title: Lamina-specific anatomic magnetic resonance imaging of the human retina.
abstract: OBJECTIVE
  Magnetic resonance imaging (MRI) of the human retina faces two major challenges: eye movement and hardware limitation that could preclude human retinal MRI with adequate spatiotemporal resolution. This study investigated eye-fixation stability and high-resolution anatomic MRI of the human retina on a 3-Tesla (T) MRI scanner. Comparison was made with optical coherence tomography (OCT) on the same subjects.
  
  
  METHODS
  Eye-fixation stability of protocols used in MRI was evaluated on four normal volunteers using an eye tracker. High-resolution MRI (100 × 200 × 2000 μm) protocol was developed on a 3-T scanner. Subjects were instructed to maintain stable eye fixation on a target with cued blinks every 8 seconds during MRI. OCT imaging of the retina was performed. Retinal layer thicknesses measured with MRI and OCT were analyzed for matching regions of the same eyes close to the optic nerve head.
  
  
  RESULTS
  The temporal SDs of the horizontal and vertical displacements were 78 ± 51 and 130 ± 51 μm (±SD, n = 4), respectively. MRI detected three layers within the human retina, consistent with MRI findings in rodent, feline, and baboon retinas. The hyperintense layer 1 closest to the vitreous likely consisted of nerve fiber, ganglion cell, and inner nuclear layer; the hypointense layer 2, the outer nuclear layer and the inner and outer segments; and the hyperintense layer 3, the choroid. The MRI retina/choroid thickness was 711 ± 37 μm, 19% (P < 0.05) thicker than OCT thickness (579 ± 34 μm).
  
  
  CONCLUSIONS
  This study reports high-resolution MRI of lamina-specific structures in the human retina. These initial results are encouraging. Further improvement in spatiotemporal resolution is warranted.
authors.affiliation: Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas 78229, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Oscar San Emeterio
authors.initials: OS
authors.lastname: Nateras
authors.forename: Qi
authors.initials: Q
authors.lastname: Peng
authors.forename: Roman V
authors.initials: RV
authors.lastname: Kuranov
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Harrison
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Milner
authors.forename: Timothy Q
authors.initials: TQ
authors.lastname: Duong
mesh_terms: D000328:Adult; D001485:Basement Membrane / Q000033:anatomy & histology*; D001767:Blinking; D005260:Female; D005403:Fixation, Ocular; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012160:Retina / Q000033:anatomy & histology*; D016683:Supine Position; D041623:Tomography, Optical Coherence; D055815:Young Adult