{"id":760,"date":"2026-08-20T16:57:39","date_gmt":"2026-08-20T13:57:39","guid":{"rendered":"https:\/\/cdfhub.com\/?p=760"},"modified":"2026-08-27T08:25:32","modified_gmt":"2026-08-27T05:25:32","slug":"two-geometric-methods-for-cbct-defacing-a-technical-note-preprint","status":"publish","type":"post","link":"https:\/\/cdfhub.com\/?p=760","title":{"rendered":"Two Geometric Methods for CBCT Defacing: A Technical Note (preprint)"},"content":{"rendered":"\n<h1 class=\"wp-block-heading\"><strong>\u0394\u03cd\u03bf \u0393\u03b5\u03c9\u03bc\u03b5\u03c4\u03c1\u03b9\u03ba\u03ad\u03c2 \u039c\u03ad\u03b8\u03bf\u03b4\u03bf\u03b9 \u0391\u03c0\u03bf\u03c0\u03c1\u03bf\u03c3\u03c9\u03c0\u03bf\u03c0\u03bf\u03af\u03b7\u03c3\u03b7\u03c2 CBCT: \u03a4\u03b5\u03c7\u03bd\u03b9\u03ba\u03cc \u03a3\u03b7\u03bc\u03b5\u03af\u03c9\u03bc\u03b1<\/strong> (<strong>\u03c0\u03c1\u03bf\u03b4\u03b7\u03bc\u03bf\u03c3\u03af\u03b5\u03c5\u03c3\u03b7<\/strong>)<\/h1>\n\n\n\n<p><\/p>\n\n\n\n<p>\u0397 \u03c0\u03c1\u03bf\u03b4\u03b7\u03bc\u03bf\u03c3\u03af\u03b5\u03c5\u03c3\u03b7 \u03c4\u03b7\u03c2 \u03b5\u03c1\u03b3\u03b1\u03c3\u03af\u03b1\u03c2 \u201c<strong>\u0394\u03cd\u03bf \u0393\u03b5\u03c9\u03bc\u03b5\u03c4\u03c1\u03b9\u03ba\u03ad\u03c2 \u039c\u03ad\u03b8\u03bf\u03b4\u03bf\u03b9 \u0391\u03c0\u03bf\u03c0\u03c1\u03bf\u03c3\u03c9\u03c0\u03bf\u03c0\u03bf\u03af\u03b7\u03c3\u03b7\u03c2 CBCT: \u03a4\u03b5\u03c7\u03bd\u03b9\u03ba\u03cc \u03a3\u03b7\u03bc\u03b5\u03af\u03c9\u03bc\u03b1<\/strong>\u201d \u03b5\u03af\u03bd\u03b1\u03b9 \u03b4\u03b9\u03b1\u03b8\u03ad\u03c3\u03b9\u03bc\u03b7.<\/p>\n\n\n\n<p>doi: <a href=\"https:\/\/zenodo.org\/records\/22121731\">https:\/\/zenodo.org\/records\/22121731<\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Two Geometric Methods for CBCT Defacing: A Technical Note (preprint)<\/h1>\n\n\n\n<p><\/p>\n\n\n\n<p><em><strong>Abstract<\/strong><\/em><\/p>\n\n\n\n<p><em><br><strong>Purpose:<\/strong> Protecting personal data in large-field-of-view (FOV) CBCT examinations presents a<br>challenge, as simple anonymization of DICOM metadata does not eliminate the possibility of<br>identification from the external facial morphology. The purpose of this technical note was to<br>evaluate two simple geometric methods for CBCT defacing.<br><\/em><\/p>\n\n\n\n<p><em><strong>Materials and Methods:<\/strong> Thirty CBCT examinations were evaluated. Following anonymization,<br>nine examinations with insufficient external facial morphology were excluded and 21 were<br>included in the evaluation. Two methods were applied: a semi-automated curve-based defacing<br>method and a manual shell-based defacing method. Both methods were implemented exclusively<br>using geometric tools within an open-source software environment.<br><\/em><\/p>\n\n\n\n<p><em><strong>Results:<\/strong> Both methods successfully removed or covered recognizable external facial features.The<br>Curve-based method demonstrated higher anatomical preservation and reproducibility. Neither<br>method involved spatial cropping, volume clipping, or pixel\/voxel resampling. The mean<br>processing time was 33.8 \u00b1 3.3 sec for the curve-based method and 151 \u00b1 16.7 sec for the shell-<br>based method.<br><\/em><\/p>\n\n\n\n<p><em><strong>Conclusion: <\/strong>Both methods demonstrated consistent and uniform performance in the evaluated<br>CBCT dataset and may provide simple, open-source, locally executable approaches for CBCT<br>defacing. Further external validation is required.<\/em><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p><strong><em>\u03a0\u03b5\u03c1\u03af\u03bb\u03b7\u03c8\u03b7<\/em><\/strong><\/p>\n\n\n\n<p><em><strong>\u03a3\u03ba\u03bf\u03c0\u03cc\u03c2:<\/strong> \u0397 \u03c0\u03c1\u03bf\u03c3\u03c4\u03b1\u03c3\u03af\u03b1 \u03c4\u03c9\u03bd \u03c0\u03c1\u03bf\u03c3\u03c9\u03c0\u03b9\u03ba\u03ce\u03bd \u03b4\u03b5\u03b4\u03bf\u03bc\u03ad\u03bd\u03c9\u03bd \u03c3\u03b5 CBCT \u03bc\u03b5 \u03bc\u03b5\u03b3\u03ac\u03bb\u03bf Field of View (FOV) \u03b1\u03c0\u03bf\u03c4\u03b5\u03bb\u03b5\u03af \u03c0\u03c1\u03cc\u03ba\u03bb\u03b7\u03c3\u03b7, \u03ba\u03b1\u03b8\u03ce\u03c2 \u03b7 \u03b1\u03c0\u03bb\u03ae \u03b1\u03bd\u03c9\u03bd\u03c5\u03bc\u03bf\u03c0\u03bf\u03af\u03b7\u03c3\u03b7 \u03c4\u03c9\u03bd DICOM \u03bc\u03b5\u03c4\u03b1\u03b4\u03b5\u03b4\u03bf\u03bc\u03ad\u03bd\u03c9\u03bd \u03b4\u03b5\u03bd \u03b5\u03be\u03b1\u03bb\u03b5\u03af\u03c6\u03b5\u03b9 \u03c4\u03b7\u03bd \u03c0\u03b9\u03b8\u03b1\u03bd\u03cc\u03c4\u03b7\u03c4\u03b1 \u03b1\u03bd\u03b1\u03b3\u03bd\u03ce\u03c1\u03b9\u03c3\u03b7\u03c2 \u03b1\u03c0\u03cc \u03c4\u03b7\u03bd \u03b5\u03be\u03c9\u03c4\u03b5\u03c1\u03b9\u03ba\u03ae \u03bc\u03bf\u03c1\u03c6\u03bf\u03bb\u03bf\u03b3\u03af\u03b1 \u03c4\u03bf\u03c5 \u03c0\u03c1\u03bf\u03c3\u03ce\u03c0\u03bf\u03c5. \u03a3\u03ba\u03bf\u03c0\u03cc\u03c2 \u03c4\u03bf\u03c5\u03c0\u03b1\u03c1\u03cc\u03bd\u03c4\u03bf\u03c2 \u03c4\u03b5\u03c7\u03bd\u03b9\u03ba\u03bf\u03cd \u03c3\u03b7\u03bc\u03b5\u03b9\u03ce\u03bc\u03b1\u03c4\u03bf\u03c2 \u03ae\u03c4\u03b1\u03bd \u03b7 \u03b1\u03be\u03b9\u03bf\u03bb\u03cc\u03b3\u03b7\u03c3\u03b7 \u03b4\u03cd\u03bf \u03b1\u03c0\u03bb\u03ce\u03bd \u03b3\u03b5\u03c9\u03bc\u03b5\u03c4\u03c1\u03b9\u03ba\u03ce\u03bd \u03bc\u03b5\u03b8\u03cc\u03b4\u03c9\u03bd \u03b1\u03c0\u03bf\u03c0\u03c1\u03bf\u03c3\u03c9\u03c0\u03bf\u03c0\u03bf\u03af\u03b7\u03c3\u03b7\u03c2 (defacing) CBCT.<\/em><\/p>\n\n\n\n<p><em><strong>\u03a5\u03bb\u03b9\u03ba\u03ac \u03ba\u03b1\u03b9 \u03bc\u03ad\u03b8\u03bf\u03b4\u03bf\u03b9:<\/strong> \u0391\u03be\u03b9\u03bf\u03bb\u03bf\u03b3\u03ae\u03b8\u03b7\u03ba\u03b1\u03bd 30 CBCT \u03b5\u03be\u03b5\u03c4\u03ac\u03c3\u03b5\u03b9\u03c2. \u039c\u03b5\u03c4\u03ac \u03c4\u03b7\u03bd \u03b1\u03bd\u03c9\u03bd\u03c5\u03bc\u03bf\u03c0\u03bf\u03af\u03b7\u03c3\u03b7, 9 \u03b5\u03be\u03b5\u03c4\u03ac\u03c3\u03b5\u03b9\u03c2 \u03bc\u03b5 \u03b1\u03bd\u03b5\u03c0\u03b1\u03c1\u03ba\u03ae \u03b5\u03be\u03c9\u03c4\u03b5\u03c1\u03b9\u03ba\u03ae \u03bc\u03bf\u03c1\u03c6\u03bf\u03bb\u03bf\u03b3\u03af\u03b1 \u03c0\u03c1\u03bf\u03c3\u03ce\u03c0\u03bf\u03c5 \u03b1\u03c0\u03bf\u03ba\u03bb\u03b5\u03af\u03c3\u03c4\u03b7\u03ba\u03b1\u03bd \u03ba\u03b1\u03b9 21 \u03c7\u03c1\u03b7\u03c3\u03b9\u03bc\u03bf\u03c0\u03bf\u03b9\u03ae\u03b8\u03b7\u03ba\u03b1\u03bd \u03b3\u03b9\u03b1 \u03c4\u03b7\u03bd \u03b1\u03be\u03b9\u03bf\u03bb\u03cc\u03b3\u03b7\u03c3\u03b7. \u0395\u03c6\u03b1\u03c1\u03bc\u03cc\u03c3\u03c4\u03b7\u03ba\u03b1\u03bd \u03b4\u03cd\u03bf \u03bc\u03ad\u03b8\u03bf\u03b4\u03bf\u03b9: \u03bc\u03af\u03b1 \u03b7\u03bc\u03b9\u03b1\u03c5\u03c4\u03cc\u03bc\u03b1\u03c4\u03b7 \u03bc\u03ad\u03b8\u03bf\u03b4\u03bf\u03c2 \u03b2\u03b1\u03c3\u03b9\u03c3\u03bc\u03ad\u03bd\u03b7 \u03c3\u03b5 \u03ba\u03b1\u03bc\u03c0\u03cd\u03bb\u03b7 (Curve-based Defacing) \u03ba\u03b1\u03b9 \u03bc\u03af\u03b1 \u03c7\u03b5\u03b9\u03c1\u03bf\u03ba\u03af\u03bd\u03b7\u03c4\u03b7 \u03bc\u03ad\u03b8\u03bf\u03b4\u03bf\u03c2 \u03b2\u03b1\u03c3\u03b9\u03c3\u03bc\u03ad\u03bd\u03b7 \u03c3\u03b5 \u03ba\u03ad\u03bb\u03c5\u03c6\u03bf\u03c2 (Shell-based Defacing). \u039a\u03b1\u03b9 \u03bf\u03b9 \u03b4\u03cd\u03bf \u03c5\u03bb\u03bf\u03c0\u03bf\u03b9\u03ae\u03b8\u03b7\u03ba\u03b1\u03bd \u03b1\u03c0\u03bf\u03ba\u03bb\u03b5\u03b9\u03c3\u03c4\u03b9\u03ba\u03ac \u03bc\u03b5 \u03b3\u03b5\u03c9\u03bc\u03b5\u03c4\u03c1\u03b9\u03ba\u03ac \u03b5\u03c1\u03b3\u03b1\u03bb\u03b5\u03af\u03b1 \u03b1\u03bd\u03bf\u03b9\u03ba\u03c4\u03bf\u03cd \u03bb\u03bf\u03b3\u03b9\u03c3\u03bc\u03b9\u03ba\u03bf\u03cd.<\/em><\/p>\n\n\n\n<p><em><strong>\u0391\u03c0\u03bf\u03c4\u03b5\u03bb\u03ad\u03c3\u03bc\u03b1\u03c4\u03b1:<\/strong> \u039a\u03b1\u03b9 \u03bf\u03b9 \u03b4\u03cd\u03bf \u03bc\u03ad\u03b8\u03bf\u03b4\u03bf\u03b9 \u03c0\u03ad\u03c4\u03c5\u03c7\u03b1\u03bd \u03c4\u03b7\u03bd \u03b1\u03c6\u03b1\u03af\u03c1\u03b5\u03c3\u03b7 \u03ae \u03ba\u03ac\u03bb\u03c5\u03c8\u03b7 \u03c4\u03c9\u03bd \u03b1\u03bd\u03b1\u03b3\u03bd\u03c9\u03c1\u03af\u03c3\u03b9\u03bc\u03c9\u03bd \u03b5\u03be\u03c9\u03c4\u03b5\u03c1\u03b9\u03ba\u03ce\u03bd \u03c7\u03b1\u03c1\u03b1\u03ba\u03c4\u03b7\u03c1\u03b9\u03c3\u03c4\u03b9\u03ba\u03ce\u03bd. \u0397 \u03bc\u03ad\u03b8\u03bf\u03b4\u03bf\u03c2 \u03c0\u03bf\u03c5 \u03b2\u03b1\u03c3\u03af\u03b6\u03b5\u03c4\u03b1\u03b9 \u03c3\u03c4\u03b7\u03bd \u03ba\u03b1\u03bc\u03c0\u03cd\u03bb\u03b7 (Curve-based method) \u03ad\u03b4\u03b5\u03b9\u03be\u03b5 \u03bc\u03b5\u03b3\u03b1\u03bb\u03cd\u03c4\u03b5\u03c1\u03b7 \u03b1\u03bd\u03b1\u03c4\u03bf\u03bc\u03b9\u03ba\u03ae \u03b4\u03b9\u03b1\u03c4\u03ae\u03c1\u03b7\u03c3\u03b7 \u03ba\u03b1\u03b9 \u03b1\u03bd\u03b1\u03c0\u03b1\u03c1\u03b1\u03b3\u03c9\u03b3\u03b9\u03bc\u03cc\u03c4\u03b7\u03c4\u03b1. \u039a\u03b1\u03bc\u03af\u03b1 \u03bc\u03ad\u03b8\u03bf\u03b4\u03bf\u03c2 \u03b4\u03b5\u03bd \u03c0\u03b5\u03c1\u03b9\u03b5\u03bb\u03ac\u03bc\u03b2\u03b1\u03bd\u03b5 \u03c7\u03c9\u03c1\u03b9\u03ba\u03ae \u03b1\u03c0\u03bf\u03ba\u03bf\u03c0\u03ae (spatial cropping), \u03b1\u03c0\u03bf\u03ba\u03bf\u03c0\u03ae \u03cc\u03b3\u03ba\u03bf\u03c5 (volume clipping) \u03ae \u03b5\u03c0\u03b1\u03bd\u03b1\u03b4\u03b5\u03b9\u03b3\u03bc\u03b1\u03c4\u03bf\u03bb\u03b7\u03c8\u03af\u03b1 \u03b5\u03b9\u03ba\u03bf\u03bd\u03bf\u03c3\u03c4\u03bf\u03b9\u03c7\u03b5\u03af\u03c9\u03bd (pixel\/voxel resampling). \u039f \u03bc\u03ad\u03c3\u03bf\u03c2 \u03c7\u03c1\u03cc\u03bd\u03bf\u03c2 \u03b5\u03c0\u03b5\u03be\u03b5\u03c1\u03b3\u03b1\u03c3\u03af\u03b1\u03c2 \u03ae\u03c4\u03b1\u03bd 33,8\u00b13,3 sec \u03b3\u03b9\u03b1 \u03c4\u03b7\u03bd Curve-based \u03ba\u03b1\u03b9 151\u00b116,7 sec \u03b3\u03b9\u03b1 \u03c4\u03b7 Shell-based \u03bc\u03ad\u03b8\u03bf\u03b4\u03bf.<\/em><\/p>\n\n\n\n<p><em><strong>\u03a3\u03c5\u03bc\u03c0\u03b5\u03c1\u03ac\u03c3\u03bc\u03b1\u03c4\u03b1:<\/strong> \u039f\u03b9 \u03b4\u03cd\u03bf \u03bc\u03ad\u03b8\u03bf\u03b4\u03bf\u03b9 \u03c0\u03b1\u03c1\u03bf\u03c5\u03c3\u03af\u03b1\u03c3\u03b1\u03bd \u03c3\u03c4\u03b1\u03b8\u03b5\u03c1\u03ae \u03ba\u03b1\u03b9 \u03bf\u03bc\u03bf\u03b9\u03cc\u03bc\u03bf\u03c1\u03c6\u03b7 \u03b1\u03c0\u03cc\u03b4\u03bf\u03c3\u03b7 \u03c3\u03c4\u03bf \u03c3\u03c5\u03b3\u03ba\u03b5\u03ba\u03c1\u03b9\u03bc\u03ad\u03bd\u03bf \u03c3\u03cd\u03bd\u03bf\u03bb\u03bf CBCT \u03ba\u03b1\u03b9 \u03bc\u03c0\u03bf\u03c1\u03bf\u03cd\u03bd \u03bd\u03b1 \u03b1\u03c0\u03bf\u03c4\u03b5\u03bb\u03ad\u03c3\u03bf\u03c5\u03bd \u03b1\u03c0\u03bb\u03ad\u03c2, \u03b1\u03bd\u03bf\u03b9\u03ba\u03c4\u03ad\u03c2 \u03ba\u03b1\u03b9 \u03c4\u03bf\u03c0\u03b9\u03ba\u03ac \u03b5\u03ba\u03c4\u03b5\u03bb\u03ad\u03c3\u03b9\u03bc\u03b5\u03c2 \u03c0\u03c1\u03bf\u03c3\u03b5\u03b3\u03b3\u03af\u03c3\u03b5\u03b9\u03c2 \u03b3\u03b9\u03b1 \u03c4\u03b7\u03bd \u03b1\u03c0\u03bf\u03c0\u03c1\u03bf\u03c3\u03c9\u03c0\u03bf\u03c0\u03bf\u03af\u03b7\u03c3\u03b7 CBCT. \u0391\u03c0\u03b1\u03b9\u03c4\u03b5\u03af\u03c4\u03b1\u03b9 \u03c0\u03b5\u03c1\u03b1\u03b9\u03c4\u03ad\u03c1\u03c9 \u03b5\u03be\u03c9\u03c4\u03b5\u03c1\u03b9\u03ba\u03ae \u03b5\u03c0\u03b9\u03ba\u03cd\u03c1\u03c9\u03c3\u03b7.<\/em><\/p>\n\n\n\n<p><\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u0394\u03cd\u03bf \u0393\u03b5\u03c9\u03bc\u03b5\u03c4\u03c1\u03b9\u03ba\u03ad\u03c2 \u039c\u03ad\u03b8\u03bf\u03b4\u03bf\u03b9 \u0391\u03c0\u03bf\u03c0\u03c1\u03bf\u03c3\u03c9\u03c0\u03bf\u03c0\u03bf\u03af\u03b7\u03c3\u03b7\u03c2 CBCT: \u03a4\u03b5\u03c7\u03bd\u03b9\u03ba\u03cc \u03a3\u03b7\u03bc\u03b5\u03af\u03c9\u03bc\u03b1 (\u03c0\u03c1\u03bf\u03b4\u03b7\u03bc\u03bf\u03c3\u03af\u03b5\u03c5\u03c3\u03b7) \u0397 \u03c0\u03c1\u03bf\u03b4\u03b7\u03bc\u03bf\u03c3\u03af\u03b5\u03c5\u03c3\u03b7 \u03c4\u03b7\u03c2 \u03b5\u03c1\u03b3\u03b1\u03c3\u03af\u03b1\u03c2 \u201c\u0394\u03cd\u03bf \u0393\u03b5\u03c9\u03bc\u03b5\u03c4\u03c1\u03b9\u03ba\u03ad\u03c2 \u039c\u03ad\u03b8\u03bf\u03b4\u03bf\u03b9 \u0391\u03c0\u03bf\u03c0\u03c1\u03bf\u03c3\u03c9\u03c0\u03bf\u03c0\u03bf\u03af\u03b7\u03c3\u03b7\u03c2 CBCT: \u03a4\u03b5\u03c7\u03bd\u03b9\u03ba\u03cc \u03a3\u03b7\u03bc\u03b5\u03af\u03c9\u03bc\u03b1\u201d \u03b5\u03af\u03bd\u03b1\u03b9 \u03b4\u03b9\u03b1\u03b8\u03ad\u03c3\u03b9\u03bc\u03b7. doi: https:\/\/zenodo.org\/records\/22121731 Two Geometric Methods for CBCT Defacing: A Technical Note (preprint) Abstract Purpose: Protecting personal data in large-field-of-view (FOV) CBCT examinations presents achallenge, as simple anonymization of DICOM metadata does not eliminate 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