Virtual reality presurgical planning for cerebral gliomas adjacent to motor pathways in an integrated 3-D stereoscopic visualization of structural MRI and DTI tractography

The impact of extended reality on surgery: a scoping review

PURPOSE

Extended reality (XR) is defined as a spectrum of technologies that range from purely virtual environments to enhanced real-world environments. In the past two decades, XR-assisted surgery has seen an increase in its use and also in research and development. This scoping review aims to map out the historical trends in these technologies and their future prospects, with an emphasis on the reported outcomes and ethical considerations on the use of these technologies.

METHODS

A systematic search of PubMed, Scopus, and Embase for literature related to XR-assisted surgery and telesurgery was performed using Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR) guidelines. Primary studies, peer-reviewed articles that described procedures performed by surgeons on human subjects and cadavers, as well as studies describing general surgical education, were included. Non-surgical procedures, bedside procedures, veterinary procedures, procedures performed by medical students, and review articles were excluded. Studies were classified into the following categories: impact on surgery (pre-operative planning and intra-operative navigation/guidance), impact on the patient (pain and anxiety), and impact on the surgeon (surgical training and surgeon confidence).

RESULTS

One hundred and sixty-eight studies were included for analysis. Thirty-one studies investigated the use of XR for pre-operative planning concluded that virtual reality (VR) enhanced the surgeon's spatial awareness of important anatomical landmarks. This leads to shorter operating sessions and decreases surgical insult. Forty-nine studies explored the use of XR for intra-operative planning. They noted that augmented reality (AR) headsets highlight key landmarks, as well as important structures to avoid, which lowers the chance of accidental surgical trauma. Eleven studies investigated patients' pain and noted that VR is able to generate a meditative state. This is beneficial for patients, as it reduces the need for analgesics. Ten studies commented on patient anxiety, suggesting that VR is unsuccessful at altering patients' physiological parameters such as mean arterial blood pressure or cortisol levels. Sixty studies investigated surgical training whilst seven studies suggested that the use of XR-assisted technology increased surgeon confidence.

CONCLUSION

The growth of XR-assisted surgery is driven by advances in hardware and software. Whilst augmented virtuality and mixed reality are underexplored, the use of VR is growing especially in the fields of surgical training and pre-operative planning. Real-time intra-operative guidance is key for surgical precision, which is being supplemented with AR technology. XR-assisted surgery is likely to undertake a greater role in the near future, given the effect of COVID-19 limiting physical presence and the increasing complexity of surgical procedures.

Advantages of a Training Course for Surgical Planning in Virtual Reality for Oral and Maxillofacial Surgery: Crossover Study

BACKGROUND

As an integral part of computer-assisted surgery, virtual surgical planning (VSP) leads to significantly better surgery results, such as for oral and maxillofacial reconstruction with microvascular grafts of the fibula or iliac crest. It is performed on a 2D computer desktop screen (DS) based on preoperative medical imaging. However, in this environment, VSP is associated with shortcomings, such as a time-consuming planning process and the requirement of a learning process. Therefore, a virtual reality (VR)-based VSP application has great potential to reduce or even overcome these shortcomings due to the benefits of visuospatial vision, bimanual interaction, and full immersion. However, the efficacy of such a VR environment has not yet been investigated.

OBJECTIVE

This study aimed to demonstrate the possible advantages of a VR environment through a substep of VSP, specifically the segmentation of the fibula (calf bone) and os coxae (hip bone), by conducting a training course in both DS and VR environments and comparing the results.

METHODS

During the training course, 6 novices were taught how to use a software application in a DS environment (3D Slicer) and in a VR environment (Elucis) for the segmentation of the fibula and os coxae, and they were asked to carry out the maneuvers as accurately and quickly as possible. Overall, 13 fibula and 13 os coxae were segmented for each participant in both methods (VR and DS), resulting in 156 different models (78 fibula and 78 os coxae) per method (VR and DS) and 312 models in total. The individual learning processes in both environments were compared using objective criteria (time and segmentation performance) and self-reported questionnaires. The models resulting from the segmentation were compared mathematically (Hausdorff distance and Dice coefficient) and evaluated by 2 experienced radiologists in a blinded manner.

RESULTS

A much faster learning curve was observed for the VR environment than the DS environment (β=.86 vs β=.25). This nearly doubled the segmentation speed (cm³/min) by the end of training, leading to a shorter time (P<.001) to reach a qualitative result. However, there was no qualitative difference between the models for VR and DS (P=.99). The VR environment was perceived by participants as more intuitive and less exhausting, and was favored over the DS environment.

CONCLUSIONS

The more rapid learning process and the ability to work faster in the VR environment could save time and reduce the VSP workload, providing certain advantages over the DS environment.

A data-centric artificial intelligent and extended reality technology in smart healthcare systems

Extended reality (XR) solutions are quietly maturing, and their novel use cases are already being investigated, particularly in the healthcare industry. By 2022, the extended reality market is anticipated to be worth $209 billion. Certain diseases, such as Alzheimer's, Schizophrenia, Stroke rehabilitation stimulating specific areas of the patient's brain, healing brain injuries, surgeon training, realistic 3D visualization, touch-free interfaces, and teaching social skills to children with autism, have shown promising results with XR-assisted treatments. Similar effects have been used in video game therapies like Akili Interactive's EndeavorRx, which has previously been approved by the Food and Drug Administration (FDA) as a treatment regimen for children with attention deficit hyperactivity disorder (ADHD). However, while these improvements have received positive feedback, the field of XR-assisted patient treatment is in its infancy. The growth of XR in the healthcare sphere has the potential to transform the delivery of medical services. Imagine an elderly patient in a remote setting having a consultation with a world-renowned expert without ever having to leave their house. Rather than operating on cadavers in a medical facility, a surgical resident does surgery in a virtual setting at home. On the first try, a nurse uses a vein finder to implant an IV. Through cognitive treatment in a virtual world, a war veteran recovers from post-traumatic stress disorder (PTSD). The paper discusses the potential impact of XR in transforming the healthcare industry, as well as its use cases, challenges, XR tools and techniques for intelligent health care, recent developments of XR in intelligent healthcare services, and the potential benefits and future aspects of XR techniques in the medical domain.

Validation of Presurgical Simulation of White Matter Damage Using Diffusion Tensor Imaging

BACKGROUND

The understanding of white matter (WM) was revolutionized by the emergence of tractography based on diffusion tensor imaging (DTI). Currently, DTI simulations are implemented in preoperative planning to optimize surgical approaches. The reliability of these simulations has been questioned and investigated seeking for correlation between neurological performance and anomalies in DTI parameters. However, the ability of preoperative WM simulations to predict a surgical injury has not been thoroughly evaluated. Our objective was to assess the reliability of preoperatively simulated WM injuries for conventional neurosurgical procedures.

METHODS

WM surgical damage was preoperatively simulated by creating a 3-dimensional volume representing the endoscope or the surgical trajectory. This volume was used as an additional region of interest in the fascicle reconstruction to be subtracted from the original fascicle. Simulated, injured fascicles were compared in terms of the number of fibers and volume to those created from postoperative DTI studies. Reliability was assimilated into the correlation between the simulation and the postoperative reconstruction; evaluated using the intraclass correlation coefficient or Lin's Concordance correlation coefficient (CCC), and represented on Bland-Altman plots.

RESULTS

The preoperative and postoperative DTI studies of 30 patients undergoing various neurosurgical approaches were processed. The correlation between simulated injuries and postoperative studies was high in terms of fibers (Concordance correlation coefficient = Rho.C = 0.989 [95% confidence interval = 0.979-0.995]) and volume (intraclass correlation coefficient = 0.95 [95% CI = 0.89-0.97]). Bland-Altman plots demonstrated that the great majority of cases fell within the mean ± 2 Standard deviations.

CONCLUSIONS

Presurgical simulation of WM fascicles based on DTI is consistent with postoperative DTI studies. These findings require further validation by neurophysiological and clinical correlation.

Glioma invasion along white matter tracts: A dilemma for neurosurgeons

Invasive growth along white matter (WM) tracts is one of the most prominent clinicopathological features of glioma and is also an important reason for surgical treatment failure in glioma patients. A full understanding of relevant clinical features and mechanisms is of great significance for finding new therapeutic targets and developing new treatment regimens and strategies. Herein, we review the imaging and histological characteristics of glioma patients with WM tracts invasion and summarize the possible molecular mechanism. On this basis, we further discuss the correlation between glioma molecular typing, radiotherapy and tumor treating fields (TTFields) and the invasion of glioma along WM tracts.

Examining the benefits of extended reality in neurosurgery: A systematic review

While well-established in other surgical subspecialties, the benefits of extended reality, consisting of virtual reality (VR), augmented reality (AR), and mixed reality (MR) technologies, remains underexplored in neurosurgery despite its increasing utilization. To address this gap, we conducted a systematic review of the effects of extended reality (XR) in neurosurgery with an emphasis on the perioperative period, to provide a guide for future clinical optimization. Seven primary electronic databases were screened following guidelines outlined by PRISMA and the Institute of Medicine. Reported data related to outcomes in the perioperative period and resident training were all examined, and a focused analysis of studies reporting controlled, clinical outcomes was completed. After removal of duplicates, 2548 studies were screened with 116 studies reporting measurable effects of XR in neurosurgery. The majority (82%) included cranial based applications related to tumor surgery with 34% showing improved resection rates and functional outcomes. A rise in high-quality studies was identified from 2017 to 2020 compared to all previous years (p = 0.004). Primary users of the technology were: 56% neurosurgeon (n = 65), 28% residents (n = 33) and 5% patients (n = 6). A final synthesis was conducted on 10 controlled studies reporting patient outcomes. XR technologies have demonstrated benefits in preoperative planning and multimodal neuronavigation especially for tumor surgery. However, few studies have reported patient outcomes in a controlled design demonstrating a need for higher quality data. XR platforms offer several advantages to improve patient outcomes and specifically, the patient experience for neurosurgery.

Optimization of skull base exposure using navigation-integrated, virtual reality templates

In many skull base procedures, arriving at the optimal bone exposure is important. Whereas insufficient exposure can jeopardize the operation itself, over-doing the exposure might lead to complications. We developed a new technique, harnessing the strength of Virtual Reality (VR) technology in planning, rehearsal and navigation, to achieve the optimal skull base exposure for resection of tumors. VR models of patient-specific anatomy were used to rehearse the surgical exposure. From the altered models, the one with the ideal exposure was chosen, integrated with the navigation system in the operating suite, and used as a template to achieve the optimal exposure in surgery. The use of these VR templates is demonstrated in two cases involving skull base tumors. In both cases, over-zealous bone removal could have increased the risk of complications, and inadequate exposure would jeopardize the tumor resection. Navigation guided by the VR templates aided the creation of the "ideal" surgical exposure to reach the surgical goals. Complete resections were achieved and neither patient suffered any approach-related complications. In conclusion, virtual reality is a powerful tool to improve the safety and efficacy of neurosurgical procedures. With preoperatively-altered VR templates, the surgeon is no longer navigating just to find bearings, but to duplicate an opening designed to simultaneously provide sufficient exposure while limiting postoperative complications. Intuitively useful and successful in early application, there has been no identifiable disadvantages to date.

Tractography in Neurosurgery: A Systematic Review of Current Applications

The ability to visualize the brain's fiber connections noninvasively in vivo is relatively young compared with other possibilities of functional magnetic resonance imaging. Although many studies showed tractography to be of promising value for neurosurgical care, the implications remain inconclusive. An overview of current applications is presented in this systematic review. A search was conducted for (("tractography" or "fiber tracking" or "fibre tracking") and "neurosurgery") that produced 751 results. We identified 260 relevant articles and added 20 more from other sources. Most publications concerned surgical planning for resection of tumors (n = 193) and vascular lesions (n = 15). Preoperative use of transcranial magnetic stimulation was discussed in 22 of these articles. Tractography in skull base surgery presents a special challenge (n = 29). Fewer publications evaluated traumatic brain injury (TBI) (n = 25) and spontaneous intracranial bleeding (n = 22). Twenty-three articles focused on tractography in pediatric neurosurgery. Most authors found tractography to be a valuable addition in neurosurgical care. The accuracy of the technique has increased over time. There are articles suggesting that tractography improves patient outcome after tumor resection. However, no reliable biomarkers have yet been described. The better rehabilitation potential after TBI and spontaneous intracranial bleeding compared with brain tumors offers an insight into the process of neurorehabilitation. Tractography and diffusion measurements in some studies showed a correlation with patient outcome that might help uncover the neuroanatomical principles of rehabilitation itself. Alternative corticofugal and cortico-cortical networks have been implicated in motor recovery after ischemic stroke, suggesting more complex mechanisms in neurorehabilitation that go beyond current models. Hence tractography may potentially be able to predict clinical deficits and rehabilitation potential, as well as finding possible explanations for neurologic disorders in retrospect. However, large variations of the results indicate a lack of data to establish robust diagnostical concepts at this point. Therefore, in vivo tractography should still be interpreted with caution and by experienced surgeons.

Patient-specific 3-dimensionally printed models for neurosurgical planning and education

OBJECTIVE

Advances in 3-dimensional (3D) printing technology permit the rapid creation of detailed anatomical models. Integration of this technology into neurosurgical practice is still in its nascence, however. One potential application is to create models depicting neurosurgical pathology. The goal of this study was to assess the clinical value of patient-specific 3D printed models for neurosurgical planning and education.

METHODS

The authors created life-sized, patient-specific models for 4 preoperative cases. Three of the cases involved adults (2 patients with petroclival meningioma and 1 with trigeminal neuralgia) and the remaining case involved a pediatric patient with craniopharyngioma. Models were derived from routine clinical imaging sequences and manufactured using commercially available software and hardware.

RESULTS

Life-sized, 3D printed models depicting bony, vascular, and neural pathology relevant to each case were successfully manufactured. A variety of commercially available software and hardware were used to create and print each model from radiological sequences. The models for the adult cases were printed in separate pieces, which had to be painted by hand, and could be disassembled for detailed study, while the model for the pediatric case was printed as a single piece in separate-colored resins and could not be disassembled for study. Two of the models were used for patient education, and all were used for presurgical planning by the surgeon.

CONCLUSIONS

Patient-specific 3D printed models are useful to neurosurgical practice. They may be used as a visualization aid for surgeons and patients, or for education of trainees.

Presurgical simulation for neuroendoscopic procedures: Virtual study of the integrity of neurological pathways using diffusion tensor imaging tractography

Background:

White matter (WM) transgression is an unexplored concept in neuroendoscopy. Diffusion tensor image (DTI) tractography could be implemented as a planning and postoperative evaluation tool in functional disconnection procedures (FDPs), which are, currently, the subject of technological innovations. We intend to prove the usefulness of this planning method focused on the assessment of WM injury that is suitable for planning FDPs.

Methods:

Ten cranial magnetic resonance studies (20 sides) without pathological findings were processed. Fascicles were defined by two regions of interest (ROIs) using the fiber assignment method by the continuous tracking approach. Using three-dimensional (3D) simulation and DTI tractography, we created an 8-mm virtual endoscope and an uninjured inferior fronto-occipital fasciculus (IFOF) from two ROIs. The injured tract was generated using a third ROI built from the 3D model of the intersection of the oriented trajectory of the endoscope with the fascicle. Data and images were quantitatively and qualitatively analyzed.

Results:

The average percentage of the injured fibers was 32.0% (range: 12.4%–70%). The average intersected volume was 1.1 cm³ (range: 0.3–2.3 cm³). Qualitative analysis showed the inferior medial quadrant of the inferior fronto-occipital fasciculus (IFOF) as the most frequently injured region. No hemispherical asymmetry was found (P > 0.5).

Conclusion:

DTI tractography is a useful surgical planning tool that could be implemented in several endoscopic procedures. Together with a functional atlas, the presented technique provides a noninvasive method to assess the potential sequelae and thus to optimize the surgical route. The suggested method could be implemented to analyze pathological WM fascicles and to assess the surgical results of FDP such as hemispherotomy or amygdalohippocampectomy. More studies are needed to overcome the limitations of the tractography based information and to develop more anatomically and functionally reliable planning systems.

Is patient-specific pre-operative preparation feasible in a clinical environment? A systematic review and meta-analysis

Technical difficulty of an operation is associated with patient and disease characteristics, indicating the necessity for surgeons to exercise patient-specific preparation. Such methods have been shown to be effective in the simulation suite, however, application in a real clinical environment has been sporadic. This systematic review attempts to answer if patient-specific preparation in challenging surgical procedures is feasible. A systematic review of OvidMedline, Embase and all Evidence Based Medicine review databases, was conducted in search of studies who described surgical rehearsals in all specialties. Following the application of defined inclusion and exclusion criteria relevant data were extracted and summarised. Descriptive synthesis was performed for all included studies and meta-analysis of data was applied when possible. Of fourty-nine studies included, thirty-seven were case-series, ten were non-randomised comparative trials and two randomised controlled trials. Accuracy of applied methods ranged from 66.7 to 100% and a good outcome was seen in 60-100% of operations. Meta-analysis of studies comparing rehearsals to real procedures (same patients) showed that simulated procedures were significantly faster than real ones (SMD = -1.56 [-2.19, -0.93] p < 0.00001) but were similar in other outcomes (fluoroscopy time: SMD = -0.1 [-0.63, 0.42] p = 0.7, fluoroscopy volume: SMD = -0.43[-0.97, 0.11], p = 0.12). Meta-analysis of studies comparing pre-operative rehearsals to standard treatment (two distinct groups of patients), demonstrated that real procedures were performed quicker if pre-operative rehearsal took place (SMD = -0.47 [-0.79, -0.16], P  = 0.003) but the immediate clinical outcome was similar for practiced and not practiced operations (SMD =0.03[-0.23, 0.29], p = 0.82). Current evidence suggests that patient-specific pre-operative preparation is feasible and safe and decreases operational time.

Presurgical and Intraoperative Augmented Reality in Neuro-Oncologic Surgery: Clinical Experiences and Limitations

Virtual reality (VR) and augmented reality (AR) represent novel adjuncts for neurosurgical planning in neuro-oncology. In addition to established use in surgical and medical training, VR/AR are gaining traction for clinical use preoperatively and intraoperatively. To understand the utility of VR/AR in the clinical setting, we conducted a literature search in Ovid MEDLINE and EMBASE with various search terms designed to capture the use of VR/AR in neurosurgical procedures for resection of cranial tumors. The search retrieved 302 articles, of which 35 were subjected to full-text review; 19 full-text articles were included in the review. Key findings highlighted by the individual authors were extracted and summarized into themes to present the value of VR/AR in the clinical setting. These studies included various VR/AR systems applied to surgeries involving heterogeneous pathologies and outcome measures. Overall, VR/AR were found to be qualitatively advantageous due to enhanced visualization of complex anatomy and improved intraoperative lesion localization. When these technologies were compared with existing neuronavigation systems, quantitative clinical benefits were also reported. The capacity to visualize three-dimensional images superimposed on patient anatomy is a potentially valuable tool in complex neurosurgical environments. Surgical limitations may be addressed through future advances in image registration and tracking as well as intraoperatively acquired imaging with the ability to yield real-time virtual models.

Virtual reality and augmented reality in the management of intracranial tumors: A review

Neurosurgeons are faced with the challenge of planning, performing, and learning complex surgical procedures. With improvements in computational power and advances in visual and haptic display technologies, augmented and virtual surgical environments can offer potential benefits for tests in a safe and simulated setting, as well as improve management of real-life procedures. This systematic literature review is conducted in order to investigate the roles of such advanced computing technology in neurosurgery subspecialization of intracranial tumor removal. The study would focus on an in-depth discussion on the role of virtual reality and augmented reality in the management of intracranial tumors: the current status, foreseeable challenges, and future developments.

Patient-specific mental rehearsal with interactive visual aids: a path worth exploring?

Background

Surgeons of today are faced with unprecedented challenges; necessitating a novel approach to pre-operative preparation which takes into account the specific tests each case poses. In this study, we examine patient-specific mental rehearsal for pre-surgical practice and assess whether this method has an additional effect when compared to generic mental rehearsal.

Methods

Sixteen medical students were trained how to perform a simulated laparoscopic cholecystectomy (SLC). After baseline assessments, they were randomised to two equal groups and asked to complete three SLCs involving different anatomical variants. Prior to each procedure, Group A practiced mental rehearsal with the use of a pre-prepared checklist and Group B mental rehearsal with the checklist combined with virtual models matching the anatomical variations of the SLCs. The performance of the two groups was compared using simulator provided metrics and competency assessment tool (CAT) scoring by two blinded assessors.

Results

The participants performed equally well when presented with a “straight-forward” anatomy [Group A vs. Group B—time sec: 445.5 vs. 496 p = 0.64—NOM: 437 vs. 413 p = 0.88—PL cm: 1317 vs. 1059 p = 0.32—per: 0.5 vs. 0 p = 0.22—NCB: 0 vs. 0 p = 0.71—DVS: 0 vs. 0 p = 0.2]; however, Group B performed significantly better [Group A vs. B Total CAT score—Short Cystic Duct (SCD): 20.5 vs. 26.31 p = 0.02 η² = 0.32—Double cystic Artery (DA): 24.75 vs. 30.5 p = 0.03 η² = 0.28] and committed less errors (Damage to Vital Structures—DVS, SCD: 4 vs. 0 p = 0.03 η²=0.34, DA: 0 vs. 1 p = 0.02 η² = 0.22). in the cases with more challenging anatomies.

Conclusion

These results suggest that patient-specific preparation with the combination of anatomical models and mental rehearsal may increase operative quality of complex procedures.

Neurosurgical Virtual Reality Simulation for Brain Tumor Using High-definition Computer Graphics: A Review of the Literature

Simulation and planning of surgery using a virtual reality model is becoming common with advances in computer technology. In this study, we conducted a literature search to find trends in virtual simulation of surgery for brain tumors. A MEDLINE search for “neurosurgery AND (simulation OR virtual reality)” retrieved a total of 1,298 articles published in the past 10 years. After eliminating studies designed solely for education and training purposes, 28 articles about the clinical application remained. The finding that the vast majority of the articles were about education and training rather than clinical applications suggests that several issues need be addressed for clinical application of surgical simulation. In addition, 10 of the 28 articles were from Japanese groups. In general, the 28 articles demonstrated clinical benefits of virtual surgical simulation. Simulation was particularly useful in better understanding complicated spatial relations of anatomical landmarks and in examining surgical approaches. In some studies, Virtual reality models were used on either surgical navigation system or augmented reality technology, which projects virtual reality images onto the operating field. Reported problems were difficulties in standardized, objective evaluation of surgical simulation systems; inability to respond to tissue deformation caused by surgical maneuvers; absence of the system functionality to reflect features of tissue (e.g., hardness and adhesion); and many problems with image processing. The amount of description about image processing tended to be insufficient, indicating that the level of evidence, risk of bias, precision, and reproducibility need to be addressed for further advances and ultimately for full clinical application.

Assessment of the Accuracy and Errors of Head-Up Display by an Optical Neuronavigation System in Brain Tumor Surgery

BACKGROUND: A head-up display (HUD) in which navigational information is projected into the microscope view may enable surgeons to perform operations more efficiently. Projecting depictions of both tumor and important intracranial structures on the HUD may facilitate safe surgery.

OBJECTIVE: To investigate accuracy and errors regarding important intracranial structures, errors due to brain shifts, and preservation rates for important intracranial structures.

METHODS: A total of 184 surgeries in 172 patients were performed using this operation system. Postoperatively, we determined accuracy and errors for actual structures and virtual reality on the HUD and performed statistical analyses.

RESULTS: Preresection accuracy for important intracranial structures was highest for the internal carotid artery (ICA; 90.4%) and lowest for the posterior inferior cerebellar artery (53.6%). Differences between pre- and postresection accuracy were greatest, in descending order, for the cortical vein (P &lt; .0001), V4 segment of vertebral artery (P &lt; .0001), and anterior inferior cerebellar artery (P = .00780), whereas differences between pre- and postresection errors were smallest for the cranial nerve V (P = .500), middle cerebral artery (P = .0313), and ICA (P = .0313). Cases of poor preresection accuracy and large differences in pre- to postresection accuracy were seen in the prone position.

CONCLUSION: A reliable surgical resection rate was achieved using the HUD, and reliable preservation of important intracranial structures was also possible. Accuracy was concluded to be within an acceptable range.

Evaluation of monoscopic and stereoscopic displays for visual-spatial tasks in medical contexts

In the medical field, digital images are present in diagnosis, pre-operative planning, minimally invasive surgery, instruction, and training. The use of medical digital imaging has afforded new ways to interact with a patient, such as seeing fine details inside a body. This increased usage also raises many basic research questions on human perception and performance when utilizing these images. The work presented here attempts to answer the question: How would adding the stereopsis depth cue affect relative position tasks in a medical context compared to a monoscopic view? By designing and conducting a study to isolate the benefits between monoscopic 3D and stereoscopic 3D displays in a relative position task, the following hypothesis was tested: stereoscopic 3D displays are beneficial over monoscopic 3D displays for relative position judgment tasks in a medical visualization setting. 44 medical students completed a series of relative position judgments tasks. The results show that stereoscopic condition yielded a higher score than the monoscopic condition with regard to the hypothesis.

The role of probabilistic tractography in the surgical treatment of thalamic gliomas

BACKGROUND

Thalamic gliomas represent a great challenge for neurosurgeons because of the high surgical risk of damaging the surrounding anatomy. Preoperative planning may considerably help the surgeon find the most ideal operative trajectory, avoiding thalamic nuclei and important white matter pathways adjacent to the tumor tissue. Thalamic segmentation is a promising imaging tool based on diffusion tensor magnetic resonance imaging. It provides the possibility to predict the relationship of the tumor to thalamic nuclei.

OBJECTIVE

To propose a new tool in thalamic glioma surgery that may help to differentiate between normal thalamus and tumor tissue, making preoperative planning possible and facilitating the choice of the optimal surgical approach and trajectory for neuronavigation-assisted surgery.

METHODS

Four patients with thalamic gliomas preoperatively underwent conventional and diffusion-weighted magnetic resonance imaging conducted on 1.5 T. Subsequently, probabilistic tractography and thalamic segmentation were performed with the FSL Software as preoperative planning. We also present a case when thalamic segmentation was applied retrospectively using preoperative images. All patients went through neuronavigation-assisted surgery (1 partial, 4 subtotal resections).

RESULTS

Surgery performed based on the output of thalamic segmentation caused no deterioration in the neurological symptoms of our patients. Indeed, we noticed improvement in the neurological condition in 3 cases; furthermore, in 2 patients, a concern-free state was achieved.

CONCLUSION

We suggest that thalamic segmentation may be applied successfully and routinely in the surgical treatment of thalamic gliomas.

fMRI-Driven DTT Assessment of Corticospinal Tracts Prior to Cortex Resection

Background:

The role of diffusion tensor tractography (DTT) has become increasingly important in the preoperative mapping of brain white matter. Recently, functional magnetic resonance imaging (fMRI) driven DTT has provided the ability to evaluate the spatial relationship between the corticospinal tract (CST) and motor resection tumor boundaries. The main objective of this study was improvement of the preoperative assessment of the CST in patients with gliomas involving the motor cortical areas.

Methods:

Seventeen patients with gliomas involving motor cortical areas underwent 3 dimensions (3D) T1-weighted imaging for anatomical referencing, using both fMRI and diffusion tensor imaging (DTI). We used the fast-marching tractography (FMT) algorithm to define the 3D connectivity maps within the whole brain using seed points selected in the white matter adjacent to the location of fMRI activation. The target region of interest (ROI) was placed in the cerebral peduncle. Karnofsky performance status (KPS) scores were evaluated for each patient before and after surgery.

Results:

The CST of a total seventeen patients were successfully tracked by choosing seed and target ROI on the path of the fibers. What is more, DTT can indicate preoperatively the possibility for total glioma removal or the maximum extent of surgical resection. The postoperative average KPS score for the seventeen patients enrolled increased by more than 10 points.

Conclusions:

Incorporation of fMRI driven DTT showed a maximum benefit in surgical treatment of gliomas. Our study of the assessment precision should enhance the accuracy of glioma operations with a resulting improvement in postoperative patient outcome.

Clinical use of diffusion tensor image-merged functional neuronavigation for brain tumor surgeries: review of preoperative, intraoperative, and postoperative data for 123 cases

PURPOSE

To achieve maximal safe resection during brain tumor surgery, functional image-merged neuronavigation is widely used. We retrospectively reviewed our cases in which diffusion tensor image (DTI)-merged functional neuronavigation was performed during surgery.

MATERIALS AND METHODS

Between November 2008 and May 2010, 123 patients underwent surgery utilizing DTI-merged neuronavigation. Anatomical magnetic resonance images (MRI) were obtained preoperatively and fused with DTI of major white matter tracts, such as the corticospinal tract, optic radiation, or arcuate fasciculus. We used this fused image for functional neuronavigation during brain tumor surgery of eloquent areas. We checked the DTI images together with postoperative MRI images and evaluated the integrity of white matter tracts.

RESULTS

A single white matter tract was inspected in 78 patients, and two or more white matter tracts were checked in 45 patients. Among the 123 patients, a grossly total resection was achieved in 90 patients (73.2%), subtotal resection in 29 patients (23.6%), and partial resection in 4 patients (3.3%). Postoperative neurologic outcomes, compared with preoperative function, included the following: 100 patients (81.3%) displayed improvement of neurologic symptoms or no change, 7 patients (5.7%) experienced postoperative permanent neurologic deterioration (additional or aggravated neurologic symptoms), and 16 patients (13.0%) demonstrated transient worsening.

CONCLUSION

DTI-merged functional neuronavigation could be a useful tool in brain tumor surgery for maximal safe resection. However, there are still limitations, including white matter tract shift, during surgery and in DTI itself. Further studies should be conducted to overcome these limitations.

Diffusion tensor tractography in the presurgical assessment of cerebral gliomas

Glioma is the most common intra-axial brain tumor characterized by invasion into the surrounding white matter (WM) tracts. These tumors are usually diagnosed by conventional MRI, but this method is unable to describe the relationship between tumor and neighboring WM tracts. Diffusion tensor tractography (DTT) is a new imaging modality which can solve this problem. The current study evaluated the application of DTT imaging in the presurgical assessment of gliomas, and introduces this new modality and its importance to physicians and imaging centers in Iran. Ten patients with intra-axial brain tumor and suspicion of glioma underwent conventional brain MRI pulse sequences and DTT imaging between December 2011 and February 2013 with a 1.5 Tesla system using 64 independent diffusion encoding directions. Acquired images were assessed by the neuroradiologist and neurosurgeon. The treatment strategies were recognized and compared using data before and after the tractography. On the basis of DTT data, the treatment strategy changed from radiotherapy to the craniotomy in seven patients, and in one patient, the neurosurgeon preferred to avoid surgery. In one patient, the treatment technique did not change, and in the last one radiosurgery was replaced by craniotomy. As we can infer from this study, based on the tractography results, the treatment strategy may be changed, and the treatment technique could be devised more accurately and may lead to fewer postoperative neurological deficits and better outcomes.

Diffusion tensor imaging fiber tracking with reliable tracking orientation and flexible step size

We propose a method of reliable tracking orientation and flexible step size fiber tracking. A new directional strategy was defined to select one optimal tracking orientation from each directional set, which was based on the single-tensor model and the two-tensor model. The directional set of planar voxels contained three tracking directions: two from the two-tensor model and one from the single-tensor model. The directional set of linear voxels contained only one principal vector. In addition, a flexible step size, rather than fixable step sizes, was implemented to improve the accuracy of fiber tracking. We used two sets of human data to assess the performance of our method; one was from a healthy volunteer and the other from a patient with low-grade glioma. Results verified that our method was superior to the single-tensor Fiber Assignment by Continuous Tracking and the two-tensor eXtended Streamline Tractography for showing detailed images of fiber bundles.

Clinical application of motor pathway mapping using diffusion tensor imaging tractography and intraoperative direct subcortical stimulation in cerebral glioma surgery: a prospective cohort study

BACKGROUND

Glioma surgery in eloquent areas remains a challenge because of the risk of postoperative motor deficits.

OBJECTIVE

To prospectively evaluate the efficiency of using a combination of diffusion tensor imaging (DTI) tractography functional neuronavigation and direct subcortical stimulation (DsCS) to yield a maximally safe resection of cerebral glioma in eloquent areas.

METHODS

A prospective cohort study was conducted in 58 subjects with an initial diagnosis of primary cerebral glioma within or adjacent to the pyramidal tract (PT). The white matter beneath the resection cavity was stimulated along the PT, which was visualized with DTI tractography. The intercept between the PT border and DsCS site was measured. The sensitivity and specificity of DTI tractography for PT mapping were evaluated. The efficiency of the combined use of both techniques on motor function preservation was assessed.

RESULTS

Postoperative analysis showed gross total resection in 40 patients (69.0%). Seventeen patients (29.3%) experienced postoperative worsening; 1-month motor deficit was observed in 6 subjects (10.3%). DsCS verified a high concordance rate with DTI tractography for PT mapping. The sensitivity and specificity of DTI were 92.6% and 93.2%, respectively. The intercepts between positive DsCS sites and imaged PTs were 2.0 to 14.7 mm (5.2 ± 2.2 mm). The 6-month Karnofsky performance scale scores in 50 postoperative subjects were significantly increased compared with their preoperative scores.

CONCLUSION

DTI tractography is effective but not completely reliable in delineating the descending motor pathways. Integration of DTI and DsCS favors patient-specific surgery for cerebral glioma in eloquent areas.

3D preoperative planning in the ER with OsiriX®: when there is no time for neuronavigation

The evaluation of patients in the emergency room department (ER) through more accurate imaging methods such as computed tomography (CT) has revolutionized their assistance in the early 80s. However, despite technical improvements seen during the last decade, surgical planning in the ER has not followed the development of image acquisition methods. The authors present their experience with DICOM image processing as a navigation method in the ER. The authors present 18 patients treated in the Emergency Department of the Hospital das Clínicas of the University of Sao Paulo. All patients were submitted to volumetric CT. We present patients with epidural hematomas, acute/subacute subdural hematomas and contusional hematomas. Using a specific program to analyze images in DICOM format (OsiriX^®), the authors performed the appropriate surgical planning. The use of 3D surgical planning made it possible to perform procedures more accurately and less invasively, enabling better postoperative outcomes. All sorts of neurosurgical emergency pathologies can be treated appropriately with no waste of time. The three-dimensional processing of images in the preoperative evaluation is easy and possible even within the emergency care. It should be used as a tool to reduce the surgical trauma and it may dispense methods of navigation in many cases.

Advanced 3-Dimensional Planning in Neurosurgery

During the past decades, medical applications of virtual reality technology have been developing rapidly, ranging from a research curiosity to a commercially and clinically important area of medical informatics and technology. With the aid of new technologies, the user is able to process large amounts of data sets to create accurate and almost realistic reconstructions of anatomic structures and related pathologies. As a result, a 3-diensional (3-D) representation is obtained, and surgeons can explore the brain for planning or training. Further improvement such as a feedback system increases the interaction between users and models by creating a virtual environment. Its use for advanced 3-D planning in neurosurgery is described. Different systems of medical image volume rendering have been used and analyzed for advanced 3-D planning: 1 is a commercial “ready-to-go” system (Dextroscope, Bracco, Volume Interaction, Singapore), whereas the others are open-source-based software (3-D Slicer, FSL, and FreesSurfer). Different neurosurgeons at our institution experienced how advanced 3-D planning before surgery allowed them to facilitate and increase their understanding of the complex anatomic and pathological relationships of the lesion. They all agreed that the preoperative experience of virtually planning the approach was helpful during the operative procedure. Virtual reality for advanced 3-D planning in neurosurgery has achieved considerable realism as a result of the available processing power of modern computers. Although it has been found useful to facilitate the understanding of complex anatomic relationships, further effort is needed to increase the quality of the interaction between the user and the model.

A systematic review of functional magnetic resonance imaging and diffusion tensor imaging modalities used in presurgical planning of brain tumour resection

Historically, brain tumour resection has relied upon standardised anatomical atlases and classical mapping techniques for successful resection. While these have provided adequate results in the past, the emergence of new technologies has heralded a wave of less invasive, patient-specific techniques for the mapping of brain function. Functional magnetic resonance imaging (fMRI) and, more recently, diffusion tensor imaging (DTI) are two such techniques. While fMRI is able to highlight localisation of function within the cortex, DTI represents the only technique able to elucidate white matter structures in vivo. Used in conjunction, both of these techniques provide important presurgical information for thorough preoperative planning, as well as intraoperatively via integration into frameless stereotactic neuronavigational systems. Together, these techniques show great promise for improved neurosurgical outcomes. While further research is required for more widespread clinical validity and acceptance, results from the literature provide a clear road map for future research and development to cement these techniques into the clinical setup of neurosurgical departments globally.

Stereoscopic virtual reality models for planning tumor resection in the sellar region

BACKGROUND

It is difficult for neurosurgeons to perceive the complex three-dimensional anatomical relationships in the sellar region.

METHODS

To investigate the value of using a virtual reality system for planning resection of sellar region tumors. The study included 60 patients with sellar tumors. All patients underwent computed tomography angiography, MRI-T1W1, and contrast enhanced MRI-T1W1 image sequence scanning. The CT and MRI scanning data were collected and then imported into a Dextroscope imaging workstation, a virtual reality system that allows structures to be viewed stereoscopically. During preoperative assessment, typical images for each patient were chosen and printed out for use by the surgeons as references during surgery.

RESULTS

All sellar tumor models clearly displayed bone, the internal carotid artery, circle of Willis and its branches, the optic nerve and chiasm, ventricular system, tumor, brain, soft tissue and adjacent structures. Depending on the location of the tumors, we simulated the transmononasal sphenoid sinus approach, transpterional approach, and other approaches. Eleven surgeons who used virtual reality models completed a survey questionnaire. Nine of the participants said that the virtual reality images were superior to other images but that other images needed to be used in combination with the virtual reality images.

CONCLUSIONS

The three-dimensional virtual reality models were helpful for individualized planning of surgery in the sellar region. Virtual reality appears to be promising as a valuable tool for sellar region surgery in the future.

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.

Intraoperative image guidance in neurosurgery: development, current indications, and future trends

Introduction. As minimally invasive surgery becomes the standard of care in neurosurgery, it is imperative that surgeons become skilled in the use of image-guided techniques. The development of image-guided neurosurgery represents a substantial improvement in the microsurgical treatment of tumors, vascular malformations, and other intracranial lesions. Objective. There have been numerous advances in neurosurgery which have aided the neurosurgeon to achieve accurate removal of pathological tissue with minimal disruption of surrounding healthy neuronal matter including the development of microsurgical, endoscopic, and endovascular techniques. Neuronavigation systems and intraoperative imaging should improve success in cranial neurosurgery. Additional functional imaging modalities such as PET, SPECT, DTI (for fiber tracking), and fMRI can now be used in order to reduce neurological deficits resulting from surgery; however the positive long-term effect remains questionable for many indications. Method. PubMed database search using the search term "image guided neurosurgery." More than 1400 articles were published during the last 25 years. The abstracts were scanned for prospective comparative trials. Results and Conclusion. 14 comparative trials are published. To date significant data amount show advantages in intraoperative accuracy influencing the perioperative morbidity and long-term outcome only for cerebral glioma surgery.

Automated delineation of white matter fiber tracts with a multiple region-of-interest approach

White matter fiber bundles of the brain can be delineated by tractography utilizing multiple regions-of-interest (MROI) defined by anatomical landmarks. These MROI can be used to specify regions in which to seed, select, or reject tractography fibers. Manual identification of anatomical MROI enables the delineation of white matter fiber bundles, but requires considerable training to develop expertise, considerable time to carry out and suffers from unwanted inter- and intra-rater variability. In a study of 20 healthy volunteers, we compared three methodologies for automated delineation of the white matter fiber bundles. Using these methodologies, fiber bundle MROI for each volunteer were automatically generated. We assessed three strategies for inferring the automatic MROI utilizing nonrigid alignment of reference images and projection of template MROI. We assessed the bundle delineation error associated with alignment utilizing T1-weighted MRI, fractional anisotropy images, and full tensor images. We confirmed the smallest delineation error was achieved using the full tensor images. We then assessed three projection strategies for automatic determination of MROI in each volunteer. Quantitative comparisons were made using the root-mean-squared error observed between streamline density images constructed from fiber bundles identified automatically and by manually drawn MROI in the same subjects. We demonstrate that a multiple template consensus label fusion algorithm generated fiber bundles most consistent with the manual reference standard.