# US 7,609,802 B2 · Method and system for reconstructing image volumes from helical scan acquisitions > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,802 B2 - Document ID: US7609802B2 - Status: Granted - Kind: B2 - Application number: 11/740,002 - Filed: 2007-04-25 - Published: 2008-10-30 - Granted: 2009-10-27 - Earliest claimed: 2007-04-25 - Assignees: General Electric Company - Inventors: David Allen Langan; Peter Michael Edic; Xiaoye Wu; Jed Douglas Pack - Web page: https://patentgrep.com/patent/US7609802B2 ## CPC - G06T 12/20: Inverse problem, i.e. transformations from projection space into object space - A61B 6/027: {characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral} - G06T 2211/421: Filtered back projection [FBP] - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract A method, computed tomography (CT) system and computer-readable medium for reconstructing an image volume of an object scanned in helical mode. An embodiment of the method includes determining discrete focal lengths within an imaging plane of the reconstructed field of view comprising the image volume; generating a circular scan sinogram(s) for the discrete focal lengths by interpolating the helical views; selecting within a backprojection operation a circular scan sonogram(s), for one or more image points within the imaging plane, over one or more circular views. The method then includes using the selected circular scan sinogram(s), in the backprojection of the image points point(s) over the circular views view(s) and performing a backprojection for all the image points over all the circular views to generate a reconstructed image of the object. ## Claims ### Claim 1 A method for reconstructing an image volume of an object scanned in helical mode, the method comprising: obtaining one or more helical views corresponding to an image volume of an object; determining a plurality of discrete focal lengths within an imaging plane of a reconstructed field of view comprising the image volume; generating a plurality of circular scan sinograms for the plurality of discrete focal lengths, wherein the plurality of circular scan sinograms are generated by interpolating the one or more helical views; selecting one or more circular scan sinograms, from the plurality of circular scan sinograms, based on the plurality of discrete focal lengths, wherein the selection is performed within a backprojection operation, for one or more image points, over one or more circular views; using one or more of the selected circular scan sinograms, in the backprojection of one or more of the image points within the imaging plane over one or more of the circular views; and performing a backprojection for the one or more image points, over the one or more circular views to generate a reconstructed image of the object. ### Claim 2 (depends on 1) The method of claim 1, wherein the plurality of discrete focal lengths represent a plurality of distances of the image point within the imaging plane from a detector over a rotation of an X-ray source and the detector about the image volume. ### Claim 3 (depends on 2) The method of claim 2, wherein the plurality of discrete focal lengths are located at a plurality of focal depths along a trajectory followed by the image point within the imaging plane over the rotation of the X-ray source and the detector about the image volume. ### Claim 4 (depends on 3) The method of claim 3, wherein the trajectory followed by the image point is represented by a sinusoidal variation of the discrete focal lengths for the image point from the detector, over the rotation of the X-ray source and the detector about the image volume. ### Claim 5 (depends on 1) The method of claim 1, wherein selecting an appropriate circular scan sonogram further comprises interpolating between one or more of the circular scan sinograms, based on the plurality of discrete focal lengths within the imaging plane. ### Claim 6 (depends on 1) The method of claim 1, wherein the one or more helical views are acquired using a computed tomography (CT) system. ### Claim 7 (depends on 6) The method of claim 6, wherein the CT system is configured to image objects in high-throughput applications. ### Claim 8 (depends on 7) The method of claim 7, wherein the applications comprise at least one of industrial CT applications, security CT applications, and luggage scanning CT applications. ### Claim 9 (depends on 1) The method of claim 1, further comprising performing a two-dimensional (2D) filtered backprojection reconstruction of the one or more image points within the imaging plane to generate the reconstructed image of the object. ### Claim 10 A computed tomography (CT) system for reconstructing an image volume of an object scanned in helical mode, the computed tomography system comprising: an X-ray source configured to project a plurality of X-ray beams through the object from a plurality of projection angles; a detector configured to produce a plurality of electrical signals corresponding to the plurality of X-ray beams; and a processor configured to process the electrical signals to generate one or more helical views corresponding to the imaged object, wherein the processor is configured to: determine a plurality of discrete focal lengths within an imaging plane of a reconstructed field of view comprising the image volume; generate a plurality of circular scan sinograms for the plurality of discrete focal lengths, wherein the plurality of circular scan sinograms are generated by interpolating the one or more helical views; select one or more circular scan sinograms from the plurality of circular scan sinograms, based on the plurality of discrete focal lengths, wherein the selection is performed within a projection operation, for one or more image points within the imaging plane, over one or more circular views; and use one or more of the selected circular scan sinograms, in the backprojection of one or more of the image points over one or more of the circular views; and performing a backprojection for the one or more image points, over the one or more circular views to generate a reconstructed image of the object. ### Claim 11 (depends on 10) The CT system of claim 10, wherein the plurality of discrete focal lengths represent a plurality of distances of the image point within the imaging plane from a detector over a rotation of an X-ray source and the detector about the image volume. ### Claim 12 (depends on 11) The CT system of claim 11, wherein the plurality of discrete focal lengths are located at a plurality of focal depths approximating the trajectory followed by the image point within the imaging plane over the rotation of the X-ray source and the detector about the image volume. ### Claim 13 (depends on 12) The CT system of claim 12, wherein the trajectory followed by the image point within the imaging plane is represented by a sinusoidal variation of the discrete focal lengths from the detector, over the rotation of the X-ray source and the detector about the image volume. ### Claim 14 (depends on 10) The CT system of claim 10, wherein the processor is further configured to select an appropriate circular scan by interpolating between one or more of the circular scan sinograms, based on the based on the plurality of discrete focal lengths. ### Claim 15 (depends on 10) The CT system of claim 10, wherein the CT system is configured to image objects in high throughput applications. ### Claim 16 (depends on 15) The CT system of claim 15, wherein the applications comprise at least one of industrial CT applications, security CT applications and luggage scanning CT applications. ### Claim 17 (depends on 10) The CT system of claim 10, wherein the processor is further configured to perform a two-dimensional (2D) filtered backprojection reconstruction of the one or more image points to generate the reconstructed image of the object. ### Claim 18 A computer-readable medium storing computer instructions for instructing a computer system for reconstructing an image volume of an object scanned in helical mode, the computer instructions comprising: obtaining one or more helical views corresponding to an image volume of an object; determining a plurality of discrete focal lengths within an imaging plane of a reconstructed field of view comprising the image volume; generating a plurality of circular scan sinograms for the plurality of discrete focal lengths, wherein the plurality of circular scan sinograms are generated by interpolating the one or more helical views; selecting one or more circular scan sinograms, from the plurality of circular scan sinograms, based on the plurality of discrete focal lengths, wherein the selection is performed within a backprojection operation, for one or more image points within the imaging plane, over one or more circular views; using one or more of the selected circular scan sinograms, in the backprojection of one or more of the image points over one or more of the circular views; and, performing a backprojection for the one or more image points, over the one or more circular views to generate a reconstructed image of the object. ### Claim 19 (depends on 18) The computer-readable medium of claim 18, wherein the plurality of discrete focal lengths represent a plurality of distances of the image point within the imaging plane from a detector over a rotation of an X-ray source and the detector about the image volume. ### Claim 20 (depends on 19) The computer-readable medium of claim 19, wherein the plurality of discrete focal lengths are located at a plurality of focal depths along a trajectory followed by the image point within the imaging plane over the rotation of the X-ray source and the detector about the image volume. ### Claim 21 (depends on 20) The computer-readable medium of claim 20, wherein the trajectory followed by the focal point is represented by a sinusoidal variation of the discrete focal lengths for the image point within the imaging plane from the detector, over the rotation of the X-ray source and the detector about the image volume. ### Claim 22 (depends on 18) The computer-readable medium of claim 18, wherein selecting an appropriate circular scan sinogram further comprises interpolating between one or more of the circular scan sinograms, based on the plurality of discrete focal lengths. ### Claim 23 (depends on 18) The computer-readable medium of claim 18, further comprising performing a two-dimensional (2D) filtered backprojection reconstruction of the one or more image points to generate the reconstructed image of the object.