Diffusion Tensor MRI Scan Improves Imaging of Brain Changes

Conventional magnetic resonance imaging (MRI) scans, up to now, have been unable to produce adequate images of nerve bundles. However, this is now possible by an MRI technique called diffusion tensor imaging (DTI). This new technology helped a Dutch investigator to generate more effective images of the damage that radiotherapy and chemotherapy cause in young leukemia patients.

With MRI, images can be obtained of various parts of the body. Regrettably, these scans are not sufficiently refined for the imaging of nerve bundles. Dr. Matthan Caan succeeded in improving the DTI method during his PhD research at Delft University of Technology (TU; Delft; The Netherlands), which concentrated on adjusting the conventional MRI technique with DTI, so that better images of the nerve bundles could be obtained.

Utilizing DTI, a technology that is still being refined, changes in the so-called white matter of the brain can be mapped. These changes can be caused by the aging process or by disorders such as Alzheimer's disease. The white matter contains the connections between the nerve cells, and the principle of DTI concerns the movement of water molecules within the white matter. The molecules can move easily along the length of the nerve bundle, but not so easily on the perpendicular. This is because they are obstructed by the wall of the nerve cell and a protective layer (of myelin). Using DTI, the difference in the water molecules' freedom of movement allows conclusions to be drawn on the health of the nerve bundles in the white matter.

Dr. Caan succeeded in improving the DTI technique during his research in collaboration with his supervisor, Dr. Frans Vos. He demonstrated this at the Academic Medical Center (Amsterdam, The Netherlands), through research into the side effects of chemotherapy on the brains of young cancer patients. "Usually, the scans are examined point by point. We combine measurements over a much bigger range, examining the whole nerve bundle.”

This allowed Dr. Caan to show that a lower dose of chemotherapy treatment causes much less damage to the brain. "In a conventional DTI analysis, all the voxels [3D pixels] are considered independently,” stated Dr. Caan. "However, we expect that, because of the many connections in the brain, more areas are involved in complex brain diseases, such as schizophrenia. We have therefore introduced a self-learning system that can perform a comparative study of these areas.”

DTI images could ultimately be used for early diagnosis of Alzheimer's disease, for example. This would be possible by examining alteration in the white matter among large groups. Extensive population studies are necessary in order to allow differences between groups of patients to be shown statistically.

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