# US 10,478,148 B2 · Self-calibrating projection geometry for volumetric image reconstruction > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,478,148 B2 - Document ID: US10478148B2 - Status: Granted - Kind: B2 - Application number: 15/436,042 - Filed: 2017-02-17 - Published: 2017-08-24 - Granted: 2019-11-19 - Earliest claimed: 2016-02-19 - Assignees: The Johns Hopkins University - Applicants: The Johns Hopkins University - Inventors: Jeffrey H. Siewerdsen; Yoshito Otake; Joseph Webster Stayman; Ali Uneri; Adam S. Wang; Sarah Ouadah - Web page: https://patentgrep.com/patent/US10478148B2 ## CPC - A61B 6/584: {determining position of components of the apparatus or device using images of the phantom} - A61B 6/025: {Tomosynthesis} - A61B 6/032: {Transmission computed tomography [CT]} - A61B 6/4085: {Cone-beams} - A61B 6/4441: {the rigid structure being a C-arm or U-arm} - A61B 6/466: {adapted to display 3D data} - A61B 6/501: {for diagnosis of the head, e.g. neuroimaging or craniography} - A61B 6/5205: {involving processing of raw data to produce diagnostic data} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract The present invention is directed to a method for enabling volumetric image reconstruction from unknown projection geometry of tomographic imaging systems, including CT, cone-beam CT (CBCT), and tomosynthesis systems. The invention enables image reconstruction in cases where it was not previously possible (e.g., custom-designed trajectories on robotic C-arms, or systems using uncalibrated geometries), and more broadly offers improved image quality (e.g., improved spatial resolution and reduced streak artifact) and robustness to patient motion (e.g., inherent compensation for rigid motion) in a manner that does not alter the patient setup or imaging workflow. The method provides a means for accurately estimating the complete geometric description of each projection acquired during a scan by simulating various poses of the x-ray source and detector to determine their unique, scan-specific positions relative to the patient, which is often unknown or inexactly known (e.g., a custom-designed trajectory, or scan-to-scan variability in source and detector position). ## Claims ### Claim 1 A method for self-calibrating projection geometry for a volumetric image reconstruction comprising: selecting a prior volumetric representation of a patient; dividing a cone-beam computed tomography (CBCT) scan from a CBCT scanner to be self-calibrated into a number of projections; selecting a projection from the number of projections; registering the projection to the prior volumetric representation in order to determine a 9-degree-of freedom geometric calibration of the selected projection; applying the 9-degree-of-freedom geometric calibration of the selected projection; generating a projection matrix from the 9-degree-of-freedom geometric calibration of the selected projection; and generating and displaying a three-dimensional, volumetric reconstruction of the CBCT scan using a plurality of the projection matrix for self-calibration of the CBCT scanner. ### Claim 2 (depends on 1) The method of claim 1 further comprising using a preoperative CT as the prior volumetric representation of the patient. ### Claim 3 (depends on 1) The method of claim 1 further comprising using an CMA-ES optimization algorithm for applying a 9-degree-of-freedom geometric calibration of the selected projection. ### Claim 4 (depends on 1) The method of claim 1 further comprising using an NGI similarity metric for applying a 9-degree-of-freedom geometric calibration of the selected projection. ### Claim 5 (depends on 1) The method of claim 1 further comprising applying fixed intrinsic parameters such that the 9-degree-of-freedom geometric calibration is limited to a 6-degree-of-freedom geometric calibration. ### Claim 6 (depends on 1) The method of claim 1 further comprising initializing the 9-degree-of-freedom geometric calibration of the selected projection with the 9-degree-of-freedom geometric calibration result of another projection. ### Claim 7 (depends on 1) The method of claim 1 wherein the cone-beam computed tomography CBCT scan takes the form of a tomosynthesis scan and the volumetric reconstruction of the CBCT scan is instead a volumetric reconstruction of the tomosynthesis scan. ### Claim 8 (depends on 1) The method of claim 1 further comprising repeating the 9-degree-of-freedom, self-calibration for each of the projection of the number of projections. ### Claim 9 (depends on 1) The method of claim 1 further comprising performing an FDK three-dimensional, volumetric reconstruction. ### Claim 10 (depends on 1) The method of claim 1 further comprising performing an MBIR three-dimensional, volumetric reconstruction. ### Claim 11 (depends on 1) The method of claim 1 further comprising using a non-transitory computer readable medium programmed for executing steps of the method. ### Claim 12 (depends on 1) The method of claim 1 further comprising estimating intrinsic and extrinsic parameters of the selected projection using the 9-degree-of-freedom geometric calibration. ### Claim 13 A system for self-calibrating projection geometry for a volumetric image reconstruction of a subject comprising: a cone-beam computed tomography (CBCT) scanner for generating CBCT image data for the subject, wherein the CBCT scanner is to be self-calibrated; a non-transitory computer readable medium programmed for: selecting a prior volumetric representation of a subject; dividing a CBCT scan into a number of projections; selecting a projection from the number of projections; registering the projection to the prior volumetric representation in order to determine a 9-degree-of freedom geometric calibration of the selected projection; applying a 9-degree-of-freedom geometric calibration of the selected projection; generating a projection matrix from the 9-degree-of-freedom geometric calibration of the selected projection; generating and displaying a three-dimensional, volumetric reconstruction of the CBCT scan using a plurality of the projection matrix for self-calibration of the CBCT scanner. ### Claim 14 (depends on 13) The system of claim 13 further comprising using a preoperative CT as the prior volumetric representation of the patient. ### Claim 15 (depends on 13) The system of claim 13 further comprising using a CMA-ES optimization algorithm for applying a 9-degree-of-freedom geometric calibration of the selected projection. ### Claim 16 (depends on 13) The system of claim 13 further comprising using a NGI similarity metric for applying a 9-degree-of-freedom geometric calibration of the selected projection. ### Claim 17 (depends on 13) The system of claim 13 further comprising applying fixed intrinsic parameters such that the 9-degree-of-freedom geometric calibration is limited to a 6-degree-of-freedom geometric calibration. ### Claim 18 (depends on 13) The system of claim 13 further comprising initializing the 9-degree-of-freedom geometric calibration of the selected projection with the 9-degree-of-freedom geometric calibration result of another projection. ### Claim 19 (depends on 13) The system of claim 13 wherein the cone-beam computed tomography CBCT scan takes the form of a tomosynthesis scan and the volumetric reconstruction of the CBCT scan is instead a volumetric reconstruction of the tomosynthesis scan. ### Claim 20 (depends on 13) The system of claim 13 further comprising repeating the 9-degree-of-freedom, self-calibration for each of the projection of the number of projections.