Stealthstation s8

As part of the pre-surgical protocol, all patients underwent a 3-Tesla magnetic resonance imaging (MRI) under sedation, with targeting performed using in parallel both, the StealthStation S8 (Medtronic Inc., Minneapolis, MN, USA) and the BrainLab Elements® software (BrainLab AG, Much, Germany). MRI-direct visual anatomical targeting of the Subthalamic Nucleus (STN) was used. The stereotactic frame (Leksell-G; Elekta AB, Stockholm, Sweden) was fixed, and stereotactic coordinates were obtained from stereotactic computed tomography (CT) and image datasets coregistration. Electrode placement for PD in the STN was performed under general anesthesia, using a direct electrode placement method without microelectrode recordings. Intraoperative verification of electrode placement was done using the O-arm 3D fluoroscopic imaging system (Medtronic Inc., Minneapolis, MN, USA). After electrode placement, extension wires and an implantable pulse generator were implanted, and the electrode position was verified using postoperative 3D computed tomography co-registered utilizing preoperative magnetic resonance planning images.

Patients with tumorous conditions in the brain that required surgical resection from January 2021 to June 2022 were included in the study. They consisted of various types of brain tumors such as meningiomas, astrocytomas, pituitary adenomas, and metastatic tumors. All experiments using human tissues were performed with the approval of the Institutional Review Board of Korea University Anam Hospital in strict accordance with the Code of Ethics of the World Medical Association for experiments (approval number: 2019AN0133). Before elective brain tumor surgery, voluntary informed consent was obtained from the patients and their legal guardians after they were fully informed about the study design and that the experiments were conducted using ex vivo methods, which is not be potentially harmful to the patients. Patients were excluded if the resected tissue was inadequate for examination by CLE, such as presence of hemorrhagic changes or a small amount of volume <0.0314cm³ (suspected volume of one-piece tumor tissue via stereotactic navigation biopsy system, StealthStation S8, Medtronic, Minneapolis, MN, USA). The flowchart of the study was presented in Figure 1.

A latest generation ultrasound device (Esaote MyLab Twice, Italy) with a 3–11 MHz linear probe (Esaote LA332—Genova, Italy) was used, and multiple ultrasonographic modalities were adopted: these were B-mode, color Doppler Doppler, elastosonography, and contrast-enhanced intraoperative ultrasound (CEUS). CEUS was performed through the administration of ultrasound contrast agent (UCA) made with sulfur hexafluoride-filled microbubbles (SonoVue—Bracco Imaging, Italy). In selected cases, IOUS was combined with neuronavigation (Medtronic StealthStation S8—Minneapolis, USA) and the administration of 5-aminolevulinic acid (5-ALA) as tumor-specific fluorescent dye.

This is a prospective single-centre cohort study from May 2019 to November 2020 at a tertiary neuro-oncology hospital. The inclusion criteria were age ≥ 18, intra-axial, parietal lesions, informed consent for intra-operative neuro-monitoring (IONM), and preoperative surgical mapping (navigated transcranial magnetic stimulation (nTMS) and/or tractography). Ethics committee approval was not sought as the methodology of this study did not alter the surgical methods, and instead only added as operative adjuncts. The exclusion criteria were emergency admission and unavailability of IONM.
All patients underwent image-guided surgery with neuro-navigation (StealthStation S8 Medtronic). Augmented reality gained 3D visualisation of the tumour and tracts intra-operatively (object-brain overlay technique).
Post-operatively, all patients received a pre- and post-gadolinium Magnetic Resonance Imaging (MRI) scan (within 48 h). Gross total resection (GTR) was determined by no contrast enhancement (reported by a consultant neuroradiologists), and a subtotal resection (STR) by residual enhancement. The Cavity-to-Tract Distance (CTD) was calculated by merging the postoperative T1-weighted with Gadolinium MRI with the preoperative tractography (affine co-registration) as previously described by other authors [13 (link)].

Intraoperative 3D cone-bean CT (Medtronic O-arm O2, Minneapolis, MN, USA) covering the whole head is acquired at the beginning of the surgery using the Stereotaxic mode and 40 cm FOV (field-of-view). The gantry of the O-arm is positioned to have the patient’s head in the isocentre. If necessary, the gantry can be tilted to achieve the best possible alignment with the patient’s head. After the scan is finished, the exact scanning position of the gantry is saved, and the gantry is moved horizontally towards the patient’s legs to free up space for the surgeon. The acquired 3D image is automatically transferred to the neuro-navigation Stealth Station S8 (Medtronic, Minneapolis, MN, USA) and co-registered using rigid registration (6 degrees of freedoms–3 translations, 3 rotations) with the reference preoperative CT image to allow precise intraoperative navigation.
Three O-arm scans are made during the surgery in total. The first O-arm scan is performed at the beginning of the surgery to localise entries for the electrodes. The second O-arm scan is performed after attaching the reference frame (NexFrame, Medtronic, Minneapolis, MN, USA) to the right side of the patient’s head. The third O-arm scan is performed after attaching the reference frame to the left side of the patient’s head.

The preoperative images were downloaded and coregistered on a frameless neuronavigation system (StealthStation S8, Medtronic Inc., USA). The navigation system was also used for trajectory and target planning. Registration between the images and the patient’s physical anatomy was performed by tracing the scalp; then, the trajectory was locked. Errors between the trace and the preoperative images (registration error) and between the locked and planned trajectories (targeting error) were noted. The instruments were held in place by an AutoGuide^® (Medtronic Inc., USA). The coordinates of the instruments in the navigation space were logged through the developer mode in the navigation system. Images, metadata, and coordinate points were exported from the navigation system for further analysis in Python.