SURG-04. Robotic alignment system Cirq (Brainlab) for navigated brain tumor biopsies in children

BACKGROUND: With the incorporation of the robotic alignment system Cirq (Brainlab, Munich, Germany) into our neurosurgical armamentarium, we deemed it important to study application accuracy of this new device. As a baseline, we retrospectively reviewed our historical data on brain tumor biopsies using the non-robotic alignment instrument Varioguide (Brainlab, Munich, Germany). Because of relatively high target registration errors in this historical series, we sought to improve our registration with the introduction of Cirq. AIMS: 1.Share our experience with the new robotic alignment system Cirq for navigated brain tumor biopsies. 2. Compare patient-to-image registration methods. 3. Evaluate the accuracy of Cirq robotic system as compared to the non-robotic instrument Varioguide. METHODS: All patients (0-19 years old) who underwent a brain tumor biopsy at the Princess Máxima Center, Utrecht, were included. Over the period 2018-2020, data were collected retrospectively (cohort “Varioguide” in which patient-to-image registration was based on preoperative MRI with adhesive scalp fiducials). From 2021 onwards, data were collected prospectively (cohort “Cirq” in which patient-to-image registration was done using 1. A preoperative MRI with adhesive scalp fiducials and 2. An intraoperative CT head scan with bone screw fiducials). For both cohorts, Euclidian distances were calculated between the intended target and the obtained target using postoperative MRI scans. PRELIMINARY RESULTS : Nineteen patients were biopsied with Varioguide and nine patients with Cirq. The Cirq robotic system was convenient and safe in use with no intraoperative complications. Patient-to-image registration was more accurate when based on bone screw fiducials as compared to scalp fiducials. The Cirq robotic system, combined with bone fiducial registration, resulted in a high target accuracy with a maximum target error of 2 millimeters. CONCLUSION: The Cirq robotic alignment system, combined with bone screw fiducial registration, provides a safe and highly accurate method for brain tumor biopsies in children.