# US 9,752,995 B2 · Correction of spatial artifacts in radiographic images > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,752,995 B2 - Document ID: US9752995B2 - Status: Granted - Kind: B2 - Application number: 13/490,935 - Filed: 2012-06-07 - Published: 2013-12-12 - Granted: 2017-09-05 - Earliest claimed: 2012-06-07 - Assignees: Varex Imaging Corporation - Applicants: Kevin Matthew Holt - Inventors: Kevin Matthew Holt - Web page: https://patentgrep.com/patent/US9752995B2 ## CPC - G01N 23/04: and forming images of the material - G01N 2223/3307: source and detector fixed; object moves - G01N 2223/401: image processing - G01N 2223/631: large structures, walls - G09G 2340/10: Mixing of images, i.e. displayed pixel being the result of an operation, e.g. adding, on the corresponding input pixels - G09G 2340/125: wherein one of the images is motion video - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) ## Abstract The present invention encompasses methods, apparati, and computer-readable media for correcting spatial artifacts in composite radiographic images of an object (1). A method embodiment of the present invention comprises the steps of generating the composite image from a plurality of views of the object (1); estimating a shift profile; and re-generating the image by shifting the views using the shift profile. ## Claims ### Claim 1 A method for correcting spatial artifacts within a composite radiographic image of an object, said method comprising the steps of: generating the composite image by assembling a plurality of views of the object imaged by a radiographic scanner, wherein each view represents a different time, relative motion exists between the radiographic scanner and the object, and each view corresponds to a portion of data used to generate the composite image and where each view is no more than two pixels wide in a horizontal direction and many pixels tall in a vertical direction to cover entire height of the object; estimating a correctional shift profile comprising tailored correctional shifts for at least two of the views; correcting the views using the corresponding correctional shifts; and re-generating the image by assembling the corrected views. ### Claim 2 (depends on 1) The method of claim 1 wherein the correctional shift profile is represented by s[k], where k is a view number representing a time when the corresponding view was obtained. ### Claim 3 (depends on 1) The method of claim 1 further comprising performing, between the estimating step and the re-generating step, the step of applying a smoothing filter to the correctional shift profile. ### Claim 4 (depends on 1) The method of claim 1 wherein the re-generating step is accomplished by interpolation. ### Claim 5 (depends on 4) The method of claim 4 wherein the interpolation is from the group of interpolations consisting of bi-linear, cubic B-spline, and sinc. ### Claim 6 (depends on 1) The method of claim 1 wherein the step of estimating a correctional shift profile utilizes an optimization algorithm. ### Claim 7 (depends on 1) The method of claim 1 wherein the composite radiographic image is produced by x-rays. ### Claim 8 (depends on 1) The method of claim 1 wherein each view is one pixel wide and many pixels tall, the re-generating step comprises concatenating corrected views, and the concatenation is performed horizontally. ### Claim 9 (depends on 1) The method of claim 1 wherein more than one image is re-generated using the same correctional shift profile. ### Claim 10 (depends on 1) The method of claim 1 wherein fewer than all of the views are corrected. ### Claim 11 (depends on 10) The method of claim 10 comprising the following steps: examining the image to identify one or more artifact-related features; identifying one or more subsets of views relative to locations of the artifact-related feature(s); and correcting only the identified subset(s) of views. ### Claim 12 (depends on 11) The method of claim 11 where the artifact-related features are wheels on a car or truck. ### Claim 13 (depends on 1) The method of claim 1 wherein the step of re-generating the image comprises concatenating the corrected views. ### Claim 14 (depends on 1) The method of claim 1 wherein the composite image is a two dimensional (2D) image, and each view is a portion of the 2D image. ### Claim 15 (depends on 1) The method of claim 1 wherein the correctional shifts correct a spatial artifact, and the spatial artifact is a wiggle that appears along one direction. ### Claim 16 A method for correcting spatial artifacts within a composite radiographic image of an object, said method comprising the steps of: generating the composite image by assembling a plurality of views of the object imaged by a radiographic scanner, wherein each view represents a different time, relative motion exists between the radiographic scanner and the object, and each view corresponds to a portion of data used to generate the composite image; estimating a correctional shift profile comprising tailored correctional shifts for at least two of the views; correcting the views using the corresponding correctional shifts; and re-generating the image by assembling the corrected views; wherein the step of estimating a correctional shift profile utilizes an optimization algorithm; and the optimization algorithm is applied to find the correctional shift profile that minimizes a sum of a set of penalty functions such that the optimization algorithm at least approximately satisfies a set of hard constraints, wherein each hard constraint uses a Fourier transform to constrain high frequency components of the shift profile to be within a preselected value. ### Claim 17 (depends on 16) The method of claim 16 wherein the penalty function(s) comprise(s) at least one function from the group consisting of a squared error function, an absolute error function, and a Huber function. ### Claim 18 (depends on 16) The method of claim 16 wherein: each penalty function and each constraint is from one of two classes of criteria: a shift criterion class and an image criterion class; the shift criterion class governs the shift profile expressed as a discrete function of time; the image criterion class governs that the re-generated image is relatively free of wiggles; and criteria from both classes are employed by the optimization algorithm. ### Claim 19 (depends on 18) The method of claim 18, wherein each class is represented by at least one penalty function or constraint. ### Claim 20 (depends on 18) The method of claim 18 wherein the shift criterion class is enforced by at least one step from the following: using finite differences; encouraging derivatives of the shift profile to be small; hard penalizing a Fourier or other transform; soft penalizing a Fourier or other transform; using group sparsity. ### Claim 21 (depends on 18) The method of claim 18 wherein the image criterion class is satisfied by at least one step from the following: performing an edge detection on the image, producing a corrected image, and encouraging edges in the corrected image to have a desired shape; calculating a displacement field and encouraging some component of the shift profile to be similar to the displacement field; encouraging the corrected image to be smooth. ### Claim 22 (depends on 21) The method of claim 21 wherein the step of encouraging the corrected image to be smooth comprises at least one of: encouraging total energy in the gradient of the corrected image to be small; using a Total Variation semi-norm; using a Huber function. ### Claim 23 (depends on 16) The method of claim 16 wherein the optimization is solved using a convex programming solver. ### Claim 24 At least one non-transitory computer-readable medium containing computer program instructions for correcting spatial artifacts within a composite radiographic image of an object, said instructions performing the steps of: generating the composite image by assembling a plurality of views of the object imaged by a radiographic scanner, wherein each view represents a different time, relative motion exists between the radiographic scanner and the object, and each view corresponds to a portion of data used to generate the composite image and where each view is no more than two pixels wide in a horizontal direction and many pixels tall in a vertical direction to cover entire height of the object; estimating a correctional shift profile comprising tailored correctional shifts to be applied to at least two of the views; correcting the views using the corresponding correctional shifts; and re-generating the image by assembling the corrected views. ### Claim 25 Apparatus for correcting spatial artifacts within a composite radiographic image of an object, said apparatus comprising: a radiographic image scanner adapted to produce a plurality of views of the object, wherein each view represents a different time, relative motion exists between the radiographic scanner and the object, and each view corresponds to a portion of data used to generate the composite image and where each view is no more than two pixels wide in a horizontal direction and many pixels tall in a vertical direction to cover entire height of the object; coupled to the radiographic image scanner, means for estimating a correctional shift profile comprising tailored correctional shifts to be applied to at least two of the views; coupled to the estimating means, means for correcting the views using the corresponding correctional shifts; and coupled to the correcting means, means for assembling the corrected views to form a corrected image. ### Claim 26 (depends on 25) The apparatus of claim 25 wherein the estimating means includes an optimization algorithm that is applied to find the shift profile that minimizes a sum of a set of penalty functions such that the optimization algorithm at least approximately satisfies a set of hard constraints.