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. 2009 Jun;61(6):1528-32.
doi: 10.1002/mrm.21962.

Temporal changes in the T1 and T2 relaxation rates (DeltaR1 and DeltaR2) in the rat brain are consistent with the tissue-clearance rates of elemental manganese

Kai-Hsiang Chuang  1 , Alan P Koretsky, Christopher H Sotak
Affiliations

Temporal changes in the T1 and T2 relaxation rates (DeltaR1 and DeltaR2) in the rat brain are consistent with the tissue-clearance rates of elemental manganese

Kai-Hsiang Chuang et al. Magn Reson Med. 2009 Jun.

Abstract

Temporal changes in the T(1) and T(2) relaxation rates (DeltaR(1) and DeltaR(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 DeltaR(1), DeltaR(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.

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Figures

Fig. 1
Fig. 1
Time series calculated (a) T1 and (b) T2 maps intersecting the OB and cortex in the same rat acquired before (control) and at 1, 7, 28, and 35 days after intravenous infusion of 176 mg/kg MnCl2.
Fig. 2
Fig. 2
Temporal changes in (a, b) ΔR1 (open square), (c, d) ΔR2 as a function of Mn concentration (gray diamond) in the OB and cortex. The star symbols (gray for Mn concentration; black for ΔR1 or ΔR2) represent statistical significance compared to day 0: * p < 0.05; ** p < 0.01; error bar = 1 standard deviation.
Fig. 3
Fig. 3
(a) R1 and (b) R2 versus Mn concentration in the OB and cortex for the various time points shown in Fig. 2.
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