Temporal changes in the T1 and T2 relaxation rates (ΔR1 and ΔR2) in the rat brain are consistent with the tissue-clearance rates of elemental manganese
✍ Scribed by Kai-Hsiang Chuang; Alan P. Koretsky; Christopher H. Sotak
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- English
- Weight
- 293 KB
- Volume
- 61
- Category
- Article
- ISSN
- 0740-3194
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✦ Synopsis
Abstract
Temporal changes in the T~1~ and T~2~ relaxation rates (Δ__R__~1~ and Δ__R__~2~) in rat olfactory bulb (OB) and cortex were compared with the absolute manganese (Mn) concentrations from the corresponding excised tissue samples. In vivo T~1~ and T~2~ relaxation times were measured before, and at 1, 7, 28, and 35 d after intravenous infusion of 176 mg/kg MnCl~2~. The values of Δ__R__~1~, Δ__R__~2~, and absolute Mn concentration peaked at day 1 and then declined to near control levels after 28 to 35 d. The Mn bioelimination rate from the rat brain was significantly faster than that reported using radioisotope techniques. The R~1~ and R~2~ relaxation rates were linearly proportional to the underlying tissue Mn concentration and reflect the total absolute amount of Mn present in the tissue. The in vivo Mn r~1~ and r~2~ tissue relaxivities were comparable to the in vitro values for aqueous Mn^2+^. These results demonstrate that loss of manganese‐enhanced MRI (MEMRI) contrast after systemic Mn^2+^ administration is due to elimination of Mn^2+^ from the brain. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.