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  • Title: Blood-retinal barrier breakdown investigated by real-time magnetic resonance imaging after gadolinium-diethylenetriaminepentaacetic acid injection.
    Author: Berkowitz BA, Sato Y, Wilson CA, de Juan E.
    Journal: Invest Ophthalmol Vis Sci; 1991 Oct; 32(11):2854-60. PubMed ID: 1917389.
    Abstract:
    Recent magnetic resonance imaging (MRI) studies show that gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) entry into the vitreous space can be used as a qualitative marker of blood-retinal barrier (BRB) disruption. To determine if a more quantitative measurement of BRB breakdown could be obtained, the utility of acquiring real-time, T1-weighted proton images was studied after Gd-DTPA injection. Two days before the MRI experiment, panretinal photocoagulation was done. The mean signal intensity over selected regions-of-interest (ROI) in the vitreous and anterior chamber was followed before and after (0, 10, 20, 30, 45, and 60 min) Gd-DTPA injection (1.0 mmol/kg, intravenously). At every laser power setting used in this study (0, 200, 400, 600, and 800 mW), the change in the mean signal intensity could be approximated by a simple exponential equation. However, the time constants determined for these curves were too imprecise to be useful as correlates between laser power and BRB breakdown. The slope of the line fit to the data in the first 20 min postinjection (ie, an initial-rate analysis) was a more precise correlate between BRB breakdown and laser power. This slope represented the rate of change in mean signal intensity in the ROI as a result of the entry of Gd-DTPA, and it was called the "leakiness" parameter. The leakiness parameter reflected changes in the permeability surface area product of the BRB if the blood flow and the Gd-DTPA arterial concentration immediately after injection were approximately the same between animals.
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