Diffuusiokuvantamisen

Diffuusiokuvantaminen, often translated as diffusion imaging or diffusion MRI, is a magnetic resonance imaging (MRI) technique that measures the diffusion of water molecules within biological tissues. This diffusion is not random but is influenced by the microstructure of the tissue, such as cell membranes, myelin sheaths, and tissue barriers. By tracking the random motion of water molecules, diffuusiokuvantaminen provides valuable information about tissue organization and integrity, which is not visible with conventional MRI.

The principle behind diffuusiokuvantaminen relies on the fact that water molecules move more freely in areas with less structural impediment. In white matter, for instance, the highly organized structure of axons and their myelin sheaths restricts the diffusion of water in certain directions. This directional dependence of diffusion is what diffuusiokuvantaminen exploits. The technique uses diffusion gradients, which are strong magnetic field gradients applied during the MRI scan, to sensitize the image to the motion of water molecules.

The data acquired from diffusion imaging can be processed to generate various maps. Diffusion tensor imaging (DTI) is a common method that models the diffusion of water as an ellipsoid, allowing for the calculation of parameters like fractional anisotropy (FA) and mean diffusivity (MD). FA quantifies the degree of directional diffusion, while MD measures the average diffusion magnitude. These parameters can reveal subtle changes in tissue structure, such as those occurring in neurodegenerative diseases, stroke, or traumatic brain injury, often before they are apparent on standard MRI. Furthermore, tractography, derived from DTI data, allows for the in-vivo reconstruction of white matter pathways, aiding in the study of brain connectivity.