Current Clinical Applications of Diffusion-Tensor Imaging in Neurological Disorders

Woo-Suk Tae, Byung-Joo Ham, Sung-Bom Pyun, Shin-Hyuk Kang, Byung-Jo Kim
2018 Journal of Clinical Neurology  
Diffusion-tensor imaging (DTI) is a noninvasive medical imaging tool used to investigate the structure of white matter. The signal contrast in DTI is generated by differences in the Brownian motion of the water molecules in brain tissue. Postprocessed DTI scalars can be used to evaluate changes in the brain tissue caused by disease, disease progression, and treatment responses, which has led to an enormous amount of interest in DTI in clinical research. This review article provides insights
more » ... DTI scalars and the biological background of DTI as a relatively new neuroimaging modality. Further, it summarizes the clinical role of DTI in various disease processes such as amyotrophic lateral sclerosis, multiple sclerosis, Parkinson's disease, Alzheimer's dementia, epilepsy, ischemic stroke, stroke with motor or language impairment, traumatic brain injury, spinal cord injury, and depression. Valuable DTI postprocessing tools for clinical research are also introduced. Fractional anisotropy (FA), which is the most widely used scalar in DTI, is calculated by dividing the square root of the sum of squares (SRSS) of the diffusivity differences by the SRSS of the diffusivities. 9 The FA represents the amount of diffusional asymmetry in a voxel. FA values of 0 and 1 correspond to infinite isotropy (i.e., the ellipsoid is a sphere) and infinite anisotropy (i.e., the ellipsoid is highly elongated), respectively. The ellipsoid itself has three axes called the eigenvectors, which are usually a long axis (λ1) and two small axes (λ2 and λ3) representing the width and depth, respectively. All three axes are perpendicular to each other and cross at the center point of the ellipsoid. The measured lengths of three axes are the eigenvalues. The diffusivity along the principal axis of the neural tract, which is the longest (λ1), is called the axial diffusivity (AD) or parallel diffusivity. The diffusivity of the mean of the two minor axes (λ2 and λ3) is called the radial diffusivity (RD) or perpendicular diffusivity. The mean of the three orthogonal diffusivities (λ1, λ2, and λ3) is known as the mean diffusivity (MD), while the summarized total diffusivity of www.thejcn.com 131 Tae WS et al.
doi:10.3988/jcn.2018.14.2.129 pmid:29504292 pmcid:PMC5897194 fatcat:alz5viikuvhwpao5wddk4mre3e