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Magnetic Resonance Imaging

Diffusion Imaging

Diffusion-weighted MRI can resolve anatomic substructure that cannot be resolved by conventional structural MRI methods. Diffusion MRI measures the molecular diffusion of the water particles in brain tissue. Two aspects of diffusion MRI make the technique very powerful. The diffusion signal is sensitive to the microstructural composition of the tissue so that a slight alteration in, for example, the cell size or membrane permeability can have an appreciable effect on the measured diffusion signal. Secondly, the diffusion signal is sensitive to the orientation of the nerve fibers, a phenomenon referred to as diffusion anisotropy. This enables diffusion MRI to map the orientation of the nerve fibers in the brain. Diffusion MRI is currently being applied in stroke, preoperative planning for neurosurgery, autism, schizophrenia, normal aging, and Alzheimer’s disease, to name just a few examples. Researchers are also exploring whether diffusion MRI may be able to trace neural pathways non-invasively, which is a long sought-after goal of brain imaging.

For more information see:

Le Bihan D. Looking into the functional architecture of the brain with diffusion MRI. Nat Rev Neurosci. 2003 Jun;4(6):469-80.

Ramnani N, Behrens TE, Penny W, Matthews PM. New approaches for exploring anatomical and functional connectivity in the human brain. Biol Psychiatry. 2004 Nov 1;56(9):613-9.

Sundgren PC, Dong Q, Gomez-Hassan D, Mukherji SK, Maly P, Welsh R. Diffusion tensor imaging of the brain: review of clinical applications. Neuroradiology. 2004 May;46(5):339-50. Epub 2004 Apr 21.

Diffusion tensor image of a healthy volunteer. The color indicates the direction of the nerve fibers at every point in the image. Red indicates left-right, blue superior-inferior, and green anterior-posterior. The color-coded diffusion tensor image is superimposed on a conventional T1 structural MRI.




by D.Tuch, updated 4/2005

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