Brain and White Matter Anatomy
As the center of the nervous system, the brain plays an important role in human activities of both a physical and mental nature. The brain consists of two major components: gray matter and white matter. Gray matter is composed of neuronal cell bodies, neuropil, glial cells, and capillaries and is located mainly on the brain’s surface with a few millimeters of thickness as the cerebral cortex. White matter is composed of mainly glial cells and myelinated axons, which serve as pathways for transmitting electrical signals within local regions of the cerebrum and from the brain to the spinal cord to exert control over the whole body.
The connective structure of the axon fiber tracts in white matter is thought to provide insight on complex brain function. However, noninvasive observation of white matter fiber structures was impossible until the end of the twentieth century using conventional imaging techniques. The advent of dMRI, which quantifies the diffusion of water molecules in biological structures, allows for noninvasive visualization of fiber tract structures in live subjects. In addition to the characterization of normal structures of white matter, dMRI can also be used to quantify pathological structures, such as tumors and infarctions via measurement of diffusion properties. Thus, the use of dMRI revolutionized techniques for brain anatomy and pathology analysis.