Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany.
Neuroimage. 2012 Nov 1;63(2):812-7. doi: 10.1016/j.neuroimage.2012.06.073. Epub 2012 Jul 14.
This work compares magnetization transfer (MT) MRI of living mice with contrast-enhanced MT MRI using intraventricular administration of gadopentetate dimeglumine (Gd-DTPA), systemic administration of MnCl2, and both. In MT MRI at 9.4 T, the contrast-to-noise ratio (CNR) between white matter (WM) and gray matter (GM) increased by 85% after Gd-DTPA injection into the lateral ventricle. When applied in conjunction with manganese-enhanced MT MRI (117 μm isotropic resolution, 6 min measuring time), Gd-DTPA boosted the CNR increase from +56% to +117%. Additional T1 measurements at 2.35 T revealed that intraventricular Gd-DTPA shortens the T1 of GM much more than that of WM, which corresponds to estimated extracellular spaces of 26% in GM and only 15% in WM. These results explain the additional MT contrast enhancement by Gd-DTPA and demonstrate that the T1 shortening by intracellular Mn2+ is well complemented by extracellular Gd-DTPA. The data suggest a high myelin and low water content to hinder access of hydrophilic paramagnetic agents, so that the resulting differential accumulation effectively reduces the MT saturation in water-rich tissues and thereby facilitates the mapping of myelin-rich tissues. Finally, a 156% CNR increase between GM and WM for contrast-enhanced MT MRI at 9.4T using both Gd-DTPA and manganese allowed for 60μm isotropic resolution (102 min measuring time), which delineated myelinated fibers and layers even within GM areas such as the thalamus and cerebellar cortex. Improved MT contrasts were also seen in the cervical spinal cord.
本工作比较了活体小鼠的磁化传递（MT）MRI 与脑室内注射钆喷酸葡胺（Gd-DTPA）、系统给予氯化锰（MnCl2）以及两者联合应用的对比增强 MT MRI。在 9.4T 的 MT MRI 中，Gd-DTPA 注射到侧脑室后，白质（WM）和灰质（GM）之间的对比噪声比（CNR）增加了 85%。当与锰增强 MT MRI （117μm 各向同性分辨率，6 分钟测量时间）联合应用时，Gd-DTPA 将 CNR 增加从+56%提高到+117%。在 2.35T 进行的额外 T1 测量显示，脑室 Gd-DTPA 使 GM 的 T1 缩短幅度远大于 WM，这与 GM 中估计的细胞外空间为 26%，而 WM 中仅为 15%相对应。这些结果解释了 Gd-DTPA 引起的额外 MT 对比增强，并证明细胞内 Mn2+引起的 T1 缩短很好地补充了细胞外 Gd-DTPA。这些数据表明，高髓鞘和低含水量阻碍了亲水性顺磁剂的进入，因此，由此产生的差异积累有效地减少了富含水的组织中的 MT 饱和，从而有利于富含髓鞘的组织的绘图。最后，使用 Gd-DTPA 和锰在 9.4T 进行对比增强 MT MRI 时，GM 和 WM 之间的 CNR 增加了 156%，实现了 60μm 各向同性分辨率（102 分钟测量时间），甚至可以在 GM 区域（如丘脑和小脑皮层）内描绘出髓鞘纤维和层。在颈脊髓中也观察到了改善的 MT 对比。
