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December 2002: A Fantastic Voyage

http://www.medscape.com/viewarticle/445610

11th December 2002
Priscilla Scherer, Site Editor/Program Director
Medscape Neurology & Neurosurgery

If the last 10 years of the 20th century was the "Decade of the Brain," the first 10 years of the 21st could well be called the "Decade In the Brain." Neuroimaging has moved well beyond providing a window through which those on the outside can take a peek inside, to opening the door and inviting us all in for a visit, indeed an excursion into the brain and even the mind. This is fantastic. Forgive a middle-aged memory from thinking back to the 1980s and the first unbelievable magnetic resonance images of brain and spinal cord.

This is like a textbook, like an autopsy on a living person, we all said, and we believed it couldn't get much better than that. And, of course, it has gotten better than that, surpassing comparisons to anything that exists in vivo.

Advances in the role of neuroimaging were prominently discussed during all 3 days of scientific sessions at this year's ANA meeting in October. Several plenaries included discussions of imaging techniques and their essential importance in diagnosis, treatment, and follow-up of a gamut of brain disorders. Sitting in on these sessions, I could not help but think that some neuroimager somewhere was already working with an experimental technique that would render those presentations obsolete by the time the Q&A was over. Indeed, when Dr. Steven Warach from the National Institute of Neurological Disorders and Stroke talked about "pushing the limits of spatial, temporal, and physiological resolution," one questioned whether any limits exist in this field anymore.

With multiphoton microscopy, we can image individual amyloid plaques and reimage them to assess the effects of treatment. With diffusion-weighted imaging, we can identify the tissue that is viable and potentially salvageable after an acute stroke. With PET and functional MRI, we have begun to localize perception, long-term vs short-term memory, emotion, and even some areas involved in moral reasoning! Absolutely dazzling.

Some of these developments are more immediately useful than others. Rohit Bakshi, MD, neuroimager, regular contributor to Medscape, and Associate Professor of Neurology at the University at Buffalo, State University of New York, believes that the most significant recent progress in neuroimaging involves 3 specific areas, all of which are transforming the practice of neurology from qualitative clinical art to quantifiable science. "Many research centers have been developing and advancing quantitative analysis of MRI with computer software programs that enable physicians to objectively assess damage and disease progression in patients with neurologic disorders," he notes.

"For a majority of medical conditions, we can measure serum levels of electrolytes, hormones, enzymes, and so on, to see whether treatment is working, how diseases are progressing, etc. With these quantitative imaging analysis techniques, we now have a tool that provides objective data from the nervous system that can be followed over time and even compared with normal brains. We can measure whole and regional brain atrophy in patients with multiple sclerosis and follow the effects of treatment on disease burden; we can look at 3-dimensional tumor volume to judge effectiveness of radiation and chemotherapies; we can assess hippocampal volume in Alzheimer's disease, and caudate nucleus volume in Huntington's."

A second major recent advance in neuroimaging is the wider availability of magnetic resonance spectroscopy (MRS), providing new insights into the neurochemistry of various diseases. Says Bakshi, "MRS is a noninvasive method of studying the biochemistry of living tissue. MRS may reveal a metabolite that is not normally present in brain tissue, or abnormal levels of a metabolite that is normally present." In this way, he explains, MRS "helps to differentiate diseases at the chemical level and, for example, can distinguish a lesion that should be biopsied from one that doesn't require biopsy."

Finally, Bakshi cites the wider availability of ultra-high-field imaging. "For routine imaging in humans, the gold standard has been 1.5 T (which generates a magnetic field that is more than 10,000 times stronger than Earth's)." And until recently, the consensus was that MRI beyond 4 T would not be safe in humans. "A few years ago, researchers at Ohio State University in Columbus developed and implemented human imaging on an 8-T unit," notes Dr. Bakshi. Now, 3-8 T imaging is not only possible but is becoming more prevalent in centers across the country. "This can improve the sensitivity for detecting blood-oxygenation changes in functional MRI studies by as much as 30-fold and will enable more sensitivity and range of chemical detection in MRS for picking up very subtle lesions."

In these times, even non-neuroimaging specialists need to know what these new techniques can measure and how they do it, if not how to read the images themselves. Shortly after the official launch of the Medscape Neurology & Neurosurgery site, late in 1999, we began posting a regular series of Neuroimaging Case Challenges . These are short, elegantly designed exercises that walk you through the images to a diagnosis, teaching the basics of neuroimaging with relatively little effort. If you have not had a look at these interactive cases (19 in all, so far) because you thought they were for the radiology crowd, please take a few minutes to go through a few of them.

For a preview of the cutting edge in imaging, we also regularly include highlights of neuroimaging research from the major neurology, neurosurgery, and neuroradiology conferences. These will also bring you up to date on the newest techniques and those of the future.
 

© 2002 Medscape