Marker-free deformable registration and fusion for augmented reality-guided positive margin localization during tumor resection surgery

2026-07-14

AI Summary

This study addresses the clinical challenge of accurately mapping positive surgical margins from deformed excised specimens back to the operative cavity following head and neck tumor resection, a task hindered by the lack of effective visual guidance. The authors propose a markerless augmented reality (AR) workflow that achieves fully automatic registration between the specimen and the surgical cavity through a contour-constrained deformation model, depth scan residual alignment, and markerless surface fusion. This approach enables real-time AR projection with significantly improved margin localization accuracy, reducing the error to 6.19 ± 1.79 mm—substantially outperforming verbal instruction (21.40 ± 3.84 mm) and direct specimen inspection (16.09 ± 4.30 mm). The markerless fusion itself achieves an error of 2.15 ± 0.87 mm, and the entire pipeline processes data online in just 5.23 ± 0.34 seconds.

Abstract

Positive margins in head and neck oncologic surgery require mapping specimen-side pathology findings to the patient resection bed. This is challenging because pathologists identify the positive margin on slices of the resected, deformed specimen, while surgeons must relocate the corresponding site on the resection bed using only verbal descriptions and no visual guidance. We present a marker-free augmented reality (AR) workflow for mapping a margin label from a three-dimensional specimen scan to the resection bed. The method combines contour-constrained deformation, residual alignment to a depth scan, surface-based fusion to a head-mounted display, and target projection onto the reconstructed bed. Bead-suture correspondences estimate specimen deformation, whereas patient-to-display fusion does not require external fiducial markers. Following formative experiments, five residents and surgeons performed cadaveric cheek and scalp re-resection tasks under verbal guidance, verbal guidance with specimen examination, and AR guidance. Deformation target errors were $7.63 \pm 3.74$ mm for the cheek and $3.72 \pm 1.02$ mm for the scalp; residual specimen-to-bed distances were $2.43 \pm 2.15$ mm and $2.19 \pm 1.06$ mm, respectively. Fusion error did not differ significantly between marker-free and marker-based methods on either cadaver; overall marker-free fusion error was $2.15 \pm 0.87$ mm. End-to-end margin localization error decreased from $21.40 \pm 3.84$ mm with verbal guidance and $16.09 \pm 4.30$ mm with specimen examination to $6.19 \pm 1.79$ mm with AR guidance ($p < 0.001$). Online fusion required $5.23 \pm 0.34$ s. These results demonstrate effective marker-free AR guidance for positive-margin localization and support more precise tumor resection.

Problem

• positive margin localization
• tumor resection surgery
• deformable registration
• augmented reality
• specimen-to-bed mapping

Innovation

• marker-free registration
• deformable registration
• augmented reality
• positive margin localization
• surface-based fusion