NMR Patent: A Matter of Infringement

Science News, January 25, 1986 | Go to article overview

NMR Patent: A Matter of Infringement


In 1974 Raymond V. Damadian, a physician, patented the design and use of a nuclear magnetic resonance (NMR) imaging device to scan the body in search of cancer. Since then, N,R scans -- now known as magnetic resonance imaging (MRI) scans -- have become a standard diagnostic technique employed by large hospitals and medical clinics throughout the world. However, only about 30 of the estimated 250 MRI machines in medical use have been made by Damadian's company, the Meville, N.Y.-based Fonar Corp. Since no one sought a license from Fonar to manufacture the device, Damadian reasoned that makers of those other machines much be infringing on his patent. He sued one such company. And in late November 1985, a jury in a Massachusetts federal district court case ruled that Johnson & Johnson Inc.'s Cleveland-based Technicare subsidiary--maker of 100 MRI medical devices--had indeed infringed upon Damadian's patent. But on Jan. 10, the judge overturned the finding of infringement, saying that, based on the evidence, the jury had rendered an invalid judgment.

The judge's ruling, which Fonar will appeal, seems to hinge on a scientific issue: Do physicians using NMR diagnose diseases--like cancer--based upon a comparison of the time it takes excited hydrogen nuclei in diseased and normal tissue to "relax" back to their ground state?

Although the spin orientation of atomic nuclei in the body is usually random, those spins will line up in a north-south polar orientation when the nuclei are acted on by a magnetic force. In NMR, such a magnetic force is applied to body tissue. Then a radio wave signal with a frequency that will be absorbed by hydrogen nuclei is beamed at the tissue. Nuclei absorbing this energy become excited, altering their alignment. When the radio signal stops, the nuclei relax back to their previous magnetic-field alignment. MRI devices measure the time it takes excited nuclei to relax, and display with a smilar contrast regions having the same relaxation time. …

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NMR Patent: A Matter of Infringement
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