JHA410H1 Lecture Notes - Lecture 3: Diffusion Mri, Kappa Publishing Group, Fractional Anisotropy
Document Summary
Lecture 3: diffusion tensor imaging (dti) part i. Key definitions: b: diffusion weighting factor, d: diffusion term or diffusion coefficient, adc = apparent diffusion coefficient. Diffusion you need complete random movement of water molecules: diffusion refers to the random microscopic movement of molecules due to thermal collisions. When molecules diffuse equally in all directions this is isotropic diffusion; however, if the shape is elongated along one axis but not others, it means there is diffusion in one direction - this is anisotropic diffusion. Dti uses anisotropic diffusion to estimate axonal organization of the brain, partly bc water should move more easily along axonal bundles rather than through axonal bundles: this gives us an image that is based on structural orientation. In dti we lose resolution in order to acquire information about how water is moving in the brain - this is bc diffusion of water is suing a different signal in the scanner.
