be possible. (Hypertension. 2012; 59: 167-172.)