7.16 VA Reading - NARR_Module3E_CTSI_Diffusion_Imaging_2014

In DWI, 3 gradient directions allow identifying CNS abnormalities such as cerebral ischemia, TBI, tumors
With more gradient directions, identifying white matter pathology including axonal injury and/or myelin damage will be optimized
Tensor model cannot resolve fiber orientation across intersecting axes (crossing fibers) within the same voxel; high angular resolution diffusion imaging (HARDI) allows more complex models of diffusion and resolve this issue
Non-tensor models of diffusion:

• Diffusion spectrum (DSI): full distribution of orientation and magnitude
• Orientation distribution function (Q-ball): no magnitude info, only orientation
• Ball-and-stick: orientation and magnitude for up to N anisotropic compartments
• Tensor (DTI): single orientation and magnitude

This diagram is a nice demonstration (Catani and Thiebaut de Schotten, 2008):