Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, USA; Department of Radiology, University of Texas Health Science Center, San Antonio, Texas 78229, USA.
Magn Reson Med. 2011 Aug;66(2):546-54. doi: 10.1002/mrm.22853. Epub 2011 Feb 28.
The goal of this study was to demonstrate high-resolution anatomical, blood oxygenation level-dependent, and blood flow MRI on large nonhuman primate retinas using a 3-Tesla clinical scanner as a first step toward translation. Baboon was chosen because of its evolutionary similarity to human. Anesthetized preparation, free of eye-movement artifacts, was used to evaluate clinical scanner hardware feasibility and optimize multimodal protocols for retinal MRI. Anatomical MRI (0.1×0.2×2.0 mm3) before contrast-agent injection detected three alternating bright-dark-bright layers. The hyperintense inner strip nearest to the vitreous was enhanced by an intravascular contrast agent, which likely included the ganglion and bipolar cell layer and the embedded retinal vessels. The hypointense middle strip showed no contrast enhancement, which likely included the avascular outer unclear layer and photoreceptor segments. The hyperintense outer strip showed contrast enhancement, which likely corresponded to the choroid vascular layer. In the posterior retina, the total thickness including the choroid was 617±101 μm (±standard deviation, n=7). Blood oxygenation level-dependent functional MRI (0.3×0.6×2.0 mm3) of oxygen inhalation relative to air increased the signals by 6.5±1.4%. Basal blood flow (2×2×2 mm3) was 83±30 mL/100 g/min (air), and hypercapnia increased blood flow by 25±9% (P<0.05). This study demonstrates multimodal MRI to image anatomy, physiology, and function on large nonhuman primate retinas using a clinical scanner, offering encouraging data to explore human applications.
本研究旨在展示使用 3T 临床扫描仪对大型非人类灵长类动物视网膜进行高分辨率解剖学、血氧水平依赖和血流 MRI，作为向人类应用探索迈出的第一步。之所以选择狒狒，是因为它在进化上与人相似。使用无眼动伪影的麻醉前准备来评估临床扫描仪硬件的可行性并优化视网膜 MRI 的多模态方案。注射造影剂前的解剖学 MRI（0.1×0.2×2.0mm3）检测到三个交替的亮-暗-亮层。最靠近玻璃体的高信号内层被血管内造影剂增强，这可能包括节细胞和双极细胞层以及嵌入的视网膜血管。低信号的中间层没有增强，可能包括无血管的外核层和光感受器节段。高信号的外层显示出增强，可能对应于脉络膜血管层。在后视网膜中，包括脉络膜在内的总厚度为 617±101μm（±标准差，n=7）。与空气相比，吸氧的血氧水平依赖功能 MRI（0.3×0.6×2.0mm3）增加了 6.5±1.4%的信号。基础血流（2×2×2mm3）为 83±30mL/100g/min（空气），高碳酸血症使血流增加 25±9%（P<0.05）。本研究使用临床扫描仪展示了多模态 MRI 对大型非人类灵长类动物视网膜的解剖学、生理学和功能成像，为探索人类应用提供了令人鼓舞的数据。
