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Abstract #0949

Differentiation of Primary & Secondary Degeneration in the Visual Pathway Using in vivo Mn-Enhanced MRI

Kevin C. Chan1, 2, Jiang Li3, 4, Iris Y. Zhou1, 5, Phillis Kau3, 4, Kwok-fai So3, 4, Ed X. Wu1, 5

1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China; 2Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; 3Department of Anatomy, The University of Hong Kong, Pokfulam, Hong Kong, China; 4State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Pokfulam, Hong Kong, China; 5Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China

This study explores the capability of high-resolution Mn-enhanced MRI (MEMRI) for in vivo, longitudinal evaluation of primary and secondary degeneration along the retinocollicular projections after partial transection of right superior optic nerve in rats. At 1 week and 6 weeks after partial optic nerve injury, a consistent T1W hypointensity by about 28% was observed in the left lateral superior colliculus (SC) relative to the contralateral hemisphere, reflective of primary loss of topological connections and Mn2+ transport in the retinocollicular projections. The left medial SC had a reduced T1W signal intensity by 11% compared to the right medial SC at Week 1. Such reduction further increased to 16% at Week 6, indicative of secondary loss of retinal ganglion cells and axons projecting through the uninjured, inferior optic nerve. The results of this study demonstrated the feasibility of in vivo, high-resolution MEMRI for assessing the primary and secondary degeneration topologically and longitudinally along the visual pathway. Future MEMRI studies are envisioned that measure the secondary changes in topological connections in various neurodegenerative diseases and injuries and upon therapeutic interventions in longitudinal studies.