Medrad, Inc. v. Mri Devices Corp.

• Decision Date: 16 March 2005
• Docket Number: No. 04-1134.,04-1134.
• Citation: 401 F.3d 1313
• Parties: MEDRAD, INC., Plaintiff-Appellant, v. MRI DEVICES CORPORATION, Defendant-Appellee.
• Court: U.S. Court of Appeals — Federal Circuit

401 F.3d 1313

MEDRAD, INC., Plaintiff-Appellant, v. MRI DEVICES CORPORATION, Defendant-Appellee.

No. 04-1134.

United States Court of Appeals, Federal Circuit.

March 16, 2005.

W. Thomas McGough, Jr., Reed Smith LLP, of Pittsburgh, Pennsylvania, argued for plaintiff-appellant. With him on the brief were Frederick H. Colen; Kirsten R. Rydstrom; and Robert D. Kucler. Of counsel on the brief was Gregory L. Bradley, Medrad, Inc., of Indianola, Pennsylvania.

James F. Hurst, Winston & Strawn LLP, of Chicago, Illinois, argued for defendant-appellee. With him on the brief were Derek J. Sarafa and Brian R. Pollack.

Before RADER, Circuit Judge, FRIEDMAN, Senior Circuit Judge, and BRYSON, Circuit Judge.

BRYSON, Circuit Judge.

Medrad, Inc., brought this action in the United States District Court for the Western District of Pennsylvania, CA No. 02-2044, alleging that MRI Devices Corp. ("MRIDC") was infringing Medrad's patent, U.S. Patent No. 6,396,273 ("the '273 patent"). The district court referred the case to a magistrate judge under 28 U.S.C. § 636(b)(1). After a hearing, the magistrate judge recommended that MRIDC's motion for partial summary judgment of invalidity be granted and that Medrad's motion for a preliminary injunction be denied. The district court adopted the magistrate judge's recommendation. We affirm.

I

This case arises from a dispute over devices known as radio frequency coils ("RF coils"), which are used in magnetic resonance imaging ("MRI"). MRI uses nuclear magnetic resonance to create detailed images of a patient's internal anatomy. See generally David D. Stark & William G. Bradley, Jr., 1 Magnetic Resonance Imaging 1-14 (3d ed.1999). In the MRI process, a portion of the patient's body is placed in an extremely strong magnetic field. The magnetic field causes the nuclei within the atoms of the body to partially align with the magnetic field in equilibrium. The partial alignment of the nuclei creates a net magnetization within the body in the direction of the magnetic field. A second, time-varying, magnetic field is then created in an orthogonal direction by applying electrical current in pulses to RF coils that surround the body. The second magnetic field drags the net magnetization of the body away from the direction of the main magnetic field. According to the laws of quantum mechanics, the affected nuclei, and thus the net magnetization, will precess around the direction of the main magnetic field at a rate known as the Larmor frequency, before dephasing and eventually realigning with the main magnetic field. E. Mark Haacke, Magnetic Resonance Imaging: Physical Principles and Sequence Design 5-8 (1999). The precession induces a current in the RF coils, which can be measured. That signal can then be used to reconstruct an image of the internal tissues of the portion of the patient's body that was under study.

It was well known in the prior art that the current in the RF coils could be detected at a much higher signal-to-noise ratio if many small overlapping RF coils were used in a "phased array" to receive the signal from the precessing nuclei. It was advantageous for the same coils to be used both to create the time-varying magnetic field ("transmission") and to receive the resulting signal from the precessing nuclei ("reception"). The problem, however, was that identical pulses of current could not be passed through the overlapping coils during transmission, because that would result in the magnetic field in the overlap region being roughly twice as large as in the areas of the coil outside of the overlap. According to the inventor, George J. Misic, that is the problem the '273 patent was meant to solve.

II

Claim 1 of the '273 patent is representative of the six claims that Medrad asserted against MRIDC. It provides as follows:

A magnetic resonance imaging system for forming images of a region of interest, comprising:

a first phased array coil formed of a plurality of electrically conductive members and defining a first array volume a second phased array coil formed of a second plurality of electrically conductive members and defining a second array volume, said second phased array coil disposed at least partially within the first array volume, said first and second array phased array coils cooperating to define a coil subsystem; and

a coil interface subsystem operably coupled to the coil subsystem, said coil interface subsystem, in a first selectable state, processing RF power such that a substantially uniform first magnetic field is applied to the region of interest, and, in a second selectable state, receiving a response of the region of interest to the first magnetic field.

The district court granted summary judgment of invalidity of the six asserted claims based on its construction of certain terms in those claims. The magistrate judge's report and recommendation, on which the district court's ruling was predicated, found that Medrad's invention was anticipated by a prior art publication and invention. Interpreting the claim term "region of interest" to refer to the portion of the patient's body being scanned and the claim term "substantially uniform first magnetic field" to mean "a sufficient uniformity to give a good image," the magistrate judge concluded that all of the elements of the invention were found in the cited prior art. The magistrate judge rejected Medrad's argument on invalidity because he concluded that Medrad's proposed definitions of the pertinent claim terms were "not supported by the ordinary use of the language or the language of the '273 patent." In addition to granting summary judgment of invalidity, the district court denied the motion for a preliminary injunction and dismissed the motion for summary judgment of noninfringement as moot.

For purposes of invalidity, the parties contest the court's construction of the terms "substantially uniform magnetic field" and "region of interest." For purposes of infringement and the preliminary injunction, the parties additionally contest the court's construction of the terms "selectable state" and "phased array coil." We review the district court's construction of claims de novo. Markman v. Westview Instruments, Inc., 52 F.3d 967, 979-81 (Fed.Cir.1995).

A

As Mr. Misic explained, the '273 patent sought to address how to make the time-varying magnetic field spatially uniform across the imaged area in an arrangement with overlapping RF coils. A uniform magnetic field is a benefit to magnetic resonance imaging because it "provides greater image uniformity." '273 patent, col. 2, II. 38-39. The patent solves that problem by pulsing the current to the overlapping coils with a phase delay. Id., col. 5, II. 56-57. When an appropriate delay is applied to the pulses, the magnetic field from one coil partially constructively interferes and partially deconstructively interferes with the magnetic field from the second coil in the overlap region "to provide the most uniform transmit field possible." Id., col. 6, II. 6-7. The main dispute among the parties is how uniform the magnetic field has to be and over what spatial extent, or region of interest.

1. The district court defined the claim term "region of interest" as "the portion of the body that is being scanned." Medrad insists that such a definition is inconsistent with the purpose of the invention, which is to make it possible to take MRI images over overlapping coils. See id., col. 5, II. 49-52. In other words, as claim 1 states, the invention concerns a phased array "for forming images of a region of interest" and a phased array must include at least two coils. Thus Medrad maintains it is impossible to define "region of interest" in such a way that permits the region of interest to be located within only one coil, as the district court's definition implicitly does. Medrad therefore urges us to construe the region of interest as the entire three-dimensional volume of the coil array system or, at the very least, the portion of the patient's anatomy lying within both coils.

Medrad's restrictive construction fails for a number of reasons. First, the claim calls for "phased array coils"; it does not call for a phased array. The coils may act in certain instances as a phased array, but that does not mean they must always act as a phased array. Instead, they could act individually, allowing the region of interest to lie only within one coil. By analogy, a car may have four-wheel drive, but that does not mean that the car is incapable of delivering power to only two wheels.

Second, it is impossible to read both claim 1 and dependent claim 2 together while maintaining Medrad's definition. Wright Med. Tech., Inc. v. Osteonics Corp., 122 F.3d 1440, 1445 (Fed.Cir.1997) ("We must not interpret an independent claim in a way that is inconsistent with a claim which depends from it."). Claim 1 states that in the "first selectable state" the coil interface subsystem "process[es] RF power such that a substantially uniform first magnetic field is applied to the region of interest." Claim 2 claims the imaging system of claim 1, but with the further limitation that the coil interface subsystem is required to process and direct the RF power to "said first phased array coil or said second phased array coil" in the first selectable state. In the invention of claim 2, the RF power thus goes to one coil or the other, but not both. The magnetic field is created by one coil and is substantially uniform only within that coil. That means that the region of interest may lie entirely within one coil and does not have to be the entire three-dimensional volume of the coil subsystem, as Medrad maintains.

Third, the district court's definition is consistent with Mr. Misic's own description of the claimed invention. At his deposition, he asserted that his invention applied to situations in which only one of the two coils was transmitting. In fact, at trial he suggested that doing so might have...