Matteo de Notaris

Cochlear implantation (CI) is the treatment of choice for patients with severe or profound sensorineural deafness, providing substantial improvements in hearing perception and quality of life.Howev...

Objective: Mixed reality (MR) guidance enables real-time superimposition of virtual anatomical models onto the surgical field but is inherently affected by spatial instability due to tracking limitations, sensor noise and head-mounted display dynamics. These frame-to-frame fluctuations may lead to transient mislocalisation of neuroanatomical structures and are not adequately captured by conventional static registration metrics. This study aimed to develop and validate a clinically interpretable metric for continuous assessment of registration stability in MR-guided neurosurgery. Methods: The Registration Quality Index (RQI) was introduced as an automated, surface-based metric quantifying virtual–physical alignment through pixel-level boundary proximity analysis. A higher RQI value indicates greater boundary displacement, corresponding to worse registration quality. Validation was performed using a rigid skull phantom, a Varjo XR-3 mixed reality headset and ArUco-based optical tracking across fifteen experimental trials and seventy-five viewing configurations. RQI values were compared with established neuronavigation accuracy metrics, including Fiducial Registration Error (FRE) and Target Registration Error (TRE). Results: Strong correlations were observed between RQI and FRE ( r = 0.89 (95% CI 0.69–0.96), p < 0.001) and between RQI and TRE ( r = 0.93 (95% CI 0.80–0.98), p < 0.001). Regression analysis demonstrated that each 1% increase in RQI corresponded to a 0.195 mm increase in FRE and a 0.244 mm increase in TRE. Real-time computation at 30 Hz was achieved without workflow disruption. RQI variability was significantly influenced by viewing angle, with lateral perspectives yielding higher displacement values than frontal views. Conclusions: As a technical proof of concept, RQI enables continuous, automated monitoring of registration stability in MR-guided neurosurgical navigation, addressing a critical limitation of current static accuracy assessments. While the current proof-of-concept validation on rigid phantoms demonstrates strong construct validity, the interpretability ranges reported here are exploratory and further clinical studies involving in vivo conditions are required to establish clinically actionable decision boundaries and assess performance in the presence of brain shift and soft tissue deformation.

BACKGROUND AND OBJECTIVES: Endoscopic endonasal surgery (EEA) is a standard approach for treating pituitary tumors, requiring a specialized operating room setup, surgical skills and technique, and step-by-step protocol. This translational study optimizes different algorithms of photogrammetry (PGM) and videogrammetry (VGM) to create interactive 3D models for EEA while maintaining intraoperative efficiency, sterility, and data privacy. This investigation aimed to implement an optimal and efficient intraoperative endoscopic PGM and VGM algorithm to generate detailed and interactive 3D models of key surgical steps, EEA, without compromising sterility and efficiency. METHODS: PGM and VGM were first tested in an anatomy laboratory to refine an algorithm for endoscopic scanning. Eighty photographs or 2 minutes of endoscopic video were sufficient to create 3D models. Later, this approach was applied intraoperatively in EEA. Patient positioning and important surgical steps were scanned using a smartphone camera (2-dimensional photographs and LiDAR sensor) and a high-definition 30° endoscope video was recorded with an endoscopic camera. A dedicated PGM software enabling the creation of detailed 3D models was used. RESULTS: Six 3D anatomic and intraoperative models were developed, illustrating key surgical steps, anatomic landmarks, and the operative environment from various endoscopic perspectives. The process maintained intraoperative sterility and efficiency. Two explanatory videos were produced. CONCLUSION: PGM and VGM offer an effective, intraoperative 3D data acquisition tool in EEA. These techniques enhance surgical documentation and training by providing high-resolution, interactive models offering a detailed understanding of the operative corridor and critical procedural steps without compromising safety, sterility, or the time of the surgical procedure.

Background/Objectives: The endoscopic transorbital approach (ETOA) is a minimally invasive surgical route that provides access to the lateral skull base through the superior eyelid. Originally developed as an endoscopic procedure, ETOA has recently been explored using alternative visualization tools such as the exoscope. This study evaluates the effectiveness of exoscopic visualization across the different steps of transorbital surgery. Methods: Eight formalin-fixed cadaveric specimens (16 sides) were dissected by four teams of neurosurgeons trained in ETOA. The dissection protocol consisted of three stages: skin, orbital, and intracranial. The teams were assigned to four groups: the first performed a pure endoscopic ETOA (group A) and the second and third performed a combined exoscopic/endoscopic ETOA, using exoscopic visualization, respectively, for the skin phase only (group B) or for the skin and orbital phases (group C), while the fourth group performed a pure exoscopic ETOA All surgeons rotated across groups. Operative time was recorded. After each procedure, surgeons rated operative comfort, maneuverability, and image quality on a 0–5 scale. Pre- and postoperative CT scans were used for volumetric analysis, comparing surgical cavity size with and without the endoscope in place. In addition, an illustrative exoscopic case was included. Results: Exoscopic visualization proved to be more effective during the skin phase. In the orbital phase, it improved access and reduced crowding during lateral wall drilling. However, endoscopic visualization provided superior image clarity and magnification for deep and medial orbital structures. CT-based analysis confirmed that the exoscope significantly improves the working space during orbital dissection. Moreover, the combined approaches (Groups B and C) achieved shorter operative times and higher subjective ratings. Conclusions: The exoscope could be a valuable visualizing tool for transorbital surgery. While the skin phase benefits most from exoscopic visualization, the endoscope remains essential for the intracranial phase. The orbital phase can be effectively performed with either technique, each offering specific advantages and limitations.