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Abstract #3764

From in situ to ex vivo: the effect of autolysis and fixation on quantitative MRI markers for myelin

Siawoosh Mohammadi1,2,3, Jan Sedlacik4, Martina F Callaghan2, Jens Fiehler4, Gunther Helms5, and Christian Sprenger1,6

1Department of Systems Neuroscience, Medical Center Hamburg-Eppendorf, Hamburg, Germany, 2UCL Institute of Neurology, University College London, London, GA, United Kingdom, 3Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 4Department of Neuroradiology, Medical Center Hamburg-Eppendorf, Hamburg, Germany, 5Medical Radiation Physics, Lund University, Sweden, 6Department of Engineering, University of Cambridge, United Kingdom

Ex vivo histology remains the gold standard against which MRI biophysical models, e.g. the MR g-ratio which characterises the fraction of a fibre’s diameter that is myelinated, are evaluated. The MR g-ratio model requires a measure of myelin density, for which magnetization transfer saturation (MT) has been used as a biomarker. However, changes occurring post mortem, e.g. autolysis, temperature changes and fixation, significantly alter the MRI signal. Here we investigate how these changes impact MT. We found that MT decreased post mortem but greatly increased upon fixation. These effects are similar to reported changes of other established MRI myelin-markers.

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