Fully automated image updating for brain shift compensation after dural opening.

Objective: In open cranial procedures, intraoperative brain shift can degrade the accuracy of surgical navigation on the basis of preoperative MR (pMR) images as soon as the cortical surface is exposed. The aim of this study was to develop a fully automated image updating system to address brain shift at the start of open cranial surgery and to evaluate its accuracy and efficiency.

Methods: This study included patients undergoing open cranial procedures at a single center. Intraoperative stereovision (iSV) images of the surgical field were acquired as an easily integrated nondisruptive source of high-resolution image data on surgical surface deformation and were integrated with a computational model to compensate for volumetric brain shift after dural opening by updating the coregistered preoperative images. A Fast Segment Anything Model algorithm segmented the exposed cortical surface on iSV images automatically. Vessel and sulcus features were also segmented automatically from both iSV and pMR images and registered using a two-step registration method. Extracted nonrigid cortical displacements were assimilated by a finite element model to estimate whole-brain deformation. Updated MR (uMR) images were generated by deforming pMR by the resulting displacement field. A tracked stylus sampled the exposed cortical surface to provide independent measurements for error assessments. The uMR images were evaluated in terms of the misfit between model estimates and measured displacements, target registration error (TRE), and point-to-surface distance (PSD) relative to their pMR counterparts.

Results: Fifteen patients (age range 45-85 years) who underwent open cranial procedures were included in the study. The overall accuracy of reconstructed iSV surfaces relative to stylus positions was 0.8 ± 0.7 mm. The overall mean misfit, TRE, and PSD of uMR images were 2.1 ± 1.2 mm, 1.9 ± 1.0 mm, and 1.6 ± 1.0 mm, respectively, compared with 6.5 ± 1.3 mm, 6.2 ± 1.2 mm, and 4.5 ± 1.2 mm for pMR images. Image updating was completed automatically without any user intervention in an overall mean of 3.9 ± 0.6 minutes.

Conclusions: Automatic image updating compensated for brain shift due to dural opening and achieved clinically acceptable accuracy and efficiency. The system required no user intervention or expertise and caused minimal interruptions to surgical flow, suggesting it has potential for future integration into open cranial procedures.