MetraSens Inc v. Kopp Keith

1. Case Identification

• Case #: IPR2022-01224
• Patent #: 7,489,128
• Filed: July 1, 2022
• Petitioner(s): Metrasens, Inc. and Metrasens, Ltd.
• Patent Owner(s): Keith A. Kopp
• Challenged Claims: 1-20

2. Patent Overview

• Title: Protection Arrangement for MRI Apparatus
• Brief Description: The ’128 patent discloses a protection arrangement for detecting ferrous materials at an access opening to a Magnetic Resonance Imaging (MRI) suite. The system uses an array of passive magnetic field sensors arranged around the periphery of the opening to passively monitor the MRI's residual magnetic field and provide a safety response if a change indicative of a ferrous object is detected.

3. Grounds for Unpatentability

Ground 1: Claims 1-20 are obvious over Votruba in view of Jaquet and Finn, as evidenced by Seton.

• Prior Art Relied Upon: Votruba (Patent 4,990,850), Jaquet (Patent 3,971,983), Finn (a 1985 journal article), and Seton (a 1999 journal article).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that the combination of references teaches all limitations of the challenged claims. Votruba was argued to teach a protection arrangement with Hall effect sensors configured as a gradiometer to monitor the residual magnetic field at the entrance of an MRI room. Jaquet was argued to teach arranging an array of gradiometers around a doorway to create multiple detection zones, thereby improving locational accuracy. Finn was cited for teaching the use of both gradiometers and simpler, cheaper non-gradiometer sensors (e.g., a DC sensor) to detect ferromagnetic items in an MRI environment. Seton was presented as further evidence that gradiometers were known to function effectively with MRI systems prior to 2001.
  • Motivation to Combine: Petitioner argued a person of ordinary skill in the art (POSITA) would combine Votruba's MRI-specific detector with Jaquet's sensor array to improve the accuracy and safety of ferrous object detection, a known problem. A POSITA would also be motivated by Finn to consider using cheaper, non-gradiometer sensors as a known and viable alternative to the gradiometers in Votruba, or to understand that both sensor types were suitable for the application. The simple substitution of known elements to achieve predictable results was also cited as a motivation.
  • Expectation of Success: Petitioner contended a POSITA would have a reasonable expectation of success because the references demonstrate the functionality of the components in the target environment. Petitioner specifically argued that the patent owner's arguments during prosecution—that gradiometers could not work in an MRI's non-uniform field—were scientifically incorrect. Finn and Seton were presented as evidence that gradiometers were known to work in such environments, and a POSITA would have known how to select sensors with an appropriate dynamic range to avoid saturation.

Ground 2: Claims 1-20 are obvious over Jaquet in view of Votruba, as evidenced by Finn and Seton.

• Prior Art Relied Upon: Jaquet (Patent 3,971,983), Votruba (Patent 4,990,850), Finn (a 1985 journal article), and Seton (a 1999 journal article).
• Core Argument for this Ground:
  • Prior Art Mapping: This alternate ground began with Jaquet's teaching of a walkthrough detector with an array of gradiometers for pinpointing ferrous objects. Votruba was argued to provide the context of applying such a detector to the known problem of screening for ferrous objects at the entrance to an MRI room. The teachings of Finn and Seton were used, as in Ground 1, to demonstrate the viability of using both gradiometer and non-gradiometer sensors in the MRI environment and to rebut the patent owner's prosecution arguments.
  • Motivation to Combine: Petitioner argued a POSITA would be motivated to adapt Jaquet's established sensor array arrangement to the specific application of an MRI room entrance, as taught by Votruba, to improve safety and detection accuracy. This combination addressed a recognized need in the art.
  • Expectation of Success: The expectation of success argument was identical to that in Ground 1, focusing on evidence from the prior art that gradiometers function properly in non-uniform magnetic fields, contrary to the patent owner's earlier assertions to the USPTO.

4. Key Claim Construction Positions

• "an array of passive magnetic field sensors" (Claims 1 and 15): Petitioner argued this term should be construed as "spaced apart Hall effect sensors, not being configured as gradiometers."
  • This proposed construction was based on the doctrine of prosecution disclaimer. Petitioner asserted that the patent owner, during prosecution, repeatedly and unequivocally disavowed gradiometers to distinguish the invention from prior art like Jaquet. The patent owner allegedly overcame rejections by arguing that the gradiometers of the prior art were "incapable of proper operation" in the non-uniform magnetic field of an MRI, thereby limiting the claim scope to non-gradiometer configurations.

5. Key Technical Contentions (Beyond Claim Construction)

• The petition's central technical contention was that the premise for the patent's allowance was scientifically flawed. Petitioner argued that the patent owner's assertion during prosecution that gradiometers cannot function in the non-uniform residual magnetic field of an MRI is incorrect.
• Citing its expert and the teachings of Votruba, Finn, and Seton, Petitioner contended that gradiometers are not only capable of operating in such fields but are specifically designed to measure field gradients (i.e., non-uniformities). A POSITA would have known to select sensors with an appropriate dynamic range for the intended environment.

6. Arguments Regarding Discretionary Denial

• §325(d): Petitioner argued against discretionary denial because the petition presented new prior art not before the examiner (Finn and Seton) and new arguments regarding previously considered art. Specifically, Petitioner claimed the examiner committed a "material error in fact" by overlooking Votruba's own disclosure of sensors operating in a "gradiometer mode," which directly contradicted the patent owner's arguments that led to allowance.
• Fintiv Factors: Petitioner argued against denial under Fintiv, stating that the parallel district court case was in an early stage, discovery was not advanced, and a trial date was not imminent. Petitioner also noted it had filed a Sotera stipulation, agreeing not to pursue in district court the same grounds raised in the IPR. Finally, Petitioner asserted that the merits of the petition were particularly strong, weighing in favor of institution.

7. Relief Requested

• Petitioner requested the institution of an inter partes review (IPR) and the cancellation of claims 1-20 of Patent 7,489,128 as unpatentable.