糖尿病患者视网膜氧合反应的磁共振研究

目的利用磁共振成像（MRI）技术探讨糖尿病视网膜病变患者在吸入100％纯氧后视网膜氧合反应（△PO2）的变化规律。设计前瞻性病例对照研究。研究对象6例糖尿病患者及年龄相匹配的6例健康受试者。方法应用GE1．5T磁共振扫描仪对研究对象先后间断吸人室内空气和100％纯氧进行数据采集，扫描时间持续约50分钟。NIHIMAGE软件包用于数据分析。主要指标视网膜前玻璃体信号强度、△PO2。结果健康受试者整个视网膜的△PO2空间变化是非均一的。在高浓度吸氧状态下初期，健康受试者视乳头区的视网膜前玻璃体信号强度迅速增高，而视网膜颞侧及鼻侧区信号强度不同程度下降。随着吸氧时间延长，各部位视网膜前玻璃体信号强度略有波动，但趋向逐渐增高。任一时间点的△PO2与其余时相间比较，差异均无统计学意义（P均〉0．05）。糖尿病组，视网膜前玻璃体的信号强度持续增高，且显著高于对照组（P均〈0．05）。高浓度吸氧结束后，健康受试者非视乳头区域视网膜前玻璃体信号强度呈不同程度的延迟强化效应。随后，各区域△PO2均迅速下降。而糖尿病组患者在吸氧结束后其△PO2迅速下降。对照组△PO2与年龄呈显著线性正相关。结论高浓度吸氧能够诱导视网膜前玻璃体区域特异性的信号变化。糖尿病患者△PO2升高可能与视网膜血管调节异常有关。MRI可作为探测视网膜病理状态下氧合反应机制的有效工具。

The detection of retinal oxygenation response with magnetic resonance imaging in diabetes patients

Objective To detect changes in inner retinal oxygenation response（△PO2） following 100% oxygen inhalation with magnetic resonance imaging（MRl） in patients with diabetes. Design Prospective case-control study. Participants Six patients with diabetes and six age-matched healthy individuals. Methods MRI was performed on a 1.5-T GE scanner system. After obtaining ophthalmologic data, participants were given room air and 100% oxygen inhalation with different intervals. Then MRI T1 weighted image （T1WI） data were collected for 50 min. Data were analyzed with NIH IMAGE software. Main Outcome Measures Preretinal vitreous water signals, △PO2. Results In control subjects, △PO2 was not uniform panretinally, changes in oxygenation response were spatially inhomogeneous. During the initial phase （i.e., before 5 min） of 100% oxygen inhalation, preretinal vitreous water signals in region of papilla optica in creased rapidly in the control subjects, but in other regions, on the contrary, signals declined; In the following later periods, △PO2 panretinally was fluctuated and increased slowly and attained homeostasis（i.e., 35 rain）. There was no significant difference （P〉0.05） in the value of △PO2 at either time point during hyperoixa in the control subjects. However, the patients with diabetes exhibited a significant increase in the preretinal vitreous signal intensity continuously. And they also demonstrated significant difference in △PO2 measured during oxygen inhalation between these two groups （P〈0.05）; After hyperoxia, delayed-enhancement of preretinal vitreous water signals in other than papilla optica region occurred （i.e., 45 rain）, and then dropped down. However, △PO2 immediately dropped down after hyperoxia in patients with diabetes. Conclusions These results reveal that hyperoxia can induce region-specific signal changes in preretinal vitreous water. Impaired vascular activity of retinal vessels network may be the mechanism of increase in △PO2 in patients with diabetes.