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Published on: July 22, 2014
Manganese-enhanced MRI reveals multiple cellular and vascular layers in normal and degenerated retinas
Govind Nair1, Machelle T Pardue, Moon Kim
1Graduate 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.
Purpose:
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.
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.
Insights
Manganese-enhanced MRI (MEMRI) can visualize distinct retinal layers and vascular structures in rats. This technique detects neurodegenerative changes in retinal diseases, offering a new tool for research.
Area of Science:
- Neuroimaging
- Ophthalmology
- Histology
Background:
- The retina has complex layered structures crucial for vision.
- Detecting structural changes in retinal diseases is vital for diagnosis and treatment.
- Current imaging techniques may lack the resolution to differentiate all retinal layers.
Purpose of the Study:
- To utilize manganese-enhanced magnetic resonance imaging (MEMRI) for high-resolution imaging of rat retinal and vascular layers.
- To assess the capability of MEMRI in differentiating specific retinal strata.
- To evaluate MEMRI's potential in identifying structural alterations in a model of photoreceptor degeneration.
Main Methods:
- Intraocular manganese-chloride injections were administered to normal and Royal College of Surgeons (RCS) rats.
- Manganese-enhanced MRI (MEMRI) was performed at 4.7 T.
- Contrast-enhanced MRI with Gd-DTPA was used to highlight vascular layers, followed by histological comparison.
Main Results:
- MEMRI revealed seven distinct bands in normal rat retinas, corresponding to specific histological layers from the ganglion cell layer to the choroidal vascular layer.
- Gd-DTPA enhanced vascular layers, confirming their delineation by MEMRI.
- In RCS rats, MEMRI identified the loss of outer retinal layers, consistent with photoreceptor degeneration.
Conclusions:
- MEMRI enables lamina-specific imaging of retinal structures.
- The technique can detect neurodegenerative changes in retinal layers.
- MEMRI shows promise as a tool for studying retinal diseases.
