AUTHOR=Moon Yeji , Yang Jin-Ju , Lee Won June , Lee Ji Young , Kim Yu Jeong , Lim Han Woong ,  The Alzheimer's Disease Neuroimaging Initiative (ADNI) , Weiner Michael W , Aisen Paul , Petersen Ronald , Jack Clifford , Bernstein Matthew , Fox Nick , Thompson Paul , Schuff Norbert , DeCArli Charles , Borowski Bret , Gunter Jeff , Senjem Matt , Vemuri Prashanthi , Jones David , Kantarci Kejal , Ward Chad , Beckett Laurel 

TITLE=In vivo Analysis of Normal Optic Nerve in an Elderly Population Using Diffusion Magnetic Resonance Imaging Tractography

JOURNAL=Frontiers in Neurology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2021.680488

DOI=10.3389/fneur.2021.680488

ISSN=1664-2295

ABSTRACT=<p><bold>Purpose:</bold> To quantitatively investigate the microstructural properties of the optic nerve (ON) <italic>in vivo</italic> using diffusion magnetic resonance imaging (dMRI) tractography in an elderly population and to determine the differences between the ON diffusion properties stratified by basic demographics.</p><p><bold>Methods:</bold> We measured fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) of the intraorbital ON in cognitively normal controls selected from the Alzheimer's Disease Neuroimaging Initiative 3 database (<italic>n</italic> =104; mean age = 73. 8 ± 8.1 years) using dMRI probabilistic tractography and evaluated the correlation between diffusion parameters and demographic factors. Diffusion parameters were measured in 20 equidistant nodes along the tract, and the data from proximal 70% (14 nodes) of the intraorbital ON were averaged.</p><p><bold>Results:</bold> The mean FA of the intraorbital ON was 0.392 ± 0.063, and the mean MD was 1.163 ± 0.165 μm<sup>2</sup>/s. The mean RD was 0.882 ± 0.152 μm<sup>2</sup>/s, and the mean AD was 1.693 ± 0.183 μm<sup>2</sup>/s. The multiple linear regression model showed a negative correlation between FA and age. FA in females was significantly higher than males, whereas RD in female was significantly lower.</p><p><bold>Conclusions:</bold> We measured the diffusion properties of the intraorbital ON using dMRI tractography in an elderly cognitively normal population. The diffusion properties detected by dMRI tractography may substantially reflect the microstructure of the ON.</p>