The U.S. Court of Appeals for the Federal Circuit affirmed the district court’s summary judgment that Medrad’s patent is invalid as anticipated by the prior art. The Court held it is proper to consider how the invention functions in construing disputed claim terms. Medrad, Inc. v. MRI Devices Corp., Case No. 04-1134 (Fed. Cir. Mar. 16, 2005) (Bryson, J.).
Medrad’s patent claims a two-coil magnetic imaging (or MRI) system. Whether the claims were anticipated turned on how "uniform" the magnetic field of the claims had to be and over what "region of interest."
The district court defined "region of interest" to mean "the portion of a patient’s body being scanned" within one coil of the system. In determining that "region of interest" did not refer to the anatomy residing within both coils, as Medrad argued, the district court adopted a construction consistent with the broad usage in the specification, the dependant claims, inventor testimony describing the claimed invention, Medrad’s own expert testimony and the district court’s understanding of how the invention was intended to function. The Federal Circuit agreed that all of this evidence was properly considered.
The district court read a functional requirement into the term "substantially uniform magnetic field," construing it to mean "substantially uniform to obtain useful MRI images." The district court declined to adopt Medrad’s proposed construction (a magnetic field that has largely, but not wholly, the same form throughout). In affirming, the Federal Circuit held that where the usage of the term in the claim is ambiguous (in this case, as to how much the field may deviate before it is no longer uniform), the meaning of the term must be considered in the context of the function of the invention as revealed in the written description and file history: it is "entirely proper to consider the functions of an invention in seeking to determine the meaning of particular claim language.
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