Varian Medical Systems Inc v. Best Medical Intl Inc

1. Case Identification

• Case #: IPR2020-00076
• Patent #: 7,015,490
• Filed: October 15, 2019
• Petitioner(s): Varian Medical Systems, Inc.
• Patent Owner(s): Best Medical International, Inc.
• Challenged Claims: 1, 4, 17-19

2. Patent Overview

• Title: Method and Apparatus For Optimization of Collimator Angles in Intensity Modulated Radiation Therapy Treatment
• Brief Description: The ’490 patent discloses a method and apparatus for optimizing the collimator angle of a multi-leaf collimator (MLC) used in intensity modulated radiation therapy (IMRT). The patent purports to provide a new algorithm that enhances treatment delivery efficiency by considering factors like the number of beam segments and monitor units, which it alleges were ignored by prior art techniques that focused primarily on conforming the radiation beam to the target's shape.

3. Grounds for Unpatentability

Ground 1: Obviousness over Otto, Chang, Webb, and Mohan - Claims 1, 4, and 17-19 are obvious over the combination of four prior art references.

• Prior Art Relied Upon: Otto (Application # 2003/0086530), Chang (Patent 6,853,705), Webb (a 1993 textbook on radiation therapy), and Mohan (a scientific journal article).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that the challenged claims combine known elements from the prior art to achieve a predictable result. Independent claims 1 and 17 recite a method and apparatus for determining a collimator angle using a cost function that incorporates parameters for both enhancing conformity to a target shape and enhancing delivery efficiency.
    • Otto provided the foundational framework, disclosing a computer-implemented optimization process for IMRT that iteratively varies parameters, including the collimator angle, to determine a treatment plan.
    • Chang supplied the key motivation missing from Otto’s general framework. Chang taught that an optimal collimator angle should be chosen to fulfill the dual objectives of conforming the beam to the target’s contour and improving treatment delivery efficiency. This directly addressed the ’490 patent’s alleged point of novelty.
    • Webb, a foundational textbook, established that using a "cost function" was a standard, well-known mathematical technique in radiation therapy to optimize treatment plans by minimizing the function’s value. Webb specifically described using a cost function to enhance conformity to a target shape, a technique known as "Brahme's Theory of Orientation."
    • Mohan provided the specific mathematical tool for the "delivery efficiency" component. It taught a known mathematical function for calculating and minimizing the required monitor units (MUs), a direct measure of delivery efficiency. Mohan explicitly taught optimizing the collimator angle to find orientations that "minimize fluctuations" in beam intensity, which in turn reduces the required MUs.
  • Motivation to Combine: A person of ordinary skill in the art (POSITA), starting with Otto’s general optimization system, would combine the teachings of the other references. A POSITA seeking to implement Otto’s system would look to analogous art for specific optimization criteria. Chang provided the express motivation to consider both conformity and delivery efficiency. To implement these dual objectives, a POSITA would naturally use a standard cost function, as taught by Webb. For the conformity component, Webb’s disclosure of Brahme’s theory was directly applicable. For the efficiency component taught by Chang, a POSITA would look to a reference like Mohan, which provided a precise mathematical function to quantify and minimize MUs. All references are from the same narrow and collaborative field of IMRT optimization, making their combination logical and predictable.
  • Expectation of Success: Petitioner asserted a POSITA would have had a high expectation of success. The combination involved applying a standard optimization tool (Webb's cost function) to a known system (Otto) to achieve explicitly stated goals from the prior art (Chang's dual objectives) using a known mathematical equation for efficiency (Mohan). This represented a straightforward implementation of known principles to achieve a predictable improvement in treatment planning. Dependent claims 4 and 18-19 add further details taught or suggested by the combination, such as rejecting changes that decrease conformity (an inherent result of minimizing a cost function) and using parameters related to "maximum effective length," which corresponds to the total MUs calculated by Mohan's equations.

4. Arguments Regarding Discretionary Denial

• Petitioner argued against discretionary denial under 35 U.S.C. §325(d). While Otto and the application that became Chang were cited during prosecution of the ’490 patent, Petitioner contended they were not substantively discussed, and no rejections were ever issued. More importantly, the references Webb and Mohan were not before the Examiner. Therefore, the Examiner never considered the specific combination of Otto, Chang, Webb, and Mohan, meaning the petition did not present "the same or substantially the same prior art or arguments" previously evaluated by the USPTO.

5. Relief Requested

• Petitioner requested the institution of an inter partes review and the cancellation of claims 1, 4, and 17-19 of the ’490 patent as unpatentable.