Chuang Kai-Hsiang, Koretsky Alan P, Sotak Christopher H
Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
Magn Reson Med. 2009 Jun;61(6):1528-32. doi: 10.1002/mrm.21962.
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.
将大鼠嗅球（OB）和皮质中T(1)和T(2)弛豫率（ΔR(1)和ΔR(2)）的时间变化与相应切除组织样本中的绝对锰（Mn）浓度进行了比较。在静脉注射176 mg/kg MnCl(2)之前以及之后的1、7、28和35天测量体内T(1)和T(2)弛豫时间。ΔR(1)、ΔR(2)和绝对Mn浓度的值在第1天达到峰值，然后在28至35天后降至接近对照水平。大鼠脑中Mn的生物消除率明显快于使用放射性同位素技术报道的速率。R(1)和R(2)弛豫率与基础组织Mn浓度呈线性比例，并反映组织中存在的Mn的总绝对量。体内Mn的r(1)和r(2)组织弛豫率与体外Mn(2+)水溶液的值相当。这些结果表明，全身给予Mn(2+)后锰增强磁共振成像（MEMRI）对比度的丧失是由于Mn(2+)从脑中消除所致。
