Structural and functional MRI reveals multiple retinal layers
Structural and functional MRI reveals multiple retinal layers
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DOI：
10.1073/pnas.0605790103
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发表时间：
2006-11-14
影响因子：
11.1
通讯作者：
Duong, Timothy Q.
中科院分区：
文献类型：
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作者：
Cheng, Haiying;Nair, Govind;Duong, Timothy Q.
磁共振成像（MRI）是一种无创的诊断方式，它能在体内显示解剖结构、生理机能和功能，且不受深度限制，也没有光学干扰。然而，将MRI应用于视网膜仍然具有挑战性。我们提高了空间分辨率，以分辨视网膜中特定层的结构和功能反应，并在一种已建立的视网膜变性动物模型中证实了层状分辨率。正常大鼠视网膜的结构MRI显示出三个条带，从组织学角度对应于：（i）神经节细胞层/内核层复合体以及嵌入其中的视网膜血管；（ii）无血管的外核（光感受器）层及其光感受器节段；（iii）脉络膜血管层。使用血管内造影剂（钆 - 二乙烯三胺五乙酸）成像增强了围绕视网膜的视网膜和脉络膜血管层，但未增强无血管的外核层和玻璃体。同样，血氧水平依赖（BOLD）功能MRI显示出对高氧和高碳酸血症的特定层反应。重要的是，两个血管层中特定层的BOLD反应是不同的，这表明这两个血管系统受到不同的调节。为了证实敏感性和特异性，我们应用特定层MRI来记录皇家外科医师学院大鼠的光感受器变性。与组织学结果一致，特定层MRI检测到外核层的变性。令人惊讶的是，MRI显示皇家外科医师学院大鼠视网膜中脉络膜血管层厚度增加，并且对高氧和高碳酸血症的BOLD反应减弱，这表明光感受器缺失继发血管反应性紊乱。我们得出结论，MRI是一种强大的研究工具，能够分辨视网膜中特定层的结构和功能反应，并探测视网膜疾病中特定层的变化。
MRI is a noninvasive diagnostic modality that reveals anatomy, physiology, and function in vivo without depth limitation or optical interference. MRI application to the retina, however, remains challenging. We improved spatial resolution to resolve layer-specific structure and functional responses in the retina and confirmed the laminar resolution in an established animal model of retinal degeneration. Structural MRI of normal rat retinas revealed three bands corresponding histologically to (i) the combined ganglion cell layer/inner nuclear layer plus the embedded retinal vessels, (ii) the avascular outer nuclear (photoreceptor) layer and its photoreceptor segments, and (iii) the choroidal vascular layer. Imaging with an intravascular contrast agent (gadolinium-diethylene-tri-amine-pentaacetic acid) enhanced the retinal and choroidal vascular layers bounding the retina, but not the avascular outer nuclear layer and the vitreous. Similarly, blood-oxygen-level-dependent (BOLD) functional MRI revealed layer-specific responses to hyperoxia and hypercapnia. Importantly, layer-specific BOLD responses in the two vascular layers were divergent, suggesting the two vasculatures are differentially regulated. To corroborate sensitivity and specificity, we applied layer-specific MRI to document photoreceptor degeneration in Royal Cc-liege of Surgeons rats. Consistent with histology, layer-specific MRI detected degeneration of the outer nuclear layer. Surprisingly, MRI revealed increased thickness in the choroidal vascular layer and diminished BOLD responses to hyperoxia and hypercapnia in the Royal College of Surgeons rat retinas, suggesting perturbation of vascular reactivity secondary to photoreceptor loss. We conclude that MRI is a powerful investigative tool capable of resolving lamina-specific structures and functional responses in the retina as well as probing lamina-specific changes in retinal diseases.