Pictures of the Future      Fall 2005

The Hubble Telescope of Brain Research

Neurologists are exploring the deepest areas of the brain. New and extremely powerful magnetic resonance tomographs make it possible to not only observe individual living cells as they work, but also monitor the path that biochemical molecules travel through the brain.

The university hospital in Magdeburg, Germany, is home to one of the world’s most powerful magnetic resonance (MR) tomographs. The magnetic flow density in the device’s interior measures seven Tesla, which is 140,000 times stronger than the Earth’s magnetic field. The colossus weighs 32 t and consists of a superconducting niobium-titanium wire that is 400 km in length, but which is rolled up into a coil and cooled to -269 °C. This 7-Tesla MR machine is the first of its kind in Europe and one of only six in the world to date (three of which were built by Siemens). Siemens Medical Solutions delivered the unit to the Leibniz Institute for Neurobiology (IfN) in February 2005. "The technology had already proved its value in day-to-day clinical operations, which is one reason why we decided to go with Siemens," says Dr. André Brechmann, head of the Noninvasive Imaging lab at IfN. "We were also able to take a look at a functioning reference unit at Massachusetts General Hospital (MGH) in Boston."

Researchers in Boston have been using their 7-Tesla MR machine—the first ever supplied by Siemens—for three years now (see "What happens when we think" – for a description of how magnetic resonance works). Dr. Lawrence Wald, who is responsible for scanner facilities at MGH, is thrilled with the possibilities the 7-Tesla machine offers, and describes the scanner as "the Hubble telescope of brain research." Researchers at IfN are also expecting great things from their new ultra highfield MR tomograph, which they plan to use for basic research and for early and reliable diagnosis of diseases such as Alzheimer’s, epilepsy, schizophrenia, and multiple sclerosis. The device’s high spatial resolution enables doctors to identify even the tiniest changes in tissue.

"When you look at the very first images of the brain taken with the unit, you can see details measuring less than a tenth of a millimeter," says Brechmann. It will also be possible to use the scanner to monitor thinking processes in near time in areas of the brain with a volume of less than one cubic millimeter. "This will enable us to observe for the very first time even relatively small functional units in the cerebral cortex as they go about their work," Brechmann explains. Among other things, he and his colleagues will attempt to find out how the brain processes acoustic signals—for example, by determining which regions of the brain process subliminal emotional messages in spoken sentences. "Our goal is to make a comprehensive map of the functioning of the human brain," says Brechmann.

Researchers and physicians at IfN also plan to use a technology known as spectroscopy to examine brain metabolism and determine which biochemical substances play a role in various diseases. One thing they will attempt to find out is whether the neurotransmitter GABA (gamma-amino butyric acid) contributes to the development of schizophrenia, as many neurologists suspect.

Using spectroscopy, they hope to be able to identify those areas of the brain actually affected by medications used to treat neurological diseases. The higher the strength of the tomograph’s magnetic field, the easier it is to differentiate between various substances. Whereas GABA can be identified only with great effort using a special procedure on a 3-Tesla MR machine, it can be easily quantified with a 7-Tesla scanner by means of a standard measurement procedure.

In order to further improve MR’s diagnostic possibilities, Herbert Thein, Siemens project manager for the development of the 7-Tesla scanner, is working with colleagues in Erlangen on creating new gradient and high-frequency coils that will be specially adapted to 7T’s unique physical para­meters. As such, the nextgeneration 7-Tesla machines will have 32 radio frequency channels instead of the previous one or eight. "We’ll then be able to more precisely determine the location in the brain from which a signal originates, which in turn will lead to higher resolution images," says Thein, who is delighted with demand for the new devices. "Nine next-generation 7-Tesla scanners have already been ordered," he reports.

The race to achieve even higher field strength is already under way again. CEA (the French Atomic Energy Agency) has launched the "Neurospin" project to promote the simultaneous development of medical imaging systems and specific types of contrast agents for neurological examinations. The ultimate goal here is "molecular imaging"—the depiction of individual cells as they go about their work. The core focus of the project is the development of an 11.7-Tesla scanner. "Such a unit should be feasible in the next five years," says Dr. Robert Krieg, head of the working group for Molecular MR Imaging at Siemens, who has already conducted a feasibility study with his team on behalf of the CEA. Krieg is certain that advances expected to be achieved through develop­ment of such a super magnet (e.g. improved cooling, new materials, a more simplified radiation protection system) will also improve today’s standard lower field strength MR scanners, even in terms of image interpretation. As Krieg points out, "You learn an unbelievable number of things when you’re working on a pioneering project."
                                                                                                                         Ute Kehse