cs.CVMar 7, 2026

Virtual Intraoperative CT (viCT): Sequential Anatomic Updates for Modeling Tissue Resection Throughout Endoscopic Sinus Surgery

Authors: Nicole M. Gunderson, Graham J. Harris, Jeremy S. Ruthberg, Pengcheng Chen, Di Mao, Randall A. Bly, Waleed M. Abuzeid, Eric J. Seibel

Organizations: Department of Mechanical Engineering, University of Washington, Seattle, WA, USA. · Department of Otolaryngology–Head and Neck Surgery, University of Washington Medical Center, University of Washington, Seattle, WA, USA.

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Abstract

Purpose: Incomplete dissection is a common cause of persistent disease and revision endoscopic sinus surgery (ESS) in chronic rhinosinusitis. Current image-guided surgery systems typically reference static preoperative CT (pCT), and do not model evolving resection boundaries. We present Virtual Intraoperative CT (viCT), a method for sequentially updating pCT throughout ESS using intraoperative 3D reconstructions from monocular endoscopic video to enable visualization of evolving anatomy in CT format. Methods: Monocular endoscopic video is processed using a depth-supervised NeRF framework with virtual stereo synthesis to generate metrically scaled 3D reconstructions at multiple surgical intervals. Reconstructions undergo rigid, landmark-based registration in 3D Slicer guided by anatomical correspondences, and are then voxelized into the pCT grid. viCT volumes were generated using a ray-based occupancy comparison between pCT and reconstruction to delete outdated voxels and remap preserved anatomy and updated boundaries. Performance is evaluated in a cadaveric feasibility study of four specimens across four ESS stages using volumetric overlap (DSC, Jaccard) and surface metrics (HD95, Chamfer, MSD, RMSD), and qualitative comparisons to ground-truth CT. Results: viCT updates show agreement with ground-truth anatomy across surgical stages, with submillimeter mean surface errors. Dice Similarity Coefficient (DSC) = 0.88 +/- 0.05 and Jaccard Index = 0.79 +/- 0.07, and Hausdorff Distance 95% (HD95) = 0.69 +/- 0.28 mm, Chamfer Distance = 0.09 +/- 0.05 mm, Mean Surface Distance (MSD) = 0.11 +/- 0.05 mm, and Root Mean Square Distance (RMSD) = 0.32 +/- 0.10 mm. Conclusion: viCT enables CT-format anatomic updating in an ESS setting without ancillary hardware. Future work will focus on fully automating registration, validation in live cases, and optimizing runtime for real-time deployment.

Figures & tables

Figure 1: Flowchart of simulated stereoscopy NeRF-based reconstruction workflow.
Figure 2: Ray-based viCT updating workflow and example of tissue resection modeling.
(a) Post Maxillary surgical interval
(a) Post Ethmoid surgical interval
Figure 5: Qualitative comparison of viCT updates with ground-truth postoperative CT across surgical intervals. (A) Post Maxillary, (B) Post Ethmoid, and (C) Complete. Axial, coronal, and sagittal views demonstrate close correspondence between updated viCT volumes and postoperative ground-truth anatomy.
Figure 6: Summarized quantitative data across the four cadaveric specimens.
Appendix figures & tables11 assets

Supplementary material from the paper’s appendix.

Appendix

Figure 7: Sample monocular endoscopic views from videos used as input to the 3D reconstruction and viCT algorithms.
(a) Post Maxillary surgical interval
(a) Post Ethmoid surgical interval
Figure 10: Qualitative comparison of viCT updates with ground-truth postoperative CT across surgical intervals. (A) Post Maxillary, (B) Post Ethmoid, and (C) Complete. Axial, coronal, and sagittal views demonstrate close correspondence between updated viCT volumes and postoperative ground-truth anatomy.
(a) Post Maxillary surgical interval
(a) Post Ethmoid surgical interval
Figure 13: Qualitative comparison of viCT updates with ground-truth postoperative CT across surgical intervals. (A) Post Maxillary, (B) Post Ethmoid, and (C) Complete. Axial, coronal, and sagittal views demonstrate close correspondence between updated viCT volumes and postoperative ground-truth anatomy.
(a) Post Maxillary surgical interval
(a) Post Ethmoid surgical interval
Figure 16: Qualitative comparison of viCT updates with ground-truth postoperative CT across surgical intervals. (A) Post Maxillary, (B) Post Ethmoid, and (C) Complete. Axial, coronal, and sagittal views demonstrate close correspondence between updated viCT volumes and postoperative ground-truth anatomy.
Figure 17: Full quantitative data across the four cadaveric specimens.
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