Department of Ophthalmology, Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, USA.
Magn Reson Med. 2011 Nov;66(5):1416-21. doi: 10.1002/mrm.22935. Epub 2011 May 20.
The retina consists of multiple cellular and synaptic layers and is nourished by two distinct (retinal and choroidal) circulations bounding the retina, separated by an avascular layer. High spatiotemporal resolution, layer-specific MRI of the retina remains challenging due to magnetic inhomogeneity-induced artifacts. This study reports passband balanced steady-state free-precession (bSSFP) MRI at 45×45×500 μm and 1.6 s temporal resolution to image the mouse retina, overcoming geometric distortion and signal dropout while maintaining rapid acquisition and high signal-to-noise ratio. bSSFP images revealed multiple alternating dark-bright-dark-bright retinal layers. Hypoxic (10% O(2) ) inhalation decreased bSSFP signals in the two layers bounding the retina, corresponding to the retinal and choroidal vasculatures. The layer in between showed no substantial response and was assigned the avascular photoreceptor layers. Choroidal responses (-25.9 ± 6.4%, mean ± SD, n=6) were significantly (P<0.05) larger than retinal vascular responses (-11.6±2.4%). bSSFP offers very high spatiotemporal resolution and could have important applications in imaging layer-specific changes in retinal diseases.
视网膜由多个细胞和突触层组成，由两个不同的（视网膜和脉络膜）循环滋养，这些循环由一个无血管层隔开。由于磁共振成像（MRI）中的磁场不均匀性会导致伪影，因此高时空分辨率的视网膜层特异性 MRI 仍然具有挑战性。本研究报告了在 45×45×500μm 分辨率和 1.6s 时间分辨率下，通过带通平衡稳态自由进动（bSSFP）MRI 来对小鼠视网膜进行成像，该方法克服了几何变形和信号丢失的问题，同时保持了快速采集和高信噪比。bSSFP 图像显示了多个交替的暗-亮-暗-亮的视网膜层。缺氧（10% O(2)）吸入降低了围绕视网膜的两层的 bSSFP 信号，这对应于视网膜和脉络膜血管系统。中间的层没有明显的反应，被分配给无血管的光感受器层。脉络膜的反应（-25.9 ± 6.4%，平均值 ± 标准差，n=6）明显大于视网膜血管的反应（-11.6±2.4%）（P<0.05）。bSSFP 提供了非常高的时空分辨率，在成像视网膜疾病的特定层变化方面可能具有重要应用。
