Joseph Helpern, Ph.D., Professor of Radiology and Director of the Center for High Field MR Research, and other researchers at the School of Medicine eagerly await the delivery of the steel shield and the magnet that will follow. He expects the MRI machine will allow researchers to obtain incredibly detailed snapshots of metabolic pathways in the living brain, leading to a far better understanding of how the brain's metabolism is affected by disease. This information could lead to earlier diagnosis and treatment of a variety of diseases, including multiple sclerosis and Alzheimer's disease, which may help prevent the progression of these debilitating brain diseases.
The machine, which can scan the entire body, will be used initially in brain research at the School of Medicine. A few numbers illustrate the machine's power. The magnet has a "field strength" of 7 Tesla, weighs 30 tons, and holds some 420 kilometers of superconducting wire. Tesla, named after the famous inventor Nikola Tesla, is a unit of magnetic flux density that describes the "strength" of the magnet. One Tesla equals 10,000 Gauss. The Earth's magnetic field, which is strong enough to turn a needle on a compass, is 0.5 Gauss. A 7-Tesla magnet is 70,000 Gauss, or 140,000 times stronger than the earth's magnetic field. The octagon-shaped steel shield surrounding the magnet will contain its stray magnetic field.
"These high-field strength machines are incredibly important to the future of our understanding of how the brain works," says Robert Grossman, M.D., Chairman of the Department of Radiology at NYU School of Medicine. "They will ultimately help us find answers to some of the most challenging questions that face the medical profession."
New MRI Applications with High-Field Magnets
Dr. Helpern is the Principal Investigator of a $2 million grant recently awarded to the medical center from the National Institutes of Health (NIH), which will help purchase the 7-Tesla magnet. Thirteen years ago, he led a team of scientists that designed and installed the world's first 3-Telsa MRI system specifically for brain research. "People always wonder why we need bigger magnets, and I always point out that using a bigger, more powerful magnet is like using an electron microscope as opposed to a conventional bench-top light microscope," says Dr. Helpern, who led the design team for the 7-Tesla shield and who will oversee the installation and operation of the new machine. "The detail with which we can see things with a stronger magnet is incomparable. It puts us in an entirely different realm of resolution."
MRI machines work by causing certain atomic nuclei to wobble or resonate and this movement is picked up by a detection system. The element with the most sensitive nucleus is hydrogen, which is abundant in living tissues. (Water is composed of hydrogen and oxygen.) Lower-field strength magnets, which are used routinely to provide images of the body, are mainly picking up variations in the concentration and physical characteristics of water in the body. These variations are stored in a computer and analyzed, producing a three-dimensional image. Higher field magnets like the 7 Tesla can be used for imaging and for measuring the amounts of various biochemicals, which is called magnetic resonance spectroscopy (MRS).
Higher field magnets permit the detection of many more elements, such as carbon and phosphorus, which make up key compounds in the body. These biochemicals are also important to study, but at lower field strengths their signals are too faint and often overlap. Physicists have also figured how to mask the signal from water, allowing the signals of other compounds to emerge over a wider spectrum at higher field strengths. "The massive proton signal from water, which makes up approximately 70% of our bodies, swamps all the other signals that you want to look at," explains Dr. Helpern. "It's like trying to listen to a weak radio station. With the more powerful magnets, we can find all these other signals buried beneath the water signal that are really interesting to look at, and these signals also are more distinct because they no longer overlap."
Molecular Imaging
The ability to tune into these other signals is expanding the applications of MRI, and causing a lot of excitement in the field. The applications are part of the emerging field of "molecular imaging," and will enable researchers to distinguish minute amounts of metabolites in the brain, such as glutathione, taurine, and aspartate, as well as neurotransmitters used for neuronal communication, such as glutamate and gamma aminobutyric acid (GABA).
Researchers are interested in characterizing diseases as diverse as multiple sclerosis, epilepsy, depression, alcoholism, Alzheimer's, Parkinson's and schizophrenia by their biochemical brain signatures. These signatures could provide early clues to chemical changes in the brain that are occurring due to disease, and potentially offer new treatment options that could modify these alterations. For example, Dr. Grossman's laboratory has identified the signature of a chemical called N-acetyl aspartate in the brains of people with multiple sclerosis. Early studies suggest that patients with an imbalance in this chemical may benefit most from aggressive therapy.
In addition, the field of molecular imaging allows researchers to look at more of the fine details of the brain itself. In Dr. Helpern's laboratory, for example, high-field MR is being used to identify plaques in the brain that are one of the hallmarks of Alzheimer's disease. It is hoped that the ability to identify these plaques with a technique that is "noninvasive" will lead to earlier diagnosis of Alzheimer's than is now possible, and therefore to earlier and more effective treatments.
"There is so much more that we will be able to do with a 7-Tesla magnet," says Dr. Helpern. "We will be one of the few places in the world with this kind of capability."
Siemens and NYU School of Medicine
The 7 Tesla magnet, which will be used only for research purposes, is being brought to the School of Medicine as part of a seven-year collaborative agreement with Siemens Medical Solutions, U.S.A that will make NYU Medical Center one of the nation's premier imaging centers. The agreement makes Siemens the Medical Center's exclusive supplier of a wide array of highly advanced imaging equipment for research and clinical care.