D11 Structural neuroimaging (CT, MRI, DTI)

Title

Structural magnetic resonance generates tissue contrast from the differences in the relaxation times T1 (recovery of longitudinal magnetization) and T2 (decay of transverse magnetization) between different tissues, allowing the differentiation of gray matter, white matter and cerebrospinal fluid. Diffusion tensor imaging (DTI) extends this principle by measuring the anisotropic diffusion of water in white matter tissue, characterized by a diffusivity tensor whose eigenvalues allow the calculation of fractional anisotropy (FA), a direct measure of the microstructural integrity of axonal tracts, applicable as a quantitative extension of the myelination variable M used in E14, A4 and M4. The mean diffusivity summarizes the overall magnitude of the diffusion, and tractography reconstructs the trajectory of the fiber bundles by integrating the main direction of the tensor along the tissue. Volumetric segmentation of specific structures (for example, hippocampus in Alzheimer's or substantia nigra in Parkinson's) allows objective quantification of atrophy or structural damage associated with series A pathologies.

ID:4307