Creating a Comprehensive Research Platform for Surgical Technique and Operative Outcome in Primary Brain Tumor Neurosurgery.

BACKGROUND: The operative environment poses many challenges to studying the relationship between surgical acts and patient outcomes in intracranial oncological neurosurgery. We sought to develop a framework in which neurosurgical performance and extent of resection could be precisely quantified in a controlled setting. METHODS: The stiffness of an alginate hydrogel-based tumor was modified with differing concentrations of the cross-linking agent calcium sulfate until biomechanical properties similar to those of human primary brain tumors measured at resection were achieved. The artificial tumor was subsequently incorporated into an ex-vivo animal brain as a final model. Magnetic resonance imaging enhancement and ultraviolet fluorescence was achieved by incorporating gadolinium and fluorescein solution, respectively. Video recordings from the operative microscope, ceiling cameras, and instrument-mounted fiducial markers within a surgical suite environment captured operative performance. RESULTS: A total of 24 rheometer measurements were conducted on alginate hydrogels containing 10-, 11-, and 12-mM concentrations of calcium sulfate. Sixty-eight stiffness measurements were conducted on eight patient tumor samples. No differences were found between the alginate and brain tumor stiffness values [Kruskal-Wallis χ2(4) = 9.187; P = 0.057]. Tumor was identified using ultraviolet fluorescence and ultrasonography. The volume and location of the resected white and gray matter and residual tumor could be quantified in 0.003-mm3 increments using a 7T magnetic resonance imaging coil. Ultrasonic aspirator and bipolar electrocautery movement data were successfully transformed into performance metrics. CONCLUSION: The developed framework can offer clinicians, learners, and researchers the ability to perform operative rehearsal, teaching, and studies involving brain tumor surgery in a controlled laboratory environment and represents a crucial step in the understanding and training of expertise in neurosurgery.

Intravascular optical coherence tomography to validate finite-element simulation of angioplasty balloon inflation.

Concrete methods are lacking to examine angioplasty simulation results. For the first time, we explored the application of intravascular optical coherence tomography (IVOCT) to experimentally validate results obtained from finite-element simulation of angioplasty balloon deployment. In order to simulate each experimental scenario, IVOCT images were used to create initial geometrical models for the balloon and the phantoms. The study comprised three scenarios. The first scenario involved experimentally monitoring as well as simulating free expansion of the balloon. The second scenario involved experimentally monitoring as well as simulating balloon inflation inside three artery phantoms with different mechanical properties. The third scenario involved experimentally monitoring as well as simulating balloon unfolding and inflation inside a multilayer phantom. Using the first scenario, a constitutive model was developed for the balloon and was tuned to fit the IVOCT balloon inflation monitoring results. This model was used to simulate the balloon's response in simulations involving phantoms corresponding to the second and third scenarios. Diameter values were calculated both from images and simulation results. These values were then compared for each scenario. The obtained results highlight the potentials of IVOCT monitoring to validate simulation procedures.

Neurosurgical virtual reality simulation metrics to assess psychomotor skills during brain tumor resection.

PURPOSE: Virtual reality simulator technology together with novel metrics could advance our understanding of expert neurosurgical performance and modify and improve resident training and assessment. This pilot study introduces innovative metrics that can be measured by the state-of-the-art simulator to assess performance. Such metrics cannot be measured in an operating room and have not been used previously to assess performance. METHODS: Three sets of performance metrics were assessed utilizing the NeuroTouch platform in six scenarios with simulated brain tumors having different visual and tactile characteristics. Tier 1 metrics included percentage of brain tumor resected and volume of simulated "normal" brain tissue removed. Tier 2 metrics included instrument tip path length, time taken to resect the brain tumor, pedal activation frequency, and sum of applied forces. Tier 3 metrics included sum of forces applied to different tumor regions and the force bandwidth derived from the force histogram. RESULTS: The results outlined are from a novice resident in the second year of training and an expert neurosurgeon. The three tiers of metrics obtained from the NeuroTouch simulator do encompass the wide variability of technical performance observed during novice/expert resections of simulated brain tumors and can be employed to quantify the safety, quality, and efficiency of technical performance during simulated brain tumor resection. Tier 3 metrics derived from force pyramids and force histograms may be particularly useful in assessing simulated brain tumor resections. CONCLUSION: Our pilot study demonstrates that the safety, quality, and efficiency of novice and expert operators can be measured using metrics derived from the NeuroTouch platform, helping to understand how specific operator performance is dependent on both psychomotor ability and cognitive input during multiple virtual reality brain tumor resections.

Assessing performance in brain tumor resection using a novel virtual reality simulator.

PURPOSE: NeuroTouch is a virtual reality (VR) simulator developed for neurosurgical skill training. Validation demonstrating that the system is useful and reliable is required for formal adoption into training curriculums. Face and content validity have been demonstrated for some neurosurgical simulators, but construct validity remains difficult to establish. A pilot validation study was conducted for a NeuroTouch training exercise. METHODS: Participants completed the internal resection of a simulated convexity meningioma and filled out questionnaires to provide feedback on the experience. Performance metrics included volume of tissues removed, tool path lengths, duration of excessive forces applied and efficient use of the aspirator. Results were analyzed according to participants' level of training, gender, handedness, surgical experience in meningioma removal and hours/week playing musical instruments or video games. RESULTS: Seventy-two participants (10 medical students, 18 junior residents and 44 senior residents) were enrolled. Analyses demonstrated statistically significant increase in tumor removed and efficiency of ultrasonic aspirator use between medical students and residents, but not between junior and senior residents. After covariate adjustment for the number of meningioma cases operated on, multivariate analysis of the level of training became nonsignificant. Participants judged the exercise appropriate and realistic, desiring use of the system in current training programs. CONCLUSION: We have conducted a pilot validation study for the NeuroTouch tumor resection scenario and demonstrated for the first time, face, content and construct validity of a VR neurosurgical simulation exercise. Future full-scale studies will be conducted in noncompetitive settings and incorporate expert participants.

The development of a virtual simulator for training neurosurgeons to perform and perfect endoscopic endonasal transsphenoidal surgery.

BACKGROUND: A virtual reality (VR) neurosurgical simulator with haptic feedback may provide the best model for training and perfecting surgical techniques for transsphenoidal approaches to the sella turcica and cranial base. Currently there are 2 commercially available simulators: NeuroTouch (Cranio and Endo) developed by the National Research Council of Canada in collaboration with surgeons at teaching hospitals in Canada, and the Immersive Touch. Work in progress on other simulators at additional institutions is currently unpublished. OBJECTIVE: This article describes a newly developed application of the NeuroTouch simulator that facilitates the performance and assessment of technical skills for endoscopic endonasal transsphenoidal surgical procedures as well as plans for collecting metrics during its early use. METHODS: The main components of the NeuroTouch-Endo VR neurosurgical simulator are a stereovision system, bimanual haptic tool manipulators, and high-end computers. The software engine continues to evolve, allowing additional surgical tasks to be performed in the VR environment. Device utility for efficient practice and performance metrics continue to be developed by its originators in collaboration with neurosurgeons at several teaching hospitals in the United States. Training tasks are being developed for teaching 1- and 2-nostril endonasal transsphenoidal approaches. Practice sessions benefit from anatomic labeling of normal structures along the surgical approach and inclusion (for avoidance) of critical structures, such as the internal carotid arteries and optic nerves. CONCLUSION: The simulation software for NeuroTouch-Endo VR simulation of transsphenoidal surgery provides an opportunity for beta testing, validation, and evaluation of performance metrics for use in neurosurgical residency training. ABBREVIATIONS: CTA, cognitive task analysisVR, virtual reality.

Intravascular optical coherence tomography to characterize tissue deformation during angioplasty: preliminary experiments with artery phantoms.

We explored the potential of intravascular optical coherence tomography (IVOCT) to assess deformation during angioplasty balloon inflation. Using a semi-compliant balloon and artery phantoms, we considered two experimental scenarios. The goal for the first scenario was to investigate if variation in the elasticity of the structure surrounding the balloon could be sensed by IVOCT monitoring. In this scenario, we used three single-layer phantoms with various mechanical properties. Image analysis was performed to extract the inner and outer diameters of the phantoms at various pressures. The goal for the second scenario was twofold. First, we investigated the IVOCT capability to monitor a more complex balloon inflation process. The balloon was in a folded state prior to inflation. This allowed studying two stages of deformation: during balloon unfolding and during balloon expansion. Second, we investigated IVOCT capability to monitor the deformation in a three-layer phantom used to better mimic a true artery. So, not only were the IVOCT images processed to provide the inner and outer diameters of the phantom, but the layer thicknesses were also determined. In both scenarios, IVOCT monitoring revealed to be very efficient in providing relevant information about the phantom deformation during balloon inflation.

Review of tissue simulating phantoms with controllable optical, mechanical and structural properties for use in optical coherence tomography.

We review the development of phantoms for optical coherence tomography (OCT) designed to replicate the optical, mechanical and structural properties of a range of tissues. Such phantoms are a key requirement for the continued development of OCT techniques and applications. We focus on phantoms based on silicone, fibrin and poly(vinyl alcohol) cryogels (PVA-C), as we believe these materials hold the most promise for durable and accurate replication of tissue properties.

Evaluation of reducibility of trunk asymmetry in lateral bending.

The value of the lateral bending test is important in the assessment of spinal curve mobility and prediction of surgical outcome in the treatment of adolescent idiopathic scoliosis (AIS). However, radiographic bending tests are unable to assess the reducibility of trunk asymmetry. This study aims to exploit surface topography measurement in order to evaluate the changes in shape of the trunk (a) between bending and neutral standing positions, and (b) between standing pre- and post-operative visits, in a cohort of adolescents with AIS having undergone surgical correction; and to correlate the differences measured in cases (a) and (b). Our cohort includes 13 patients with right thoracic AIS. Each patient had their 3D trunk surface digitized with a multi-head InSpeck system in standing posture (at the pre-op and post-op visits) and in maximum voluntary right and left bending (at the pre-op visit). We developed a novel trunk shape analysis method which produces a set of inclined trunk cross-sections allowing comparison between different postures. Two asymmetry indices, trunk rotation (TR) and back surface rotation (BSR), were computed in all cases and a statistical analysis was performed. Our correlation study (Pearson test) showed fair correlations in most cases between the changes in side-bending and those post-surgery, with the strongest relationship (p-value < 0.01) when combining the TR measurements from both bendings. These results provide evidence that the bending test can be used to assess trunk asymmetry reducibility. The proposed approach could provide a non-invasive trunk asymmetry reducibility test for routine clinical use in AIS surgery planning.

Mechanical characterization of atherosclerotic arteries using finite-element modeling: feasibility study on mock arteries.

Clinical studies on lipid-lowering therapy have shown that changing the composition of lipid pools reduced significantly the risk of cardiac events associated with plaque rupture. It has been shown also that changing the composition of the lipid pool affects its mechanical properties. However, knowledge about the mechanical properties of human atherosclerotic lesions remains limited due to the difficulty of the experiments. This paper aims to assess the feasibility of characterizing a lipid pool embedded in the wall of a pressurized vessel using finite-element simulations and an optimization algorithm. Finite-element simulations of inflation experiments were used together with nonlinear least squares algorithm to estimate the material model parameters of the wall and of the inclusion. An optimal fit of the simulated experiment and the real experiment was sought with the parameter estimation algorithm. The method was first tested on a single-layer polyvinyl alcohol (PVA) cryogel stenotic vessel, and then, applied on a double-layered PVA cryogel stenotic vessel with a lipid inclusion.

Reliability of trunk shape measurements based on 3-D surface reconstructions.

This study aimed to estimate the reliability of 3-D trunk surface measurements for the characterization of external asymmetry associated with scoliosis. Repeated trunk surface acquisitions using the Inspeck system (Inspeck Inc., Montreal, Canada), with two different postures A (anatomical position) and B (''clavicle'' position), were obtained from patients attending a scoliosis clinic. For each acquisition, a 3-D model of the patient's trunk was built and a series of measurements was computed. For each measure and posture, intraclass correlation coefficients (ICC) were obtained using a bivariate analysis of variance, and the smallest detectable difference was calculated. For posture A, reliability was fair to excellent with ICC from 0.91 to 0.99 (0.85 to 0.99 for the lower bound of the 95% confidence interval). For posture B, the ICC was 0.85 to 0.98 (0.74 to 0.99 for the lower bound of the 95% confidence interval). The smallest statistically significant differences for the maximal back surface rotation was 2.5 and 1.5 degrees for the maximal trunk rotation. Apparent global asymmetry and axial trunk rotation indices were relatively robust to changes in arm posture, both in terms of mean values and within-subject variations, and also showed a good reliability. Computing measurements from cross-sectional analysis enabled a reduction in errors compared to the measurements based on markers' position. Although not yet sensitive enough to detect small changes for monitoring of curve natural progression, trunk surface analysis can help to document the external asymmetry associated with different types of spinal curves as well as the cosmetic improvement obtained after surgical interventions. The anatomical posture is slightly more reliable as it allows a better coverage of the trunk surface by the digitizing system.

3D reconstruction and analysis of the whole trunk surface for non-invasive follow-up of scoliotic deformities.

The purpose of this study was to evaluate the 3D reconstruction accuracy of a new technology that allows the acquisition of the whole trunk and to develop a software to analyse the trunk surface asymmetry. A non-invasive active vision system provides a 3D textured reconstruction of the whole trunk. The analysis system provides the clinician with quantitative indices that characterize the whole external trunk asymmetry.