Dynamic contrast enhanced MRI in patients with diabetic macular edema: initial results.

To assess the ability of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) to detect blood retinal barrier (BRB) damage in patients with diabetic macular edema (DME). DCE-MRI with 0.1 mmol Gd-DTPA was used to measure BRB permeability in 10 healthy and visually normal subjects and eight patients with DME, including five patients with non-clinically significant (NCS) DME and three patients with clinically significant (CS) DME. For each subject, the enhancement of the MRI signal intensity in the pre-macular vitreous was measured as a function of time following contrast injection. A linear regression analysis was performed on each subject and the slopes of the contrast enhancement functions were compared. The DCE-MRI procedure was well tolerated by all 18 subjects. However, in four subjects, excessive eye movements resulted in spurious results. Consequently, 78% (14/18) of the subjects provided usable data. The mean slope of the control group was not significantly (p>0.05) different from zero (i.e. signal intensity in the pre-macular vitreous space was constant as a function of time post-contrast injection). For the diabetic patients, the average slope of the contrast enhancement function was significantly greater than in the control group (p<0.01). Furthermore, for both diabetic sub-groups, the average slopes were greater (p<0.05) than that for the control group but not significantly (p>0.05) different from each other. This 'proof of concept' study demonstrated that DCE-MRI detects passive leakage through the BRB in diabetic patients with either NCS or CS macular edema. In future studies, DCE-MRI may be useful for early quantitative evaluation of drug treatment effects in patients with DME.