P07.02.b Frameless Robot-Assisted Biopsy Using Stealth Autoguide: A Comparative Study With Frame-Based Technique

BACKGROUND Histopathological diagnosis is still indispensable for the precise classification and management of brain tumors, despite the substantial advancements in neuroimaging technologies. Traditionally, frame-based stereotactic biopsy has been the standard approach. However, recent innovations in frameless robotic systems offer new possibilities for minimally invasive and more flexible procedures. This study aims to compare the tissue sampling success and safety between the conventional frame-based stereotactic biopsy and the frameless robot-assisted biopsy using the Stealth Autoguide system®. METHODS This single institutional retrospective study was approved in our institutional review board. A total of 66 patients underwent frame-based stereotactic biopsy using the Leksell frame with regular burr hole technique between 2007 and March 2023, while 50 patients underwent frameless robot-assisted biopsy with twist drill technique using the Stealth Autoguide system® between April 2023 and April 2025. Tissue sampling success was evaluated by measuring postoperative intracranial air volume and actual brain shift, both of which are related to intraoperative brain displacement and can affect the precision of needle targeting. Intracranial air volume and brain shift, and volume of hemorrhage at target lesion were compared between two groups using the Mann-Whitney U test, while postoperative hemorrhage was analyzed using the Fisher’s exact test. RESULTS Diagnostic tissue was successfully obtained in all cases. The twist drill technique group showed a significantly lower volume of postoperative intracranial air compared to the regular burr hole technique group (p < 0.0001). Moreover, we found that the patients with narrower sulci by tumor/edema exhibited significantly less intracranial air compared to those with normal or widened sulci in both frame-based (p = 0.0051) and frameless (p = 0.0134) groups, respectively. There was no significant difference in postoperative hemorrhage rates between the two groups, indicating comparable procedural safety. CONCLUSION The frameless robot-assisted biopsy with the twist drill technique using the Stealth Autoguide system® offers a safe and effective alternative to the conventional frame-based method. It significantly reduces postoperative intracranial air volume and brain shift, potentially improving the precision of needle targeting. Our study also showed that the anatomical factors such as sulcal width influenced the brain shift.