Sodium-MR-imaging of the brain: initial clinical results

Twelve patients with different diseases of the brain were examined with sodium and proton MRI at 1.5 Tesla and the results of both studies compared. Due to the 1500-fold lower concentration in the body, the decreased sensitivity and the shorter relaxation times of sodium compared with hydrogen a sequence with gradient reversal and a volume imaging method was applied to achieve a short echo time (4.5 ms). As a result of the mainly extracellular distribution of sodium the CSF spaces are depicted by their high signal intensity while the normal parenchyma is not visible. Changes induced by encephalitis, ischemic infarction and tumors can also be detected by their increased sodium content. Different tumors provided different signal intensities, not always permitting a distinction between tumor, surrounding edema and CSF. The diagnostic impact of these findings is discussed.