Friday, October 29, 2010

Three-dimensional maps of brain wiring

A team of researchers at the Eindhoven University of Technology has developed a software tool that physicians can use to easily study the wiring of the brains of their patients. The tool converts MRI scans using special techniques to three-dimensional images.

An image of 'brain wiring' made with the new tool.

This now makes it possible to view a total picture of the winding roads and their contacts without having to operate. Doctors can virtually browse along the spaghetti-like "wiring" of the brain, with this new tool. Researcher Vesna Prčkovska defended her PhD thesis on this subject last week.

To know accurately where the main nerve bundles in the brain are located is of immense importance for neurosurgeons, explains Bart ter Haar Romenij (professor of Biomedical Image Analysis, at the Department of Biomedical Engineering). As an example he cites ‘deep brain stimulation’, with which vibration seizures in patients with Parkinson’s disease can be suppressed. "With this new tool, you can determine exactly where to place the stimulation electrode in the brain. The guiding map has been improved: because we now see the roads on the map, we know better where to stick the needle." The technique may also yield many new insights into neurological and psychiatric disorders. And it is important for brain surgeons to know in advance where the critical nerve bundles are, to avoid damaging them.

The accuracy of the tool is a great step forward. Especially intersections of nerve bundles were difficult to identify till now. Ter Haar Romenij: "You can now see for the first time the spaghetti-like structures and their connections." We are far from seeing all brain connections; there are many more smaller compounds in the brains, who are not seen by the new tool. A microscope observed them. "But you cannot, of course, dissect a live patient into slices for under a microscope," the professor smiles.

The tool was developed by TU/e researcher Anna Vilanova, with her PhD students Vesna Prčkovska, Tim Peeters and Paulo Rodrigues.

High angular resolution diffusion imaging (HARDI) is a diffusion weighted MRI technique that overcomes some of the decisive limitations of its predecessor diffusion tensor imaging (DTI) in the areas of composite nerve fiber structure. Despite the advantages, HARDI raises several issues: complex modeling of the data, non-intuitive and computationally demanding visualization, inability to interactively explore and transform the data etc. To overcome these drawbacks, we present a novel, multi-field visualization framework that adopts the benefits of both DTI and HARDI. By applying a classification scheme based on HARDI anisotropy measures, the most suitable model per imaging voxel is automatically chosen. This classification allows simplification of the data in areas with single fiber bundle coherence. To accomplish fast and interactive visualization for both HARDI and DTI modalities, we exploit the capabilities of modern GPUs for glyph rendering and adopt DTI fiber tracking in suitable regions. The resulting framework, allows user-friendly data exploration of fused HARDI and DTI data. Many incorporated features like sharpening, normalization, maxima enhancement and different types of color coding of the HARDI glyphs, simplify the data and enhance its features. The tool is based on a recently developed technology called HARDI (High Angular Resolution Diffusion Imaging). The MRI measuring technique for HARDI was already there, the research team took care of the processing, interpretation and interactive visualization of these very complex data, so that doctors can get to work.

Bart ter Haar Romenij expects that the tool can be ready at relatively short notice for use in the hospital within a few years. "We need to validate the package. We now need to prove that the images match reality." Also, there is still work to do on the speed of the corresponding MRI scan. For a detailed view, a patient needs to be one hour in the scanner, which is too long. Moreover, the tool is already widely in use by other scientists, says the professor.

The research was supported by NWO (Dutch Organization for Scientific Research). The thesis of Vesna Prčkovska is titled: High Angular Resolution Diffusion Imaging, Processing & Visualization. She graduated last Wednesday, October 20, 2010.


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