DTi

Diffusion Tensor Imaging (DTI) is an MRI-based neuroimaging technique that measures the diffusion of water molecules to infer tissue microstructure. In white matter, water diffusion is hindered by cell membranes and myelin, and tends to be more rapid along fiber tracts than across them. By fitting a diffusion tensor at each voxel, DTI provides metrics such as fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD). FA reflects directional coherence and integrity of white matter, while MD indicates overall diffusion magnitude. Tractography uses the diffusion tensor to reconstruct probable white matter pathways, aiding the study of brain connectivity.

DTI data are acquired with diffusion-weighted MRI using multiple gradient directions and a range of b-values, typically around b=1000 s/mm^2, and are often combined with high-resolution anatomical MRI. Preprocessing includes motion correction, eddy current correction, and susceptibility distortion correction. Limitations include sensitivity to subject motion, partial volume effects, and difficulties in regions with complex fiber architecture where a single tensor is insufficient. Advanced models and high-angular-resolution diffusion imaging (HARDI) methods address some limitations by capturing multiple fiber populations within a voxel.

DTI has been applied in research and clinical contexts to study development, aging, multiple sclerosis, traumatic brain injury, and neurodegenerative diseases, as well as in pre-surgical planning to map critical tracts. The diffusion tensor model is one of several diffusion models; newer approaches include diffusion spectrum imaging and q-ball imaging.

DTI may also refer to debt-to-income ratio, a financial metric used by lenders to evaluate a borrower's ability to manage monthly payments. It is calculated as total monthly debt payments divided by gross monthly income.