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.

Role of virtual modules to supplement neurosurgery education during COVID-19.

The advent of the COVID-19 pandemic has disrupted all aspects of neurosurgery education, and it is now challenging to conduct routine sessions. Maintenance of essential standard education among novice neurosurgeons during the pandemic is of paramount importance. The aim of this study was the development of virtual modules and validation of its role to supplement the neurosurgery education program. We developed the virtual modules relevant to neuro-anatomy, neurosurgical procedures, instrumentation, and neurosurgical planning. These modules were virtually demonstrated to twenty-seven resident neurosurgeons through CiscoWebexonline platform. They provided their rating on the aptness of virtual modules for different neurosurgery applications on various parameters using 10 points Likert scale. The parameters included quality, learning, confidence building capacity, usefulness, and overall satisfaction. The results obtained for each module were analysed and the average score was used for the comparison. The highest rating on quality was obtained by the neurosurgical instrumentation module. The highest rating for learning and confidence building capacity was given to neurosurgical procedure animation. The usefulness and overall satisfaction were highly rated for neurosurgical planning module. The results show that developed virtual modules provide an effective method to supplement the neurosurgery education program in the current scenario involving physical distancing and shift rearrangements. These virtual modules help in limiting the visits to operation room, anatomy and surgical training labs, and allow residents to learn online at their pace.

A Review of Physical Simulators for Neuroendoscopy Skills Training.

BACKGROUND: Minimally invasive neurosurgical approaches reduce patient morbidity by providing the surgeon with better visualization and access to complex lesions, with minimal disruption to normal anatomy. The use of rigid or flexible neuroendoscopes, supplemented with a conventional stereoscopic operating microscope, has been integral to the adoption of these techniques. Neurosurgeons commonly use neuroendoscopes to perform the ventricular and endonasal approaches. It is challenging to learn neuroendoscopy skills from the existing apprenticeship model of surgical education. The training methods, which use simulation-based systems, have achieved wide acceptance. Physical simulators provide anatomic orientation and hands-on experience with repeatability. Our aim is to review the existing physical simulators on the basis of the skills training of neuroendoscopic procedures. METHODS: We searched Scopus, Google Scholar, PubMed, IEEE Xplore, and dblp. We used the following keywords "neuroendoscopy," "training," "simulators," "physical," and "skills evaluation." A total of 351 articles were screened based on development methods, evaluation criteria, and validation studies on physical simulators for skills training in neuroendoscopy. RESULTS: The screening of the articles resulted in classifying the physical training methods developed for neuroendoscopy surgical skills into synthetic simulators and box trainers. The existing simulators were compared based on their design, fidelity, trainee evaluation methods, and validation studies. CONCLUSIONS: The state of simulation systems demands collaborative initiatives among translational research institutes. They need improved fidelity and validation studies for inclusion in the surgical educational curriculum. Learning should be imparted in stages with standardization of performance metrics for skills evaluation.

A review of virtual reality simulators for neuroendoscopy.

Neurosurgery is a challenging surgical specialty that demands many technical and cognitive skills. The traditional surgical training approach of having a trainee coached in the operating room by the faculty is time-consuming, costly, and involves patient risk factors. Simulation-based training methods are suitable to impart the surgical skills outside the operating room. Virtual simulators allow high-fidelity repeatable environment for surgical training. Neuroendoscopy, a minimally invasive neurosurgical technique, demands additional skills for limited maneuverability and eye-hand coordination. This study provides a review of the existing virtual reality simulators for training neuroendoscopic skills. Based on the screening, the virtual training methods developed for neuroendoscopy surgical skills were classified into endoscopic third ventriculostomy and endonasal transsphenoidal surgery trainers. The study revealed that a variety of virtual reality simulators have been developed by various institutions. Although virtual reality simulators are effective for procedure-based skills training, the simulators need to include anatomical variations and variety of cases for improved fidelity. The review reveals that there should be multi-centric prospective and retrospective cohort studies to establish concurrent and predictive validation for their incorporation in the surgical educational curriculum.

A Virtual Repository of Neurosurgical Instrumentation for Neuroengineering Research and Collaboration.

BACKGROUND: Advancements in microscopy and more recently in neuroendoscopy have revolutionized the field of neurosurgery. Handheld neurosurgical instruments are integral components of these procedures. However, these instruments have many limitations, such as poor ergonomics, constrained maneuverability, and limited degrees of freedom. A need for developing better instruments is commonly felt by neurosurgeons. Also, the focus of modern neurosurgical training is shifting toward simulation models. The baseline data of surgical instruments play a vital role in the development of virtual and physical simulators. A primary factor impeding development of novel instruments and simulators is lack of a comprehensive surgical instrument database. The aim of this study was to develop and validate a virtual repository of microscopic and neuroendoscopic instruments. METHODS: Standard neurosurgical instrument sets were scanned, reverse engineered, and stored in various file formats at the file transfer protocol server. The developed database was validated by 4 groups of experts by creating different neurosurgery applications. RESULTS: Four groups of experts used the repository content to create novel ergonomic instrument designs, e-learning material, computer vision-based surgical skills evaluation and virtual reality and validated the contents. The validation results showed that quality of content (75%), usefulness of content (85.6%), and time saving using content (88.1%) received high scores, and the effectiveness of the virtual repository contents was appreciated. CONCLUSIONS: The virtual database is an efficient starting aid to foster research collaborations related to neurosurgical instruments and surgical simulation platforms.

Validation of Reverse-Engineered and Additive-Manufactured Microsurgical Instrument Prototype.

With advancements in imaging techniques, neurosurgical procedures are becoming highly precise and minimally invasive, thus demanding development of new ergonomically aesthetic instruments. Conventionally, neurosurgical instruments are manufactured using subtractive manufacturing methods. Such a process is complex, time-consuming, and impractical for prototype development and validation of new designs. Therefore, an alternative design process has been used utilizing blue light scanning, computer-aided designing, and additive manufacturing direct metal laser sintering (DMLS) for microsurgical instrument prototype development. Deviations of DMLS-fabricated instrument were studied by superimposing scan data of fabricated instrument with the computer-aided designing model. Content and concurrent validity of the fabricated prototypes was done by a group of 15 neurosurgeons by performing sciatic nerve anastomosis in small laboratory animals. Comparative scoring was obtained for the control and study instrument. T test was applied to the individual parameters and P values for force (P < .0001) and surface roughness (P < .01) were found to be statistically significant. These 2 parameters were further analyzed using objective measures. Results depicts that additive manufacturing by DMLS provides an effective method for prototype development. However, direct application of these additive-manufactured instruments in the operating room requires further validation.

Design and Validation of an Open-Source, Partial Task Trainer for Endonasal Neuro-Endoscopic Skills Development: Indian Experience.

BACKGROUND: Box trainers are ideal simulators, given they are inexpensive, accessible, and use appropriate fidelity. OBJECTIVE: The development and validation of an open-source, partial task simulator that teaches the fundamental skills necessary for endonasal skull-base neuro-endoscopic surgery. METHODS: We defined the Neuro-Endo-Trainer (NET) SkullBase-Task-GraspPickPlace with an activity area by analyzing the computed tomography scans of 15 adult patients with sellar suprasellar parasellar tumors. Four groups of participants (Group E, n = 4: expert neuroendoscopists; Group N, n =19: novice neurosurgeons; Group R, n = 11: neurosurgery residents with multiple iterations; and Group T, n = 27: neurosurgery residents with single iteration) performed grasp, pick, and place tasks using NET and were graded on task completion time and skills assessment scale score. RESULTS: Group E had lower task completion times and greater skills assessment scale scores than both Group N and R (P ≤ 0.03, 0.001). The performance of Groups N and R was found to be equivalent; in self-assessing neuro-endoscopic skill, the participants in these groups were found to have equally low pretraining scores (4/10) with significant improvement shown after NET simulation (6, 7 respectively). Angled scopes resulted in decreased scores with tilted plates compared with straight plates (30° P ≤ 0.04, 45° P ≤ 0.001). With tilted plates, decreased scores were observed when we compared the 0° with 45° endoscope (right, P ≤ 0.008; left, P ≤ 0.002). CONCLUSIONS: The NET, a face and construct valid open-source partial task neuroendoscopic trainer, was designed. Presimulation novice neurosurgeons and neurosurgical residents were described as having insufficient skills and preparation to practice neuro-endoscopy. Plate tilt and endoscope angle were shown to be important factors in participant performance. The NET was found to be a useful partial-task trainer for skill building in neuro-endoscopy.

Quantitative analysis of the Kawase versus the modified Dolenc-Kawase approach for middle cranial fossa lesions with variable anteroposterior extension.

OBJECT: The surgical corridor to the upper third of the clivus and ventral brainstem is hindered by critical neurovascular structures, such as the cavernous sinus, petrous apex, and tentorium. The traditional Kawase approach provides a 10 × 5-mm fenestration at the petrous apex of the temporal bone between the 5th cranial nerve and internal auditory canal. Due to interindividual variability, sometimes this area proves to be insufficient as a corridor to the posterior cranial fossa. The authors describe a modification to the technique of the extradural anterior petrosectomy consisting of additional transcavernous exploration and medial mobilization of the cisternal component of the trigeminal nerve. This approach is termed the modified Dolenc-Kawase (MDK) approach. METHODS: The authors describe a volumetric analysis of temporal bones with 3D laser scanning of dry and drilled bones for respective triangles and rhomboid areas, and they compare the difference of exposure with traditional versus modified approaches on cadaver dissection. Twelve dry temporal bones were laser scanned, and mesh-based volumetric analysis was done followed by drilling of the Kawase triangle and MDK rhomboid. Five cadaveric heads were drilled on alternate sides with both approaches for evaluation of the area exposed, surgical freedom, and angle of approach. RESULTS: The MDK approach provides an approximately 1.5 times larger area and 2.0 times greater volume of bone at the anterior petrous apex compared with the Kawase's approach. Cadaver dissection objectified the technical feasibility of the MDK approach, providing nearly 1.5-2 times larger fenestration with improved view and angulation to the posterior cranial fossa. Practical application in 6 patients with different lesions proves clinical applicability of the MDK approach. CONCLUSIONS: The larger fenestration at the petrous apex achieved with the MDK approach provides greater surgical freedom at the Dorello canal, gasserian ganglion, and prepontine area and better anteroposterior angulation than the traditional Kawase approach. Additional anterior clinoidectomy and transcavernous exposure helps in dealing with basilar artery aneurysms.

Quantitative analysis of variable extent of anterior clinoidectomy with intradural and extradural approaches: 3-dimensional analysis and cadaver dissection.

BACKGROUND: Drilling of the anterior clinoid process (ACP) is an integral component of surgical approaches for central and paracentral skull base lesions. The technique to drill ACP has evolved from pure intradural to extradural and combined techniques. OBJECTIVE: To describe the computerized morphometric evaluation of exposure of optic nerve and internal carotid artery with proposed tailored intradural (IDAC) and complete extradural (EDAC) anterior clinoidectomy. METHODS: We describe a morphometric subdivision of ACP into 4 quadrangles and 1 triangle on the basis of fixed bony landmarks. Computerized volumetric analysis with 3-dimensional laser scanning of dry-drilled bones for respective tailored IDAC and EDAC was performed. Both approaches were compared for the area and length of the optic nerve and internal carotid artery. Five cadaver heads were dissected on alternate sides with intradural and extradural techniques to evaluate exposure, surgical freedom, and angulation of approach. RESULTS: Complete anterior clinoidectomy provides a 2.5-times larger area and 2.7-times larger volume of ACP. Complete clinoidectomy deroofed the optic nerve to an equal extent as by proposed the partial tailored clinoidectomy approach. Tailored IDAC exposes only the distal dural ring, whereas complete EDAC exposes both the proximal and distal dural rings with complete exposure of the carotid cave. CONCLUSION: Quantitative comparative evaluation provides details of exposure and surgical ease with both techniques. We promote hybrid/EDAC technique for vascular pathologies because of better anatomic orientation. Extradural clinoidectomy is the preferred technique for midline cranial neoplasia. An awareness of different variations of clinoidectomy can prevent dependency on any particular approach and facilitate flexibility.

Neurosurgery apps: novel knowledge boosters.

AIM: The utilization of technology for purpose of imparting knowledge, especially in high-end branches like neurosurgery, has gained prominence in the contemporary academic scenario. The technological advancements have brought about outstanding transformation to education and patient care. The connectivity through smartphone applications (apps) has transcended the spatial and temporal limitations, thereby enabling easy access to virtually infinite storehouse of knowledge. Although there are numerous neurosurgery related apps, yet there is still a dearth of quality apps that may serve the purpose. MATERIAL AND METHODS: Relevant apps were searched and evaluated on PlayStore and Apple App store, based on their content, user interface, performance, and utility in routine practice and compared with their cost, size and popularity. They were categorized into apps related to textbooks, scoring systems, patient education, operative procedures, blogs, journals, conferences and promotional. RESULTS: 159 relevant apps were hosted on App stores; 54.7% apps were free of cost. "Neuromind" was the most downloaded app because of its simplicity, free access and applicability. Students and practitioners prefer various apps linked to scoring systems, textbooks and operative illustrations. Apps have helped patients in better understanding of their diseases and management options. CONCLUSION: Development of web-based technologies has divided medical professionals into traditional and modernized learners. Mobile apps permit knowledge to be structured visually to facilitate its easy diffusion in the peer community. A technologically demanding branch like Neurosurgery inevitably needs innovative, cost effective apps with trust worthy content. Relevant apps have a high potential to be used as an excellent resource for effectual neurosurgical education beyond the limitations of time and place.

Free-access open-source e-learning in comprehensive neurosurgery skills training.

BACKGROUND: Since the end of last century, technology has taken a front seat in dispersion of medical education. Advancements of technology in neurosurgery and traditional training methods are now being challenged by legal and ethical concerns of patient safety, resident work-hour restriction and cost of operating-room time. To supplement the existing neurosurgery education pattern, various e-learning platforms are introduced as structured, interactive learning system. MATERIALS AND METHODS: This study focuses on the concept, formulation, development and impact of web based learning platforms dedicated to neurosurgery discipline to disseminate education, supplement surgical knowledge and improve skills of neurosurgeons. 'Neurosurgery Education and Training School (NETS), e-learning platform' has integration of web-based technologies like 'Content Management System' for organizing the education material and 'Learning Management System' for updating neurosurgeons. NETS discussion forum networks neurosurgeons, neuroscientists and neuro-technologists across the globe facilitating collaborative translational research. RESULTS: Multi-authored neurosurgical e-learning material supplements the deficiencies of regular time-bound education. Interactive open-source, global, free-access e-learning platform of NETS has around 1) 425 visitors/month from 73 countries; ratio of new visitors to returning visitors 42.3; 57.7 (2); 64,380 views from 190 subscribers for surgical videos, 3-D animation, graphics based training modules (3); average 402 views per post. CONCLUSION: The e-Learning platforms provide updated educational content that make them "quick, surf, find and extract" resources. e-Learning tools like web-based education, social interactive platform and question-answer forum will save unnecessary expenditure of time and travel of neurosurgeons seeking knowledge. The need for free access platforms is more pronounced for the neurosurgeons and patients in developing nations.