Manganese-enhanced MRI reveals multiple cellular and vascular layers in normal and degenerated retinas

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Abstract

Purpose:

To use manganese-enhanced magnetic resonance imaging (MEMRI) at 25 × 25 × 800 μm3 to image different retinal and vascular layers in the rat retinas.

Materials and Methods:

Manganese-chloride was injected intraocularly in normal (n = 5) and Royal College of Surgeons (RCS, an model of photoreceptor degeneration) (n = 5) rats at postnatal day 90. MEMRI at 4.7 T was performed 24 hours later. MRI was repeated following intravenous Gd-DTPA in the same animals to highlight the vasculatures. Layer assignment and thickness were compared to histology.

Results:

MEMRI 24 hours after intravitreal manganese-chloride injection revealed seven bands of alternating hyper- and hypointensities, corresponding histologically to the ganglion cell layer, inner plexiform layer, inner nuclear layer, outer plexiform layer, outer nuclear layer, photoreceptor-segment layer, and choroidal vascular layer. Intravenous Gd-DTPA—which does not cross the blood–retinal barrier and the retinal pigment epithelium—further enhanced the two layers bounding the retina, corresponding to the retinal and choroidal vascular layers, but not the avascular outer nuclear layer and the photoreceptor-segment layer. MEMRI of the RCS retinas revealed the loss of the outer plexiform layer, outer nuclear layer, and photoreceptor-segment layer. Histological analysis corroborated the MRI laminar assignments and thicknesses.

Conclusion:

Lamina-specific retinal structures neurodegenerative changes to structure in retinal diseases can be detected using MEMRI. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.

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