# US 2019/0378310 A1 · System for the detection and display of metal obscured regions in cone beam ct > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0378310 A1 - Document ID: US20190378310A1 - Status: Published application - Kind: A1 - Application number: 16/476,635 - Filed: 2017-01-09 - Published: 2019-12-12 - Earliest claimed: 2017-01-09 - Assignees: Carestream Dental Technology Topco Limited - Applicants: Carestream Dental Technology Topco Limited - Inventors: Jay S. Schildkraut; Krishnamoorthy Subramanyan - Web page: https://patentgrep.com/patent/US20190378310A1 ## CPC - G06T 12/10: Image preprocessing, e.g. calibration, positioning of sources or scatter correction - G06T 12/20: Inverse problem, i.e. transformations from projection space into object space - G06T 12/30: Image post-processing, e.g. metal artefact correction - A61B 6/4085: {Cone-beams} - G06T 2211/421: Filtered back projection [FBP] - G06T 2211/436: Limited angle - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract A method for rendering metal obscured regions in a volume radiographic image reconstructs a first 3D image using a plurality of 2D projection images obtained over a scan angle range relative to the subject and identifies metal in the first 3D image or metal shadows in the plurality of 2D projection images. Then, metal obscured regions are determined in a reconstructed 3D image of the object, and an alternative reconstruction being a limited angle reconstruction is performed for the metal obscured regions and displayed to the user with an indication of the spatial relationship to a corresponding metal obscured region. ## Claims ### Claim 1 A method for processing volume image data of a subject, the method executed at least in part on a computer, comprising: scanning a subject to obtain a plurality of 2D radiographic images of the subject on a radiographic detector, where the 2D radiographic images are obtained with the radiographic detector and a radiation source at a different scan angle relative to the subject; reconstructing the plurality of 2D radiographic images into a 3D volume image reconstruction; identifying metal obstructed regions in the 3D volume image reconstruction; alternately reconstructing each of one or more metal obstructed regions by a limited angle reconstruction technique using a limited subset of the plurality of 2D radiographic images; and displaying, storing, or transmitting the 3D volume image reconstruction, at least one of the alternately limited angle reconstructed metal obstructed regions, and an indication of the spatial relationship therebetween. ### Claim 2 (depends on 1) The method of claim 1, where the limited angle reconstruction technique is a tomosynthesis reconstruction technique. ### Claim 3 (depends on 1) The method of claim 1, where the limited angle reconstruction technique results in anisotropic reconstructed voxels. ### Claim 4 (depends on 1) The method of claim 1, where identifying metal voxels in the 3D volume image reconstruction comprises: identifying metal voxels in the 3D volume image reconstruction; forward-projection the identified metal voxels through the 3D volume image reconstruction to generate a second plurality of modified projections in which shadows of the metal voxels can be determined; and back-projecting the metal shadow regions in the second plurality of projections to determine one or more regions in the scanned subject that are obstructed by metal. ### Claim 5 (depends on 1) The method of claim 1, where the identifying metal obstructed regions in the 3D volume image reconstruction is automatically performed. ### Claim 6 (depends on 1) The method of claim 1, where reconstructing the plurality of 2D radiographic images into a 3D volume image reconstruction uses metal artifact reduction (MAR) in the 3D volume image reconstruction. ### Claim 7 (depends on 1) The method of claim 1, where the first plurality of two-dimensional radiographic images are obtained from a cone-beam computed tomography system or obtained from a fan-beam computed tomography system, where the generating the three-dimensional volume image comprises using filtered back projection. ### Claim 8 A method for processing volume image data of a subject, the method executed at least in part on a computer, comprising: scanning a subject to obtain a plurality of 2D radiographic images of the subject on an radiographic detector, where the 2D radiographic images are obtained with the radiographic detector and a radiation source at a different scan angle relative to the subject; reconstructing the plurality of 2D radiographic images into a 3D volume image reconstruction; identifying metal obstructed regions in the 3D volume image reconstruction; alternately displaying each of the one or more metal obstructed regions by a limited angle technique using a limited subset of the plurality of 2D radiographic images, where each alternately displayed metal obstructed regions is a single projection image, several projection images or a limited angle tomosynthesis reconstruction; and displaying, storing, or transmitting the 3D volume image reconstruction, at least one of the alternately displayed metal obstructed regions, and an indication of the spatial relationship therebetween. ### Claim 9 (depends on 8) The method of claim 8, where the limited angle tomosynthesis reconstruction results in anisotropic reconstructed voxels. ### Claim 10 (depends on 8) The method of claim 8, where the several projection images are less than 5 projection images. ### Claim 11 (depends on 8) The method of claim 8, where the single projection image and the several projection images have overlapping tissue removed. ### Claim 12 (depends on 8) The method of claim 8, where the identifying metal obstructed regions in the 3D volume image reconstruction is automatically performed.