MRI provides glimpse into ancient bones.
For the first time, scientists have used magnetic resonance imaging (MRI) to probe fossil remains, paving the way for in-depth studies of bone diseases that afflicted ancient animals.
"It's a technique that I think can be useful in the future because you can see internal structures without cutting the bone to pieces," says radiologist Jeno I. Sebes of the University of Tennessee in Memphis. He described the work last week at the annual meeting of the Society of Vertebrate Paleontology in Lawrence, Kan.
In the MRI procedure, a strong magnet aligns the spin axes of all free protons in a subject. As the protons return to their normal, random orientations, detectors monitor the radio waves they emit, providing three-dimensional data about the structure of bone and other tissue. In contrast, X-ray techniques such as CAT scanning do not penetrate well through the thick, rock-hard fossil bones of large animals.
Sebes and his colleagues turned to MRI to examine the 12-million-year-old vertebrae of a dolphin. Because fossilized bone contains few free protons, the researchers had to soak the vertebrae in water for 45 minutes.
The resulting images revealed interior bands of thickened bone along the length of the vertebrae. Physicians who have observed similar bands in human bones have interpreted them as signs of arrested bone growth and have proposed a number of possible causes, including scurvy, heavy metal poisoning, hyper-thyroidism and rickets. Sebes suspects that such bands instead reflect normal periods of accelerated bone growth.
MRI can help paleontologists identify a variety of bone tumors and arthritic changes that affected extinct animals, he says. The new approach poses several practical problems, however. Many fossils may be too fragile to withstand the necessary immersion in liquid, and the technique's current expense would prohibit widespread paleontological use, Sebes notes. His group is now testing MRI fossil probes using less expensive magnets.
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|Title Annotation:||magnetic resonance imaging|
|Date:||Oct 20, 1990|
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