Construction of a three-dimensional interactive model of the skull base and cranial nerves

Narrative review of patient-specific 3D visualization and reality technologies in skull base neurosurgery: enhancements in surgical training, planning, and navigation

Recent advances in medical imaging, computer vision, 3-dimensional (3D) modeling, and artificial intelligence (AI) integrated technologies paved the way for generating patient-specific, realistic 3D visualization of pathological anatomy in neurosurgical conditions. Immersive surgical simulations through augmented reality (AR), virtual reality (VR), mixed reality (MxR), extended reality (XR), and 3D printing applications further increased their utilization in current surgical practice and training. This narrative review investigates state-of-the-art studies, the limitations of these technologies, and future directions for them in the field of skull base surgery. We begin with a methodology summary to create accurate 3D models customized for each patient by combining several imaging modalities. Then, we explore how these models are employed in surgical planning simulations and real-time navigation systems in surgical procedures involving the anterior, middle, and posterior cranial skull bases, including endoscopic and open microsurgical operations. We also evaluate their influence on surgical decision-making, performance, and education. Accumulating evidence demonstrates that these technologies can enhance the visibility of the neuroanatomical structures situated at the cranial base and assist surgeons in preoperative planning and intraoperative navigation, thus showing great potential to improve surgical results and reduce complications. Maximum effectiveness can be achieved in approach selection, patient positioning, craniotomy placement, anti-target avoidance, and comprehension of spatial interrelationships of neurovascular structures. Finally, we present the obstacles and possible future paths for the broader implementation of these groundbreaking methods in neurosurgery, highlighting the importance of ongoing technological advancements and interdisciplinary collaboration to improve the accuracy and usefulness of 3D visualization and reality technologies in skull base surgeries.

Three-Dimensional Modeling and Extended Reality Simulations of the Cross-Sectional Anatomy of the Cerebrum, Cerebellum, and Brainstem

BACKGROUND

Understanding the anatomy of the human cerebrum, cerebellum, and brainstem and their 3-dimensional (3D) relationships is critical for neurosurgery. Although 3D photogrammetric models of cadaver brains and 2-dimensional images of postmortem brain slices are available, neurosurgeons lack free access to 3D models of cross-sectional anatomy of the cerebrum, cerebellum, and brainstem that can be simulated in both augmented reality (AR) and virtual reality (VR).

OBJECTIVE

To create 3D models and AR/VR simulations from 2-dimensional images of cross-sectionally dissected cadaveric specimens of the cerebrum, cerebellum, and brainstem.

METHODS

The Klingler method was used to prepare 3 cadaveric specimens for dissection in the axial, sagittal, and coronal planes. A series of 3D models and AR/VR simulations were then created using 360° photogrammetry.

RESULTS

High-resolution 3D models of cross-sectional anatomy of the cerebrum, cerebellum, and brainstem were obtained and used in creating AR/VR simulations. Eleven axial, 9 sagittal, and 7 coronal 3D models were created. The sections were planned to show important deep anatomic structures. These models can be freely rotated, projected onto any surface, viewed from all angles, and examined at various magnifications.

CONCLUSION

To our knowledge, this detailed study is the first to combine up-to-date technologies (photogrammetry, AR, and VR) for high-resolution 3D visualization of the cross-sectional anatomy of the entire human cerebrum, cerebellum, and brainstem. The resulting 3D images are freely available for use by medical professionals and students for better comprehension of the 3D relationship of the deep and superficial brain anatomy.

Evolution of microneurosurgical anatomy with special reference to the history of anatomy, surgical anatomy, and microsurgery: historical overview

This article reviews the evolution of microneurosurgical anatomy (MNA) with special reference to the development of anatomy, surgical anatomy, and microsurgery. Anatomy can be said to have started in the ancient Greek era with the work of Hippocrates, Galen, and others as part of the pursuit of natural science. In the sixteenth century, Vesalius made a great contribution in reviving Galenian knowledge while adding new knowledge of human anatomy. Also in the sixteenth century, Ambroise Paré can be said to have started modern surgery. As surgery developed, more detailed anatomical knowledge became necessary for treating complicated diseases. Many noted surgeons at the time were also anatomists eager to spread anatomical knowledge in order to enhance surgical practice. Thus, surgery and anatomy developed together, with advances in each benefiting the other. The concept of surgical anatomy evolved in the eighteenth century and became especially popular in the nineteenth century. In the twentieth century, microsurgery was introduced in various surgical fields, starting with Carl O. Nylen in otology. It flourished and became popularized in the second half of the century, especially in the field of neurosurgery, following Jacobson and Suarez's success in microvascular anastomosis in animals and subsequent clinical application as developed by M.G. Yasargil and others. Knowledge of surgical anatomy as seen under the operating microscope became important for surgeons to perform microneurosurgical procedures accurately and safely, which led to the fuller development of MNA as conducted by many neurosurgeons, among whom A.L. Rhoton, Jr. might be mentioned as representative.

Development of Integrated 3-Dimensional Computer Graphics Human Head Model

BACKGROUND

Understanding the complex anatomy of neurostructures is very important in various stages of medical education, from medical students to experienced neurosurgeons, and, ultimately, for the knowledge of human beings.

OBJECTIVE

To develop an interactive computer graphics (CG) anatomic head model and present the current progress.

METHODS

Based on the prior head 3-dimensional CG (3DCG) polygon model, 23 additional published papers and textbooks were consulted, and 2 neurosurgeons and 1 CG technician performed revision and additional polygon modeling. Three independent neurosurgeons scored the clear visibility of anatomic structures relevant to neurosurgical procedures (anterior petrosal and supracerebellar infratentorial approaches) in the integrated 3DCG model (i model) and patients' radiological images (PRIs) such as those obtained from computed tomography, magnetic resonance imaging, and angiography.

RESULTS

The i model consisted of 1155 parts (.stl format), with a total of 313 763 375 polygons, including 10 times more information than the foundation model. The i model was able to illustrate complex and minute neuroanatomic structures that PRIs could not as well as extracranial structures such as paranasal sinuses. Our subjective analysis showed that the i model had better clear visibility scores than PRIs, particularly in minute nerves, vasculatures, and dural structures.

CONCLUSION

The i model more clearly illustrates minute anatomic structures than PRIs and uniquely illustrates nuclei and fibers that radiological images do not. The i model complements cadaveric dissection by increasing accessibility according to spatial, financial, ethical, and social aspects and can contribute to future medical education.

Mapping the rest of the human connectome: Atlasing the spinal cord and peripheral nervous system

The emergence of diffusion, structural, and functional neuroimaging methods has enabled major multi-site efforts to map the human connectome, which has heretofore been defined as containing all neural connections in the central nervous system (CNS). However, these efforts are not structured to examine the richness and complexity of the peripheral nervous system (PNS), which arguably forms the (neglected) rest of the connectome. Despite increasing interest in an atlas of the spinal cord (SC) and PNS which is simultaneously stereotactic, interactive, electronically dissectible, scalable, population-based and deformable, little attention has thus far been devoted to this task of critical importance. Nevertheless, the atlasing of these complete neural structures is essential for neurosurgical planning, neurological localization, and for mapping those components of the human connectome located outside of the CNS. Here we recommend a modification to the definition of the human connectome to include the SC and PNS, and argue for the creation of an inclusive atlas to complement current efforts to map the brain's human connectome, to enhance clinical education, and to assist progress in neuroscience research. In addition to providing a critical overview of existing neuroimaging techniques, image processing methodologies and algorithmic advances which can be combined for the creation of a full connectome atlas, we outline a blueprint for ultimately mapping the entire human nervous system and, thereby, for filling a critical gap in our scientific knowledge of neural connectivity.

Key anatomical landmarks for middle fossa surgery: a surgical anatomy study

OBJECTIVE

Middle fossa surgery is challenging, and reliable surgical landmarks are essential to perform accurate and safe surgery. Although many descriptions of the middle fossa components have been published, a clinically practical description of this very complex anatomical region is lacking. Small structure arrangements in this area are often not well visualized or accurately demarcated with neuronavigation systems. The objective is to describe a "roadmap" of key surgical reference points and landmarks during middle fossa surgery to help the surgeon predict where critical structures will be located.

METHODS

The authors studied 40 dry skulls (80 sides) obtained from the anatomical board at their institution. Measurements of anatomical structures in the middle fossa were made with a digital caliper and a protractor, taking as reference the middle point of the external auditory canal (MEAC). The results were statistically analyzed.

RESULTS

The petrous part of the temporal bone was found at a mean of 16 mm anterior and 24 mm posterior to the MEAC. In 87% and 99% of the sides, the foramen ovale and foramen spinosum, respectively, were encountered deep to the zygomatic root. The posterior aspect of the greater superficial petrosal nerve (GSPN) groove was a mean of 6 mm anterior and 25 mm medial to the MEAC, nearly parallel to the petrous ridge. The main axis of the IAC projected to the root of the zygoma in all cases. The internal auditory canal (IAC) porus was found 5.5 mm lateral and 4.5 mm deep to the lateral aspect of the trigeminal impression along the petrous ridge (mean measurement values). A projection from this point to the middle aspect of the root of the zygoma, being posterior to the GSPN groove, could estimate the orientation of the IAC.

CONCLUSIONS

In middle fossa approaches, the external acoustic canal is a reliable reference before skin incision, whereas the zygomatic root becomes important after the skin incision. Deep structures can be related to these 2 anatomical structures. An easy method to predict the location of the IAC in surgery is described. Careful study of the preoperative imaging is essential to adapt this knowledge to the individual anatomy of the patient.

The microneurosurgical anatomy legacy of Albert L. Rhoton Jr., MD: an analysis of transition and evolution over 50 years

The authors chronologically categorized the 160 original articles written by Dr. Rhoton and his fellows to show why they selected their themes and how they carried out their projects. The authors note that as neurosurgery progresses and new techniques and approaches are developed, accurate and safe treatment will depend upon continued clarification of microsurgical anatomy.

Evaluation of an animation tool developed to supplement dental student study of the cranial nerves

INTRODUCTION

The structure/function of the cranial nerves is a core topic for dental students. However, due to the perceived complexity of the subject, it is often difficult for students to develop a comprehensive understanding of key concepts using textbooks and models. It is accepted that the acquisition of anatomical knowledge can be facilitated by visualisation of structures. This study aimed to develop and assess a novel cranial nerve animation as a supplemental learning aid for dental students.

MATERIALS AND METHODS

A multidisciplinary team of anatomists, neuroscientists and a computer scientist developed a novel animation depicting the cranial nerves. The animation was viewed by newly enrolled first-year dental students, graduate entry dental students (year 1) and dental hygiene students (year 1). A simple life scenario employing the use of the cranial nerves was developed using a cartoon-type animation with a viewing time of 3.58 minutes. The animation was developed with emphasis on a life scenario. The animation was placed online for 2 weeks with open access or viewed once in a controlled laboratory setting. Questionnaires were designed to assess the participants' attitude towards the animation and their knowledge of the cranial nerves before and after visualisation. This study was performed before the delivery of core lectures on the cranial nerves.

RESULTS

Our findings indicate that the use of the animation can act as a supplemental tool to improve student knowledge of the cranial nerves. Indeed, data indicate that a single viewing of the animation, in addition to 2-week access to the animation, can act as a supplemental learning tool to assist student understanding of the structure and function of cranial nerves. The animation significantly enhanced the student's opinion that their cranial nerve knowledge had improved. From a qualitative point of view, the students described the animation as an enjoyable and useful supplement to reading material/lectures and indicated that the animation was a useful tool in understanding the cranial nerves.

CONCLUSION

Overall, these findings indicate that an animation demonstrating the cranial nerves in a simple, everyday functional scenario may act as a learning aid in the study of cranial nerves.

Quantification of Surgical Route Parameters for Exposure of the Jugular Foramen Via a Trans-Mastoidal Approach Exposing Jugular Foramen in Three-Dimensional Visualization Model

OBJECTIVE

Surgical operation within the region of the jugular foramen presents a great challenge. The authors characterized the quantitative impact of surgical window parameters on the exposure of the jugular foramen via a trans-mastoidal approach.

METHODS

Computed tomography and magnetic resonance imaging data were used to establish a 3-dimensional model of the jugular foramen region. The mastoidale, posterior edge of the mastoid, and the superior edge of the bony external acoustic meatus were selected as points a, b, and c. The anterior edge of the tuberculum jugulare was selected as point d. The midpoints of line segments ab, ac, and bc were selected as points e, f, and g. Triangle abc was divided into triangles aef, beg, cfg, and efg. Surgical corridors of the triangular pyramid were outlined by connecting the above triangles to point d. Anatomic exposure was evaluated by measuring the area and volume of various structures within each route. Statistical comparisons were performed via analysis of variance.

RESULTS

The model allowed for adequate visualization of all structures. The areas of triangles beg and efg were greater than those of triangles aef and cfg (P < 0.05). The volumes of triangular pyramids d-beg and d-cfg were greater than those of triangular pyramids d-aef and d-efg (P = 0.000). Statistically significant differences were also observed for volumes of osseous, venous, and cranial nerve structures in all divided routes (P = 0.000).

CONCLUSION

Our results indicate that 3-dimensional modeling may aid in the quantification of surgical exposure and that division of the craniotomy window may allow for more precise operation.

Effect of Stereoscopic Anaglyphic 3-Dimensional Video Didactics on Learning Neuroanatomy

BACKGROUND

The teaching of neuroanatomy in medical education has historically been based on didactic instruction, cadaveric dissections, and intraoperative experience for students. Multiple novel 3-dimensional (3D) modalities have recently emerged. Among these, stereoscopic anaglyphic video is easily accessible and affordable, however, its effects have not yet formally been investigated.

OBJECTIVE

This study aimed to investigate if 3D stereoscopic anaglyphic video instruction in neuroanatomy could improve learning for content-naive students, as compared with 2-dimensional (2D) video instruction.

METHODS

A single-site controlled prospective case control study was conducted at the School of Education. Content knowledge was assessed at baseline, followed by the presentation of an instructional neuroanatomy video. Participants viewed the video in either 2D or 3D format and then completed a written test of skull base neuroanatomy. Pretest and post-test performances were analyzed with independent Student's t-tests and analysis of covariance.

RESULTS

Our study was completed by 249 subjects. At baseline, the 2D (n = 124, F = 97) and 3D groups (n = 125, F = 96) were similar, although the 3D group was older by 1.7 years (P = 0.0355) and the curricula of participating classes differed (P < 0.0001). Average scores for the 3D group were higher for both pretest (2D, M = 19.9%, standard deviation [SD] = 12.5% vs. 3D, M = 23.9%, SD = 14.9%, P = 0.0234) and post-test performances (2D, M = 68.5%, SD = 18.6% vs. 3D, M = 77.3%, SD = 18.8%, P = 0.003), but the magnitude of improvement across groups did not reach statistical significance (2D, M = 48.7%, SD = 21.3%, vs. 3D, M = 53.5%, SD = 22.7%, P = 0.0855).

CONCLUSION

Incorporation of 3D video instruction into curricula without careful integration is insufficient to promote learning over 2D video.

Virtual and stereoscopic anatomy: when virtual reality meets medical education

OBJECTIVE The authors sought to construct, implement, and evaluate an interactive and stereoscopic resource for teaching neuroanatomy, accessible from personal computers. METHODS Forty fresh brains (80 hemispheres) were dissected. Images of areas of interest were captured using a manual turntable and processed and stored in a 5337-image database. Pedagogic evaluation was performed in 84 graduate medical students, divided into 3 groups: 1 (conventional method), 2 (interactive nonstereoscopic), and 3 (interactive and stereoscopic). The method was evaluated through a written theory test and a lab practicum. RESULTS Groups 2 and 3 showed the highest mean scores in pedagogic evaluations and differed significantly from Group 1 (p < 0.05). Group 2 did not differ statistically from Group 3 (p > 0.05). Size effects, measured as differences in scores before and after lectures, indicate the effectiveness of the method. ANOVA results showed significant difference (p < 0.05) between groups, and the Tukey test showed statistical differences between Group 1 and the other 2 groups (p < 0.05). No statistical differences between Groups 2 and 3 were found in the practicum. However, there were significant differences when Groups 2 and 3 were compared with Group 1 (p < 0.05). CONCLUSIONS The authors conclude that this method promoted further improvement in knowledge for students and fostered significantly higher learning when compared with traditional teaching resources.

Japanese neurosurgeons and microsurgical anatomy: a historical review

Research in microneurosurgical anatomy has contributed to great advances in neurosurgery in the last 40 years. Many Japanese neurosurgeons have traveled abroad to study microsurgical anatomy and played major roles in advancing and spreading the knowledge of anatomy, overcoming their disadvantage that the cadaver study has been strictly limited inside Japan. In Japan, they initiated an educational system for surgical anatomy that has contributed to the development and standardization of Japanese neurosurgery. For example, the Japanese Society for Microsurgical Anatomy started an annual educational meeting in the middle of 1980s and published its proceedings in Japanese every year for approximately 20 years. These are some of the achievements that bring worldwide credit to Japanese neurosurgeons. Not only should Japanese neurosurgeons improve their educational system but they should also contribute to the international education in this field, particularly in Asia.

The cranial nerve skywalk: A 3D tutorial of cranial nerves in a virtual platform

Visualization of the complex courses of the cranial nerves by students in the health-related professions is challenging through either diagrams in books or plastic models in the gross laboratory. Furthermore, dissection of the cranial nerves in the gross laboratory is an extremely meticulous task. Teaching and learning the cranial nerve pathways is difficult using two-dimensional (2D) illustrations alone. Three-dimensional (3D) models aid the teacher in describing intricate and complex anatomical structures and help students visualize them. The study of the cranial nerves can be supplemented with 3D, which permits the students to fully visualize their distribution within the craniofacial complex. This article describes the construction and usage of a virtual anatomy platform in Second Life™, which contains 3D models of the cranial nerves III, V, VII, and IX. The Cranial Nerve Skywalk features select cranial nerves and the associated autonomic pathways in an immersive online environment. This teaching supplement was introduced to groups of pre-healthcare professional students in gross anatomy courses at both institutions and student feedback is included.

Endoscopic skull base training using 3D printed models with pre-existing pathology

Endoscopic base of skull surgery has been growing in acceptance in the recent past due to improvements in visualisation and micro instrumentation as well as the surgical maturing of early endoscopic skull base practitioners. Unfortunately, these demanding procedures have a steep learning curve. A physical simulation that is able to reproduce the complex anatomy of the anterior skull base provides very useful means of learning the necessary skills in a safe and effective environment. This paper aims to assess the ease of learning endoscopic skull base exposure and drilling techniques using an anatomically accurate physical model with a pre-existing pathology (i.e., basilar invagination) created from actual patient data. Five models of a patient with platy-basia and basilar invagination were created from the original MRI and CT imaging data of a patient. The models were used as part of a training workshop for ENT surgeons with varying degrees of experience in endoscopic base of skull surgery, from trainees to experienced consultants. The surgeons were given a list of key steps to achieve in exposing and drilling the skull base using the simulation model. They were then asked to list the level of difficulty of learning these steps using the model. The participants found the models suitable for learning registration, navigation and skull base drilling techniques. All participants also found the deep structures to be accurately represented spatially as confirmed by the navigation system. These models allow structured simulation to be conducted in a workshop environment where surgeons and trainees can practice to perform complex procedures in a controlled fashion under the supervision of experts.

Evaluation of a temporal bone prototype by experts in otology

BACKGROUND

Inexperienced otologists require training on the temporal bone drilling process, prior to any surgical activity. The shortage of cadaveric temporal bones exerts pressure to create realistic physical prototypes. This paper describes the evaluation by otology experts of a specially developed temporal bone resin model.

METHODS

Computed tomography images were transformed into digital files, and anatomically identical right temporal bone models were created using stereolithography. These hand-painted resin prototypes were sent to 25 otologists, accompanied by a 20-item questionnaire.

RESULTS

Satisfaction rate was 92 per cent. The overall prototype score was 48.87 out of 60. Average scores were: 12.63 out of 15 for anatomy-morphology, 6.98 out of 9 for quality of drilling, 16.74 out of 21 for identification of anatomical elements and 7.41 out of 9 for stages of drilling. Limitations of the model included an excessively vivid facial nerve colour and difficulty in identifying the posterior semicircular canal. Disadvantages related to the thickness of the resin and its residues were identified.

CONCLUSION

The prototype appears to provide an attractive solution to the shortage of cadaveric temporal bones. However, interest in the model for drilling technique training for inexperienced otologists has not yet been assessed.

Shortening the learning curve in endoscopic endonasal skull base surgery: a reproducible polymer tumor model for the trans-sphenoidal trans-tubercular approach to retro-infundibular tumors

BACKGROUND

Endoscopic endonasal skull base surgery attracts an increasing number of young neurosurgeons. This recent technique requires specific technical skills for the approaches to non-pituitary tumors (expanded endoscopic endonasal surgery). Actual residents' busy schedules carry the risk of compromising their laboratory training by limiting significantly the dedicated time for dissections.

OBJECTIVE

To enhance and shorten the learning curve in expanded endoscopic endonasal skull base surgery, we propose a reproducible model based on the implantation of a polymer via an intracranial route to provide a pathological retro-infundibular expansive lesion accessible to a virgin expanded endoscopic endonasal route, avoiding the ethically-debatable need to hundreds of pituitary cases in live patients before acquiring the desired skills.

METHODS

A polymer-based tumor model was implanted in 6 embalmed human heads via a microsurgical right fronto-temporal approach through the carotido-oculomotor cistern to mimic a retro-infundibular tumor. The tumor's position was verified by CT-scan. An endoscopic endonasal trans-sphenoidal trans-tubercular trans-planum approach was then carried out on a virgin route under neuronavigation tracking.

RESULTS

Dissection of the tumor model from displaced surrounding neurovascular structures reproduced live surgery's sensations and challenges. Post-implantation CT-scan allowed the pre-removal assessment of the tumor insertion, its relationships as well as naso-sphenoidal anatomy in preparation of the endoscopic approach.

CONCLUSION

Training on easily reproducible retro-infundibular approaches in a context of pathological distorted anatomy provides a unique opportunity to avoid the need for repetitive live surgeries to acquire skills for this kind of rare tumors, and may shorten the learning curve for endoscopic endonasal surgery.

Computer modeled multiportal approaches to the skull base

Skull base surgical approaches have evolved significantly to minimize collateral tissue damage and improve access to complex anatomic regions. Many endoscopic surgical portals have been described, and these can be combined in multiportal approaches that permit improved angles for visualization and instrumentation. To assist in the choice of entry portal and surgical pathway analysis, a three-dimensional computer model with virtual endoscopy was created. The model was evaluated on transnasal and transorbital approaches to access 11 specified sellar and parasellar target locations on 14 computed tomography (CT) scans. Data were collected on length of approach, angle between instruments, and approach angle with respect to anatomical planes. Optimal multiportal approach combinations were derived. The data demonstrated that the shortest, most direct pathway to many sellar and parasellar targets was through transorbital portals. Distances were reduced by 35% for certain target locations; combining transorbital and transnasal portals increased the angle between instruments 4-fold for many targets. The predicted values from the model were validated on four cadaver specimens. Computer modeling holds the potential to play an integral role in the design, analysis, and testing of new surgical approaches, as well as in the selection of optimal approach strategies for the unique pathology of individual patients.

The use of a three-dimensional novel computer-based model for analysis of the endonasal endoscopic approach to the midline skull base

OBJECTIVES

To apply a three-dimensional geometric model to various endoscopic endonasal approaches to analyze the bony anatomy of this area, quantify preoperatively bone removal, and optimize surgical planning.

METHODS

Investigators dissected 18 human cadaveric heads at the Laboratory of Surgical NeuroAnatomy (LSNA) of the University of Barcelona (Spain). Before and after each dissection, a computed tomography (CT) scan was performed to create a three-dimensional geometric model of the approach performed in the dissection room. The model protocol was designed as follows: (i) a preliminary exploration of each specimen using the preoperative CT scan, (ii) creation of a computer-generated three-dimensional virtual model of the approach, (iii) cadaveric anatomic dissection, and (iv) development of a CT-based model of the approach as a result of the superimposition of predissection and postdissection digital imaging and communications in medicine (DICOM) images of specimens.

RESULTS

This method employing preliminary virtual exploration of each specimen, the creation of a three-dimensional virtual model of the approach, and the overlapping of the predissection and postdissection three-dimensional models was useful to define the exact boundaries of the endoscopic endonasal craniectomy.

CONCLUSIONS

Aside from laboratory anatomic dissection itself, this model is very effective in providing a depiction of bony landmarks and visual feedback of the amount of bone removed, improving the design of the craniectomy in the endoscopic endonasal midline skull base approach.

Development of a computer-assisted cranial nerve simulation from the visible human dataset

Advancements in technology and personal computing have allowed for the development of novel teaching modalities such as online web-based modules. These modules are currently being incorporated into medical curricula and, in some paradigms, have been shown to be superior to classroom instruction. We believe that these modules have the potential of significantly enriching anatomy education by helping students better appreciate spatial relationships, especially in areas of the body with greater anatomical complexity. Our objective was to develop an online module designed to teach the anatomy and function of the cranial nerves. A three-dimensional model of the skull, brainstem, and thalamus were reconstructed using data from the Visible Human Project and Amira®. The paths of the cranial nerves were overlaid onto this 3D reconstruction. Videos depicting these paths were then rendered using a "roller coaster-styled" camera approach. Interactive elements adding textual information and user control were inserted into the video using Adobe Creative Suite® 4, and finally, the module was exported as an Adobe Flash movie to be viewable on Internet browsers. Fourteen Flash-based modules were created in total. The primary user interface comprises a website encoded in HTML/CSS and contains links to each of the 14 Flash modules as well as a user tutorial.

Explorable three-dimensional digital model of the female pelvis, pelvic contents, and perineum for anatomical education

The anatomy of the pelvis is complex, multilayered, and its three-dimensional organization is conceptually difficult for students to grasp. The aim of this project was to create an explorable and projectable stereoscopic, three-dimensional (3D) model of the female pelvis and pelvic contents for anatomical education. The model was created using cryosection images obtained from the Visible Human Project, in conjunction with a general-purpose three-dimensional segmentation and surface-rendering program. Anatomical areas of interest were identified and labeled on consecutive images. Each 2D slice was reassembled, forming a three-dimensional model. The model includes the pelvic girdle, organs of the pelvic cavity, surrounding musculature, the perineum, neurovascular structures, and the peritoneum. Each structure can be controlled separately (e.g. added, subtracted, made transparent) to reveal organization and/or relationships between structures. The model can be manipulated and/or projected stereoscopically to visualize structures and relationships from different angles with excellent spatial perception. Because of its ease of use and versatility, we expect this model may provide a powerful teaching tool for learning in the classroom or in the laboratory.

Preliminary experience with a new three-dimensional computer-based model for the study and the analysis of skull base approaches

PURPOSE

The goal of the present study was to develop a three-dimensional (3D) geometrical model based on pre- and post-dissection Digital Imaging and Communication in Medicine (DICOM) images of both transcranial and endonasal skull base approaches. Such model was structured for either teaching surgical anatomy and to evaluate the amount of bone removal over the skull base surface through a 3D digital perspective.

METHODS

Twenty-five human cadaveric heads were dissected at the Laboratory of Surgical NeuroAnatomy (LSNA) of the University of Barcelona (Spain) between 2007 and 2009. Before and after each dissection, a computed tomography-scan (CT-scan) was obtained in order to create a 3D geometrical model of the same approach performed in the dissection laboratory. The model protocol was designed as follows: (1) preoperative CT-scan of the specimens; (2) creation of a computer-generated 3D model of the specimen using specific imaging software for visualization and manipulation of biomedical data; (3) dissection of the specimens; (4) development of a 3D CT-based model of the approach as a result of the overlapping of the DICOM data of the specimens before and after the dissection.

RESULTS

The fusion of the pre- and post-dissection 3D models allowed evaluation of the amount of bone removal over the skull base surface.

CONCLUSIONS

Measurements of the bony landmarks as well as the visual feedback of the drilled bone over the skull base provided by our 3D model gives the opportunity to improve the tailoring of each approach to the different skull base areas.

Skull base tumor model

OBJECT

Resident duty-hours restrictions have now been instituted in many countries worldwide. Shortened training times and increased public scrutiny of surgical competency have led to a move away from the traditional apprenticeship model of training. The development of educational models for brain anatomy is a fascinating innovation allowing neurosurgeons to train without the need to practice on real patients and it may be a solution to achieve competency within a shortened training period. The authors describe the use of Stratathane resin ST-504 polymer (SRSP), which is inserted at different intracranial locations to closely mimic meningiomas and other pathological entities of the skull base, in a cadaveric model, for use in neurosurgical training.

METHODS

Silicone-injected and pressurized cadaveric heads were used for studying the SRSP model. The SRSP presents unique intrinsic metamorphic characteristics: liquid at first, it expands and foams when injected into the desired area of the brain, forming a solid tumorlike structure. The authors injected SRSP via different passages that did not influence routes used for the surgical approach for resection of the simulated lesion. For example, SRSP injection routes included endonasal transsphenoidal or transoral approaches if lesions were to be removed through standard skull base approach, or, alternatively, SRSP was injected via a cranial approach if the removal was planned to be via the transsphenoidal or transoral route. The model was set in place in 3 countries (US, Italy, and The Netherlands), and a pool of 13 physicians from 4 different institutions (all surgeons and surgeons in training) participated in evaluating it and provided feedback.

RESULTS

All 13 evaluating physicians had overall positive impressions of the model. The overall score on 9 components evaluated--including comparison between the tumor model and real tumor cases, perioperative requirements, general impression, and applicability--was 88% (100% being the best possible achievable score where the evaluator strongly agreed with the proposed factor). Individual components had scores at or above 80% (except for 1). The only score that was below 80% was related to radiographic visibility of the model for adequate surgical planning (score of 74%). The highest score was given to usefulness in neurosurgical training (98%).

CONCLUSIONS

The skull base tumor model is an effective tool to provide more practice in preoperative planning and technical skills.