Magnetic resonance imaging of tissue and vascular layers in the cat retina.
OBJECTIVE
To report the visual resolution of multiple cell and vascular "layers" in the cat retina using MRI.


METHODS
T2- and diffusion-weighted MRI at 4.7 Tesla was performed. Layer-specific thickness, T2, spin density, apparent diffusion coefficient perpendicular (ADC(perpendicular)) and parallel (ADC(parallel)) to the retinal surface were tabulated. T1-weighted MRI was acquired before and after intravenous administration of Gd-DTPA and subtraction images were obtained. Histology was performed for validation.


RESULTS
Three distinct "layers" were observed. The inner strip nearest to the vitreous (exhibiting large T2, ADC, spin density with Gd-DTPA enhancement) overlapped the ganglion cell layer, bipolar cell layer, and the embedded retinal vascular layer. The middle strip (exhibiting small T2, ADC, spin density without Gd-DTPA enhancement) overlapped the photoreceptor cell layer and the inner and outer segments. The outer strip (exhibiting large T2, ADC, spin density with Gd-DTPA enhancement) overlapped the tapetum and choroidal vascular layer. T2, spin density, ADC(perpendicular) and ADC(parallel) of different "layers" were tabulated. The inner strip was slightly thicker than the other two strips. The total thickness, including neural and nonneural retina, was 358 +/- 13 microm (N = 6) by MRI and 319 +/- 77 microm (N = 5) by histology.


CONCLUSIONS
MRI provides a noninvasive tool to study the retina with laminar specificity without depth limitation.
Shen
Qiang
Q
Yerkes Imaging Center, Division of Neuroscience, Department of Neurology, Emory University, Atlanta, Georgia 30329, USA.
Cheng
Haiying
H
Pardue
Machelle T
MT
Chang
Thomas F
TF
Nair
Govind
G
Vo
Van Toi
VT
Shonat
Ross D
RD
Duong
Timothy Q
TQ
D000818:Animals; D002415:Cats; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D019786:Gadolinium DTPA; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D012160:Retina / Q000033:anatomy & histology*; D013382:Subtraction Technique
D003287:Contrast Media; D019786:Gadolinium DTPA