Manganese-Enhanced MRI Reveals Multiple Cellular and Vascular Layers in Normal and Degenerated Retinas

• Type of Material: Article
• Authors: Govind Nair, University of Massachusetts; Machelle Pardue, Emory University; Moon Kim, Atlanta Veterans Affairs Medical Center; Timothy Q. Duong, University of Texas Health Science Center at San Antonio
• Language: English
• Date: 2011-12-01
• Publisher: Wiley
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: Copyright © 2011 Wiley Periodicals, Inc.
• Final Published Version (URL): http://dx.doi.org/10.1002/jmri.22719
• Title of Journal or Parent Work: Journal of Magnetic Resonance Imaging
• ISSN: 1053-1807
• Volume: 34
• Issue: 6
• Start Page: 1422
• End Page: 1429
• Keywords: RCS; RCS RAT; TRANSPORT; retinal degeneration; MRI microscopy; magnetic resonance imaging; MEMRI; Science & Technology; Radiology, Nuclear Medicine & Medical Imaging; OPTICAL COHERENCE TOMOGRAPHY; RESOLUTION; CLEARANCE; FUNCTIONAL MRI; high resolution imaging; BRAIN; RAT RETINA; CONTRAST; VISUAL PATHWAY; Life Sciences & Biomedicine
• Research Categories: Biology, Neuroscience; Health Sciences, Opthamology; Health Sciences, Radiology

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.