CFIN seminar: Risto A. Kauppinen
Risto A. Kauppinen, Faculty of Engineering, University of Bristol, Bristol, UK is visiting CFIN and will give a talk on: "Relaxation Anisotropy in Human White Matter: An Unexplored Avenue for Microstructural Imaging".
Info about event
Thalamus meeting room, CFIN South, Building 1710, Universitetsbyen 3
Risto A. Kauppinen, Faculty of Engineering, University of Bristol, Bristol, UK
Relaxation Anisotropy in Human White Matter: An Unexplored Avenue for Microstructural Imaging
High degree of structural order by white matter (WM) fibre tracts creates physico-chemical environment where water relaxations are rendered anisotropic. Diamagnetic susceptibility gradients across WM fibres and their immediate surroundings impacts transverse relaxation. Susceptibility anisotropy in WM influences coherence lifetime of spins making T2 shorter around the fibres running perpendicular to B0 than in those parallel to the field. Recently, angularly dependent longitudinal relaxation has also been observed in human WM. T1 at 3T measured either by a variable flip angle or MP2RAGE methods shows variation according to the fibre-to-field-angle. We have studied interrelationships between WM microstructure and T1 at 3T and 7T using multi-shell dMRI and MP2RAGE. We observed that in WM with high degree of structural anisotropy and/or low orientation dispersion of fibres T1 at 3T is longer around the fibre-to-field angle of 54o by up to 8% than in those either parallel or perpendicular to B0. T1 at 7T shows different angular patterns to those recorded at 3T. First, the long T1 ‘hump’ is centred at 40o and second, T1 is longer in fibres running parallel than perpendicular to B0. These data point to a further role of myelinated tracts in WM to that of ‘a relaxation agent’, i.e. making both T1 and T2 relaxation anisotropic. Physical underpinnings of relaxation anisotropy in WM will be discussed.
ALL ARE WELCOME.