Augmented reality in the surgery of cerebral aneurysms: a technical report

[Augmented reality as a method of neuronavigation in microsurgical treatment of cerebrovascular diseases: description of the method and clinical experience]

Augmented reality (AR) is a promising area in microsurgical treatment of cerebrovascular pathologies that can significantly facilitate preoperative planning and intraoperative understanding of anatomy.

OBJECTIVE

To describe AR-assisted neuronavigation in microsurgical treatment of intracranial aneurysms, arteriovenous malformations and cavernomas; to evaluate accuracy and applicability of AR-assisted neuronavigation.

MATERIAL AND METHODS

The study involved 22 patients with cerebral aneurysms, arteriovenous and cavernous malformations. Microsoft Hololens 2 HMD glasses and «Medgital» software for AR navigation were used. Accuracy of registration (TRE and FRE) and time for preoperative preparation were evaluated.

RESULTS. MEAN

TRE when using QR code was 0.6±0.2 cm, when combining through craniometric points - 1.4±0.6 cm. Time for preoperative image processing was 24.7±5.1 minutes, application setup in the operating theatre - 1.6±0.2 minutes. Combination using QR code provided higher accuracy of registration compared to craniometric points. AR-assisted navigation improved visualization and planning of surgeries for aneurysms, arteriovenous malformations, microvascular anastomoses and cavernous angiomas.

CONCLUSION

AR-assisted navigation is an innovative method with specific advantages that can potentially improve microsurgical treatment of cerebrovascular diseases. Further research is needed to confirm these findings and develop AR technology in neurosurgery.

A decade of progress: bringing mixed reality image-guided surgery systems in the operating room

Advancements in mixed reality (MR) have led to innovative approaches in image-guided surgery (IGS). In this paper, we provide a comprehensive analysis of the current state of MR in image-guided procedures across various surgical domains. Using the Data Visualization View (DVV) Taxonomy, we analyze the progress made since a 2013 literature review paper on MR IGS systems. In addition to examining the current surgical domains using MR systems, we explore trends in types of MR hardware used, type of data visualized, visualizations of virtual elements, and interaction methods in use. Our analysis also covers the metrics used to evaluate these systems in the operating room (OR), both qualitative and quantitative assessments, and clinical studies that have demonstrated the potential of MR technologies to enhance surgical workflows and outcomes. We also address current challenges and future directions that would further establish the use of MR in IGS.

Wallenberg Syndrome Secondary to Vertebrobasilar Aneurysm Associated With Subclavian Steal Syndrome

Wallenberg syndrome, also known as lateral medullary syndrome, is a rare condition affecting the vertebrobasilar circulation, causing symptoms such as vertigo, nystagmus, dysarthria, and hemifacial weakness. Typically linked to ischemic strokes, it can also arise from vertebrobasilar aneurysms. In rare cases, subclavian steal syndrome (SSS), involving retrograde flow in the vertebral artery due to subclavian stenosis, complicates the picture, as observed in this case of a 66-year-old woman with both conditions and a vertebrobasilar aneurysm. This study was conducted at the Neurosurgery Department of Centro Médico Nacional 20 de Noviembre, Mexico City. The patient, a 66-year-old woman with hypertension and chronic smoking, presented with vertigo, diplopia, and quadriparesis. Imaging revealed a vertebrobasilar aneurysm and SSS. Despite recommendations for further invasive studies, the patient declined angiography and therapeutic interventions, opting for voluntary discharge without treatment. This case underscores the rare association of Wallenberg syndrome with a vertebrobasilar aneurysm and SSS. Hemodynamic stress from retrograde vertebral artery flow likely contributed to aneurysm formation. Advanced imaging is vital for diagnosis, and while the patient refused treatment, multidisciplinary management, including future innovations such as three-dimensional printing and endovascular techniques, holds promise for improving outcomes in such complex cases.

Augmented Reality in Extratemporal Lobe Epilepsy Surgery

Background: Epilepsy surgery for extratemporal lobe epilepsy (ETLE) is challenging, particularly when MRI findings are non-lesional and seizure patterns are complex. Invasive diagnostic techniques are crucial for accurately identifying the epileptogenic zone and its relationship with surrounding functional tissue. Microscope-based augmented reality (AR) support, combined with navigation, may enhance intraoperative orientation, particularly in cases involving subtle or indistinct lesions, thereby improving patient outcomes and safety (e.g., seizure freedom and preservation of neuronal integrity). Therefore, this study was conducted to prove the clinical advantages of microscope-based AR support in ETLE surgery. Methods: We retrospectively analyzed data from ten patients with pharmacoresistant ETLE who underwent invasive diagnostics with depth and/or subdural grid electrodes, followed by resective surgery. AR support was provided via the head-up displays of the operative microscope, with navigation based on automatic intraoperative computed tomography (iCT)-based registration. The surgical plan included the suspected epileptogenic lesion, electrode positions, and relevant surrounding functional structures, all of which were visualized intraoperatively. Results: Six patients reported complete seizure freedom following surgery (ILAE 1), one patient was seizure-free at the 2-year follow-up, and one patient experienced only auras (ILAE 2). Two patients developed transient neurological deficits that resolved shortly after surgery. Conclusions: Microscope-based AR support enhanced intraoperative orientation in all cases, contributing to improved patient outcomes and safety. It was highly valued by experienced surgeons and as a training tool for less experienced practitioners.

Development and assessment of case-specific physical and augmented reality simulators for intracranial aneurysm clipping

BACKGROUND

Microsurgical clipping is a delicate neurosurgical procedure used to treat complex Unruptured Intracranial Aneurysms (UIAs) whose outcome is dependent on surgeon's experience. Simulations are emerging as excellent complements to standard training, but their adoption is limited by the realism they provide. The aim of this study was to develop and validate a microsurgical clipping simulator platform.

METHODS

Physical and holographic simulators of UIA clipping have been developed. The physical phantom consisted of a 3D printed hard skull and five (n = 5) rapidly interchangeable, perfused and fluorescence compatible 3D printed aneurysm silicone phantoms. The holographic clipping simulation included a real-time finite-element-model of the aneurysm sac, allowing interaction with a virtual clip and its occlusion. Validity, usability, usefulness and applications of the simulators have been assessed through clinical scores for aneurysm occlusion and a questionnaire study involving 14 neurosurgical residents (R) and specialists (S) for both the physical (p) and holographic (h) simulators by scores going from 1 (very poor) to 5 (excellent).

RESULTS

The physical simulator allowed to replicate successfully and accurately the patient-specific anatomy. UIA phantoms were manufactured with an average dimensional deviation from design of 0.096 mm and a dome thickness of 0.41 ± 0.11 mm. The holographic simulation executed at 25-50 fps allowing to gain unique insights on the anatomy and testing of the application of several clips without manufacturing costs. Aneurysm closure in the physical model evaluated by fluorescence simulation and post-operative CT revealed Raymond 1 (full) occlusion respectively in 68.89% and 73.33% of the cases. For both the simulators content validity, construct validity, usability and usefulness have been observed, with the highest scores observed in clip selection usefulness Rp=4.78, Sp=5.00 and Rh=4.00, Sh=5.00 for the printed and holographic simulators.

CONCLUSIONS

Both the physical and the holographic simulators were validated and resulted usable and useful in selecting valid clips and discarding unsuitable ones. Thus, they represent ideal platforms for realistic patient-specific simulation-based training of neurosurgical residents and hold the potential for further applications in preoperative planning.

Microscope-Based Augmented Reality: A New Approach in Intraoperative 3D Visualization in Microvascular Decompression?

Neurovascular compression (NVC) syndromes such as trigeminal neuralgia (TN) are causally treated with microvascular decompression (MVD). Semiautomatic segmentation of high-resolution magnetic resonance imaging (MRI) data and constructive interference in steady state (CISS)/time-of-flight (TOF) sequences are utilized for the three-dimensional (3D) visualization of underlying causative vessels at the root entry zones of the relevant cranial nerves. Augmented reality (AR) of neurovascular structures was introduced especially in the resection of brain tumors or aneurysmatic operations. In this report, the potential feasibility of the implementation of microscope-based AR into the intraoperative microsurgical set-up of MVD was investigated. This article recommends the preoperative evaluation of 3D visualization besides the microscopical view of the surgeon. The implementation of multiple imaging data by AR into the operating microscope may afflict the experienced surgeon's view, which should be examined prospectively.

The Inaugural "Century" of Mixed Reality in Cranial Surgery: Virtual Reality Rehearsal/Augmented Reality Guidance and Its Learning Curve in the First 100-Case, Single-Surgeon Series

BACKGROUND AND OBJECTIVE

Virtual reality (VR) refers to a computer-generated three-dimensional space in which a surgeon can interact with patient-specific anatomic models for surgical planning. Augmented reality (AR) is the technology that places computer-generated objects, including those made in VR, into the surgeon's visual space. Together, VR and AR are called mixed reality (MxR), and it is gaining importance in neurosurgery. MxR is helpful for selecting and creating templates for an optimal surgical approach and identifying key anatomic landmarks intraoperatively. By reporting our experience with the first 100 consecutive cases planned with VR and executed with AR, our objective is to detail the learning curve and encountered obstacles while adopting the new technology.

METHODS

This series includes the first 100 consecutive complex cranial cases of a single surgeon for which MxR was intended for use. Effectiveness of the VR rehearsal and AR guidance was analyzed for four specific contributions: (1) opening size, (2) precise craniotomy placement, (3) guidance toward anatomic landmarks or target, and (4) antitarget avoidance. Seventeen cases in the study cohort were matched with historical non-MxR cases for comparison of outcome parameters. The cases in which MxR failed were plotted over time to determine the nature of the "learning curve."

RESULTS

AR guidance was abandoned in eight operations because of technical problems, but problem-free application of MxR increased between the 44th and 63rd cases. This provides some evidence of proficiency acquisition in between. Comparing the 17 pairs of matched MxR and non-MxR cases, no statistically significant differences exist in the groups regarding blood loss, length of stay nor duration of surgery. Cases where MxR had above-expectation performances are highlighted.

CONCLUSION

MxR is a powerful tool that can help tailor operations to patient-specific anatomy and provide efficient intraoperative guidance without additional time for surgery or hospitalization.

Augmented reality simulation as training model of ventricular puncture: Evidence in the improvement of the quality of punctures

BACKGROUND

Ventricular puncture is a common procedure in neurosurgery and the first that resident must learn. Ongoing education is critical to improving patient outcomes. However, training at the expense of potential risk to patients warrants new and safer training methods for residents.

METHODS

An augmented reality (AR) simulator for the practice of ventricular punctures was designed. It consists of a navigation system with a virtual 3D projection of the anatomy over a 3D-printed patient model. Forty-eight participants from neurosurgery staff performed two free-hand ventricular punctures before and after a training session.

RESULTS

Participants achieved enhanced accuracy in reaching the target at the Monro foramen after practicing with the system. Additional metrics revealed significantly better trajectories after the training.

CONCLUSION

The study confirms the feasibility of AR as a training tool. This motivates future work towards standardising new educative methodologies in neurosurgery.

Application of virtual and mixed reality for 3D visualization in intracranial aneurysm surgery planning: a systematic review

Background

Precise preoperative anatomical visualization and understanding of an intracranial aneurysm (IA) are fundamental for surgical planning and increased intraoperative confidence. Application of virtual reality (VR) and mixed reality (MR), thus three-dimensional (3D) visualization of IAs could be significant in surgical planning. Authors provide an up-to-date overview of VR and MR applied to IA surgery, with specific focus on tailoring of the surgical treatment.

Methods

A systematic analysis of the literature was performed in accordance with the PRISMA guidelines. Pubmed, and Embase were searched to identify studies reporting use of MR and VR 3D visualization in IA surgery during the last 25 years. Type and number of IAs, category of input scan, visualization techniques (screen, glasses or head set), inclusion of haptic feedback, tested population (residents, fellows, attending neurosurgeons), and aim of the study (surgical planning/rehearsal, neurosurgical training, methodological validation) were noted.

Results

Twenty-eight studies were included. Eighteen studies (64.3%) applied VR, and 10 (35.7%) used MR. A positive impact on surgical planning was documented by 19 studies (67.9%): 17 studies (60.7%) chose the tailoring of the surgical approach as primary outcome of the analysis. A more precise anatomical visualization and understanding with VR and MR was endorsed by all included studies (100%).

Conclusion

Application of VR and MR to perioperative 3D visualization of IAs allowed an improved understanding of the patient-specific anatomy and surgical preparation. This review describes a tendency to utilize mostly VR-platforms, with the primary goals of a more accurate anatomical understanding, surgical planning and rehearsal.

Augmented Reality in Neurosurgery: A New Paradigm for Training

Augmented reality (AR) involves the overlay of computer-generated images onto the user's real-world visual field to modify or enhance the user's visual experience. With respect to neurosurgery, AR integrates preoperative and intraoperative imaging data to create an enriched surgical experience that has been shown to improve surgical planning, refine neuronavigation, and reduce operation time. In addition, AR has the potential to serve as a valuable training tool for neurosurgeons in a way that minimizes patient risk while facilitating comprehensive training opportunities. The increased use of AR in neurosurgery over the past decade has led to innovative research endeavors aiming to develop novel, more efficient AR systems while also improving and refining present ones. In this review, we provide a concise overview of AR, detail current and emerging uses of AR in neurosurgery and neurosurgical training, discuss the limitations of AR, and provide future research directions. Following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), 386 articles were initially identified. Two independent reviewers (GH and AC) assessed article eligibility for inclusion, and 31 articles are included in this review. The literature search included original (retrospective and prospective) articles and case reports published in English between 2013 and 2023. AR assistance has shown promise within neuro-oncology, spinal neurosurgery, neurovascular surgery, skull-base surgery, and pediatric neurosurgery. Intraoperative use of AR was found to primarily assist with surgical planning and neuronavigation. Similarly, AR assistance for neurosurgical training focused primarily on surgical planning and neuronavigation. However, studies included in this review utilize small sample sizes and remain largely in the preliminary phase. Thus, future research must be conducted to further refine AR systems before widespread intraoperative and educational use.

Shifted-windows transformers for the detection of cerebral aneurysms in microsurgery

Purpose

Microsurgical Aneurysm Clipping Surgery (MACS) carries a high risk for intraoperative aneurysm rupture. Automated recognition of instances when the aneurysm is exposed in the surgical video would be a valuable reference point for neuronavigation, indicating phase transitioning and more importantly designating moments of high risk for rupture. This article introduces the MACS dataset containing 16 surgical videos with frame-level expert annotations and proposes a learning methodology for surgical scene understanding identifying video frames with the aneurysm present in the operating microscope’s field-of-view.

Methods

Despite the dataset imbalance (80% no presence, 20% presence) and developed without explicit annotations, we demonstrate the applicability of Transformer-based deep learning architectures (MACSSwin-T, vidMACSSwin-T) to detect the aneurysm and classify MACS frames accordingly. We evaluate the proposed models in multiple-fold cross-validation experiments with independent sets and in an unseen set of 15 images against 10 human experts (neurosurgeons).

Results

Average (across folds) accuracy of 80.8% (range 78.5–82.4%) and 87.1% (range 85.1–91.3%) is obtained for the image- and video-level approach, respectively, demonstrating that the models effectively learn the classification task. Qualitative evaluation of the models’ class activation maps shows these to be localized on the aneurysm’s actual location. Depending on the decision threshold, MACSWin-T achieves 66.7–86.7% accuracy in the unseen images, compared to 82% of human raters, with moderate to strong correlation.

Conclusions

Proposed architectures show robust performance and with an adjusted threshold promoting detection of the underrepresented (aneurysm presence) class, comparable to human expert accuracy. Our work represents the first step towards landmark detection in MACS with the aim to inform surgical teams to attend to high-risk moments, taking precautionary measures to avoid rupturing.

Augmented Reality in Stereotactic Neurosurgery: Current Status and Issues

Stereotactic neurosurgery is an established technique, but it has several limitations. In frame-based stereotaxy using a stereotactic frame, frame setting errors may decrease the accuracy of the procedure. Frameless stereotaxy using neuronavigation requires surgeons to shift their view from the surgical field to the navigation display and to advance the needle while assuming a physically uncomfortable position. To overcome these limitations, several researchers have applied augmented reality in stereotactic neurosurgery. Augmented reality enables surgeons to visualize the information regarding the target and preplanned trajectory superimposed over the actual surgical field. In frame-based stereotaxy, a researcher applies tablet computer-based augmented reality to check for the setting errors of the stereotactic frame, thereby improving the safety of the procedure. Several researchers have reported performing frameless stereotaxy guided by head-mounted-display-based augmented reality that enables surgeons to advance the needle at a more natural posture. These studies have shown that augmented reality can address the limitations of stereotactic neurosurgery. Conversely, they have also revealed the limited accuracy of current augmented reality systems for small targets, which indicates that further development of augmented reality systems is needed.

Augmented Reality to Compensate for Navigation Inaccuracies

This study aims to report on the capability of microscope-based augmented reality (AR) to evaluate registration and navigation accuracy with extracranial and intracranial landmarks and to elaborate on its opportunities and obstacles in compensation for navigation inaccuracies. In a consecutive single surgeon series of 293 patients, automatic intraoperative computed tomography-based registration was performed delivering a high initial registration accuracy with a mean target registration error of 0.84 ± 0.36 mm. Navigation accuracy is evaluated by overlaying a maximum intensity projection or pre-segmented object outlines within the recent focal plane onto the in situ patient anatomy and compensated for by translational and/or rotational in-plane transformations. Using bony landmarks (85 cases), there was two cases where a mismatch was seen. Cortical vascular structures (242 cases) showed a mismatch in 43 cases and cortex representations (40 cases) revealed two inaccurate cases. In all cases, with detected misalignment, a successful spatial compensation was performed (mean correction: bone (6.27 ± 7.31 mm), vascular (3.00 ± 1.93 mm, 0.38° ± 1.06°), and cortex (5.31 ± 1.57 mm, 1.75° ± 2.47°)) increasing navigation accuracy. AR support allows for intermediate and straightforward monitoring of accuracy, enables compensation of spatial misalignments, and thereby provides additional safety by increasing overall accuracy.

Effects of a Mixed-Reality Headset on Procedural Outcomes in the Cardiac Catheterization Laboratory

BACKGROUND

Mixed reality head-mounted displays (MR-HMD) are a novel and emerging tool in healthcare. There is a paucity of data on the safety and efficacy of the use of MR-HMD in the cardiac catheterization laboratory (CCL). We sought to analyze and compare fluoroscopy time, procedure time, and complication rates with right heart catheterizations (RHCs) and coronary angiographies (CAs) performed with MR-HMD versus standard LCD medical displays.

METHODS

This is a non-randomized trial that included patients who underwent RHC and CA with MR-HMD between August 2019 and January 2020. Their outcomes were compared to a control group during the same time period. The primary endpoints were procedure time, fluoroscopy time, and dose area product (DAP). The secondary endpoints were contrast volume and intra and postprocedural complications rate.

RESULTS

50 patients were enrolled in the trial, 33 had a RHC done, and 29 had a diagnostic CA performed. They were compared to 232 patients in the control group. The use of MR-HMD was associated with a significantly lower procedure time (20 min (IQR 14-30) vs. 25 min (IQR 18-36), p = 0.038). There were no significant differences in median fluoroscopy time (1.5 min (IQR 0.7-4.9) in the study group vs. 1.3 min (IQR 0.8-3.1), p = 0.84) or median DAP (165.4 mGy·cm² (IQR 13-15,583) in the study group vs. 913 mGy·cm² (IQR 24-6291), p = 0.17). There was no significant increase in intra- or post-procedure complications.

CONCLUSION

MR-HMD use is safe and feasible and may decrease procedure time in the CCL.

A systematic comparison of the accuracy of monocular RGB tracking and LiDAR for neuronavigation

With the advent of augmented reality (AR), the use of AR-guided systems in the field of medicine has gained traction. However, the wide-scale adaptation of these systems requires highly accurate and reliable tracking. In this work, the tracking accuracy of two technology platforms, LiDAR and Vuforia, are developed and rigorously tested for a catheter placement neurological procedure. Several experiments (900) are performed for each technology across various combinations of catheter lengths and insertion trajectories. This analysis shows that the LiDAR platform outperformed Vuforia; which is the state-of-the-art in monocular RGB tracking solutions. LiDAR had 75% less radial distance error and 26% less angle deviation error. Results provide key insights into the value and utility of LiDAR-based tracking in AR guidance systems.

Segmentation techniques of brain arteriovenous malformations for 3D visualization: a systematic review

BACKGROUND

Visualization, analysis and characterization of the angioarchitecture of a brain arteriovenous malformation (bAVM) present crucial steps for understanding and management of these complex lesions. Three-dimensional (3D) segmentation and 3D visualization of bAVMs play hereby a significant role. We performed a systematic review regarding currently available 3D segmentation and visualization techniques for bAVMs.

METHODS

PubMed, Embase and Google Scholar were searched to identify studies reporting 3D segmentation techniques applied to bAVM characterization. Category of input scan, segmentation (automatic, semiautomatic, manual), time needed for segmentation and 3D visualization techniques were noted.

RESULTS

Thirty-three studies were included. Thirteen (39%) used MRI as baseline imaging modality, 9 used DSA (27%), and 7 used CT (21%). Segmentation through automatic algorithms was used in 20 (61%), semiautomatic segmentation in 6 (18%), and manual segmentation in 7 (21%) studies. Median automatic segmentation time was 10 min (IQR 33), semiautomatic 25 min (IQR 73). Manual segmentation time was reported in only one study, with the mean of 5-10 min. Thirty-two (97%) studies used screens to visualize the 3D segmentations outcomes and 1 (3%) study utilized a heads-up display (HUD). Integration with mixed reality was used in 4 studies (12%).

CONCLUSIONS

A golden standard for 3D visualization of bAVMs does not exist. This review describes a tendency over time to base segmentation on algorithms trained with machine learning. Unsupervised fuzzy-based algorithms thereby stand out as potential preferred strategy. Continued efforts will be necessary to improve algorithms, integrate complete hemodynamic assessment and find innovative tools for tridimensional visualization.

Evolution and Revolution of Imaging Technologies in Neurosurgery

We understand only a small fraction of the events happening in our brains; therefore, despite all the progress made thus far, a whole array of questions remains. Nonetheless, neurosurgeons invented new tools to circumvent the challenges that had plagued their predecessors. With the manufacturing boom of the 20th century, technological innovations blossomed enabling the neuroscientific community to study and operate upon the living brain in finer detail and with greater precision while avoiding harm to the nervous system. The purpose of this chronological review is to 1) raise awareness among future neurosurgeons about the latest advances in the field, 2) become familiar with innovations such as augmented reality (AR) that should be included in education given their ready applicability in surgical training, and 3) be comfortable with customizing these technologies to real-life cases like in the case of mixed reality.

Use of Neuronavigation and Augmented Reality in Transsphenoidal Pituitary Adenoma Surgery

The aim of this study was to report on the clinical experience with microscope-based augmented reality (AR) in transsphenoidal surgery compared to the classical microscope-based approach. AR support was established using the head-up displays of the operating microscope, with navigation based on fiducial-/surface- or automatic intraoperative computed tomography (iCT)-based registration. In a consecutive single surgeon series of 165 transsphenoidal procedures, 81 patients underwent surgery without AR support and 84 patients underwent surgery with AR support. AR was integrated straightforwardly within the workflow. ICT-based registration increased AR accuracy significantly (target registration error, TRE, 0.76 ± 0.33 mm) compared to the landmark-based approach (TRE 1.85 ± 1.02 mm). The application of low-dose iCT protocols led to a significant reduction in applied effective dosage being comparable to a single chest radiograph. No major vascular or neurological complications occurred. No difference in surgical time was seen, time to set-up patient registration prolonged intraoperative preparation time on average by twelve minutes (32.33 ± 13.35 vs. 44.13 ± 13.67 min), but seems justifiable by the fact that AR greatly and reliably facilitated surgical orientation and increased surgeon comfort and patient safety, not only in patients who had previous transsphenoidal surgery but also in cases with anatomical variants. Automatic intraoperative imaging-based registration is recommended.

Visualization, navigation, augmentation. The ever-changing perspective of the neurosurgeon

Introduction

The evolution of neurosurgery coincides with the evolution of visualization and navigation. Augmented reality technologies, with their ability to bring digital information into the real environment, have the potential to provide a new, revolutionary perspective to the neurosurgeon.

Research question

To provide an overview on the historical and technical aspects of visualization and navigation in neurosurgery, and to provide a systematic review on augmented reality (AR) applications in neurosurgery.

Material and methods

We provided an overview on the main historical milestones and technical features of visualization and navigation tools in neurosurgery. We systematically searched PubMed and Scopus databases for AR applications in neurosurgery and specifically discussed their relationship with current visualization and navigation systems, as well as main limitations.

Results

The evolution of visualization in neurosurgery is embodied by four magnification systems: surgical loupes, endoscope, surgical microscope and more recently the exoscope, each presenting independent features in terms of magnification capabilities, eye-hand coordination and the possibility to implement additional functions. In regard to navigation, two independent systems have been developed: the frame-based and the frame-less systems. The most frequent application setting for AR is brain surgery (71.6%), specifically neuro-oncology (36.2%) and microscope-based (29.2%), even though in the majority of cases AR applications presented their own visualization supports (66%).

Discussion and conclusions

The evolution of visualization and navigation in neurosurgery allowed for the development of more precise instruments; the development and clinical validation of AR applications, have the potential to be the next breakthrough, making surgeries safer, as well as improving surgical experience and reducing costs.

Review and Future/Potential Application of Mixed Reality Technology in Orthopaedic Oncology

In orthopaedic oncology, surgical planning and intraoperative execution errors may result in positive tumor resection margins that increase the risk of local recurrence and adversely affect patients’ survival. Computer navigation and 3D-printed resection guides have been reported to address surgical inaccuracy by replicating the surgical plans in complex cases. However, limitations include surgeons’ attention shift from the operative field to view the navigation monitor and expensive navigation facilities in computer navigation surgery. Practical concerns are lacking real-time visual feedback of preoperative images and the lead-time in manufacturing 3D-printed objects. Mixed Reality (MR) is a technology of merging real and virtual worlds to produce new environments with enhanced visualizations, where physical and digital objects coexist and allow users to interact with both in real-time. The unique MR features of enhanced medical images visualization and interaction with holograms allow surgeons real-time and on-demand medical information and remote assistance in their immediate working environment. Early application of MR technology has been reported in surgical procedures. Its role is unclear in orthopaedic oncology. This review aims to provide orthopaedic tumor surgeons with up-to-date knowledge of the emerging MR technology. The paper presents its essential features and clinical workflow, reviews the current literature and potential clinical applications, and discusses the limitations and future development in orthopaedic oncology. The emerging MR technology adds a new dimension to digital assistive tools with a more accessible and less costly alternative in orthopaedic oncology. The MR head-mounted display and hand-free control may achieve clinical point-of-care inside or outside the operating room and improve service efficiency and patient safety. However, lacking an accurate hologram-to-patient matching, an MR platform dedicated to orthopaedic oncology, and clinical results may hinder its wide adoption. Industry-academic partnerships are essential to advance the technology with its clinical role determined through future clinical studies.

Point your SmartPhone at the code above. If you have a QR code reader the video abstract will appear. Or use:

https://youtu.be/t4hl_Anh_kM

Current status of augmented reality in cerebrovascular surgery: a systematic review

Augmented reality (AR) is an adjuvant tool in neuronavigation to improve spatial and anatomic understanding. The present review aims to describe the current status of intraoperative AR for the treatment of cerebrovascular pathology. A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The following databases were searched: PubMed, Science Direct, Web of Science, and EMBASE up to December, 2020. The search strategy consisted of "augmented reality," "AR," "cerebrovascular," "navigation," "neurovascular," "neurosurgery," and "endovascular" in both AND and OR combinations. Studies included were original research articles with intraoperative application. The manuscripts were thoroughly examined for study design, outcomes, and results. Sixteen studies were identified describing the use of intraoperative AR in the treatment of cerebrovascular pathology. A total of 172 patients were treated for 190 cerebrovascular lesions using intraoperative AR. The most common treated pathology was intracranial aneurysms. Most studies were cases and there was only a case-control study. A head-up display system in the microscope was the most common AR display. AR was found to be useful for tailoring the craniotomy, dura opening, and proper identification of donor and recipient vessels in vascular bypass. Most AR systems were unable to account for tissue deformation. This systematic review suggests that intraoperative AR is becoming a promising and feasible adjunct in the treatment of cerebrovascular pathology. It has been found to be a useful tool in the preoperative planning and intraoperative guidance. However, its clinical benefits remain to be seen.

Augmented reality visualization in brain lesions: a prospective randomized controlled evaluation of its potential and current limitations in navigated microneurosurgery

Background

Augmented reality (AR) has the potential to support complex neurosurgical interventions by including visual information seamlessly. This study examines intraoperative visualization parameters and clinical impact of AR in brain tumor surgery.

Methods

Fifty-five intracranial lesions, operated either with AR-navigated microscope (n = 39) or conventional neuronavigation (n = 16) after randomization, have been included prospectively. Surgical resection time, duration/type/mode of AR, displayed objects (n, type), pointer-based navigation checks (n), usability of control, quality indicators, and overall surgical usefulness of AR have been assessed.

Results

AR display has been used in 44.4% of resection time. Predominant AR type was navigation view (75.7%), followed by target volumes (20.1%). Predominant AR mode was picture-in-picture (PiP) (72.5%), followed by 23.3% overlay display. In 43.6% of cases, vision of important anatomical structures has been partially or entirely blocked by AR information. A total of 7.7% of cases used MRI navigation only, 30.8% used one, 23.1% used two, and 38.5% used three or more object segmentations in AR navigation. A total of 66.7% of surgeons found AR visualization helpful in the individual surgical case. AR depth information and accuracy have been rated acceptable (median 3.0 vs. median 5.0 in conventional neuronavigation). The mean utilization of the navigation pointer was 2.6 × /resection hour (AR) vs. 9.7 × /resection hour (neuronavigation); navigation effort was significantly reduced in AR (P < 0.001).

Conclusions

The main benefit of HUD-based AR visualization in brain tumor surgery is the integrated continuous display allowing for pointer-less navigation. Navigation view (PiP) provides the highest usability while blocking the operative field less frequently. Visualization quality will benefit from improvements in registration accuracy and depth impression.

German clinical trials registration number.

DRKS00016955.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00701-021-05045-1.

Application of Augmented Reality in Percutaneous Procedures-Rhizotomy of the Gasserian Ganglion

BACKGROUND

Percutaneous rhizotomy of the Gasserian ganglion for trigeminal neuralgia is an effective therapeutic procedure. Yet, landmark-guided cannulation of the foramen ovale is manually challenging and difficult to learn.

OBJECTIVE

To overcome these limitations, we assessed the feasibility and accuracy of an augmented reality (AR)-guided puncture of the foramen ovale.

METHODS

A head phantom with soft tissue structures of the facial area was built. A three-dimensional (3D)-dataset of the phantom was generated using a stereotactic planning workstation. An optimal trajectory to the foramen ovale was created and then transferred to an AR headset. A total of 2 neurosurgeons and 2 neuroradiologists independently performed 8 AR-guided and 8 landmark-guided cannulations of the foramen ovale, respectively. For each AR-guided cannulation, the hologram was manually aligned with the phantom. Accuracy of the cannulation was evaluated using the Euclidean distance to the target point as well as the lateral deviation of the achieved trajectory from the planned trajectory at target point level.

RESULTS

With the help of AR guidance, a successful cannulation of the foramen ovale was achieved in 90.6% compared to the purely landmark-based method with 18.8%. Euclidean distance and lateral deviation were significantly lower with AR guidance than landmark guidance (P < .01).

CONCLUSION

AR greatly improved accuracy of simulated percutaneous rhizotomy of the Gasserian ganglion.

Computer-assisted surgery in medical and dental applications

INTRODUCTION

Computer-assisted surgery (CAS) is a broad surgical methodology that utilizes computer technology to both plan and execute surgical intervention. CAS is widespread in both medicine and dentistry as it allows for minimally invasive and precise surgical procedures. Key innovations in volumetric imaging, virtual surgical planning software, instrument tracking, and robotics have assisted in facilitating the transfer of surgical plans to precise execution of surgical procedures. CAS has long been used in certain medical specialties including neurosurgery, cardiology, orthopedic surgery, otolaryngology, and interventional radiology, and has since expanded to oral and maxillofacial application, particularly for computer-assisted implant surgery.

AREAS COVERED

This review provides an updated overview of the most current research for CAS in medicine and dentistry, with a focus on neurosurgery and dental implant surgery. The MEDLINE electronic database was searched and relevant original and review articles from 2005 to 2020 were included.

EXPERT OPINION

Recent literature suggests that CAS performs favorably in both neurosurgical and dental implant applications. Computer-guided surgical navigation is well entrenched as standard of care in neurosurgery. Whereas static computer-assisted implant surgery has become established in dentistry, dynamic computer-assisted navigation is newly poised to trend upward in dental implant surgery.

Applications of augmented reality in the neurosurgical operating room: A systematic review of the literature

Advancements in imaging techniques are key forces of progress in neurosurgery. The importance of accurate visualization of intraoperative anatomy cannot be overemphasized and is commonly delivered through traditional neuronavigation. Augmented Reality (AR) technology has been tested and applied widely in various neurosurgical subspecialties in intraoperative, clinical use and shows promise for the future. This systematic review of the literature explores the ways in which AR technology has been successfully brought into the operating room (OR) and incorporated into clinical practice. A comprehensive literature search was performed in the following databases from inception-April 2020: Ovid MEDLINE, Ovid EMBASE, and The Cochrane Library. Studies retrieved were then screened for eligibility against predefined inclusion/exclusion criteria. A total of 54 articles were included in this systematic review. The studies were sub- grouped into brain and spine subspecialties and analyzed for their incorporation of AR in the neurosurgical clinical setting. AR technology has the potential to greatly enhance intraoperative visualization and guidance in neurosurgery beyond the traditional neuronavigation systems. However, there are several key challenges to scaling the use of this technology and bringing it into standard operative practice including accurate and efficient brain segmentation of magnetic resonance imaging (MRI) scans, accounting for brain shift, reducing coregistration errors, and improving the AR device hardware. There is also an exciting potential for future work combining AR with multimodal imaging techniques and artificial intelligence to further enhance its impact in neurosurgery.

Augmented reality in the operating room: a clinical feasibility study

Background

Augmented Reality (AR) is a rapidly emerging technology finding growing acceptance and application in different fields of surgery. Various studies have been performed evaluating the precision and accuracy of AR guided navigation. This study investigates the feasibility of a commercially available AR head mounted device during orthopedic surgery.

Methods

Thirteen orthopedic surgeons from a Swiss university clinic performed 25 orthopedic surgical procedures wearing a holographic AR headset (HoloLens, Microsoft, Redmond, WA, USA) providing complementary three-dimensional, patient specific anatomic information. The surgeon’s experience of using the device during surgery was recorded using a standardized 58-item questionnaire grading different aspects on a 100-point scale with anchor statements.

Results

Surgeons were generally satisfied with image quality (85 ± 17 points) and accuracy of the virtual objects (84 ± 19 point). Wearing the AR device was rated as fairly comfortable (79 ± 13 points). Functionality of voice commands (68 ± 20 points) and gestures (66 ± 20 points) provided less favorable results. The greatest potential in the use of the AR device was found for surgical correction of deformities (87 ± 15 points). Overall, surgeons were satisfied with the application of this novel technology (78 ± 20 points) and future access to it was demanded (75 ± 22 points).

Conclusion

AR is a rapidly evolving technology with large potential in different surgical settings, offering the opportunity to provide a compact, low cost alternative requiring a minimum of infrastructure compared to conventional navigation systems. While surgeons where generally satisfied with image quality of the here tested head mounted AR device, some technical and ergonomic shortcomings were pointed out. This study serves as a proof of concept for the use of an AR head mounted device in a real-world sterile setting in orthopedic surgery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04339-w.

Neuronavigation-assisted bedside placement of bolt external ventricular drains in the intensive care setting: a technical note

BACKGROUND

The insertion of bolt external ventricular drains (EVD) on the intensive care unit (ICU) has enabled rapid cranial cerebrospinal fluid (CSF) diversion. However, bolt EVDs tend to be perceived as a more challenging technique, particularly when dealing with small ventricles or when there is midline shift distorting the ventricular morphology. Furthermore, if neuronavigation guidance is felt to be necessary, this usually assumes a transfer to an operating theatre. In this technical note, we describe the use of electromagnetic neuronavigation for bolt EVD insertion on the ICU and assess the protocol's feasibility and accuracy.

METHODS

Case series of neuronavigation-assisted bolt EVD insertion in ICU setting, using Medtronic Flat Emitter for StealthStation EM.

RESULTS

Neuronavigation-guided bolt EVDs were placed at the bedside in n = 5 patients on ICU. Their widest frontal ventricular horn diameter in the coronal plane ranged from 11 to 20 mm. No procedural complications were encountered. Post-procedural CT confirmed the optimal placement of the EVDs.

CONCLUSIONS

Electromagnetic neuronavigation is feasible at the ICU bedside and can assist the insertion of bolt EVDs in this setting. The preference for a bolt EVD to be inserted in ICU-as is standard practice at this unit-should not prohibit patients from benefitting from image guidance if required.

Augmented Reality in Medical Practice: From Spine Surgery to Remote Assistance

Background: While performing surgeries in the OR, surgeons and assistants often need to access several information regarding surgical planning and/or procedures related to the surgery itself, or the accessory equipment to perform certain operations. The accessibility of this information often relies on the physical presence of technical and medical specialists in the OR, which is increasingly difficult due to the number of limitations imposed by the COVID emergency to avoid overcrowded environments or external personnel. Here, we analyze several scenarios where we equipped OR personnel with augmented reality (AR) glasses, allowing a remote specialist to guide OR operations through voice and ad-hoc visuals, superimposed to the field of view of the operator wearing them.

Methods: This study is a preliminary case series of prospective collected data about the use of AR-assistance in spine surgery from January to July 2020. The technology has been used on a cohort of 12 patients affected by degenerative lumbar spine disease with lumbar sciatica co-morbidities. Surgeons and OR specialists were equipped with AR devices, customized with P2P videoconference commercial apps, or customized holographic apps. The devices were tested during surgeries for lumbar arthrodesis in a multicenter experience involving author's Institutions.

Findings: A total number of 12 lumbar arthrodesis have been performed while using the described AR technology, with application spanning from telementoring (3), teaching (2), surgical planning superimposition and interaction with the hologram using a custom application for Microsoft hololens (1). Surgeons wearing the AR goggles reported a positive feedback as for the ergonomy, wearability and comfort during the procedure; being able to visualize a 3D reconstruction during surgery was perceived as a straightforward benefit, allowing to speed-up procedures, thus limiting post-operational complications. The possibility of remotely interacting with a specialist on the glasses was a potent added value during COVID emergency, due to limited access of non-resident personnel in the OR.

Interpretation: By allowing surgeons to overlay digital medical content on actual surroundings, augmented reality surgery can be exploited easily in multiple scenarios by adapting commercially available or custom-made apps to several use cases. The possibility to observe directly the operatory theater through the eyes of the surgeon might be a game-changer, giving the chance to unexperienced surgeons to be virtually at the site of the operation, or allowing a remote experienced operator to guide wisely the unexperienced surgeon during a procedure.

Augmented Reality Navigated Sacral-Alar-Iliac Screw Insertion

BACKGROUND

Sacral-alar-iliac (SAI) screws are increasingly used for lumbo-pelvic fixation procedures. Insertion of SAI screws is technically challenging, and surgeons often rely on costly and time-consuming navigation systems. We investigated the accuracy and precision of an augmented reality (AR)-based and commercially available head-mounted device requiring minimal infrastructure.

METHODS

A pelvic sawbone model served to drill pilot holes of 80 SAI screw trajectories by 2 surgeons, randomly either freehand (FH) without any kind of navigation or with AR navigation. The number of primary pilot hole perforations, simulated screw perforation, minimal axis/outer cortical wall distance, true sagittal cranio-caudal inclination angle (tSCCIA), true axial medio-lateral angle, and maximal screw length (MSL) were measured and compared to predefined optimal values.

RESULTS

In total, 1/40 (2.5%) of AR-navigated screw hole trajectories showed a perforation before passing the inferior gluteal line compared to 24/40 (60%) of FH screw hole trajectories (P < .05). The differences between FH- and AR-guided holes compared to optimal values were significant for tSCCIA with -10.8° ± 11.77° and MSL -65.29 ± 15 mm vs 55.04 ± 6.76 mm (P = .001).

CONCLUSIONS

In this study, the additional anatomical information provided by the AR headset and the superimposed operative plan improved the precision of drilling pilot holes for SAI screws in a laboratory setting compared to the conventional FH technique. Further technical development and validation studies are currently being performed to investigate potential clinical benefits of the AR-based navigation approach described here.

LEVEL OF EVIDENCE

4.

Comprehensive review of surgical microscopes: technology development and medical applications

SIGNIFICANCE

Surgical microscopes provide adjustable magnification, bright illumination, and clear visualization of the surgical field and have been increasingly used in operating rooms. State-of-the-art surgical microscopes are integrated with various imaging modalities, such as optical coherence tomography (OCT), fluorescence imaging, and augmented reality (AR) for image-guided surgery.

AIM

This comprehensive review is based on the literature of over 500 papers that cover the technology development and applications of surgical microscopy over the past century. The aim of this review is threefold: (i) providing a comprehensive technical overview of surgical microscopes, (ii) providing critical references for microscope selection and system development, and (iii) providing an overview of various medical applications.

APPROACH

More than 500 references were collected and reviewed. A timeline of important milestones during the evolution of surgical microscope is provided in this study. An in-depth technical overview of the optical system, mechanical system, illumination, visualization, and integration with advanced imaging modalities is provided. Various medical applications of surgical microscopes in neurosurgery and spine surgery, ophthalmic surgery, ear-nose-throat (ENT) surgery, endodontics, and plastic and reconstructive surgery are described.

RESULTS

Surgical microscopy has been significantly advanced in the technical aspects of high-end optics, bright and shadow-free illumination, stable and flexible mechanical design, and versatile visualization. New imaging modalities, such as hyperspectral imaging, OCT, fluorescence imaging, photoacoustic microscopy, and laser speckle contrast imaging, are being integrated with surgical microscopes. Advanced visualization and AR are being added to surgical microscopes as new features that are changing clinical practices in the operating room.

CONCLUSIONS

The combination of new imaging technologies and surgical microscopy will enable surgeons to perform challenging procedures and improve surgical outcomes. With advanced visualization and improved ergonomics, the surgical microscope has become a powerful tool in neurosurgery, spinal, ENT, ophthalmic, plastic and reconstructive surgeries.

[Navigation in vascular neurosurgery]

Literature review is devoted to the role of frameless neuronavigation in surgery of distal aneurysms, cavernomas, arteriovenous malformations, Kimmerle's anomaly and revascularization surgeries. Visualization methods used in preoperative preparation of patients with vascular lesions compatible with frameless neuronavigation and the methods of intraoperative visualization as an addition to navigation are described.

Augmented Reality in Superficial Temporal Artery to Middle Cerebral Artery Bypass Surgery: Technical Note

BACKGROUND

Augmented reality (AR) applied to surgery refers to the virtual superimposition of computer-generated anatomical information on the surgical field. AR assistance in extracranial-intracranial (EC-IC) bypass revascularization surgery has been reported to be a helpful technical adjunct.

OBJECTIVE

To describe our experience of using AR in superficial temporal artery to middle cerebral artery (STA-MCA) bypass surgery with the additional implementation of new technical processes to improve the safety and efficacy of the procedure.

METHODS

Data sets from preoperative imaging were loaded and fused in a single 3-dimensional matrix using the neuronavigation system. Anatomical structures of interest (the STA, a selected M4 branch of the MCA, the middle meningeal artery [MMA], and the primary motor cortex [PMC]) were segmented. After the registration of the patient and the operating microscope, the structures of interest were projected into the eyepiece of the microscope and superimposed onto the patient's head, creating the AR surgical field.

RESULTS

AR was shown to be useful in patients undergoing EC-IC bypass revascularization, mostly during the following 4 surgical steps: (1) microsurgical dissection of the donor vessel (STA); (2) tailoring the craniotomy above the recipient vessel (M4 branch of the MCA); (3) tailoring the craniotomy to spare the MMA; and (4) tailoring the craniotomy and the anastomosis to spare the PMC.

CONCLUSION

AR assistance in EC-IC bypass revascularization is a versatile technical adjunct for helping surgeons to ensure the safety and efficacy of the procedure.

Amended Intraoperative Neuronavigation: Three-Dimensional Vascular Roadmapping with Selective Rotational Digital Subtraction Angiography

BACKGROUND

Accuracy of intraoperative cerebrovascular neuronavigation is difficult to maintain because of the ongoing need for brain shift correction. By including 3-dimensional rotational intraoperative digital subtraction angiography (3D-iDSA), the intraoperative cerebrovascular neuronavigation can be updated and upgraded throughout the microneurosurgical procedure. The aim of this technical note is to demonstrate the feasibility and advantage of updating and upgrading the accuracy of targeted cerebrovascular neuronavigation with an intraoperative 3D-DSA dataset.

METHODS

A preoperative diagnostic selective 3D-DSA was registered with the neuronavigation software, followed by the automated segmentation of the vascular object of interest (an aneurysm in this case). After acquiring additional 3D-iDSA volumes, these steps were repeated, thereby updating the cerebrovascular roadmap and neuronavigation accuracy (i.e., brain shift correction).

RESULTS

This technique was applied successfully in a patient who underwent elective microneurosurgical clipping of a right-sided middle cerebral artery (MCA) bifurcation aneurysm in a hybrid neurosurgical operating setting. After clipping of the MCA aneurysm, a selective 3D iDSA was performed that was then used to update the projection and accuracy of the initial 3D neurovascular object of interest (i.e., the aneurysm). In this revised rotational view, the projection refined the target segments of the clipped MCA aneurysm, the accuracy of clipping, and brain shift correction.

CONCLUSIONS

3D-iDSA vascular segmentations can update und upgrade the intraoperative neurovascular roadmap by thereby enhancing accuracy of cerebrovascular neuronavigation, as well as correcting brain shift. This technique is feasible within the hybrid operation room. Evaluation in larger series is required to support these findings.

Navigation-Linked Heads-Up Display in Intracranial Surgery: Early Experience

BACKGROUND

The use of intraoperative navigation during microscope cases can be limited when attention needs to be divided between the operative field and the navigation screens. Heads-up display (HUD), also referred to as augmented reality, permits visualization of navigation information during surgery workflow.

OBJECTIVE

To detail our initial experience with HUD.

METHODS

We retrospectively reviewed patients who underwent HUD-assisted surgery from April 2016 through April 2017. All lesions were assessed for accuracy and those from the latter half of the study were assessed for utility.

RESULTS

Seventy-nine patients with 84 pathologies were included. Pathologies included aneurysms (14), arteriovenous malformations (6), cavernous malformations (5), intracranial stenosis (3), meningiomas (27), metastasis (4), craniopharygniomas (4), gliomas (4), schwannomas (3), epidermoid/dermoids (3), pituitary adenomas (2) hemangioblastoma (2), choroid plexus papilloma (1), lymphoma (1), osteoblastoma (1), clival chordoma (1), cerebrospinal fluid leak (1), abscess (1), and a cerebellopontine angle Teflon granuloma (1). Fifty-nine lesions were deep and 25 were superficial. Structures identified included the lesion (81), vessels (48), and nerves/brain tissue (31). Accuracy was deemed excellent (71.4%), good (20.2%), or poor (8.3%). Deep lesions were less likely to have excellent accuracy (P = .029). HUD was used during bed/head positioning (50.0%), skin incision (17.3%), craniotomy (23.1%), dural opening (26.9%), corticectomy (13.5%), arachnoid opening (36.5%), and intracranial drilling (13.5%). HUD was deactivated at some point during the surgery in 59.6% of cases. There were no complications related to HUD use.

CONCLUSION

HUD can be safely used for a wide variety of vascular and oncologic intracranial pathologies and can be utilized during multiple stages of surgery.

Technical note: the use of frameless stereotactic guidance in the treatment of peripheral intracranial aneurysms

Frameless stereotactic guidance (FSG) has previously been reported to have advantages over intraoperative computed tomography (CT) and frame-based imaging guidance methods in the targeting of intracranial lesions. We report our experience using FSG to minimize brain dissection during microsurgical repair of peripheral aneurysms. We used FSG as a surgical adjunct in the management of 91 peripheral aneurysms. It was used to localise and avoid larger bridging veins, enabling us to minimise unnecessary brain dissection by coming directly down on the aneurysm dome in unruptured lesions or targeting the parent artery just proximal to the aneurysm in ruptured cases. We treated 72 aneurysms located on the distal ACA (79%), 7 on the PCA (7.7%), 6 on the MCA distal to the MCA bifurcation (6.6%), and 6 on the SCA (6.6%). There were no complications related to FSG use. However, we noted a tendency to create an overly limited corridor to the aneurysm, which did not allow sufficient proximal or distal control of the parent artery. In these cases, we had to widen our exposure by further opening the interhemispheric fissure to obtain more proximal control once the aneurysm was reached. Subsequently, we learned to avoid this problem by creating a slightly wider corridor during the initial exposure. Using FSG as a surgical adjunct for peripheral intracranial aneurysms allowed us to safely limit craniotomy size and brain dissection while more confidently exposing these unusually situated lesions, facilitating aneurysm clipping in our series.

Application of Augmented Reality to Stereotactic Biopsy

Both frame-based stereotaxy and frameless stereotaxy are established surgical procedures. However, they each have their respective disadvantages when used in the biopsy of a deep-seated lesion. To overcome the drawbacks associated with these procedures, we evaluated the feasibility of applying augmented reality (AR) to stereotactic biopsy. We applied our trans-visible navigator (TVN) to frame-based stereotactic biopsy in five cases of deep-seated lesions. This navigation system uses the AR concept, allowing surgeons to view three-dimensional virtual models of anatomical structures superimposed over the surgical field on a tablet personal computer. Using TVN, we could easily confirm a clear trajectory avoiding the important structures as well as the target point’s location in the lesion. Use of the stereotactic apparatus allowed the surgeon to easily advance the biopsy probe to the target point. Consequently, a satisfactory histopathological diagnosis without complication was achieved in all cases. In conclusion, applying AR to stereotactic biopsy is feasible and may improve the safety of the procedure.

Correlating Clinical Risk Factors and Histological Features in Ruptured and Unruptured Human Intracranial Aneurysms: The Swiss AneuX Study

Pathogenesis of intracranial aneurysm is complex and the precise biomechanical processes leading to their rupture are uncertain. The goal of our study was to characterize the aneurysmal wall histologically and to correlate histological characteristics with clinical and radiological factors used to estimate the risk of rupture. A new biobank of aneurysm domes resected at the Geneva University Hospitals (Switzerland) was used. Histological analysis revealed that unruptured aneurysms have a higher smooth muscle cell (SMC) content and a lower macrophage content than ruptured domes. These differences were associated with more collagen in unruptured samples, whereas the elastin content was not affected. Collagen content and type distribution were different between thick and thin walls of unruptured aneurysms. Classification of aneurysm domes based on histological characteristics showed that unruptured samples present organized wall rich in endothelial and SMCs compared with ruptured samples. Finally, aneurysm wall composition was altered in unruptured domes of patients presenting specific clinical factors used to predict rupture such as large dome diameter, dome irregularities, and smoking. Our study shows that the wall of aneurysm suspected to be at risk for rupture undergoes structural alterations relatively well associated with clinical and radiological factors currently used to predict this risk.

Application of second-generation Shikani optical stylet in critically ill patients undergoing cerebral aneurysm embolization

OBJECTIVE

This study was performed to compare the clinical value of the second-generation Shikani optical stylet with that of the Macintosh laryngoscope for tracheal intubation of patients undergoing cerebral aneurysm embolization.

METHODS

Thirty-six patients who underwent cerebral aneurysm embolization were included. The intubation time, intubation success rate, blood oxygen saturation, heart rate, systolic blood pressure (SBP), and diastolic blood pressure (DBP) were measured. Adverse reactions during tracheal intubation and the local tissue injury rate were recorded. Comparisons between the groups were performed with one-way analysis of variance.

RESULTS

The heart rate, SBP, and DBP upon tracheal intubation and at 1 and 3 minutes were significantly higher in the Macintosh laryngoscope group than in the Shikani optical stylet group. The time to completion of tracheal intubation was significantly shorter and the tissue injury rate was significantly lower in the Shikani optimal stylet group than in the Macintosh laryngoscope group.

CONCLUSIONS

The second-generation Shikani optical stylet is a simple, safe, and reliable tool for tracheal intubation in critically ill patients undergoing cerebral aneurysm embolization.

Gesture-based registration correction using a mobile augmented reality image-guided neurosurgery system

In image-guided neurosurgery, a registration between the patient and their pre-operative images and the tracking of surgical tools enables GPS-like guidance to the surgeon. However, factors such as brainshift, image distortion, and registration error cause the patient-to-image alignment accuracy to degrade throughout the surgical procedure no longer providing accurate guidance. The authors present a gesture-based method for manual registration correction to extend the usage of augmented reality (AR) neuronavigation systems. The authors' method, which makes use of the touchscreen capabilities of a tablet on which the AR navigation view is presented, enables surgeons to compensate for the effects of brainshift, misregistration, or tracking errors. They tested their system in a laboratory user study with ten subjects and found that they were able to achieve a median registration RMS error of 3.51 mm on landmarks around the craniotomy of interest. This is comparable to the level of accuracy attainable with previously proposed methods and currently available commercial systems while being simpler and quicker to use. The method could enable surgeons to quickly and easily compensate for most of the observed shift. Further advantages of their method include its ease of use, its small impact on the surgical workflow and its small-time requirement.

Augmented reality in dentistry: a current perspective

Augmentation reality technology offers virtual information in addition to that of the real environment and thus opens new possibilities in various fields. The medical applications of augmentation reality are generally concentrated on surgery types, including neurosurgery, laparoscopic surgery and plastic surgery. Augmentation reality technology is also widely used in medical education and training. In dentistry, oral and maxillofacial surgery is the primary area of use, where dental implant placement and orthognathic surgery are the most frequent applications. Recent technological advancements are enabling new applications of restorative dentistry, orthodontics and endodontics. This review briefly summarizes the history, definitions, features, and components of augmented reality technology and discusses its applications and future perspectives in dentistry.

Augmented Reality Visualization-guided Microscopic Spine Surgery: Transvertebral Anterior Cervical Foraminotomy and Posterior Foraminotomy

Objective:

We describe intraoperative augmented reality (AR) imaging to obtain a microscopic view in spine keyhole surgery.

Background:

Minimally invasive keyhole surgery has been developed even for spine surgery, including transvertebral anterior cervical foraminotomy and posterior cervical laminoforaminotomy. These methods are complex and require a skillful technique. Therefore, inexperienced surgeons hesitate to perform keyhole surgeries. The technology used in surgery is rapidly advancing, including intraoperative imaging devices that have enabled AR imaging and facilitated complicated surgeries in many fields. However, data are not currently available on the use of AR imaging in spine surgery. The purpose of this article was to introduce the utility of AR for spine surgery.

Methods:

We performed O-arm intraoperative imaging to create an augmented imaging model in navigation systems. Navigation data were linked to a microscope to merge the live view and AR. Augmented reality imaging shows the model plan in the real-world surgical field. We used this novel method in patients who underwent both keyhole surgeries.

Results:

We successfully performed both surgeries using the AR visualization guide.

Conclusions:

The AR navigation system facilitates complicated keyhole surgeries in patients who undergo spine surgery.

Study Design:

Technical report