title: Manganese-enhanced MRI reveals multiple cellular and vascular layers in normal and degenerated retinas.
abstract: OBJECTIVE
  To use manganese-enhanced magnetic resonance imaging (MEMRI) at 25 × 25 × 800 μm(3) to image different retinal and vascular layers in the rat retinas.
  
  
  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.
  
  
  CONCLUSIONS
  Lamina-specific retinal structures neurodegenerative changes to structure in retinal diseases can be detected using MEMRI.
authors.affiliation: Graduate School of Biomedical Science, University of Massachusetts Medical School and Worcester Polytechnic Institute, Worcester, Massachusetts, USA; Yerkes Imaging Center, Neuroscience Division, Emory University, Atlanta, Georgia, USA.
authors.forename: Govind
authors.initials: G
authors.lastname: Nair
authors.forename: Machelle T
authors.initials: MT
authors.lastname: Pardue
authors.forename: Moon
authors.initials: M
authors.lastname: Kim
authors.forename: Timothy Q
authors.initials: TQ
authors.lastname: Duong
mesh_terms: D000818:Animals; D002712:Chlorides / Q000008:administration & dosage / Q000494:pharmacology*; D019786:Gadolinium DTPA / Q000494:pharmacology; D007089:Image Enhancement / Q000379:methods; D056965:Injections, Intraocular; D008279:Magnetic Resonance Imaging / Q000379:methods*; D017895:Manganese Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000033:anatomy & histology* / Q000166:cytology / Q000473:pathology; D012162:Retinal Degeneration / Q000473:pathology*
chemical_list: D002712:Chlorides; D017895:Manganese Compounds; D019786:Gadolinium DTPA; C025340:manganese chloride