Lithium (Li) is a core for many neuropsychiatric conditions. The safe serum range of Li treatment is narrow, and regular monitoring by blood test is required, although serum levels are thought to be a poor indicator of Li concentration in the brain itself. Brain Li concentration can be measured by magnetic resonance spectroscopy. However, little data exist in the healthy human brain, and there are no studies of the relaxation properties of brain (7)Li at 3 T. Here, 11 healthy male subjects were prescribed Li over a period of 11 days. In seven subjects, the in vivo T(1) of (7)Li was measured to be 2.1 ± 0.7 s. In the remaining subjects, spectroscopic imaging (1D) yielded a mean brain (7)Li concentration of 0.71 ± 0.1 mM, with no significant difference between gray and white matter. Mean serum concentration was 0.9 ± 0.16 mM, giving a mean brain/serum ratio of 0.78 ± 0.26.
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