Chuang Kai-Hsiang, Koretsky Alan
Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, Maryland 20892-1065, USA.
Magn Reson Med. 2006 Mar;55(3):604-11. doi: 10.1002/mrm.20797.
There has been growing interest in using manganese-enhanced MRI (MEMRI) to detect neuronal activation, neural architecture, and neuronal connections. Usually Mn(2+) produces a very wide range of T(1) change. In particular, in neuronal tract tracing experiments the site of Mn(2+) injection can have very short T(1) while distant regions have small T(1) reductions, primarily due to dilution of Mn(2+). Most MEMRI studies use T(1)-weighted sequences, which can only give optimal contrast for a narrow range of T(1) changes. To improve sensitivity to the full extent of Mn(2+) concentrations and to optimize detection of low concentrations of Mn(2+), a fast T(1) mapping sequence based on the Look and Locker technique was implemented. Phantom studies demonstrated less than 6.5% error in T(1) compared to more conventional T(1) measurements. Using center-out segmented EPI, whole-brain 3D T(1) maps with 200-microm isotropic resolution were obtained in 2 h from rat brain. Mn(2+) transport from the rat olfactory bulb through appropriate brain structures could be detected to the amygdala in individual animals. The method reliably detected less than 7% reductions in T(1). With this quantitative imaging it should be possible to study more extensive pathways using MEMRI and decrease the dose of Mn(2+) used.
利用锰增强磁共振成像（MEMRI）检测神经元激活、神经结构和神经元连接的研究兴趣日益浓厚。通常，Mn(2+)会产生非常广泛的T(1)变化。特别是在神经元示踪实验中，Mn(2+)注射部位的T(1)可能非常短，而远处区域的T(1)降低幅度较小，这主要是由于Mn(2+)的稀释。大多数MEMRI研究使用T(1)加权序列，该序列仅能在狭窄的T(1)变化范围内提供最佳对比度。为了全面提高对Mn(2+)浓度的敏感性并优化低浓度Mn(2+)的检测，实施了一种基于Look和Locker技术的快速T(1)映射序列。模型研究表明，与更传统的T(1)测量相比，T(1)误差小于6.5%。使用中心向外分段回波平面成像（EPI），在2小时内从大鼠大脑获得了具有200微米各向同性分辨率的全脑三维T(1)图谱。在个体动物中，可以检测到Mn(2+)从大鼠嗅球通过适当的脑结构运输到杏仁核。该方法能够可靠地检测到T(1)降低幅度小于7%。通过这种定量成像，应该有可能使用MEMRI研究更广泛的神经通路，并减少Mn(2+)的使用剂量。
