Where are we going?

Brain IMAGING

THE NMR REVOLUTION

By the year 2020, he believes that functional magnetic resonance imaging (functional MRI) will be an everyday procedure in emergency rooms and general practitioners' surgeries: "Non-invasive imaging of the brain will mean that one can characterise the type of ischaemic stroke within a few minutes of symptoms. I'm certainly counting on it myself."

Such a use of imaging may also have beneficial effects for deciding how a drug might be best used. Research on stroke patients using functional MRI combined with a drug such as streptokinase might help to reveal the best window of opportunity for treatment.

Turner thinks that a range of new methods of diagnosis for several developmental and psychiatric disorders may eventually arise from the new functional MRI. Imaging techniques will aid in determining the presence of disorders that are currently hard to diagnose such as dyslexia and attention deficit disorder as well as helping in the tricky diagnosis of mental disorders such as the onset of schizophrenia or manic depression.

For neurosurgery the rewards look just as rosy. Research with functional MRI will allow the development of a detailed brain map, and if neurosurgeons are operating on a patient with light anaesthesia and want to know whether hand function is present all they have to do is look at the detailed image. Neurosurgeons, and for that matter any surgeons, will be able to have "wonderful" access to the scanned patient during surgery. A detailed image of the area of operation is likely to help surgeons know just where their needles are going and has implications for many aspects of keyhole surgery.

But such a scenario may appear before 2020. Several medical instrument companies have already produced "open access" MRI. These are scanners that enable the operator to reach the patient, rather than the patient being fully enclosed inside. Although not ideal, they do allow surgeons easier access to the patient.

What's up and coming in brain imaging

* Diffusion weighted imaging and magnetic resonance angiography--for diagnosing ischaemic stroke

* Perfusion imaging--for measuring blood flow through capillary beds

* Magnetisation transfer imaging--probes metabolite and water interactions, which can be altered by disease, and can measure rates of some enzyme reactions

* Magnetic resonance spectroscopy--measures several different metabolites in living tissue and is being used to map biochemical changes caused by disease

FIGURE 1 Diffusion weighted MRI showing 9 hour old stroke and associated occlusion of right middle cerebral artery. No contrast agent was used. Conventional MRI (T2 weighted) shows only subtle changes, and x ray computed tomography is usually negative for several more hours. (See article on BMJ website for more detail)

FIGURE 2 Functional MRI of brain activity (colour) caused by movement of fingers. No contrast agent

FIGURE 3 Chemical maps of brain metabolites (colour) made by MRI spectroscopic imaging in a patient with a glioblastoma multiforme (grey scale MRIs). White insets show spectra from regions indicated by small squares on the MRIs. N-acetyl aspartate (NAA) concentration is reduced in the tumour, while lactate and lipid concentrations are increased.

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