Structural and functional MRI reveals multiple retinal layers

Haiying Cheng, Govind Nair, Tiffany A. Walker, Moon K. Kim, Machelle T. Pardue, Peter M. Thulé, Darin E. Olson, Timothy Q. Duong

Research output: Contribution to journalArticlepeer-review

127 Scopus citations

Abstract

MRI is a noninvasive diagnostic modality that reveals anatomy, physiology, and function in vivo without depth limitation or optical interference. MRI application to the retina, however, remains challenging. We improved spatial resolution to resolve layer-specific structure and functional responses in the retina and confirmed the laminar resolution in an established animal model of retinal degeneration. Structural MRI of normal rat retinas revealed three bands corresponding histologically to (i) the combined ganglion cell layer/inner nuclear layer plus the embedded retinal vessels, (ii) the avascular outer nuclear (photoreceptor) layer and its photoreceptor segments, and (iii) the choroidal vascular layer. Imaging with an intravascular contrast agent (gadolinium-diethylene-tri-amine-pentaacetic acid) enhanced the retinal and choroidal vascular layers bounding the retina, but not the avascular outer nuclear layer and the vitreous. Similarly, blood-oxygen-level-dependent (BOLD) functional MRI revealed layer-specific responses to hyperoxia and hypercapnia. Importantly, layer-specific BOLD responses in the two vascular layers were divergent, suggesting the two vasculatures are differentially regulated. To corroborate sensitivity and specificity, we applied layer-specific MRI to document photoreceptor degeneration in Royal College of Surgeons rats. Consistent with histology, layer-specific MRI detected degeneration of the outer nuclear layer. Surprisingly, MRI revealed increased thickness in the choroidal vascular layer and diminished BOLD responses to hyperoxia and hypercapnia in the Royal College of Surgeons rat retinas, suggesting perturbation of vascular reactivity secondary to photoreceptor loss. We conclude that MRI is a powerful investigative tool capable of resolving lamina-specific structures and functional responses in the retina as well as probing lamina-specific changes in retinal diseases.

Original languageEnglish (US)
Pages (from-to)17525-17530
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume103
Issue number46
DOIs
StatePublished - Nov 14 2006

Keywords

  • Columnar resolution
  • High-resolution functional MRI
  • Lamina-specific MRI
  • Retinal degeneration

ASJC Scopus subject areas

  • General

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