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Abstract #1642

How can we reliably mitigate flip angle and fibre orientation dependence in MPM-based R2* estimation at 7T?

Giorgia Milotta1, Nadège Corbin1,2, Christian Lambert1, Antoine Lutti3, Siawoosh Mohammadi4,5, and Martina Callaghan1
1Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom, 2Centre de Résonance Magnétique des Systèmes Biologiques, UMR5536, CNRS/University Bordeaux, Bordeaux, France, 3Laboratory for Research in Neuroimaging, Department for Clinical Neuroscience, , Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland, 4Department of Systems Neurosciences, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, 5Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany


The apparent transverse relaxation rate ($$$R_{2}^{*}$$$) is influenced by biological features, e.g. iron and myelin content. However confounding factors, such as flip angle (α) and fibre orientation dependence, hinder interpretation. Multi-α data acquired as part of a comprehensive multi-parameter mapping approach can be used to mitigate these confounds. Here we explored how best to do so in vivo at 7T while additionally considering reproducibility. The ESTATICS approach, which assumes a common decay across flip angles, reduced these dependencies. $$$\hat{R_{2}^{*}}$$$, the α-independent component of a heuristic linear model, reduced both dependencies further but was less reproducible than ESTATICS.

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