Diffusion Tensor Imaging

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2721253

A recently developed magnetic resonance imaging technique, called diffusion tensor imaging (DTI), has become an extremely valuable tool for evaluating patients with brain injuries. DTI enables measurement of the integrity of white matter fibre tracts making the axonal organization of the brain visible. It measures the diffusion of water molecules that prefer to diffuse along white matter fibre tracts (anisotropically) and not perpendicularly to the course of the fibre tracts (Mori and Zhang, 2006). Values for fractional anisotropy (FA) range between 0 and 1, with 0 standing for isotropic, lack of directional diffusion, and 1 representing anisotropic (directional) diffusion. Factors influencing FA are myelination of fibre tracts and axonal integrity and density (Mori and Zhang, 2006; Kraus *et al.*, 2007). In a recent study, DTI was validated in a controlled cortical mouse TBI model using histology and electronmicroscopic analysis. The technique was able to detect perilesional white matter damage in a range of acute to subacute time points, thereby predicting the approximate time since trauma (Mac Donald *et al.*, 2007). DTI was also able to correlate recovery of the damaged corticospinal tract with functional improvement in a patient suffering from paraparesis after TBI (Han *et al.*, 2007). These remarkable abilities of DTI make it an extremely valuable tool in the evaluation of restorative and axon regenerative therapies in animal models of TBI. DTI has recently been used to document myelin-protective activities of a therapeutic antibody candidate in an animal multiple sclerosis model (Mi *et al.*, 2007) and is extensively used in rodent models characterized by axonal or myelin damage