ABSTRACT
Diffusion refers to the random, microscopic movement of particles due to thermal collisions. Particles suspended in a fluid are forced to move in a random motion, which is often called "Brownian motion" or pedesis resulting from their collision with the atoms or molecules in the gas or liquid. To get a feeling of the physical meaning of diffusion, consider a diffusing particle that is subjected to a variety of collisions that one can consider random, in the sense that each such event is virtually unrelated to its previous event. It makes no difference whether the particle is a molecule of perfume diffusing in air, a solute molecule in a solution, or a water molecule inside a medium diffusing due to the medium's thermal energy. The usefulness of conventional MRI in the detection of cerebral pathology has been well-established, although it can be in many cases nonspecific despite the excellent soft tissue visualization.
