Abstract #3427

Integrating a negative relaxometric constant in the χ-separation model improves the correlation between χ negative and myelin metrics

Elena Grosso¹, Antonio Ricciardi², Eleonora Lupi¹, Marios C. Yiannakas², Ferran Prados^2,3,4, Baris Kanber^2,3, Egidio D'Angelo^1,5, Claudia AM Gandini Wheeler-Kingshott^1,2,5, and Fulvia Palesi¹

¹Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy, ²NMR Research unit, Queen Square Multiple Sclerosis Centre, Department of Neuroinflammation, UCL Queen Square Institute of Neurology, Faculty of Brain Sciences, University College London, London, United Kingdom, ³Department of Medical Physics and Biomedical Engineering, UCL Hawkes Institute, University College London, London, United Kingdom, ⁴E-Health Center, Universitat Oberta de Catalunya, Barcelona, Spain, ⁵Digital Neuroscience Centre, IRCCS Mondino Foundation, Pavia, Italy

Synopsis

Keywords: Susceptibility/QSM, biology, models, methods, chi-separation, relaxometric constant, myelin, T2b, bound pool fraction

Motivation: χ-separation methods rely on assuming a single relaxometric constant (D_r) for both positive and negative susceptibility contributions and its value impacts on the resulting maps.

Goal(s): This study proposes to introduce a physiological value for the negative relaxometric constant (D_r,neg) and tests the correlation between the new negative susceptibility map and myelin metrics (bound pool fraction (BPF), T2b).

Approach: We calculated D_r,neg in the body of corpus callosum and tested the correlation between negative susceptibility and BPF,T2b in white matter for both new and standard methods.

Results: Only the new method captured a positive correlation with BPF and a negative correlation with T2b.

Impact: The integration of a physiologically plausible negative relaxometric constant in the χ-separation model will impact on how we assess the presence of positive and negative magnetic susceptibility sources in the brain, i.e. iron and myelin.

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