Evaluation of the precision of operative augmented reality compared to standard neuronavigation using a 3D-printed skull

Augmented reality in cranial surgery: Surgical planning and maximal safety in resection of brain tumors via head-mounted fiber tractography

Recent advancements in computer vision, enhanced augmented reality (AR) software and hardware are paving the way for AR to emerge as a promising and innovative tool for advancing and broadening neurosurgical pre-operative planning and intraoperative procedures. In this study, we describe the use of AR coupled with Magnetic Resonance (MR) and Diffusion Tensor Imaging (DTI) to map visual tracts around an occipital lesion, ensuring a safe resection without post-op complications. In a patient who underwent an elective craniotomy for the resection of an occipital brain tumor, preoperative MRI and Quicktome platform-based DTI MRI were uploaded onto the Medivis AR system. Pre-op and post-op fiber tractography was conducted using DSI Studio, and fiber volumes were compared. This technological setup was employed for pre-operative and intraoperative planning and further enhanced clinical decision-making for the actual tumor resection. The AR system and the preparation process are demonstrated via an illustrative video. The visual pathways were preserved during surgery consistent with the intraoperative visualization of these tracks on DTI using an AR headset. Clinically, postoperative visual field testing revealed no signs of visual loss. The volumes of the visual tracts were measured in preoperative and postoperative DTIs, showing that their volume was maintained. Our study highlights the feasibility in identifying preoperative tumor borders for incision planning and feasibility in preserving white matter tracts during tumor resection. AR FT-assisted surgery is safe and effective in planning the surgical approach for patients with brain tumors, thereby optimizing patient functional outcomes.

Surgical and clinical impacts of mixed reality-guided glioblastoma resection versus standard neuronavigation: improving tumor surgery

Background

Glioblastomas (GBM) are typically treated with surgery and radio-chemotherapy, with patient survival often depending on the extent of tumor resection. This study compares outcomes of GBM surgery using 5-ALA, intraoperative neuroelectrophysiology, and neuro-navigation, either in a standard setting (STD) or enhanced by mixed reality (MR) guidance.

Methods

This retrospective study included GBM patients who underwent resection at Geneva University Hospitals between 2015 and mid-2022, excluding biopsies and partial debulking. Primary outcomes included postoperative residual tumor volume (RV) based on postoperative contrast uptake on the MRI, while secondary outcomes were gross total resection (GTR), extent of resection (EOR), new postoperative deficits, overall survival (OS), progression-free survival (PFS), and Karnofsky performance scores. Confounding factors such as intraoperative monitoring and use of fluorescence were analyzed.

Results

Of 115 patients, 76 were in the STD group and 39 in the MR group, with comparable demographics. The MR group had significantly lower RV (median 0.01 cm³ vs. 0.34 cm³, p=0.008) and higher GTR rates (median 50% vs. 26.7%). EOR was also superior in the MR group (median 99.9% vs. 98.2%, p=0.002). New focal deficits occurred in 39% (STD) and 36% (MR) of cases (p=0.84). While median OS was not significantly different (475 vs. 375 days, p=0.63), median PFS was longer in the MR group (147 vs. 100 days, p=0.004).

Conclusion

MR guidance improves the quality of tumor resection and enhances progression-free survival without increasing postoperative deficits, although it does not significantly impact overall survival.

Pioneering Augmented and Mixed Reality in Cranial Surgery: The First Latin American Experience

INTRODUCTION

Augmented reality (AR) and mixed reality (MR) technologies have revolutionized cranial neurosurgery by overlaying digital information onto the surgical field, enhancing visualization, precision, and training. These technologies enable the real-time integration of preoperative imaging data, aiding in better decision-making and reducing operative risks. Despite challenges such as cost and specialized training needs, AR and MR offer significant benefits, including improved surgical outcomes and personalized surgical plans based on individual patient anatomy.

MATERIALS AND METHODS

This study describes three intracranial surgeries using AR and MR technologies at Hospital Ángeles Universidad, Mexico City, in 2023. Surgeries were performed with VisAR software 3 version and Microsoft HoloLens 2, transforming DICOM images into 3D models. Preoperative MRI and CT scans facilitated planning, and radiopaque tags ensured accurate image registration during surgery. Postoperative outcomes were assessed through clinical and imaging follow-up.

RESULTS

Three intracranial surgeries were performed with AR and MR assistance, resulting in successful outcomes with minimal postoperative complications. Case 1 achieved 80% tumor resection, Case 2 achieved near-total tumor resection, and Case 3 achieved complete lesion resection. All patients experienced significant symptom relief and favorable recoveries, demonstrating the precision and effectiveness of AR and MR in cranial surgery.

CONCLUSIONS

This study demonstrates the successful use of AR and MR in cranial surgery, enhancing precision and clinical outcomes. Despite challenges like training and costs, these technologies offer significant benefits. Future research should focus on long-term outcomes and broader applications to validate their efficacy and cost-effectiveness in neurosurgery.

Integrating Augmented Reality in Spine Surgery: Redefining Precision with New Technologies

INTRODUCTION

The integration of augmented reality (AR) in spine surgery marks a significant advancement, enhancing surgical precision and patient outcomes. AR provides immersive, three-dimensional visualizations of anatomical structures, facilitating meticulous planning and execution of spine surgeries. This technology not only improves spatial understanding and real-time navigation during procedures but also aims to reduce surgical invasiveness and operative times. Despite its potential, challenges such as model accuracy, user interface design, and the learning curve for new technology must be addressed. AR's application extends beyond the operating room, offering valuable tools for medical education and improving patient communication and satisfaction.

MATERIAL AND METHODS

A literature review was conducted by searching PubMed and Scopus databases using keywords related to augmented reality in spine surgery, covering publications from January 2020 to January 2024.

RESULTS

In total, 319 articles were identified through the initial search of the databases. After screening titles and abstracts, 11 articles in total were included in the qualitative synthesis.

CONCLUSION

Augmented reality (AR) is becoming a transformative force in spine surgery, enhancing precision, education, and outcomes despite hurdles like technical limitations and integration challenges. AR's immersive visualizations and educational innovations, coupled with its potential synergy with AI and machine learning, indicate a bright future for surgical care. Despite the existing obstacles, AR's impact on improving surgical accuracy and safety marks a significant leap forward in patient treatment and care.

Evolution of the meta-neurosurgeon: A systematic review of the current technical capabilities, limitations, and applications of augmented reality in neurosurgery

Background

Augmented reality (AR) applications in neurosurgery have expanded over the past decade with the introduction of headset-based platforms. Many studies have focused on either preoperative planning to tailor the approach to the patient's anatomy and pathology or intraoperative surgical navigation, primarily realized as AR navigation through microscope oculars. Additional efforts have been made to validate AR in trainee and patient education and to investigate novel surgical approaches. Our objective was to provide a systematic overview of AR in neurosurgery, provide current limitations of this technology, as well as highlight several applications of AR in neurosurgery.

Methods

We performed a literature search in PubMed/Medline to identify papers that addressed the use of AR in neurosurgery. The authors screened three hundred and seventy-five papers, and 57 papers were selected, analyzed, and included in this systematic review.

Results

AR has made significant inroads in neurosurgery, particularly in neuronavigation. In spinal neurosurgery, this primarily has been used for pedicle screw placement. AR-based neuronavigation also has significant applications in cranial neurosurgery, including neurovascular, neurosurgical oncology, and skull base neurosurgery. Other potential applications include operating room streamlining, trainee and patient education, and telecommunications.

Conclusion

AR has already made a significant impact in neurosurgery in the above domains and has the potential to be a paradigm-altering technology. Future development in AR should focus on both validating these applications and extending the role of AR.

Validation of real-time inside-out tracking and depth realization technologies for augmented reality-based neuronavigation

PURPOSE

Concomitant with the significant advances in computing technology, the utilization of augmented reality-based navigation in clinical applications is being actively researched. In this light, we developed novel object tracking and depth realization technologies to apply augmented reality-based neuronavigation to brain surgery.

METHODS

We developed real-time inside-out tracking based on visual inertial odometry and a visual inertial simultaneous localization and mapping algorithm. The cube quick response marker and depth data obtained from light detection and ranging sensors are used for continuous tracking. For depth realization, order-independent transparency, clipping, and annotation and measurement functions were developed. In this study, the augmented reality model of a brain tumor patient was applied to its life-size three-dimensional (3D) printed model.

RESULTS

Using real-time inside-out tracking, we confirmed that the augmented reality model remained consistent with the 3D printed patient model without flutter, regardless of the movement of the visualization device. The coordination accuracy during real-time inside-out tracking was also validated. The average movement error of the X and Y axes was 0.34 ± 0.21 and 0.04 ± 0.08 mm, respectively. Further, the application of order-independent transparency with multilayer alpha blending and filtered alpha compositing improved the perception of overlapping internal brain structures. Clipping, and annotation and measurement functions were also developed to aid depth perception and worked perfectly during real-time coordination. We named this system METAMEDIP navigation.

CONCLUSIONS

The results validate the efficacy of the real-time inside-out tracking and depth realization technology. With these novel technologies developed for continuous tracking and depth perception in augmented reality environments, we are able to overcome the critical obstacles in the development of clinically applicable augmented reality neuronavigation.

Evaluation Metrics for Augmented Reality in Neurosurgical Preoperative Planning, Surgical Navigation, and Surgical Treatment Guidance: A Systematic Review

BACKGROUND AND OBJECTIVE

Recent years have shown an advancement in the development of augmented reality (AR) technologies for preoperative visualization, surgical navigation, and intraoperative guidance for neurosurgery. However, proving added value for AR in clinical practice is challenging, partly because of a lack of standardized evaluation metrics. We performed a systematic review to provide an overview of the reported evaluation metrics for AR technologies in neurosurgical practice and to establish a foundation for assessment and comparison of such technologies.

METHODS

PubMed, Embase, and Cochrane were searched systematically for publications on assessment of AR for cranial neurosurgery on September 22, 2022. The findings were reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

The systematic search yielded 830 publications; 114 were screened full text, and 80 were included for analysis. Among the included studies, 5% dealt with preoperative visualization using AR, with user perception as the most frequently reported metric. The majority (75%) researched AR technology for surgical navigation, with registration accuracy, clinical outcome, and time measurements as the most frequently reported metrics. In addition, 20% studied the use of AR for intraoperative guidance, with registration accuracy, task outcome, and user perception as the most frequently reported metrics.

CONCLUSION

For quality benchmarking of AR technologies in neurosurgery, evaluation metrics should be specific to the risk profile and clinical objectives of the technology. A key focus should be on using validated questionnaires to assess user perception; ensuring clear and unambiguous reporting of registration accuracy, precision, robustness, and system stability; and accurately measuring task performance in clinical studies. We provided an overview suggesting which evaluation metrics to use per AR application and innovation phase, aiming to improve the assessment of added value of AR for neurosurgical practice and to facilitate the integration in the clinical workflow.

Through the orbit and beyond: Current state and future perspectives in endoscopic orbital surgery on behalf of the EANS frontiers committee in orbital tumors and the EANS skull base section

Introduction

Orbital surgery has always been disputed among specialists, mainly neurosurgeons, otorhinolaryngologists, maxillofacial surgeons and ophthalmologists. The orbit is a borderland between intra- and extracranial compartments; Krönlein's lateral orbitotomy and the orbitozygomatic infratemporal approach are the historical milestones of modern orbital-cranial surgery.

Research question

Since its first implementation, endoscopy has significantly impacted neurosurgery, changing perspectives and approaches to the skull base. Since its first application in 2009, transorbital endoscopic surgery opened the way for new surgical scenario, previously feasible only with extensive tissue dissection.

Material and methods

A PRISMA based literature search was performed to select the most relevant papers on the topic.

Results

Here, we provide a narrative review on the current state and future trends in endoscopic orbital surgery.

Discussion and conclusion

This manuscript is a joint effort of the EANS frontiers committee in orbital tumors and the EANS skull base section.

Assessment of Accuracy of Mixed Reality Device for Neuronavigation: Proposed Methodology and Results

Intraoperative neuronavigation is currently an essential component of neurosurgical operations in several contexts. Recent progress in mixed reality (MR) technology has attempted to overcome the disadvantages of standard neuronavigation systems allowing the surgeon to superimpose a 3D rendered image onto the patient's anatomy. We present the first study in the literature to assess the surface matching accuracy of MR rendered image. For the purposes of this study, we used HoloLens 2 with virtual surgery intelligence providing the software capability for image rendering. To assess the accuracy of using mixed reality device for neuronavigation intraoperatively. This study seeks to assess the accuracy of rendered holographic images from a mixed reality device as a means for neuronavigation intraoperatively. We used the Realistic Operative Workstation for Educating Neurosurgical Apprentices to represent a patient's skull with intracranial components which underwent standardized computed tomography (CT) and MRI imaging. Eleven predefined points were used for purposes of assessing the accuracy of the rendered image, compared with the intraoperative gold standard neuronavigation. The mean HoloLens values against the ground truth were significantly higher when compared with Stealth using CT scan as the imaging modality. Using extracranial anatomic landmarks, the HoloLens error values continued to be significantly higher in magnitude when compared with Stealth across CT and MRI. This study provides a relatively easy and feasible method to assess accuracy of MR-based navigation without requiring any additions to the established imaging protocols. We failed to show the equivalence of MR-based navigation over the current neuronavigation systems.

Intraoperative zoom lens calibration for high magnification surgical microscope

BACKGROUND AND OBJECTIVES

An augmented reality (AR)-based surgical guidance system is often used with high-magnification zoom lens systems such as a surgical microscope, particularly in neurology or otolaryngology. To superimpose the internal structures of relevant organs on the microscopy image, an accurate calibration process to obtain the camera intrinsic and hand-eye parameters of the microscope is essential. However, conventional calibration methods are unsuitable for surgical microscopes because of their narrow depth of focus at high magnifications. To realize AR-based surgical guidance with a high-magnification surgical microscope, we herein propose a new calibration method that is applicable to the highest magnification levels as well as low magnifications.

METHODS

The key idea of the proposed method is to find the relationship between the focal length and the hand-eye parameters, which remains constant regardless of the magnification level. Based on this, even if the magnification changes arbitrarily during surgery, the intrinsic and hand-eye parameters are recalculated quickly and accurately with one or two pictures of the pattern. We also developed a dedicated calibration tool with a prism to take focused pattern images without interfering with the surgery.

RESULTS

The proposed calibration method ensured an AR error of < 1 mm for all magnification levels. In addition, the variation of focal length was within 1% regardless of the magnification level, and the corresponding variation with the conventional calibration method exceeded 20% at high magnification levels.

CONCLUSIONS

The comparative study showed that the proposed method has outstanding accuracy and reproducibility for a high-magnification surgical microscope. The proposed calibration method is applicable to various endoscope or microscope systems with zoom lens.

Three-Dimensional Printing in Neurosurgery: A Review of Current Indications and Applications and a Basic Methodology for Creating a Three-Dimensional Printed Model for the Neurosurgical Practice

Introduction Three-dimensional (3D) printing is an affordable aid that is useful in neurosurgery. It allows for better visualization and tactile appreciation of the individual anatomy and regions of interest and therefore potentially lowers the risk of complications. There are various applications of this technology in the field of neurosurgery. Materials and methods In this paper, we present a basic methodology for the creation of a 3D printed model using only open-source software for medical image editing, model generation, pre-printing preparation, and analysis of the literature concerning the practical use of this methodology. Results The literature review on the current applications of 3D printed models in neurosurgery shows that they are mostly used for preoperative planning, surgical training, and simulation, closely followed by their use in patient-specific implants and instrumentation and medical education. Materialise^TM Mimics is the most frequently used commercial software for a 3D modeling for preoperative planning and surgical simulation, while the most popular open-source software for the same applications is 3D Slicer. In this paper, we present the algorithm that we employ for 3D printing using Horos^TM, Blender, and Cura software packages which are all free and open-source. Conclusion Three-dimensional printing is becoming widely available and of significance to neurosurgical practice. Currently, there are various applications of this technology that are less demanding in terms of technical knowledge and required fluency in medical imaging software. These predispositions open the field for further research on the possible use of 3D printing in neurosurgery.

Effect of the Segmentation Threshold on Computed Tomography-Based Reconstruction of Skull Bones with Reference Optical Three-Dimensional Scanning

BACKGROUND

A variety of applications related to neurosurgical procedures, education, and training require accurate reconstruction of the involved structures from the medical images such as computed tomography (CT). This study evaluates the quality of CT-based reconstruction of dry skull bones for advanced neurosurgical applications. The accuracy and precision of these models were examined with reference optical scanning.

METHODS

Three consecutive CT and optical scans of different skull bones were acquired and used to develop three-dimensional models. The accuracy of three-dimensional models was examined by manual inspection of the defined anatomical landmarks of the skull. Reproducibility was examined by deviation analysis of the models developed from repeated CT and optical scans.

RESULTS

Precision was excellent in both the techniques with less than 0.1 mm deviation error. On the interscan evaluation of the CT versus optical scan model, deviations of more than 0.1 mm were observed in 16 out of 21 instances. CT reconstruction using standard segmentation algorithms results in missing bone portions while using the default bone segmentation threshold. The segmentation threshold was varied to construct missing bone regions, and its effect on the iso-surface generation was evaluated. The threshold variation led to increased mean deviations of surfaces up to 0.6 mm.

CONCLUSIONS

The study reveals that bone structure, complexity, and segmentation threshold lead to CT reconstruction variability. The trade-off between the desirable model and accepted mean deviation should be considered as per traits of the desired application.

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.

Intraoperative MRI versus intraoperative ultrasound in pediatric brain tumor surgery: is expensive better than cheap? A review of the literature

PURPOSE

The extent of brain tumor resection (EOR) is a fundamental prognostic factor in pediatric neuro-oncology in association with the histology. In general, resection aims at gross total resection (GTR). Intraoperative imaging like intraoperative US (iOUS) and MRI have been developed in order to find any tumoral remnant but with different costs. Aim of our work is to review the current literature in order to better understand the differences between costs and efficacy of MRI and iOUS to evaluate tumor remnants intraoperatively.

METHODS

We reviewed the existing literature on PubMed until 31st December 2021 including the sequential keywords "intraoperative ultrasound and pediatric brain tumors", "iUS and pediatric brain tumors", "intraoperative magnetic resonance AND pediatric brain tumors", and "intraoperative MRI AND pediatric brain tumors.

RESULTS

A total of 300 papers were screened through analysis of title and abstract; 254 were excluded. After selection, a total of 23 articles were used for this systematic review. Among the 929 patients described, a total of 349(38%) of the cases required an additional resection after an iMRI scan. GTR was measured on 794 patients (data of 69 patients lost), and it was achieved in 552(70%) patients. In case of iOUS, GTR was estimated in 291 out of 379 (77%) cases. This finding was confirmed at the post-operative MRI in 256(68%) cases.

CONCLUSIONS

The analysis of the available literature demonstrates that expensive equipment does not always mean better. In fact, for the majority of pediatric brain tumors, iOUS is comparable to iMRI in estimating the EOR.

Virtual and Augmented Reality in Neurosurgery: The Evolution of its Application and Study Designs

BACKGROUND

As the art of neurosurgery evolves in the 21st century, more emphasis is placed on minimally invasive techniques, which require technical precision. Simultaneously, the reduction on training hours continues, and teachers of neurosurgery faces "double jeopardy"-with harder skills to teach and less time to teach them. Mixed reality appears as the neurosurgical educators' natural ally: Virtual reality facilitates the learning of spatial relationships and permits rehearsal of skills, while augmented reality can make procedures safer and more efficient. Little wonder then, that the body of literature on mixed reality in neurosurgery has grown exponentially.

METHODS

Publications involving virtual and augmented reality in neurosurgery were examined. A total of 414 papers were included, and they were categorized according to study design and analyzed.

RESULTS

Half of the papers were published within the last 3 years alone. Whereas in the earlier half, most of the publications involved experiments in virtual reality simulation and the efficacy of skills acquisition, many of the more recent publication are proof-of-concept studies. This attests to the evolution of mixed reality in neurosurgery. As the technology advances, neurosurgeons are finding more applications, both in training and clinical practice.

CONCLUSIONS

With parallel advancement in Internet speed and artificial intelligence, the utilization of mixed reality will permeate neurosurgery. From solving staff problems in global neurosurgery, to mitigating the deleterious effect of duty-hour reductions, to improving individual operations, mixed reality will have a positive effect in many aspects of neurosurgery.

The Role of 3D Printing in Planning Complex Medical Procedures and Training of Medical Professionals-Cross-Sectional Multispecialty Review

Medicine is a rapidly-evolving discipline, with progress picking up pace with each passing decade. This constant evolution results in the introduction of new tools and methods, which in turn occasionally leads to paradigm shifts across the affected medical fields. The following review attempts to showcase how 3D printing has begun to reshape and improve processes across various medical specialties and where it has the potential to make a significant impact. The current state-of-the-art, as well as real-life clinical applications of 3D printing, are reflected in the perspectives of specialists practicing in the selected disciplines, with a focus on pre-procedural planning, simulation (rehearsal) of non-routine procedures, and on medical education and training. A review of the latest multidisciplinary literature on the subject offers a general summary of the advances enabled by 3D printing. Numerous advantages and applications were found, such as gaining better insight into patient-specific anatomy, better pre-operative planning, mock simulated surgeries, simulation-based training and education, development of surgical guides and other tools, patient-specific implants, bioprinted organs or structures, and counseling of patients. It was evident that pre-procedural planning and rehearsing of unusual or difficult procedures and training of medical professionals in these procedures are extremely useful and transformative.

Holographic mixed-reality neuronavigation with a head-mounted device: technical feasibility and clinical application

OBJECTIVE

The authors aimed to evaluate the technical feasibility of a mixed-reality neuronavigation (MRN) system with a wearable head-mounted device (HMD) and to determine its clinical application and accuracy.

METHODS

A semiautomatic registration MRN system on HoloLens smart glasses was developed and tested for accuracy and feasibility. Thirty-seven patients with intracranial lesions were prospectively identified. For each patient, multimodal imaging-based holograms of lesions, markers, and surrounding eloquent structures were created and then imported to the MRN HMD. After a point-based registration, the holograms were projected onto the patient's head and observed through the HMD. The contour of the holograms was compared with standard neuronavigation (SN). The projection of the lesion boundaries perceived by the neurosurgeon on the patient's scalp was then marked with MRN and SN. The distance between the two contours generated by MRN and SN was measured so that the accuracy of MRN could be assessed.

RESULTS

MRN localization was achieved in all patients. The mean additional time required for MRN was 36.3 ± 6.3 minutes, in which the mean registration time was 2.6 ± 0.9 minutes. A trend toward a shorter time required for preparation was observed with the increase of neurosurgeon experience with the MRN system. The overall median deviation was 4.1 mm (IQR 3.0 mm-4.7 mm), and 81.1% of the lesions localized by MRN were found to be highly consistent with SN (deviation < 5.0 mm). There was a significant difference between the supine position and the prone position (3.7 ± 1.1 mm vs 5.4 ± 0.9 mm, p = 0.001). The magnitudes of deviation vectors did not correlate with lesion volume (p = 0.126) or depth (p = 0.128). There was no significant difference in additional operating time between different operators (37.4 ± 4.8 minutes vs 34.6 ± 4.8 minutes, p = 0.237) or in localization deviation (3.7 ± 1.0 mm vs 4.6 ± 1.5 mm, p = 0.070).

CONCLUSIONS

This study provided a complete set of a clinically applicable workflow on an easy-to-use MRN system using a wearable HMD, and has shown its technical feasibility and accuracy. Further development is required to improve the accuracy and clinical efficacy of this system.

Virtual dissection of the real brain: integration of photographic 3D models into virtual reality and its effect on neurosurgical resident education

OBJECTIVE

Virtual reality (VR) is increasingly being used for education and surgical simulation in neurosurgery. So far, the 3D sources for VR simulation have been derived from medical images, which lack real color. The authors made photographic 3D models from dissected cadavers and integrated them into the VR platform. This study aimed to introduce a method of developing a photograph-integrated VR and to evaluate the educational effect of these models.

METHODS

A silicone-injected cadaver head was prepared. A CT scan of the specimen was taken, and the soft tissue and skull were segmented to 3D objects. The cadaver was dissected layer by layer, and each layer was 3D scanned by a photogrammetric method. The objects were imported to a free VR application and layered. Using the head-mounted display and controllers, the various neurosurgical approaches were demonstrated to neurosurgical residents. After performing hands-on virtual surgery with photographic 3D models, a feedback survey was collected from 31 participants.

RESULTS

Photographic 3D models were seamlessly integrated into the VR platform. Various skull base approaches were successfully performed with photograph-integrated VR. During virtual dissection, the landmark anatomical structures were identified based on their color and shape. Respondents rated a higher score for photographic 3D models than for conventional 3D models (4.3 ± 0.8 vs 3.2 ± 1.1, respectively; p = 0.001). They responded that performing virtual surgery with photographic 3D models would help to improve their surgical skills and to develop and study new surgical approaches.

CONCLUSIONS

The authors introduced photographic 3D models to the virtual surgery platform for the first time. Integrating photographs with the 3D model and layering technique enhanced the educational effect of the 3D models. In the future, as computer technology advances, more realistic simulations will be possible.

Evaluation of the effect of standard neuronavigation and augmented reality on the integrity of the perifocal structures during a neurosurgical approach

OBJECTIVE

Intracranial minimally invasive procedures imply working in a restricted surgical corridor surrounded by critical structures, such as vessels and cranial nerves. Any damage to them may affect patient outcome. Neuronavigation systems may reduce the risk of such complications. In this study, the authors sought to compare standard neuronavigation (NV) and augmented reality (AR)-guided navigation with respect to the integrity of the perifocal structures during a neurosurgical approach using a novel model imitating intracranial vessels.

METHODS

A custom-made box, containing crisscrossing hard metal wires, a hidden nail at its bottom, and a wooden top, was scanned, fused, and referenced for the purpose of the study. The metal wires and an aneurysm clip applier were connected to a controller, which counted the number of contacts between them. Twenty-three naive participants were asked to 1) use NV to define an optimal entry point on the top, perform the smallest craniotomy possible on the wooden top, and to use a surgical microscope when placing a clip on the nail without touching the metal wires; and 2) use AR to preoperatively define an ideal trajectory, navigate the surgical microscope, and then perform the same task. The primary outcome was the number of contacts made between the metal wires and the clip applier. Secondary outcomes were craniotomy size, and trust in NV and AR to help avoid touching the metal wires, as assessed by a 9-level Likert scale.

RESULTS

The median number of contacts tended to be lower with the use of AR than with NV (AR, median 1 [Q1: 1, Q3: 2]; NV, median 3 [Q1: 1, Q3: 6]; p = 0.074). The size of the target-oriented craniotomy was significantly lower with the use of AR compared with NV (AR, median 4.91 cm2 [Q1: 4.71 cm2, Q3: 7.55 cm2]; and NV, median 9.62 cm2 [Q1: 7.07 cm2; Q3: 13.85 cm2]). Participants had more trust in AR than in NV (the differences posttest minus pretest were mean 0.9 [SD 1.2] and mean -0.3 [SD 0.2], respectively; p < 0.05).

CONCLUSIONS

The results of this study show a trend favoring the use of AR over NV with respect to reducing contact between a clip applier and the perifocal structures during a simulated clipping of an intracranial aneurysm. Target-guided craniotomies were smaller with the use of AR. AR may be used not only to localize surgical targets but also to prevent complications associated with damage to structures encountered during the surgical approach.

Augmented reality-assisted roadmaps during periventricular brain surgery

Visualizing major periventricular anatomical landmarks intraoperatively during brain tumor removal is a decisive measure toward preserving such structures and thus the patient's postoperative quality of life. The aim of this study was to describe potential standardized preoperative planning using standard landmarks and procedures and to demonstrate the feasibility of using augmented reality (AR) to assist in performing surgery according to these "roadmaps." The authors have depicted stepwise AR surgical roadmaps applied to periventricular brain surgery with the aim of preserving major cognitive function. In addition to the technological aspects, this study highlights the importance of using emerging technologies as potential tools to integrate information and to identify and visualize landmarks to be used during tumor removal.