PTAB

IPR2020-00073

Elekta Inc v. Best Medical Intl Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Controlling Tradeoff Between Delivery Efficiency and Dosimetric Fitness in Radiation Treatment Plans
  • Brief Description: The ’175 patent discloses methods for optimizing Intensity Modulated Radiation Therapy (IMRT) plans. The invention centers on providing user control over the trade-off between "delivery efficiency" (e.g., treatment time, number of beam segments) and "dosimetric fitness" (e.g., how well the radiation conforms to the tumor while avoiding healthy tissue) by using a hybrid cost function within an optimizer.

3. Grounds for Unpatentability

Ground 1: Obviousness over Webb - Claim 1 is obvious over Webb 2001.

  • Prior Art Relied Upon: Webb (a 2001 article in Physics in Medicine & Biology titled "A simple method to control aspects of fluence modulation in IMRT planning").
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Webb disclosed every limitation of claim 1. Webb taught a method for IMRT planning that addressed the trade-off between "high conformality in dose-space" (dosimetric fitness) and "monitor-unit efficiency" (delivery efficiency). It did so by introducing a hybrid cost function that combined a "dose-space" term with a "beam-space" term. Webb explicitly stated that this trade-off could be placed "under the control of the user" by adjusting a weighting parameter (w3) in the cost function, which provided control along a continuum from optimal dosimetric fitness to enhanced delivery efficiency.
    • Motivation to Combine (for §103 grounds): Not applicable as this ground relies on a single reference. Petitioner asserted Webb alone rendered the claim obvious.
    • Expectation of Success (for §103 grounds): Not applicable.

Ground 2: Obviousness over Webb and Bar - Claims 13 and 17 are obvious over Webb 2001 in view of Bar 2001.

  • Prior Art Relied Upon: Webb (2001 article) and Bar (a 2001 article in Physics in Medicine & Biology titled "A variable fluence step clustering and segmentation algorithm for step and shoot IMRT").
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Webb taught the core concept of a user-controlled, hybrid cost function to manage the trade-off between dosimetric fitness and delivery efficiency. Bar was introduced to teach assigning a delivery cost term based on the complexity of the intensity map, specifically using the "number of segments" as a proxy for complexity and treatment time. Bar described a "step and shoot sequencer" that could be integrated into an IMRT optimization algorithm to balance translating the dose profile accurately with minimizing the number of segments. For claim 17, Petitioner argued that Bar’s teaching of minimizing segment count directly corresponded to the claim limitation "delivery cost term represents a segment count."
    • Motivation to Combine (for §103 grounds): A POSITA would combine these references to improve upon Webb's more abstract "beam-space" cost term. Bar provided a well-understood, concrete delivery cost metric (number of segments) that directly impacted treatment time. Integrating Bar's sequencer into Webb's optimization framework was a predictable step to create more practical and efficient treatment plans.
    • Expectation of Success (for §103 grounds): A POSITA would have a high expectation of success, as Bar itself stated its sequencer was designed to be integrated into an IMRT optimization process, and Webb’s hybrid cost function was flexible enough to incorporate such delivery cost terms.

Ground 3: Obviousness over Shepard and Que - Claims 11 and 12 are obvious over Shepard 2002 in view of Que 1999.

  • Prior Art Relied Upon: Shepard (a 2002 article in Medical Physics titled "Direct aperture optimization: a turnkey solution for step-and-shoot IMRT") and Que (a 1999 article in International Journal of Medical Physics Research and Practice titled "Comparison of algorithms for multileaf collimator field segmentation").

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued this combination taught providing a user with a choice between different optimization algorithms. Shepard disclosed a "direct aperture optimization" (DAO) system that used a "global optimization algorithm" (simulated annealing) and compared it to the existing CORVUS system, which used a different approach. Shepard taught that the user could specify parameters (like the maximum number of apertures) to control the trade-off between plan complexity and dosimetric quality. Que taught that no single algorithm is best for all cases and recommended that a clinical treatment planning system should implement multiple algorithms and automatically search through them to find the most efficient delivery sequence. For claim 12, Petitioner identified Shepard's simulated annealing as the claimed "global optimization algorithm" and its discussion of gradient-based methods as the claimed "local optimization algorithm."
    • Motivation to Combine (for §103 grounds): A POSITA, reading Shepard's comparison of different optimization approaches, would be motivated by Que's explicit recommendation to implement multiple algorithms in a single system. This would provide the clinician with greater flexibility to choose the best optimization strategy (e.g., global search for dosimetric quality vs. a faster local search for efficiency) based on the specific clinical case.
    • Expectation of Success (for §103 grounds): Success would be expected, as combining known optimization algorithms into a single user-selectable interface was a known software engineering practice for providing users with options.

  • Additional Grounds: Petitioner asserted additional obviousness challenges against claims 8, 10, 19, and 20 based on combinations of Webb, Bar, Siebers (a 2002 journal article), and Shepard. These grounds primarily relied on adding teachings from Siebers and Shepard for specific limitations, such as using "total monitor units" to represent delivery efficiency and using simulated annealing for optimization.

4. Key Claim Construction Positions

  • "total monitor units": Petitioner proposed construing this term as "the total radiation beam on time of the linear accelerator used in providing the treatment." This construction was based on the specification and statements made during prosecution linking monitor units directly to beam-on time and, therefore, delivery efficiency.
  • "segment count": Petitioner proposed construing this term as "the number of segments required by a treatment plan for delivering radiation." This construction was based on an explicit definition in the ’175 patent specification.
  • "optimizer": Petitioner proposed construing this term as "an iterative optimization loop." This construction was not based on the specification but on the patentee's repeated statements during prosecution that equated the term "within an optimizer" with "within the optimization loop" to distinguish the invention from prior art.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1, 8, 10-13, 17, 19, and 20 of the ’175 patent as unpatentable.