Research Imaging Institute and Department of Ophthalmology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
Radiology. 2012 Jul;264(1):234-41. doi: 10.1148/radiol.12112033. Epub 2012 Apr 20.
To develop high-spatial-resolution magnetic resonance (MR) microangiography techniques to image the rat ocular circulation.
Animal experiments were performed with institutional Animal Care Committee approval. MR microangiography (resolution, 84×84×84 μm or 42×42×84 μm) of the rat eye (eight rats) was performed by using a custom-made small circular surface coil with an 11.7-T MR unit before and after monocrystalline iron oxide nanoparticle (MION) injection. MR microangiography measurements were made during air, oxygen, and carbogen inhalation. From three-dimensional MR microangiography, the retina was virtually flattened to enable en face views of various retinal depths, including the retinal and choroidal vascular layers. Signal intensity changes within the retinal or choroidal arteries and veins associated with gas challenges were analyzed. Statistical analysis was performed by using paired t tests, with P<.05 considered to indicate a significant difference. Bonferroni correction was used to adjust for multiple comparisons.
The central retinal artery, long posterior ciliary arteries, and choroidal vasculature could be distinguished on MR microangiograms of the eye. With MR microangiography, retinal arteries and veins could be distinguished on the basis of blood oxygen level-dependent contrast. Carbogen inhalation-enhanced MR microangiography signal intensity in both the retina (P=.001) and choroid (P=.027) compared with oxygen inhalation. Carbogen inhalation showed significantly higher signal intensity changes in the retinal arteries (P=.001, compared with oxygen inhalation), but not in the veins (P=.549). With MION administration, MR microangiography depicted retinal arterial vasoconstriction when the animals were breathing oxygen (P=.02, compared with animals breathing air).
MR microangiography of the eye allows depth-resolved imaging of small angiographic details of the ocular circulation. This approach may prove useful in studying microvascular pathologic findings and neurovascular dysfunction in the eye and retina.
开发高空间分辨率磁共振（MR）微血管成像技术，以显示大鼠眼循环。
本动物实验获得机构动物护理委员会批准。在使用 11.7-T MR 单元的定制小型圆形表面线圈进行 MR 微血管成像（分辨率为 84×84×84μm 或 42×42×84μm）之前和之后，对大鼠眼（8 只大鼠）进行单晶体氧化铁纳米颗粒（MION）注射。MR 微血管成像测量在空气、氧气和碳化氧吸入期间进行。从三维 MR 微血管成像中，视网膜实际上被压扁，以实现各种视网膜深度的面状视图，包括视网膜和脉络膜血管层。分析与气体挑战相关的视网膜或脉络膜动脉和静脉内的信号强度变化。采用配对 t 检验进行统计分析，P<.05 表示差异具有统计学意义。采用 Bonferroni 校正法进行多重比较调整。
在眼部的 MR 微血管成像中可以区分中央视网膜动脉、长睫状后动脉和脉络膜血管系统。通过 MR 微血管成像，可以根据血氧水平依赖对比区分视网膜动脉和静脉。与氧气吸入相比，碳化氧吸入增强了视网膜（P=.001）和脉络膜（P=.027）的 MR 微血管成像信号强度。碳化氧吸入在视网膜动脉中显示出明显更高的信号强度变化（P=.001，与氧气吸入相比），但在静脉中没有（P=.549）。在给予 MION 后，当动物呼吸氧气时，MR 微血管成像显示出视网膜动脉收缩（P=.02，与呼吸空气的动物相比）。
眼部的 MR 微血管成像允许对眼循环的小血管细节进行深度分辨成像。这种方法可能有助于研究眼部和视网膜的微血管病理发现和神经血管功能障碍。
