{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T15:05:09Z","timestamp":1789571109426,"version":"build-2803163510"},"reference-count":41,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T00:00:00Z","timestamp":1789516800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Bioengineering"],"abstract":"<jats:p>Breast-conserving surgery (BCS) requires accurate intraoperative localization of the tumor, which moves between the prone diagnostic and supine surgical positions. We present a projector-based augmented-reality (AR) localization system that projects a crosshair directly onto the patient\u2019s skin at the predicted tumor location. The pipeline combines rigid registration of ceramic fiducials between prone and supine CT (tumor error 0.30 mm on a real phantom), a SOFA finite-element simulation of gravity-driven prone-to-supine soft-tissue deformation (mean bead displacement 24.7 mm on a synthetic mesh; not validated on a deformable phantom), two-stage ICP surface alignment (RMSE 0.92 mm on a simulated camera; not yet validated on real D415 acquisitions), and projector\u2013camera (ProCam) extrinsic calibration driving the crosshair projection. Because the tumor and sub-surface fiducials are not visible in the live RGB-D scene, a direct non-circular in vivo target registration error (TRE) on the tumor cannot be measured in the present phantom configuration. We instead report a component-based end-to-end error budget obtained as the root-sum-square of three independently measured component errors: 2.7 mm (RSS planning estimate, not a directly measured end-to-end accuracy) \u2014rigid CT 0.30 mm, ProCam physical projection 2.50 mm, ICP 0.92 mm. The ProCam term is largest but sub-3 mm. The Gray-code reprojection residual (~11 mm in 15-pose recalibration; 8.62 mm in the deployed 4-pose calibration) overestimates the actual projection error by ~4\u00d7 (resp. ~3.4\u00d7): least-squares calibration averages the consumer-DLP vertical quantization (16-level Gray-code decode on XPR-DLP) into an accurate rigid transform, so the per-observation residual reflects observation quantization, not projection accuracy. The quantization\u2019s measurable cost is projection variance (max 5.5 mm), which motivates phase-shifting structured light. Boundary conditions on phantom rigidity, sub-surface fiducials, and simulated-camera ICP are stated explicitly.<\/jats:p>","DOI":"10.3390\/bioengineering13091078","type":"journal-article","created":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T13:50:27Z","timestamp":1789566627000},"page":"1078","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["A Projector-Based Augmented-Reality Localization Device for Breast-Conserving Surgery: Phantom Pipeline and End-to-End Error Budget"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9349-3849","authenticated-orcid":false,"given":"Xiaonan","family":"Gong","sequence":"first","affiliation":[{"name":"Department of Breast Surgery, Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"given":"Jiang","family":"Heng","sequence":"additional","affiliation":[{"name":"Cloud Valley, No. 1008 Dengcai Street, Xihu District, Hangzhou 310030, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"software","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"given":"Hao","family":"Feng","sequence":"additional","affiliation":[{"name":"Department of Radiology, Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"data-curation","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2031-5424","authenticated-orcid":false,"given":"Suzhan","family":"Zhang","sequence":"additional","affiliation":[{"name":"Cancer Institute (Key Laboratory of Cancer Prevention and Intervention, China National Ministry of Education) & Department of Colorectal Surgery, The Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang Provincial Clinical Research Center for CANCER, Cancer Center of Zhejiang University, Hangzhou 310009, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"supervision","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"154","DOI":"10.1007\/s10439-015-1496-z","article-title":"Symmetric Biomechanically Guided Prone-to-Supine Breast Image Registration","volume":"44","author":"Eiben","year":"2016","journal-title":"Ann. 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