Mayo sues Toshiba over MRI patentrelating to artifact suppression

February 14, 1996

Other vendors may also be infringing, attorney saysMRI patent litigation is in the news again, but this time it isMayo Foundation and Toshiba at legal loggerheads rather than GEand Fonar. Mayo has filed a lawsuit against Toshiba charging

Other vendors may also be infringing, attorney says

MRI patent litigation is in the news again, but this time it isMayo Foundation and Toshiba at legal loggerheads rather than GEand Fonar. Mayo has filed a lawsuit against Toshiba charging thevendor with violating an artifact-suppression patent Mayo receivedin 1987.

The Mayo Foundation for Medical Education and Research filedthe lawsuit Oct. 24 in U.S. District Court in Milwaukee againstToshiba America Medical Systems of Tustin, CA, and Toshiba AmericaMRI of South San Francisco, CA. The suit claims that five ToshibaMRI scanners violate its patent for clearing up images of softtissue by suppressing unwanted images from blood flow, accordingto Toshiba counsel Wayne Babler of Quarles & Brady in Milwaukee.Those scanners include MRT-35A, MRT-50A, MRT-150A, Flexart andAccess LPT, Mayo claims.

The patent at the center of the dispute is U.S. patent number4,715,383, "Method for reducing artifacts in NMR images."The technique eliminates artifacts caused by flow, motion andphase aliasing by using a series of saturation pulse sequencesthat are interleaved with MRI pulse sequences. The MRI pulse sequencesextract data from the region of interest, while the saturationpulse sequences excite and saturate spins in adjacent regions,according to the patent.

"The invented method includes the step of regularly applyingexcitation pulses during the NMR scan of the volume of interestsuch that spins outside the volume of interest are saturated,"the patent application states. "As a consequence, the saturatedspins cannot produce a significant NMR signal and cannot significantlyaffect the reconstructed image."

Mayo resorted to litigation after discussions with Toshibaover licensing the technology broke down, Babler said. Mayo believesthat the patent is a broad one that covers MRI scanners manufacturedby other vendors that use the technique.

"We have granted licenses to some vendors. We've offereda license to Toshiba," Babler said. "It had been Mayo'shope that a license agreement could be worked out."

In addition to Toshiba, Mayo is involved in a dispute withanother MRI vendor Babler declined to name, other than to saythat it is not GE. Mayo has not filed any litigation in that dispute,Babler said.

A Toshiba spokesperson confirmed that the vendor had been servedwith Mayo's complaint but declined further comment, citing pendinglitigation.