A preliminary feasibility study of deformation field-driven geometric updating of preoperative MRI using 3D intraoperative ultrasound for glioma surgery

Intraoperative brain shift degrades the accuracy of preoperative‑MRI‑based neuronavigation, whereas intraoperative MRI (iMRI) incurs substantial costs. This study investigated a deformation‑field framework based on 3D intraoperative ultrasound (3D-iUS) and optical navigation to warp preoperative MRI into geometrically updated virtual MRI (vMRI) for the correction of brain‑shift‑induced spatial displacement. An optical-ultrasound navigation platform unified 3D iUS and preoperative MRI coordinates. In vitro brain shift phantoms and ex vivo cadaveric specimens simulated bidirectional tumor growth-resection deformation. A B-spline free-form deformation algorithm computed tissue displacement fields from 3D iUS to generate vMRI. Target registration error (TRE) between vMRI and iMRI was calculated using implanted markers and anatomical landmarks. Algorithm performance was assessed by accuracy, real-time capability, and robustness. After deformation correction, mean TRE was 2.94 mm in vitro and 2.28 mm ex vivo, both within the clinically acceptable range (2–3 mm). Image overlay confirmed good alignment of key structures. The algorithm ran stably with a mean core computation time of approximately 2.5 min, demonstrating encouraging computational speed for the deformation-solving step, with further pipeline optimization needed to support practical intraoperative application. The “3D iUS + optical navigation + deformation field” pipeline is feasible in vitro and ex vivo, achieving registration accuracy comparable to iMRI within the clinically acceptable range, though the improvement over rigid baseline did not reach statistical significance. These findings provide a methodological foundation for future in vivo validation and iMRI-free dynamic image-guided navigation.