Study reveals why MRI brain images are so sensitive to the direction in which nerve fibres run

Published on November 4, 2012 at 11:29 PM · No Comments

World-leading experts in Magnetic Resonance Imaging from The University of Nottingham's Sir Peter Mansfield Magnetic Resonance Centre have made a key discovery which could give the medical world a new tool for the improved diagnosis and monitoring of brain diseases like multiple sclerosis.

The new study, published in the Proceedings of the National Academy of Science, reveals why images of the brain produced using the latest MRI techniques are so sensitive to the direction in which nerve fibres run.

The white matter of the brain is made up of billions of microscopic nerve fibres that pass information in the form of tiny electrical signals. To increase the speed at which these signals travel, each nerve fibre is encased by a sheath formed from a fatty substance, called myelin. Previous studies have shown that the appearance of white matter in magnetic resonance images depends on the angle between the nerve fibres and the direction of the very strong magnetic field used in an MRI scanner.

Based on knowledge of the molecular structure of myelin, the Nottingham physicists devised a new model in which the nerve fibres are represented as long thin hollow tubes with special (anisotropic) magnetic properties. This model explains the dependence of image contrast on fibre orientation in white matter and potentially allows information about the nerve fibres (such as their size and direction) to be inferred from magnetic resonance images.

Research Fellow Dr Samuel Wharton said: "While most MRI-based research focuses on tissue measurements at the millimetre length scale, our experimental scans on healthy human volunteers and modelling of the myelin sheath shows that much more detailed microscopic information relating to the size and direction of nerve fibres can be generated using fairly simple imaging techniques. The results will give clinicians more context in which to recognise and identify lesions or abnormalities in the brain and will also help them to tailor different types of scan to a particular patient."

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