Claudia Angela Michela Wheeler-Kingshott1, Olga Ciccarelli2, Torben Schneider1, Daniel C. Alexander3, Mara Cercignani4
1NMR Unit, Department of Neuroinflammation, UCL Institute of Neurology, London, United Kingdom; 2NMR Unit, Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, United Kingdom; 3Dept. Computer Science, UCL, Centre for Medical Image Computing, London, United Kingdom; 4Neuroimaging Laboratory, Fondazione Santa Lucia, Rome, Italy
A new definition of projected-axial (dp-ax) and radial (dp-rad) diffusivities in standard space has been tested in multiple sclerosis and healthy subjects using VBM. For each subject, dp-ax and dp-rad are defined as the components of the diffusion tensors (DTs) along the most probable direction of healthy tracts as defined by the eigenvectors of a super-DT dataset in standard space (calculated as the average of the DTs of a reference group of healthy subjects). The results show that in a patient with moderate disability there are areas of reduced dp-ax not revealed by the principal eigenvalue of the DT.