{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,29]],"date-time":"2026-05-29T11:20:41Z","timestamp":1780053641621,"version":"3.54.0"},"reference-count":30,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2021,3,13]],"date-time":"2021-03-13T00:00:00Z","timestamp":1615593600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"University Research Fund","award":["UAntwerp BOF-GOA 2016 33927"],"award-info":[{"award-number":["UAntwerp BOF-GOA 2016 33927"]}]},{"name":"Research Foundation - Flanders (FWO)","award":["S004217N"],"award-info":[{"award-number":["S004217N"]}]},{"name":"European Commission through the INTERREG","award":["0386"],"award-info":[{"award-number":["0386"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J. Imaging"],"abstract":"<jats:p>Compared to single source systems, stereo X-ray CT systems allow acquiring projection data within a reduced amount of time, for an extended field-of-view, or for dual X-ray energies. To exploit the benefit of a dual X-ray system, its acquisition geometry needs to be calibrated. Unfortunately, in modular stereo X-ray CT setups, geometry misalignment occurs each time the setup is changed, which calls for an efficient calibration procedure. Although many studies have been dealing with geometry calibration of an X-ray CT system, little research targets the calibration of a dual cone-beam X-ray CT system. In this work, we present a phantom-based calibration procedure to accurately estimate the geometry of a stereo cone-beam X-ray CT system. With simulated as well as real experiments, it is shown that the calibration procedure can be used to accurately estimate the geometry of a modular stereo X-ray CT system thereby reducing the misalignment artifacts in the reconstruction volumes.<\/jats:p>","DOI":"10.3390\/jimaging7030054","type":"journal-article","created":{"date-parts":[[2021,3,14]],"date-time":"2021-03-14T22:13:10Z","timestamp":1615759990000},"page":"54","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["Geometry Calibration of a Modular Stereo Cone-Beam X-ray CT System"],"prefix":"10.3390","volume":"7","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5231-6267","authenticated-orcid":false,"given":"Van","family":"Nguyen","sequence":"first","affiliation":[{"name":"Imec\u2014Vision Lab, Department of Physics, University of Antwerp, 2610 Antwerp, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9753-031X","authenticated-orcid":false,"given":"Joaquim G.","family":"Sanctorum","sequence":"additional","affiliation":[{"name":"Biophysics and BioMedical Physics (BIMEF) Lab, University of Antwerp, 2020 Antwerp, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5746-4621","authenticated-orcid":false,"given":"Sam","family":"Van Wassenbergh","sequence":"additional","affiliation":[{"name":"Functional Morphology Lab (FunMorph), University of Antwerp, 2610 Antwerp, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joris J. J.","family":"Dirckx","sequence":"additional","affiliation":[{"name":"Biophysics and BioMedical Physics (BIMEF) Lab, University of Antwerp, 2020 Antwerp, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4225-2487","authenticated-orcid":false,"given":"Jan","family":"Sijbers","sequence":"additional","affiliation":[{"name":"Imec\u2014Vision Lab, Department of Physics, University of Antwerp, 2610 Antwerp, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jan","family":"De Beenhouwer","sequence":"additional","affiliation":[{"name":"Imec\u2014Vision Lab, Department of Physics, University of Antwerp, 2610 Antwerp, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,3,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2260","DOI":"10.1249\/MSS.0000000000001350","article-title":"Assessment of Knee Kinematics in Older Adults Using High-Speed Stereo Radiography","volume":"49","author":"Kefala","year":"2017","journal-title":"Med. Sci. Sport. Exerc."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Kasten, Y., Doktofsky, D., and Kovler, I. (2020). End-To-End Convolutional Neural Network for 3D Reconstruction of Knee Bones from Bi-planar X-Ray Images. Machine Learning for Medical Image Reconstruction, Springer International Publishing.","DOI":"10.1007\/978-3-030-61598-7_12"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"158","DOI":"10.1186\/s13014-016-0735-2","article-title":"Stereoscopic X-ray imaging, cone beam CT, and couch positioning in stereotactic radiotherapy of intracranial tumors: Preliminary results from a cross-modality pilot installation","volume":"11","author":"Zollner","year":"2016","journal-title":"Radiat. Oncol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1016\/j.image.2017.03.014","article-title":"3D Reconstruction of the proximal femur shape from few pairs of x-ray radiographs","volume":"59","author":"Akkoul","year":"2017","journal-title":"Signal Process. Image Commun."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"15852","DOI":"10.1038\/s41598-018-34153-9","article-title":"Realization of real-time X-ray stereoscopic vision during interventional procedures","volume":"8","author":"Deng","year":"2018","journal-title":"Sci. Rep."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"105701","DOI":"10.1088\/1361-6501\/ab23e7","article-title":"Methods for characterization and optimisation of measuring performance of stereoscopic x-ray systems with image intensifiers","volume":"30","author":"Sanctorum","year":"2019","journal-title":"Meas. Sci. Technol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"259","DOI":"10.1016\/j.jsb.2011.11.027","article-title":"Automatic alignment and reconstruction of images for soft X-ray tomography","volume":"177","author":"Parkinson","year":"2012","journal-title":"J. Struct. Biol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"4934","DOI":"10.1118\/1.3609096","article-title":"Reliable automatic alignment of tomographic projection data by passive auto-focus","volume":"38","author":"Kingston","year":"2011","journal-title":"Med. Phys."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Jun, K., Yoon, S., and Kwon, K. (2016). Alignment Solution for CT Image Reconstruction by Fixed Point and Virtual Rotation Axis. Sci. Rep., 28.","DOI":"10.1038\/srep41218"},{"key":"ref_10","first-page":"1","article-title":"Fast Projection Matching for X-ray Tomography","volume":"7","author":"Wang","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_11","unstructured":"Liu, Y. (2017). Improve Industrial Cone-Beam Computed Tomography by Integrating Prior Information. [Ph.D. Thesis, ETH Zurich]. Available online: https:\/\/www.research-collection.ethz.ch\/handle\/20.500.11850\/219410."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"968","DOI":"10.1118\/1.1869652","article-title":"Accurate technique for complete geometric calibration of cone-beam computed tomography systems","volume":"32","author":"Cho","year":"2005","journal-title":"Med. Phys."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2829","DOI":"10.1118\/1.3589130","article-title":"Estimation of CT cone-beam geometry using a novel method insensitive to phantom fabrication inaccuracy: Implications for isocenter localization accuracy","volume":"38","author":"Zheng","year":"2011","journal-title":"Med. Phys."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1633","DOI":"10.1088\/0031-9155\/54\/6\/016","article-title":"Direct determination of geometric alignment parameters for cone-beam scanners","volume":"54","author":"Mennessier","year":"2009","journal-title":"Phys. Med. Biol."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Chang, C.H., Ni, Y.C., Huang, S.Y., Hsieh, H.H., Tseng, S.P., and Tseng, F.P. (2019). A geometric calibration method for the digital chest tomosynthesis with dual-axis scanning geometry. PLoS ONE, 14.","DOI":"10.1371\/journal.pone.0216054"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"5384","DOI":"10.1118\/1.4739506","article-title":"A robust geometry estimation method for spiral, sequential and circular cone-beam micro-CT","volume":"39","author":"Sawall","year":"2012","journal-title":"Med. Phys."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Allab, A., V\u00e1zquez, C., Cresson, T., and de Guise, J. (2019, January 23\u201327). Calibration of Stereo Radiography System for Radiostereometric Analysis Application. Proceedings of the 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Berlin, Germany.","DOI":"10.1109\/EMBC.2019.8857531"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"252","DOI":"10.1080\/10589759.2020.1774580","article-title":"A low-cost geometry calibration procedure for a modular cone-beam X-ray CT system","volume":"35","author":"Nguyen","year":"2020","journal-title":"Nondestruct. Test. Eval."},{"key":"ref_19","unstructured":"Paudel, K. (2012). Stitching of X-ray Images. [Master\u2019s Thesis, Uppsala University]. Available online: http:\/\/uu.diva-portal.org\/smash\/get\/diva2:565399\/FULLTEXT01.pdf."},{"key":"ref_20","unstructured":"Group, L. (2021, March 11). LEGO Group, A Short Presentation. Available online: https:\/\/www.lego.com\/cdn\/cs\/aboutus\/assets\/blt2278c7a21e58e900\/LEGOCompanyProfile_2020.pdf."},{"key":"ref_21","unstructured":"3D2YMOX (2021, March 11). 3-Dimensional DYnamic MOrphology Using X-rays. Available online: https:\/\/www.uantwerpen.be\/en\/research-groups\/3d2ymox\/."},{"key":"ref_22","unstructured":"Ferrucci, M. (2018). Systematic Approach to Geometrical Calibration of X-ray Computed Tomography Instruments. [Ph.D. Thesis, KU Leuven]. Available online: https:\/\/lirias.kuleuven.be\/retrieve\/521553."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Theodoridis, S., and Koutroumbas, K. (2009). Chapter 8\u2014Template Matching. Pattern Recognition, Academic Press. [4th ed.].","DOI":"10.1016\/B978-1-59749-272-0.50010-4"},{"key":"ref_24","unstructured":"Nguyen, V., De Beenhouwer, J., Bazrafkan, S., Hoang, A.T., Van Wassenbergh, S., and Sijbers, J. (2020, January 3\u20137). BeadNet: A network for automated spherical marker detection in radiographs for geometry calibration. Proceedings of the 6th International Conference on Image Formation in X-Ray Computed Tomography, 6th CTMeeting, Regensburg, Germany."},{"key":"ref_25","unstructured":"He, K., Zhang, X., Ren, S., and Sun, J. (July, January 26). Deep residual learning for image recognition. Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition, Las Vegas, NV, USA."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"231","DOI":"10.1023\/A:1008677427361","article-title":"An Interior-Point Algorithm for Nonconvex Nonlinear Programming","volume":"13","author":"Vanderbei","year":"1999","journal-title":"Comput. Optim. Appl."},{"key":"ref_27","unstructured":"Marinovszki, A., De Beenhouwer, J., and Sijbers, J. (2018, January 6\u20139). An efficient CAD projector for X-ray projection based 3D inspection with the ASTRA Toolbox. Proceedings of the 8th Conference on Industrial Computed Tomography, 18th iCT, Wels, Austria."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1016\/j.ultramic.2015.05.002","article-title":"The ASTRA Toolbox: A platform for advanced algorithm development in electron tomography","volume":"157","author":"Wim","year":"2015","journal-title":"Ultramicroscopy"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"25129","DOI":"10.1364\/OE.24.025129","article-title":"Fast and flexible X-ray tomography using the ASTRA toolbox","volume":"24","author":"Wim","year":"2016","journal-title":"Opt. Express"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"035404","DOI":"10.1088\/1361-6501\/abb33e","article-title":"Projection-angle-dependent distortion correction in high-speed image-intensifier-based x-ray computed tomography","volume":"32","author":"Sanctorum","year":"2020","journal-title":"Meas. Sci. Technol."}],"container-title":["Journal of Imaging"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2313-433X\/7\/3\/54\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:35:06Z","timestamp":1760160906000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2313-433X\/7\/3\/54"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,3,13]]},"references-count":30,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2021,3]]}},"alternative-id":["jimaging7030054"],"URL":"https:\/\/doi.org\/10.3390\/jimaging7030054","relation":{},"ISSN":["2313-433X"],"issn-type":[{"value":"2313-433X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,3,13]]}}}