MRI of Diabetic Retinopathy

糖尿病视网膜病变（DR）是工作年龄成人失明的主要原因， 45%的糖尿病患者DR通常通过疾病的晚期表现来诊断，例如视力模糊 以及眼底的异常外观。到临床诊断时，视力丧失或失明是可能的。 往往是必然的结果。临床试验的结果表明，严格的血糖控制， 糖尿病的早期阶段在降低DR的风险方面是有效的。因此， 有DR风险的患者将能够及时干预，以最大限度地降低视力丧失的风险。 视网膜由三个主要的细胞层（感光细胞层、双极细胞层和神经节细胞层）和两个血管层组成。 （视网膜和脉络膜）层界定视网膜，其中每一个都受到DR的不同影响。我们的实验室 开创了基于回波平面的创新层特异性血流和功能性MRI技术， 在~ 80 x80 x1000 µm下成像。眼睛的回波平面成像遭受磁化率伪影和图像 模糊，这妨碍了最早和最可靠的DR检测。此外，虽然荧光素 血管造影术广泛用于血管可视化和DR诊断，但它不具有层分辨率 和荧光素（一种光学造影剂）可引起严重的负面反应，特别是在糖尿病患者中， 往往肾功能受损。可提供血管层分辨率的替代方法 而不需要造影剂也将具有重要的临床意义。 我们最近探索了非回波平面成像方法来研究视网膜。我们的初步数据 显示平衡稳态自由旋进（bSSFP）MRI提供了显著改善的图像质量， 血流和功能MRI空间分辨率，而MR血管造影（MRA）提供了层特异性 视网膜和脉络膜血管在大鼠视网膜，而不使用造影剂。在这一建议中，我们的目标是：i）进一步 建立了无对比剂的bSSFP和MRA方法，以层状特异性研究大鼠视网膜 剂，ii）评估这些方法以检测链脲佐菌素诱导的视网膜中的最早变化。 糖尿病，和iii）测试严格的血糖控制逆转这些非常早期的视力丧失的假设 糖尿病视网膜病变的临床表现。我们的中心假设是异常的视网膜和脉络膜 在糖尿病视网膜病变的早期临床前阶段， 在解剖学变化之前，这些新的MRI方法可以检测到这些变化，并且可以通过严格的血糖控制来逆转。

Diabetic retinopathy (DR) is the leading cause of blindness in working-age adults and occurs in about 45% of diabetic patients. DR is often diagnosed by late manifestations of the disease, such as blurred vision and abnormal appearance of the fundus. By the time a clinical diagnosis is made, vision loss or blindness is often the inevitable outcome. Results from clinical trials have documented that strict glycemic control in the early stages of diabetes is effective in reducing the risk of DR. Thus, early identification of diabetic individuals who are at risk of DR will enable timely intervention to minimize the risk of vision loss. The retina consists of three major cell layers (photoreceptor, bipolar, and ganglion) and two vascular (retinal and choroidal) layers bounding the retina, each of which is affected differently by DR. Our laboratory has pioneered innovative layer-specific blood-flow and functional MRI techniques based on echo-planar imaging at ~80x80x1000 µm. Echo-planar imaging of the eye suffers from susceptibility artifacts and image blurring, which precludes the earliest and most reliable DR detection. Moreover, although fluorescein angiography is widely used for visualization of vessels and diagnosis of DR, it does not have layer resolution and fluorescein (an optical contrast agent) can cause severe negative reactions, especially in diabetics who often have compromised renal function. Alternative approaches that can provide vascular layer resolution without needing a contrast agent will also have important clinical significance. We have recently explored non-echo-planar imaging approaches to study the retina. Our preliminary data show that balanced steady-state free precession (bSSFP) MRI provides markedly improved image quality and spatial resolution for blood-flow and functional MRI, and that MR angiography (MRA) provides layer-specific retinal and choroid vessels in the rat retina without using a contrast agent. In this proposal, we aim: i) to further develop bSSFP and MRA methods to study the rat retina with laminar specificity without using a contrast agent, ii) to evaluate these approaches to detect the earliest changes in retina of streptozotocin-induced diabetes, and iii) to test the hypothesis that strict glycemic control reverses these very early pre-vision loss manifestations of retinal changes in diabetes. Our central hypothesis is that abnormal retinal and choroidal blood flow and neurovascular coupling in the early pre-clinical stage of retinal changes in diabetes are detectable by these novel MRI methods prior to anatomic changes, and are reversed by strict glycemic control.