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Background: Our study presents a single-center experience of resection of intradural spinal tumors either with or without using intraoperative computed tomography-based registration and microscope-based augmented reality (AR). Microscope-based AR was recently described for improved orientation in the operative field in spine surgery, using superimposed images of segmented structures of interest in a two-dimensional or three-dimensional mode., Methods: All patients who underwent surgery for resection of intradural spinal tumors at our department were retrospectively included in the study. Clinical outcomes in terms of postoperative neurologic deficits and complications were evaluated, as well as neuroradiologic outcomes for tumor remnants and recurrence., Results: 112 patients (57 female, 55 male; median age 55.8 ± 17.8 years) who underwent 120 surgeries for resection of intradural spinal tumors with the use of intraoperative neuromonitoring were included in the study, with a median follow-up of 39 ± 34.4 months. Nine patients died during the follow-up for reasons unrelated to surgery. The most common tumors were meningioma (n = 41), schwannoma (n = 37), myopapillary ependymomas (n = 12), ependymomas (n = 10), and others (20). Tumors were in the thoracic spine (n = 46), lumbar spine (n = 39), cervical spine (n = 32), lumbosacral spine (n = 1), thoracic and lumbar spine (n = 1), and 1 tumor in the cervical, thoracic, and lumbar spine. Four biopsies were performed, 10 partial resections, 13 subtotal resections, and 93 gross total resections. Laminectomy was the common approach. In 79 cases, patients experienced neurologic deficits before surgery, with ataxia and paraparesis as the most common ones. After surgery, 67 patients were unchanged, 49 improved and 4 worsened. Operative time, extent of resection, clinical outcome, and complication rate did not differ between the AR and non-AR groups. However, the use of AR improved orientation in the operative field by identification of important neurovascular structures., Conclusions: High rates of gross total resection with favorable neurologic outcomes in most patients as well as low recurrence rates with comparable complication rates were noted in our single-center experience. AR improved intraoperative orientation and increased surgeons' comfort by enabling early identification of important anatomic structures; however, clinical and radiologic outcomes did not differ, when AR was not used., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objective: We prospectively investigated how to integrate indocyanine green (ICG) angiography in an augmented reality (AR) setting for aneurysm surgery., Methods: In 20 patients with a total of 22 aneurysms, the head-up display of the operating microscope (Kinevo900) was used for AR. ICG-AR was established directly by the head-up display superimposing the ICG angiography as green live video overlay. In addition, the reconstructed outline of the three-dimensional (3D) vessel architecture was visualized by AR applying intraoperative low-dose computed tomography (vessel-AR)., Results: In all patients, ICG-AR and vessel-AR were successfully implemented. The flow in the vessels could be observed directly in the white light view of the microscope oculars without being distracted from the surgical site by looking on separate screens. This factor enabled also surgical manipulation during ICG angiography. In parallel, AR additionally visualized the 3D vessel architecture, enhancing the understanding of the 3D anatomy (target registration error, 0.71 ± 0.21 mm; intraoperative low-dose computed tomography effective dose, 42.7 μSv). Linear (n = 28; range, 1-8.5 mm) and rotational (n = 3; range, 2.9°-14.4°) navigation adjustments performed in 18 of 20 patients resulted in a close matching of the vessel-AR outline with the real vessel situation after preparation, compensating for shifting., Conclusions: ICG-AR could be successfully implemented. It facilitated surgical manipulation and flow interpretation during ICG angiography because it could be observed directly while looking through the microscope oculars in white light instead of being distracted from the surgical site while looking on separate screens. Additional AR visualizing the vessel architecture improved understanding of 3D anatomy for preparation and clipping., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Objective: To integrate 3-dimensional (3D) intraoperative ultrasound (iUS) data in spinal navigation., Methods: In 11 patients with intradural spinal tumors, 3D-iUS was performed before and after tumor resection. Intraoperative computed tomography (iCT) was used for automatic patient registration for spinal navigation; fiducial-based registration was performed in 1 case. The outlines of the vertebra were defined in preoperative image data by automatic mapping; risk and target structures were segmented manually; all these data were rigidly and if necessary non-rigidly registered with iCT. For 3D-iUS acquisition, tracked convex-shaped transducers (contact surface: 29 x 10 mm; scanning frequency: 10-3.8 MHz or 13-5 MHz) were used., Results: Navigated 3D-iUS was successfully implemented in all cases; 3D-iUS datasets were acquired and could be used as 3D image data for further navigation after iUS scanning. The 3D objects defined in preoperative image data, outlining the vertebra, target and risk structures, could be visualized in the 3D-iUS data. Navigated 3D-iUS allowed to reliably evaluate the extent of resection in all cases and updating of navigation, ensuring high navigational accuracy. The target registration error applying iCT-based automatic registration was 0.78 ± 0.23 mm. The effective dose for iCT was 0.11 ± 0.077 mSv for cervical and 1.75 ± 0.72 mSv for thoracic scans., Conclusions: Using 3D-iUS can be successfully integrated in spinal navigation. Automatic registration applying low-dose iCT and non-linear image registration offers displaying preoperative images in the same orientation as the 3D-iUS scan, as well as visualizing segmented structures in the navigated 3D-iUS data. This greatly facilitates image interpretation. Navigated 3D-iUS provides a possibility for navigation updating and immediate online quality control., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: To establish microscope-based augmented reality (AR) support for degenerative spine surgery., Methods: Head-up displays of operating microscopes were used to establish AR in a series of 10 patients. Segmentation of the vertebra and additional target structures, which were visualized by AR, was based on preoperative magnetic resonance and computed tomography (CT) images, that were nonrigidly fused to low-dose intraoperative CT (iCT) data. AR registration was achieved by automatic registration applying iCT and microscope calibration., Results: AR support could be smoothly implemented in the surgical workflow. AR allowed to visualize the target structures reliably in the surgical field, facilitating surgical orientation. Flexible placement of the reference array enabled AR implementation for anterior, lateral, posterior median, and posterior paramedian approaches. Identification of bony and artificial landmarks allowed validating registration accuracy; the measured target registration error was 1.11 ± 0.42 mm (mean ± standard deviation). The effective dose for registration scanning ranged from 0.52 to 8.71 mSv, which is on average about one-third of a standard diagnostic spine scan. This depended mainly on the scan length (mean scan length cervical/thoracic/lumbar: 99/218/118 mm). Longest scan ranges were in the mid-thoracic region to ensure unambiguous vertebra assignment as prerequisite for reliable nonlinear registration (mean cervical/thoracic/lumbar effective dose: 0.52/6.14/2.99 mSv)., Conclusions: Reliable microscope-based AR support is possible because of automatic registration based on intraoperative imaging. Application of AR in degenerative spine surgery has a big potential; it might be especially helpful in complex anatomical situations and resident education., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: We investigated how augmented reality (AR) can be applied to support transsphenoidal surgery., Methods: AR was established using the head-up displays integrated into operating microscopes. Navigation registration was performed with either fiducial-based or automatic registration using intraoperative computed tomography (iCT). Correct microscope calibration was ensured by checking the geometric overlap between the AR representation of the reference array and the 3-dimensional reality while focusing on the reference array., Results: From a consecutive single-surgeon series of 288 transsphenoidal procedures, 47 patients (16.3%) had undergone microscope-based AR to visualize the target and risk structures. AR was smoothly integrated into the surgical workflow. AR accuracy depended on navigation accuracy and microscope calibration. The target registration error in patients with fiducial-based registration was 2.33 ± 1.30 mm. Automatic, user-independent iCT-based registration significantly (P < 0.001) increased AR accuracy (target registration error, 0.83 ± 0.44 mm). Applying low-dose iCT protocols reduced the effective dose caused by iCT registration scanning to within the range of a single chest radiograph (0.041 mSv). No vascular injuries and no aggravation of neurological deficits occurred in the present series. AR greatly facilitated orientation in the reoperations and the patients with anatomical variants, thereby increasing surgeon comfort. Enhanced AR visualizations improved the 3-dimensional perception compared with the standard display of dashed lines by the head-up display of the operating microscope., Conclusions: Microscope-based AR is a reliable tool to increase patient safety in complicated transsphenoidal procedures. Intraoperative imaging-based automatic patient registration is recommended., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: Deep brain stimulation (DBS) is an effective treatment for movement disorders. Stereotactic electrode placement can be guided by intraoperative imaging, which also allows for immediate intraoperative quality control. This article is about implementation and refining a workflow applying intraoperative computed tomography (iCT) for DBS., Methods: Eighteen patients underwent DBS with bilateral implantation of directional electrodes applying a 32-slice movable computed tomography scanner in combination with microelectrode recording., Results: iCT led to a significant decrease in overall procedural time, despite performing multiple scans. In 3 of the initial 5 cases, iCT caused an adjustment of the final electrodes demonstrating the learning curve and the necessity to integrate road mapping for the exchange of microelectrode to final electrode. Implementation of low-dose computed tomography protocols added microelectrode iCT to the refined workflow, resulting in an intraoperative adjustment of a trajectory in 1 patient. Low-dose protocols lowered the total effective dose to 1.15 mSv, that is, a reduction by a factor of 3.5 compared to a standard non-iCT DBS procedure, despite repeated iCTs. Intraoperative lead detection based on final iCT revealed a radial error of 1.04 ± 0.58 mm and a vector error of 2.28 ± 0.97 mm compared to the preoperative planning, adjusted by the findings of microelectrode recording., Conclusions: iCT can be easily integrated into the surgical workflow resulting in an overall efficient time-saving procedure. Repeated intraoperative scanning ensures reliable electrode placement, although low-dose scanning protocols prevent extensive radiation exposure. iCT of microelectrodes is feasible and led to the adjustment of 1 electrode., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: To investigate how frameless navigational techniques can be implemented to support standard frame-based stereotactic procedures., Methods: In 25 patients (18 deep brain stimulation procedures, 3 stereotactic biopsies, and 4 stereoencephalography procedures), 57 trajectories were planned. A navigation reference array was attached to the stereotactic frame for automatic registration applying intraoperative computed tomography., Results: User-independent automatic registration resulted in a low navigation registration error (0.76 ± 0.30 mm). Because the stereotactic scan is performed intraoperatively, it can also be used for automatic navigation registration without additional patient radiation exposure. Low-dose intraoperative computed tomography protocols allowed the effective radiation dose to be reduced to 0.39 mSv (i.e., by a factor of 7.7) compared with standard head protocols without impeding navigational accuracy with a registration error of 0.65 ± 0.05 mm. Additional use of navigation-facilitated surgery, in which entry points and alignments of trajectory paths could be easily checked, provided additional safety. Visualizing the depth of a biopsy needle or electrode during the procedure in relation to target and risk structures greatly enhanced the understanding of the procedure., Conclusions: In a setting with intraoperative imaging, the combination of frameless and frame-based techniques offers new possibilities. Because of the high registration accuracy, the additional navigation provides improved safety and redundancy. Furthermore, the stereotactic procedure is supported by enhanced intuitive intraoperative visualization during the advancement of a biopsy needle or electrode. However, further technical refinements are necessary, such as possibilities to track microelectrodes during the advancement with a microdrive., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Objective: To establish a workflow integrating preoperative 3-dimensional (3D) angiography data and intraoperative real-time vascular information in microscope-based navigation for aneurysm and arteriovenous malformation (AVM) surgery., Methods: In 7 patients (3 with AVMs and 4 with aneurysms), preoperative 3D rotational angiography or computed tomography (CT) or magnetic resonance angiography data were navigated applying a 32-slice movable CT scanner for low-dose registration scanning. The 3D vasculature was segmented and visualized by microscope-based navigation along with navigated intraoperative real-time imaging data from indocyanin green angiography and duplex ultrasonography., Results: Automatic registration applying intraoperative CT resulted in high accuracy (registration error, 0.80 ± 0.79 mm). The effective radiation dose of the registration CT scans (0.28-0.42 mSv) was only approximately one-sixth of a standard diagnostic head CT scan. The 3D vessel architecture could be visualized accurately in the operating microscope heads-up display and on the navigation screens in the same projection as the view angle of the surgeon, both facilitating orientation in 3D space, providing a better understanding of anatomy. In addition, intraoperative real-time modalities could be coregistered with high precision, providing further information during the course of the vascular procedure., Conclusions: Registration CT imaging facilitates integrating preoperative and intraoperative vascular image data with a low registration error and low radiation exposure for the patient, improving the understanding of 3D vascular anatomy during surgery with easier identification of feeding vessels in AVMs, and of the projection and configuration of aneurysms., (Copyright © 2018 Elsevier Inc. All rights reserved.)