Brain lithium concentrations in bipolar disorder patients: Preliminary Li-7 magnetic resonance studies at 3 T

Background: This study was conducted to investigate the feasibility of huma n brain Li-7 MRS investigations at a high magnetic field (3 T), and to furt her explore the relationship between brain and serum lithium measures in li thium-treated bipolar patients. Methods: Eight bipolar disorder type I patients (5 males, 3 females; mean a ge +/- SD = 33 +/- 9 years) were studied. A 3-T scanner, using a dual-tuned (H-1 and Li-7) echoplanar Imaging (EPI) compatible radiofrequency (RF) bir d-cage coil was used. Li-7 magnetic resonance spectroscopy (MRS) signal was acquired at the frequency of 49.64 MHz using an imaging selective in vivo spectroscopy (ISIS) sequence (TR = 15 sec, 128 averages), and quantitation was obtained in reference to an external standard. Results: The mean +/- SD oral lithium dose was 1265 +/- 442 mg/day, and the mean +/- SD 12-hour serum level was 0.69 +/- 0.19 mEq/L. The measured brai n lithium concentrations varied from 0.23 to 0.55 mEq/L (mean +/- SD = 0.35 +/- 0.11 mEq/L). The brain-serum ratios varied from 0.30 to 0.80 (mean +/- SD = 0.52 +/- 0.16). Subjects on single daily doses of lithium at bedtime (n = 5) had higher brain-serum lithium ratios compared with those on twice- a-day schedules (n = 3) (0.61 +/- 0.12 and 0.37 +/- 0.07, respectively; Man n-Whitney U test, Z = -2,24, p = .03). Conclusions: This study demonstrated for the first time the feasibility of Li-7 MRS human studies at 3 T. Future studies should examine a possible rol e for this methodology in investigations of lithium refractoriness and pred iction of treatment outcome in bipolar patients. Biol Psychiatry 2001;49:43 7-443 (C) 2001 Society of Biological Psychiatry.