Obviousness

Obviousness Analysis of US10448903 Under 35 U.S.C. § 103

This analysis assesses the obviousness of US patent 10448903 under 35 U.S.C. § 103, considering combinations of prior art references cited within the patent and readily available through public search. The independent claims of US10448903 focus on a method, computer-readable medium, and system for retrospective internal gating by extracting time-activity information from image voxels to determine motion phase and generate corrected images.

Independent Claims of US10448903:

• Claim 1 (Method):
  1. Acquiring a series of images at times t1...tn including a moving object;
  2. Extracting time-activity information for voxels of the images;
  3. Determining phase information for motion of the moving object based on the time-activity information for voxels of the images; and
  4. Generating an updated series of images correcting for the motion of the moving object using the determined phase information for motion of the moving object.
• Claim 19 (Non-Transitory Computer-Readable Medium): A computer-readable medium encoded with a program to perform the method of Claim 1.
• Claim 20 (System): A system comprising one or more processors and a non-transitory computer-readable medium with instructions to perform the method of Claim 1.

Identified Prior Art References:

Several prior art references cited in US10448903 are particularly relevant to establishing obviousness. All cited patents below have priority dates earlier than the earliest priority date of US10448903 (May 4, 2007).

1. US7359535B2 (GE Medical Systems Global Technology Company, Llc): "Systems and methods for retrospective internal gating" (Priority: June 20, 2003; Publication: April 15, 2008)
   • Disclosure: This patent describes acquiring projection data for a subject over time, determining a motion function using this data, sorting the data into phases, and reconstructing an image for at least one phase. It explicitly teaches "retrospective internal gating" using acquired data to derive a motion function for phase-based image reconstruction.
2. US7574249B2 (General Electric Company): "Device-less gating of physiological movement for improved image detection" (Priority: February 8, 2005; Publication: August 11, 2009)
   • Disclosure: This patent teaches methods for physiological movement gating without a physical sensor. It includes acquiring scan data, generating a physiological gating signal from this data, sorting the scan data into phases, and reconstructing an image for at least one phase.
3. US20050123183A1 (Paul Schleyer): "Data driven motion correction for nuclear imaging" (Priority: September 2, 2003; Publication: June 9, 2005)
   • Disclosure: This application describes deriving motion information from acquired nuclear imaging data and reconstructing a motion-corrected image based on this information. It also discusses monitoring "differences in count rates for individual detector elements or regions of an image... related to physiological motion."
4. US8229187B2 (General Electric Company): "Respiratory motion extraction from tomographic projection and image data" (Priority: April 11, 2007; Publication: July 24, 2012)
   • Disclosure: This patent provides methods for detecting a respiratory motion signal from tomographic projection data and image data, characterizing the motion, and reconstructing respiratory-gated image data. It discusses using time-varying signals from regions of interest (ROIs) and filtering these signals to isolate respiratory frequencies.

Obviousness Combination and Motivation:

A person having ordinary skill in the art (PHOSITA) in medical imaging, particularly in areas like PET or CT reconstruction and motion correction, would have been motivated to combine the teachings of these prior art references to arrive at the invention claimed in US10448903.

Combination: US7359535B2 in view of US20050123183A1 and US8229187B2.

Motivation for Claim 1 Steps:

1. Acquiring a series of images at times t1...tn including a moving object: This step is a fundamental prerequisite for any motion correction technique and is implicitly or explicitly taught by all cited prior art. US7359535B2, US7574249B2, US20050123183A1, and US8229187B2 all involve acquiring imaging data over time to address motion.
2. Extracting time-activity information for voxels of the images:
   • Motivation for "Internal" or "Device-less" Gating: US7359535B2 and US7574249B2 explicitly teach "retrospective internal gating" and "device-less gating" by deriving a motion function or physiological gating signal directly from acquired scan or projection data, rather than external sensors. The background of US10448903 itself highlights the advantages of "software based methods" that are "image based, and thus machine independent," providing a clear motivation for a PHOSITA to pursue such approaches.
   • Motivation for Voxel-level Information: US20050123183A1 teaches "deriving motion information from the acquired nuclear imaging data" and suggests monitoring "differences in count rates for individual detector elements or regions of an image... related to physiological motion." A PHOSITA would readily understand that a "region of an image" can encompass individual voxels, and that monitoring activity fluctuations at the voxel level offers fine-grained spatial information about motion. US8229187B2 further strengthens this by explicitly teaching "respiratory motion extraction from tomographic projection and image data," and describing the use of "time-varying signal from these ROIs [regions of interest]" to characterize motion. Given that images are composed of voxels, analyzing the time-varying signal of individual or groups of voxels (i.e., time-activity information) to detect motion would be an obvious application of these teachings to achieve a more precise internal gating signal.
3. Determining phase information for motion of the moving object based on the time-activity information for voxels of the images: Once a time-varying signal related to motion (such as respiratory or cardiac motion) is derived from image data or voxels (as motivated above), determining phase information is a standard practice in motion gating. US7359535B2 and US7574249B2 both teach using the derived motion function/gating signal to sort data into "phases." This is the natural and expected next step for any gating process.
4. Generating an updated series of images correcting for the motion of the moving object using the determined phase information for motion of the moving object: This is the ultimate goal of all the prior art references dealing with motion correction and gating. US7359535B2, US7574249B2, US20050123183A1, and US8229187B2 all disclose the reconstruction of motion-corrected or gated images as the objective of their methods. Therefore, once phase information is determined from voxel time-activity, applying this information to generate motion-corrected images would be an obvious consequence and desired outcome for a PHOSITA.

Dependent Claims:
The dependent claims of US10448903, such as those related to assigning weighting factors (Claims 3, 4, 6, 7), filtering time-activity signals (Claims 8, 9, 10), and the iterative process for developing a time-varying object motion function (Claims 2, 11-14), would also be obvious. Weighting factors based on mean activity, spatial gradients, or signal variation are routine signal processing techniques for prioritizing data in motion detection. Filtering time-varying signals to isolate specific frequencies (e.g., respiratory) is explicitly taught by US8229187B2. The iterative combination of individual signals, accounting for phase differences, is a known approach in signal processing to enhance a composite signal and improve robustness, which a PHOSITA would apply to optimize the derived motion function.

Conclusion:

Based on the combination of US7359535B2, US7574249B2, US20050123183A1, and US8229157B2, the independent claims (1, 19, and 20) of US10448903 would be obvious to a person having ordinary skill in the art. The motivation to combine these references stems from the recognized advantages of device-less and image-based internal gating for more accurate motion correction in medical imaging, as well as the logical extension of existing motion detection techniques to voxel-level analysis for improved spatial resolution of motion information.