Department of Psychiatry Center for Comparative NeuroImaging
Retina; Cats; Anatomy, Cross-Sectional; Magnetic Resonance Imaging
Life Sciences | Medicine and Health Sciences
Purpose: To demonstrate the ability to resolve the three distinct anatomical layers of the cat retina using T2-weighted, diffusion-weighted, and contrast-enhanced magnetic resonance imaging (MRI).
Methods: MRI of the in vivo cat retina (n=5) was performed on a 4.7-Tesla MRI scanner at 50x100um or 100x100um in-plane resolution. Fast spin-echo T2-weighted images were acquired with four effective echo times, diffusion images were acquired with two b-values, and T1-weighted images were acquired before and after the intravenous administration of a magnetic-resonance contrast agent Gd-DTPA. T2 maps, apparent-diffusion-coefficient (ADC) maps, and subtraction of pre- and post-contrast images were generated for evaluation and visualization of the retinal layers.
Results: Three distinct anatomical layers within the retina were observed. The inner strip exhibited a relatively long T2, high ADC, and high water spin density, which corresponded well with the expected MRI signature from the ganglion cell layer and the retinal vasculature. The middle strip exhibited a relatively short T2, low ADC, and low water spin density, which corresponded well with the expected MRI signature from the bipolar cell layer. The outer strip exhibited similar characteristics as the inner strip, which corresponded well with the expected MRI signature from the photoreceptor layer and the choroid vascular layer. The Gd-DTPA T1-weighted images showed signal enhancement at the retina-vitreous boundary and an even greater signal enhancement at the retina-choroid boundary, both consistent with the vascular flow in the retinal and choroid vessels respectively, and with the higher choroid vascular perfusion. The overall retinal thickness including the retinal and choroid vascular complex was 400-550um, consistent with histologically determined values.
Conclusions: The potential for layer-specific imaging of the retina to yield physiologic and functional information in one setting could substantially enhance the diagnostic utility of high-resolution MRI to retinal evaluation. Furthermore, the similarity of retinal layers to the layers and the columns in the visual cortex may allow the application of the MRI techniques presented herein to the physiologic and functional studies of the visual cortex at improved spatial resolution and specificity.
DOI of Published Version
This research was eventually published as follows: Shen Q, Cheng H, Pardue MT, Chang TF, Nair G, Vo VT, Shonat RD, Duong TQ. Magnetic resonance imaging of tissue and vascular layers in the cat retina. J Magn Reson Imaging. 2006 Apr;23(4):465-72 Link to article on publisher's website
J Magn Reson Imaging
Shen, Q; Cheng, H; Chang, TF; Li, Z; Nair, G; Vo, VT; Shonat, RD
Chang, Thomas F., "Magnetic Resonance Imaging of Anatomical Layer Specificity in the Cat Retina" (2005). University of Massachusetts Medical School. Senior Scholars Program. Paper 21.