Feeling stiff? Suffering from aches and pains? If muscle stiffness is the underlying cause, then a technique now undergoing trials could pinpoint the problem precisely. Magnetic resonance elastography (MRE) is a new, painless way of measuring the stiffness of the deepest muscle fibres by taking snapshots of the problem area with a magnetic resonance imaging (MRI) scanner. By contrast, established techniques for measuring muscle stiffness rely on sensors inserted into the tissue.
MRE works by measuring the wavelength of vibrations sent through the muscle fibres by a vibrating metal plate placed on the skin. Pulsing the magnetic field in the MRI scanner in tune with the mechanical vibrations "freezes" the pattern of waves in the muscles, like a stroboscope, allowing the wavelength to be measured. The stiffness of the muscles can then be calculated using this measure, say researchers from the Department of Orthopedic Surgery at the Mayo Clinic in Rochester, Minnesota. Kai-Nan An, director of the Biomechanics Laboratory at the Mayo Clinic, and his team have been testing MRE on human volunteers with a variety of medical problems.
They say the main limitation of the technique is the need to confine patients inside an MRI scanner. This means that MRE cannot take measurements as you move around. Instead the researchers get their volunteers to tense particular muscle groups by bracing themselves against special apparatus that they wear inside the scanner. An predicts that MRE will be ready for general use within five years, benefiting athletes and people recovering from injuries, as well as stroke victims and people with cerebral palsy who cannot control their movements because their muscles will not relax. Botox injections or surgery can help, and MRE will enable doctors to target the treatment precisely.
MRE should also help doctors track the progress of diseases that cause muscle to degenerate, such as multiple sclerosis or hypothyroidism. "It could be used for many things," says An. He predicts MRE will even help physiotherapists find precisely which areas are causing pain. Representatives of the Association of Chartered Physiotherapists Interested in Neurology say the cost of using MRI machines could limit the spread of the technique, but agree it has broad potential.
Author: Michelle Knott
New Scientist issue: 15th November 2003
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