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Court’s Claim Construction Leaves MRI Patent Claims Invalid

March 16, 2005
Stach, Jason E.

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Last Month at the Federal Circuit - April 2005

Judges: Bryson (author), Rader, and Friedman

In Medrad, Inc. v. MRI Devices Corp., No. 04- 1134 (Fed. Cir. Mar. 16, 2005), the Federal Circuit affirmed a district court’s claim construction and its grant of SJ of invalidity of all asserted claims.

The claims at issue were directed to a medical MRI machine for forming an image of a “region of interest” in a patient’s body. The claimed apparatus contained two sets of coils arranged in an overlapping pattern, and the coils were pulsed with a current having a phase delay. The claimed coil system beneficially applied a “substantially uniform first magnetic field” to the “region of interest.”

Medrad, Inc. (“Medrad”) alleged error in the district court’s constructions of the phrases “region of interest” and “substantially uniform first magnetic field.” The district court defined “region of interest” as referring to the portion of the patient’s body being scanned for imaging. According to Medrad, this construction was too broad because it would encompass portions of the patient’s body lying within only one of the two coils. Medrad’s proposed construction required the imaged portion of the patient’s body to at least lie within both coils.

The Federal Circuit rejected Medrad’s construction for several reasons, including that the construction was contrary to the language of the claims, which did not require that the two sets of coils operate together at all times. Also, applying Medrad’s construction to the independent claims would render nonsensical at least those dependent claims that expressly allowed the coils to operate separately.

Medrad’s assertion of error in the district court’s construction of “substantially uniform first magnetic field” was likewise rejected. The district court construed this phrase to mean “substantially uniform to obtain useful MRI images.” Medrad, in contrast, urged a construction requiring a magnetic field “that has largely, but not wholly, the same form throughout.” Medrad’s construction was based on the Federal Circuit’s construction of “substantially uniform” in the dishwashing detergent case, Ecolab, Inc. v. Envirochem, Inc., 264 F.3d 1358 (Fed. Cir. 2001). According to Medrad, Ecolab stood for the proposition that functional limitations (e.g., “to obtain useful MRI images”) are inappropriate where the claim limitations are entirely structural.

The Federal Circuit rejected Medrad’s argument on several grounds. First, the persuasiveness of the Ecolab decision was greatly undermined because it involved different technology than that claimed. Under these circumstances, the construction of even an identical phrase in the two cases can differ, as the paramount task is to determine how one of ordinary skill in the art at issue would construe the phrase. Second, the Court rejected Medrad’s broad reading of Ecolab, which would preclude a court from ever considering how a claimed device functions in construing the claims. The Court observed that it is entirely proper to consider the functions of an invention in seeking to determine the meaning of particular claim language. Finally, the Court reviewed the record in the case and found that the district court’s construction was supported by expert testimony and the specification of the patent.

After affirming the district court’s claim construction, the Federal Circuit affirmed the district court’s judgment of invalidity based on a published abstract, a conference presentation, and a publicly used MRI coil. Medrad argued that the references were not invalidating because the devices did not produce a substantially uniform magnetic field over the region of interest. The Federal Circuit dismissed this argument as inconsistent with testimony showing that the machines disclosed and contained in the prior art produced useful MRI images. There was also ample evidence to show that the prior art used phaseshifted current pulses—one of the alleged points of novelty in the asserted claims. The Court found that Medrad failed to offer any proof that the prior art did not create a substantially uniform magnetic field over the region of interest.