Obviousness

Under 35 U.S.C. § 103, an invention is considered obvious if the differences between the claimed invention and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art (PHOSITA). The analysis requires identifying: 1) the scope and content of the prior art, 2) the differences between the prior art and the claims, 3) the level of ordinary skill in the art, and 4) any secondary considerations of non-obviousness (though none are provided in the prompt for this analysis).

The priority date for US10117625 is May 4, 2007.

Scope and Content of Prior Art

The provided patent text lists several prior art references under "Citations." Among these, US7359535B2, titled "Systems and methods for retrospective internal gating," has a priority date of June 20, 2003, which precedes the priority date of US10117625, making it highly relevant prior art.

US7359535B2: "Systems and methods for retrospective internal gating"

This patent describes a method for retrospective internal gating, particularly useful for correcting motion artifacts in medical imaging. Key teachings include:

• Acquiring images: It teaches "acquiring images at different times t1 . . . tn" to obtain a chronologically ordered image set.
• Identifying temporally cyclical signals: It describes identifying such signals, often related to physiological motion like respiration or cardiac rhythms.
• Extracting time-activity information for voxels: The patent details how "time-activity information is derived by organizing into a single discrete array the values v1 . . . vn of an individual voxel in the successive images i1 . . . in".
• Generating a time varying object motion function: This function is created by combining time-activity information from multiple voxels. The processing can be initiated by defining the function as the filtered time-activity values of the highest priority voxel, and subsequent filtered voxel time-activity values are synthesized into this function. It also describes scenarios for combining voxel data (add, subtract, unchanged) and selecting the one with the highest standard deviation.
• Determining phase information: "Final phase information for the motion of the imaged object can be extracted from the timing of the peaks and dips in the time varying object motion function". Specifically, for respiratory motion, local maxima and minima can correspond to full inspiration and expiration.
• Purpose of Gating: The background section explicitly states that "Respiratory gating in is an approach to lessen the image degradation from respiratory motion by separating the breathing cycle into different phases and generating images from data corresponding to each of these phases". The patent also highlights advantages of "software derived respiratory signals" over "hardware based methods".

Analysis of Obviousness

The independent claims of US10117625 are Claim 1 (method), Claim 19 (non-transitory computer-readable medium), and Claim 20 (system).

Obviousness of Claim 1 of US10117625 over US7359535B2

Claim 1 of US10117625 claims:

1. acquiring a series of images at times t1 . . . tn including a moving object;
   • US7359535B2 explicitly teaches "acquiring images at different times t1 . . . tn" to obtain an image set of a patient (a moving object).
2. extracting time-activity information for voxels of the images;
   • US7359535B2 teaches that "time-activity information is derived by organizing into a single discrete array the values v1 . . . vn of an individual voxel in the successive images i1 . . . in".
3. generating a time varying object motion function based on the extracted time-activity information for the voxels of the images;
   • US7359535B2 teaches that "Information is combined from many voxels' time-activity values to create a time varying object motion function". It further describes the process of initializing and synthesizing subsequent voxel time-activity values into this function.
4. determining, using the time varying object motion function, phase information for motion of the moving object;
   • US7359535B2 teaches that "Final phase information for the motion of the imaged object can be extracted from the timing of the peaks and dips in the time varying object motion function".
5. 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.
   • US7359535B2, in its background, defines respiratory gating as an approach to "lessen the image degradation from respiratory motion by separating the breathing cycle into different phases and generating images from data corresponding to each of these phases". A person having ordinary skill in the art would understand that "generating images from data corresponding to each of these phases" is precisely the step of producing motion-corrected images. The term "updated series of images correcting for the motion" is an inherent and expected outcome of applying a gating technique, as described and enabled by US7359535B2.

Motivation to Combine/Modify:
A PHOSITA would be motivated to perform all steps of Claim 1, as US7359535B2 explicitly teaches the entire process of retrospective internal gating up to determining phase information, and clearly states that the purpose of gating is to generate motion-corrected images. The act of using the determined phase information to generate such corrected images is the natural and intended culmination of the gating method, aiming to achieve the "lessen[ing of] image degradation" for which gating is performed. The patent US10117625 itself acknowledges that "the consensus in literature is that the respiratory gating of images presents a feasible solution to the image degradation introduced by respiratory motion." Therefore, a PHOSITA would naturally complete the gating process by generating images corrected for the motion using the derived phase information.

Obviousness of Claims 19 and 20 of US10117625 over US7359535B2

Claims 19 and 20 cover a non-transitory computer-readable medium and a system, respectively, configured to perform the method steps of Claim 1. Given that US7359535B2 teaches a "system and method for retrospective internal gating" and highlights the advantages of "software derived respiratory signals", it would have been obvious to a PHOSITA to implement the disclosed method using a computer system and a computer program. The implementation of algorithms for image processing and reconstruction on computer systems was well-known in the art prior to the priority date of US10117625.

Obviousness of Dependent Claims

All dependent claims of US10117625 are also rendered obvious by US7359535B2:

• Claim 2 (time-activity definition): Explicitly taught by US7359535B2.
• Claims 3-4, 6-7 (weighting factors): US7359535B2 explicitly teaches assigning weighting factors based on mean voxel activity or proximity to spatial activity gradients, and assigning zero weighting factors to unimportant voxels. A PHOSITA would find it obvious to consider signal variation (Claim 6) as another metric for weighting importance.
• Claim 5 (ungated image combination): A common practice in imaging to create a baseline image from time-series data.
• Claims 8-10 (frequency filtering): US7359535B2 explicitly teaches filtering out unwanted frequencies from time-activity signals for respiratory gating. Adjusting frequency windows (Claims 9-10) is a standard optimization technique for filtering.
• Claims 11-13 (serial processing and initial motion function): US7359535B2 teaches prioritizing voxels and initiating the time-varying object motion function with the highest priority voxel's time-activity curve.
• Claim 14 (three scenarios for combining voxel information): Explicitly taught by US7359535B2, including choosing the scenario with the highest standard deviation.
• Claim 15 (determining phase by recurring patterns): Taught by US7359535B2's extraction of phase from peaks and dips in the motion function.
• Claim 16 (mapping image data to phases): This is the functional outcome of gating, as explained in US7359535B2's background.
• Claim 17 (respiratory cycle data): US7359535B2 focuses heavily on respiratory motion.
• Claim 18 (acquiring for more than one breath cycle): Implicit in obtaining "temporally cyclical signals" for physiological motion like respiration over a "series of images".

Conclusion on Obviousness

The method, system, and computer-readable medium claims of US10117625 are rendered obvious by US7359535B2. US7359535B2 teaches all the essential steps of retrospective internal gating using internal voxel time-activity information to derive motion phase information. The final step of generating motion-corrected images, while phrased slightly differently, is the well-understood and explicitly stated purpose of the gating method described in US7359535B2. A PHOSITA would have been motivated to combine these known elements to achieve the recognized benefits of motion correction in medical imaging. Additional prior art such as US20050123183A1 ("Data driven motion correction for nuclear imaging") and US7574249B2 ("Device-less gating of physiological movement") further demonstrate the clear trend and motivation in the field towards data-driven, device-less, retrospective motion correction, reinforcing the obviousness of the claimed invention.