Diffusion Magnetic Resonance Imaging (Diffusion MRI) is a non-invasive imaging technique that captures the random movement of water molecules to produce detailed images of tissue microstructure.

The underlying principle of diffusion MRI is based on the constant motion of water molecules within biological tissues, which occurs due to thermal energy. This phenomenon, known as Brownian motion, is significantly influenced by the tissue’s structural characteristics. In areas where the tissue is densely packed, such as white matter, the movement of water molecules is notably restricted. Conversely, in regions with less dense tissue, such as grey matter, the water molecules experience more freedom of movement.

Diffusion MRI assesses the diffusion of water molecules across various directions by employing a series of magnetic field gradients. By analyzing how water molecules diffuse in multiple orientations, diffusion MRI can generate a map of the diffusion tensor. This tensor provides insight into both the direction and magnitude of water diffusion within each voxel of the image. Such information is crucial for inferring the microstructural properties of the tissue, including the orientation of axons in white matter.

The applications of diffusion MRI in neuroscience are extensive. It is instrumental in researching brain development, connectivity, and various neurological diseases. Additionally, in clinical settings, diffusion MRI is utilized to diagnose and monitor conditions such as stroke, multiple sclerosis, and brain tumors.