Improved Insights into Brain Disorders with New CT Method

The method, called small-angle X-ray-scattering computed tomography (SAXS-CT), can map the myelin sheaths of nerve cells, which are important indicators for disorders such as multiple sclerosis and Alzheimer's disease (AD).

The study's findings have been published in May 2011 in the journal NeuroImage. The myelin sheaths of nerve cells are lamellar membranes surrounding the neuronal axons. Myelin layers are important to the central nervous system as they ensure the rapid and uninterrupted communication of signals along the neuronal axons. Alterations in the myelin layers are linked with a number of neurodegenerative disorders such as cerebral malaria, multiple sclerosis, and AD.

The development of these diseases are still not fully understood, but are thought to be related to the damage of the myelin layers, so that messages from the brain reach the various areas of the body poorly or not at all. It is similar to an electric cord where the insulating components have been damaged and the current short circuits. To find ways to prevent or treat the diseases it is important to understand the connection between the diseases and the changes in the myelin.

"We have combined two well-known medical examination methods: SAXS and CT scanning. Combined with a specially developed program for data processing, we have been able to examine the variations of the myelin sheaths in a rat brain all the way down to the molecular level without surgery," explained Torben Haugaard Jensen, PhD, from the Niels Bohr Institute at the University of Copenhagen (Denmark). The method is known as molecular X-ray CT, because CT is used to examine myelin at the molecular level.

The research has been carried out in collaboration with researchers in Switzerland, France, and Germany. The experiments took place at the Paul Scherrer Institute (Villigen PSI, Switzerland), where they have a powerful X-ray source that can measure SAXS at a high resolution. Typically, such experiments would give two-dimensional X-ray images that are sharp and precise, but without information on depth. But by integrating the method from CT scanning, where you image from different angles, the researchers have managed to capture three-dimensional (3D) X-ray images.

This has not only required the development of new X-ray methods and research, but has also required the development of new methods for processing data. The extremely detailed measurements of cross sections from different angles meant that there were 800,000 images to be analyzed. Therefore, the researchers have also developed an image-processing program for the SAXS-CT technique. The result is that they can see all of the detailed information from SAXS in spatially resolved.

"We can see the myelin sheaths of the neuronal axons and we can distinguish the layers which have a thickness of 17.6 nm," explained Dr. Torben Haugaard Jensen. "Up until now, you had to cut out a little sample in order to examine the layers in one area and get a single measuring point. With the new method, we can examine 250,000 points at once without cutting into the sample. We can get a complete overview over the concentration and thickness of the myelin and this gives of the ability to determine whether the destruction of the myelin is occurring in spots or across the entire sample," he explained.

The research provides new opportunities for collaboration with investigators at Copenhagen University Hospital and the Panum Institute, with whom they already have close contact. The method cannot be used to diagnose living persons. However, the researchers can obtain a new understanding about the diseases, what kind of damage is taking place and where. They will be able to follow the development of the diseases and find out how the brain is being attacked. This knowledge could possibly be used to develop a treatment, according to the researchers.

Related Links:
Niels Bohr Institute at the University of Copenhagen
Paul Scherrer Institute