Department of Physics, Washington University, St. Louis, MO, USA.
NMR Biomed. 2014 Apr;27(4):390-8. doi: 10.1002/nbm.3073. Epub 2014 Jan 16.
Manganese-enhanced MRI (MEMRI) with topical loading of MnCl2 provides optic nerve enhancement comparable to that seen by intravitreal injection. However, the impact of this novel and non-invasive Mn(2+) loading method on visual function requires further assessments. The objective of this study is to determine the optimal topical Mn(2+) loading dosage for MEMRI and to assess visual function after MnCl2 loading. Intravitreal administration was performed to compare the two approaches of MnCl2 loading. Twenty-four hours after topical loading of 0, 0.5, 0.75, and 1 M MnCl2 , T1 -weighted, T2-weighted, diffusion tensor imaging and visual acuity (VA) assessments were performed to determine the best topical loading dosage for MEMRI measurements and to assess the integrity of retinas and optic nerves. Mice were perfusion fixed immediately after in vivo experiments for hematoxylin and eosin and immunohistochemistry staining. Topical loading of 1 M MnCl2 damaged the retinal photoreceptor layer with no detectable damage to retina ganglion cell layers or prechiasmatic optic nerves. For the topical loading, 0.75 M MnCl2 was required to see sufficient enhancement of the optic nerve. At this concentration the visual function was significantly affected, followed by a slow recovery. Intravitreal injection (0.25 μL of 0.2 M MnCl2 ) slightly affected VA, with full recovery a day later. To conclude, intravitreal MnCl2 injection provides more reproducible results with less adverse side-effects than topical loading.
锰增强磁共振成像（MEMRI）通过局部加载 MnCl2 提供与玻璃体内注射相当的视神经增强。然而，这种新的非侵入性 Mn(2+)加载方法对视觉功能的影响需要进一步评估。本研究的目的是确定 MEMRI 的最佳局部 Mn(2+)加载剂量，并评估 MnCl2 加载后的视觉功能。通过玻璃体内给药来比较 MnCl2 加载的两种方法。在局部加载 0、0.5、0.75 和 1 M MnCl2 24 小时后，进行 T1 加权、T2 加权、扩散张量成像和视力（VA）评估，以确定 MEMRI 测量的最佳局部加载剂量，并评估视网膜和视神经的完整性。在体内实验后立即对小鼠进行灌注固定，进行苏木精和伊红以及免疫组织化学染色。局部加载 1 M MnCl2 会损伤视网膜光感受器层，而对视网膜神经节细胞层或视交叉前视神经没有可检测到的损伤。对于局部加载，需要 0.75 M MnCl2 才能看到足够的视神经增强。在该浓度下，视觉功能受到显著影响，随后缓慢恢复。玻璃体内注射（0.25 μL 0.2 M MnCl2）对 VA 有轻微影响，一天后完全恢复。总之，与局部加载相比，玻璃体内注射 MnCl2 提供更可重复的结果，不良反应更少。
