Evaluating Human Performance for Image-Guided Surgical Tasks

The following work focuses on the objective evaluation of human performance for two different interventional tasks; targeted prostate biopsy tasks using a tracked biopsy device, and external ventricular drain placement tasks using a mobile-based augmented reality device for visualization and guidance. In both tasks, a human performance methodology was utilized which respects the trade-off between speed and accuracy for users conducting a series of targeting tasks using each device. This work outlines the development and application of performance evaluation methods using these devices, as well as details regarding the implementation of the mobile AR application. It was determined that the Fitts’ Law methodology can be applied for evaluation of tasks performed in each surgical scenario, and was sensitive to differentiate performance across a range which spanned experienced and novice users. This methodology is valuable for future development of training modules for these and other medical devices, and can provide details about the underlying characteristics of the devices, and how they can be optimized with respect to human performance

Study of the interaction with a virtual 3D environment displayed on a smartphone

Les environnements virtuels à 3D (EV 3D) sont de plus en plus utilisés dans différentes applications telles que la CAO, les jeux ou la téléopération. L'évolution des performances matérielles des Smartphones a conduit à l'introduction des applications 3D sur les appareils mobiles. En outre, les Smartphones offrent de nouvelles capacités bien au-delà de la communication vocale traditionnelle qui sont consentis par l'intégrité d'une grande variété de capteurs et par la connectivité via Internet. En conséquence, plusieurs intéressantes applications 3D peuvent être conçues en permettant aux capacités de l'appareil d'interagir dans un EV 3D. Sachant que les Smartphones ont de petits et aplatis écrans et que EV 3D est large, dense et contenant un grand nombre de cibles de tailles différentes, les appareils mobiles présentent certaines contraintes d'interaction dans l'EV 3D comme : la densité de l'environnement, la profondeur de cibles et l'occlusion. La tâche de sélection fait face à ces trois problèmes pour sélectionner une cible. De plus, la tâche de sélection peut être décomposée en trois sous-tâches : la Navigation, le Pointage et la Validation. En conséquence, les chercheurs dans un environnement virtuel 3D ont développé de nouvelles techniques et métaphores pour l'interaction en 3D afin d'améliorer l'utilisation des applications 3D sur les appareils mobiles, de maintenir la tâche de sélection et de faire face aux problèmes ou facteurs affectant la performance de sélection. En tenant compte de ces considérations, cette thèse expose un état de l'art des techniques de sélection existantes dans un EV 3D et des techniques de sélection sur Smartphone. Il expose les techniques de sélection dans un EV 3D structurées autour des trois sous-tâches de sélection: navigation, pointage et validation. En outre, il décrit les techniques de désambiguïsation permettant de sélectionner une cible parmi un ensemble d'objets présélectionnés. Ultérieurement, il expose certaines techniques d'interaction décrites dans la littérature et conçues pour être implémenter sur un Smartphone. Ces techniques sont divisées en deux groupes : techniques effectuant des tâches de sélection bidimensionnelle sur un Smartphone et techniques exécutant des tâches de sélection tridimensionnelle sur un Smartphone. Enfin, nous exposons les techniques qui utilisaient le Smartphone comme un périphérique de saisie. Ensuite, nous discuterons la problématique de sélection dans un EV 3D affichée sur un Smartphone. Il expose les trois problèmes identifiés de sélection : la densité de l'environnement, la profondeur des cibles et l'occlusion. Ensuite, il établit l'amélioration offerte par chaque technique existante pour la résolution des problèmes de sélection. Il analyse les atouts proposés par les différentes techniques, la manière dont ils éliminent les problèmes, leurs avantages et leurs inconvénients. En outre, il illustre la classification des techniques de sélection pour un EV 3D en fonction des trois problèmes discutés (densité, profondeur et occlusion) affectant les performances de sélection dans un environnement dense à 3D. Hormis pour les jeux vidéo, l'utilisation d'environnement virtuel 3D sur Smartphone n'est pas encore démocratisée. Ceci est dû au manque de techniques d'interaction proposées pour interagir avec un dense EV 3D composé de nombreux objets proches les uns des autres et affichés sur un petit écran aplati et les problèmes de sélection pour afficher l' EV 3D sur un petit écran plutôt sur un grand écran. En conséquence, cette thèse se concentre sur la proposition et la description du fruit de cette étude : la technique d'interaction DichotoZoom. Elle compare et évalue la technique proposée à la technique de circulation suggérée par la littérature. L'analyse comparative montre l'efficacité de la technique DichotoZoom par rapport à sa contrepartie. Ensuite, DichotoZoom a été évalué selon les différentes modalités d'interaction disponibles sur les Smartphones. Cette évaluation montre la performance de la technique de sélection proposée basée sur les quatre modalités d'interaction suivantes : utilisation de boutons physiques ou sous forme de composants graphiques, utilisation d'interactions gestuelles via l'écran tactile ou le déplacement de l'appareil lui-même. Enfin, cette thèse énumère nos contributions dans le domaine des techniques d'interaction 3D utilisées dans un environnement virtuel 3D dense affiché sur de petits écrans et propose des travaux futurs.3D Virtual Environments (3D VE) are more and more used in different applications such as CAD, games, or teleoperation. Due to the improvement of smartphones hardware performance, 3D applications were also introduced to mobile devices. In addition, smartphones provide new computing capabilities far beyond the traditional voice communication. They are permitted by the variety of built-in sensors and the internet connectivity. In consequence, interesting 3D applications can be designed by enabling the device capabilities to interact in a 3D VE. Due to the fact that smartphones have small and flat screens and that a 3D VE is wide and dense with a large number of targets of various sizes, mobile devices present some constraints in interacting on the 3D VE like: the environment density, the depth of targets and the occlusion. The selection task faces these three problems to select a target. In addition, the selection task can be decomposed into three subtasks: Navigation, Pointing and Validation. In consequence, researchers in 3D virtual environment have developed new techniques and metaphors for 3D interaction to improve 3D application usability on mobile devices, to support the selection task and to face the problems or factors affecting selection performance. In light of these considerations, this thesis exposes a state of the art of the existing selection techniques in 3D VE and the selection techniques on smartphones. It exposes the selection techniques in 3D VE structured around the selection subtasks: navigation, pointing and validation. Moreover, it describes disambiguation techniques providing the selection of a target from a set of pre-selected objects. Afterward, it exposes some interaction techniques described in literature and designed for implementation on Smartphone. These techniques are divided into two groups: techniques performing two-dimensional selection tasks on smartphones, and techniques performing three-dimensional selection tasks on smartphones. Finally, we expose techniques that used the smartphone as an input device. Then, we will discuss the problematic of selecting in 3D VE displayed on a Smartphone. It exposes the three identified selection problems: the environment density, the depth of targets and the occlusion. Afterward, it establishes the enhancement offered by each existing technique in solving the selection problems. It analysis the assets proposed by different techniques, the way they eliminates the problems, their advantages and their inconvenient. Furthermore, it illustrates the classification of the selection techniques for 3D VE according to the three discussed problems (density, depth and occlusion) affecting the selection performance in a dense 3D VE. Except for video games, the use of 3D virtual environment (3D VE) on Smartphone has not yet been popularized. This is due to the lack of interaction techniques to interact with a dense 3D VE composed of many objects close to each other and displayed on a small and flat screen and the selection problems to display the 3D VE on a small screen rather on a large screen. Accordingly, this thesis focuses on defining and describing the fruit of this study: DichotoZoom interaction technique. It compares and evaluates the proposed technique to the Circulation technique, suggested by the literature. The comparative analysis shows the effectiveness of DichotoZoom technique compared to its counterpart. Then, DichotoZoom was evaluated in different modalities of interaction available on Smartphones. It reports on the performance of the proposed selection technique based on the following four interaction modalities: using physical buttons, using graphical buttons, using gestural interactions via touchscreen or moving the device itself. Finally, this thesis lists our contributions to the field of 3D interaction techniques used in a dense 3D virtual environment displayed on small screens and proposes some future works

Evaluating 3D pointing techniques

"This dissertation investigates various issues related to the empirical evaluation of 3D pointing interfaces. In this context, the term ""3D pointing"" is appropriated from analogous 2D pointing literature to refer to 3D point selection tasks, i.e., specifying a target in three-dimensional space. Such pointing interfaces are required for interaction with virtual 3D environments, e.g., in computer games and virtual reality. Researchers have developed and empirically evaluated many such techniques. Yet, several technical issues and human factors complicate evaluation. Moreover, results tend not to be directly comparable between experiments, as these experiments usually use different methodologies and measures. Based on well-established methods for comparing 2D pointing interfaces this dissertation investigates different aspects of 3D pointing. The main objective of this work is to establish methods for the direct and fair comparisons between 2D and 3D pointing interfaces. This dissertation proposes and then validates an experimental paradigm for evaluating 3D interaction techniques that rely on pointing. It also investigates some technical considerations such as latency and device noise. Results show that the mouse outperforms (between 10% and 60%) other 3D input techniques in all tested conditions. Moreover, a monoscopic cursor tends to perform better than a stereo cursor when using stereo display, by as much as 30% for deep targets. Results suggest that common 3D pointing techniques are best modelled by first projecting target parameters (i.e., distance and size) to the screen plane.

Performance Factors in Neurosurgical Simulation and Augmented Reality Image Guidance

Virtual reality surgical simulators have seen widespread adoption in an effort to provide safe, cost-effective and realistic practice of surgical skills. However, the majority of these simulators focus on training low-level technical skills, providing only prototypical surgical cases. For many complex procedures, this approach is deficient in representing anatomical variations that present clinically, failing to challenge users’ higher-level cognitive skills important for navigation and targeting. Surgical simulators offer the means to not only simulate any case conceivable, but to test novel approaches and examine factors that influence performance. Unfortunately, there is a void in the literature surrounding these questions. This thesis was motivated by the need to expand the role of surgical simulators to provide users with clinically relevant scenarios and evaluate human performance in relation to image guidance technologies, patient-specific anatomy, and cognitive abilities. To this end, various tools and methodologies were developed to examine cognitive abilities and knowledge, simulate procedures, and guide complex interventions all within a neurosurgical context. The first chapter provides an introduction to the material. The second chapter describes the development and evaluation of a virtual anatomical training and examination tool. The results suggest that learning occurs and that spatial reasoning ability is an important performance predictor, but subordinate to anatomical knowledge. The third chapter outlines development of automation tools to enable efficient simulation studies and data management. In the fourth chapter, subjects perform abstract targeting tasks on ellipsoid targets with and without augmented reality guidance. While the guidance tool improved accuracy, performance with the tool was strongly tied to target depth estimation – an important consideration for implementation and training with similar guidance tools. In the fifth chapter, neurosurgically experienced subjects were recruited to perform simulated ventriculostomies. Results showed anatomical variations influence performance and could impact outcome. Augmented reality guidance showed no marked improvement in performance, but exhibited a mild learning curve, indicating that additional training may be warranted. The final chapter summarizes the work presented. Our results and novel evaluative methodologies lay the groundwork for further investigation into simulators as versatile research tools to explore performance factors in simulated surgical procedures

3D Pointing with Everyday Devices: Speed, Occlusion, Fatigue

In recent years, display technology has evolved to the point where displays can be both non-stereoscopic and stereoscopic, and 3D environments can be rendered realistically on many types of displays. From movie theatres and shopping malls to conference rooms and research labs, 3D information can be deployed seamlessly. Yet, while 3D environments are commonly displayed in desktop settings, there are virtually no examples of interactive 3D environments deployed within ubiquitous environments, with the exception of console gaming. At the same time, immersive 3D environments remain - in users' minds - associated with professional work settings and virtual reality laboratories. An excellent opportunity for 3D interactive engagements is being missed not because of economic factors, but due to the lack of interaction techniques that are easy to use in ubiquitous, everyday environments. In my dissertation, I address the lack of support for interaction with 3D environments in ubiquitous settings by designing, implementing, and evaluating 3D pointing techniques that leverage a smartphone or a smartwatch as an input device. I show that mobile and wearable devices may be especially beneficial as input devices for casual use scenarios, where specialized 3D interaction hardware may be impractical, too expensive or unavailable. Such scenarios include interactions with home theatres, intelligent homes, in workplaces and classrooms, with movie theatre screens, in shopping malls, at airports, during conference presentations and countless other places and situations. Another contribution of my research is to increase the potential of mobile and wearable devices for efficient interaction at a distance. I do so by showing that such interactions are feasible when realized with the support of a modern smartphone or smartwatch. I also show how multimodality, when realized with everyday devices, expands and supports 3D pointing. In particular, I show how multimodality helps to address the challenges of 3D interaction: performance issues related to the limitations of the human motor system, interaction with occluded objects and related problem of perception of depth on non-stereoscopic screens, and user subjective fatigue, measured with NASA TLX as perceived workload, that results from providing spatial input for a prolonged time. I deliver these contributions by designing three novel 3D pointing techniques that support casual, "walk-up-and-use" interaction at a distance and are fully realizable using off-the-shelf mobile and wearable devices available today. The contributions provide evidence that democratization of 3D interaction can be realized by leveraging the pervasiveness of a device that users already carry with them: a smartphone or a smartwatch.4 month

Stereoscopic bimanual interaction for 3D visualization

Virtual Environments (VE) are being widely used in various research fields for several decades such as 3D visualization, education, training and games. VEs have the potential to enhance the visualization and act as a general medium for human-computer interaction (HCI). However, limited research has evaluated virtual reality (VR) display technologies, monocular and binocular depth cues, for human depth perception of volumetric (non-polygonal) datasets. In addition, a lack of standardization of three-dimensional (3D) user interfaces (UI) makes it challenging to interact with many VE systems. To address these issues, this dissertation focuses on evaluation of effects of stereoscopic and head-coupled displays on depth judgment of volumetric dataset. It also focuses on evaluation of a two-handed view manipulation techniques which support simultaneous 7 degree-of-freedom (DOF) navigation (x,y,z + yaw,pitch,roll + scale) in a multi-scale virtual environment (MSVE). Furthermore, this dissertation evaluates auto-adjustment of stereo view parameters techniques for stereoscopic fusion problems in a MSVE. Next, this dissertation presents a bimanual, hybrid user interface which combines traditional tracking devices with computer-vision based "natural" 3D inputs for multi-dimensional visualization in a semi-immersive desktop VR system. In conclusion, this dissertation provides a guideline for research design for evaluating UI and interaction techniques

Multimodal interactions in virtual environments using eye tracking and gesture control.

Multimodal interactions provide users with more natural ways to interact with virtual environments than using traditional input methods. An emerging approach is gaze modulated pointing, which enables users to perform virtual content selection and manipulation conveniently through the use of a combination of gaze and other hand control techniques/pointing devices, in this thesis, mid-air gestures. To establish a synergy between the two modalities and evaluate the affordance of this novel multimodal interaction technique, it is important to understand their behavioural patterns and relationship, as well as any possible perceptual conflicts and interactive ambiguities. More specifically, evidence shows that eye movements lead hand movements but the question remains that whether the leading relationship is similar when interacting using a pointing device. Moreover, as gaze modulated pointing uses different sensors to track and detect user behaviours, its performance relies on users perception on the exact spatial mapping between the virtual space and the physical space. It raises an underexplored issue that whether gaze can introduce misalignment of the spatial mapping and lead to users misperception and interactive errors. Furthermore, the accuracy of eye tracking and mid-air gesture control are not comparable with the traditional pointing techniques (e.g., mouse) yet. This may cause pointing ambiguity when fine grainy interactions are required, such as selecting in a dense virtual scene where proximity and occlusion are prone to occur. This thesis addresses these concerns through experimental studies and theoretical analysis that involve paradigm design, development of interactive prototypes, and user study for verification of assumptions, comparisons and evaluations. Substantial data sets were obtained and analysed from each experiment. The results conform to and extend previous empirical findings that gaze leads pointing devices movements in most cases both spatially and temporally. It is testified that gaze does introduce spatial misperception and three methods (Scaling, Magnet and Dual-gaze) were proposed and proved to be able to reduce the impact caused by this perceptual conflict where Magnet and Dual-gaze can deliver better performance than Scaling. In addition, a coarse-to-fine solution is proposed and evaluated to compensate the degradation introduced by eye tracking inaccuracy, which uses a gaze cone to detect ambiguity followed by a gaze probe for decluttering. The results show that this solution can enhance the interaction accuracy but requires a compromise on efficiency. These findings can be used to inform a more robust multimodal inter- face design for interactions within virtual environments that are supported by both eye tracking and mid-air gesture control. This work also opens up a technical pathway for the design of future multimodal interaction techniques, which starts from a derivation from natural correlated behavioural patterns, and then considers whether the design of the interaction technique can maintain perceptual constancy and whether any ambiguity among the integrated modalities will be introduced

Towards markerless orthopaedic navigation with intuitive Optical See-through Head-mounted displays

The potential of image-guided orthopaedic navigation to improve surgical outcomes has been well-recognised during the last two decades. According to the tracked pose of target bone, the anatomical information and preoperative plans are updated and displayed to surgeons, so that they can follow the guidance to reach the goal with higher accuracy, efficiency and reproducibility. Despite their success, current orthopaedic navigation systems have two main limitations: for target tracking, artificial markers have to be drilled into the bone and calibrated manually to the bone, which introduces the risk of additional harm to patients and increases operating complexity; for guidance visualisation, surgeons have to shift their attention from the patient to an external 2D monitor, which is disruptive and can be mentally stressful. Motivated by these limitations, this thesis explores the development of an intuitive, compact and reliable navigation system for orthopaedic surgery. To this end, conventional marker-based tracking is replaced by a novel markerless tracking algorithm, and the 2D display is replaced by a 3D holographic Optical see-through (OST) Head-mounted display (HMD) precisely calibrated to a user's perspective. Our markerless tracking, facilitated by a commercial RGBD camera, is achieved through deep learning-based bone segmentation followed by real-time pose registration. For robust segmentation, a new network is designed and efficiently augmented by a synthetic dataset. Our segmentation network outperforms the state-of-the-art regarding occlusion-robustness, device-agnostic behaviour, and target generalisability. For reliable pose registration, a novel Bounded Iterative Closest Point (BICP) workflow is proposed. The improved markerless tracking can achieve a clinically acceptable error of 0.95 deg and 2.17 mm according to a phantom test. OST displays allow ubiquitous enrichment of perceived real world with contextually blended virtual aids through semi-transparent glasses. They have been recognised as a suitable visual tool for surgical assistance, since they do not hinder the surgeon's natural eyesight and require no attention shift or perspective conversion. The OST calibration is crucial to ensure locational-coherent surgical guidance. Current calibration methods are either human error-prone or hardly applicable to commercial devices. To this end, we propose an offline camera-based calibration method that is highly accurate yet easy to implement in commercial products, and an online alignment-based refinement that is user-centric and robust against user error. The proposed methods are proven to be superior to other similar State-of- the-art (SOTA)s regarding calibration convenience and display accuracy. Motivated by the ambition to develop the world's first markerless OST navigation system, we integrated the developed markerless tracking and calibration scheme into a complete navigation workflow designed for femur drilling tasks during knee replacement surgery. We verify the usability of our designed OST system with an experienced orthopaedic surgeon by a cadaver study. Our test validates the potential of the proposed markerless navigation system for surgical assistance, although further improvement is required for clinical acceptance.Open Acces

Semiautomated 3D liver segmentation using computed tomography and magnetic resonance imaging

Le foie est un organe vital ayant une capacité de régénération exceptionnelle et un rôle crucial dans le fonctionnement de l’organisme. L’évaluation du volume du foie est un outil important pouvant être utilisé comme marqueur biologique de sévérité de maladies hépatiques. La volumétrie du foie est indiquée avant les hépatectomies majeures, l’embolisation de la veine porte et la transplantation. La méthode la plus répandue sur la base d'examens de tomodensitométrie (TDM) et d'imagerie par résonance magnétique (IRM) consiste à délimiter le contour du foie sur plusieurs coupes consécutives, un processus appelé la «segmentation». Nous présentons la conception et la stratégie de validation pour une méthode de segmentation semi-automatisée développée à notre institution. Notre méthode représente une approche basée sur un modèle utilisant l’interpolation variationnelle de forme ainsi que l’optimisation de maillages de Laplace. La méthode a été conçue afin d’être compatible avec la TDM ainsi que l' IRM. Nous avons évalué la répétabilité, la fiabilité ainsi que l’efficacité de notre méthode semi-automatisée de segmentation avec deux études transversales conçues rétrospectivement. Les résultats de nos études de validation suggèrent que la méthode de segmentation confère une fiabilité et répétabilité comparables à la segmentation manuelle. De plus, cette méthode diminue de façon significative le temps d’interaction, la rendant ainsi adaptée à la pratique clinique courante. D’autres études pourraient incorporer la volumétrie afin de déterminer des marqueurs biologiques de maladie hépatique basés sur le volume tels que la présence de stéatose, de fer, ou encore la mesure de fibrose par unité de volume.The liver is a vital abdominal organ known for its remarkable regenerative capacity and fundamental role in organism viability. Assessment of liver volume is an important tool which physicians use as a biomarker of disease severity. Liver volumetry is clinically indicated prior to major hepatectomy, portal vein embolization and transplantation. The most popular method to determine liver volume from computed tomography (CT) and magnetic resonance imaging (MRI) examinations involves contouring the liver on consecutive imaging slices, a process called “segmentation”. Segmentation can be performed either manually or in an automated fashion. We present the design concept and validation strategy for an innovative semiautomated liver segmentation method developed at our institution. Our method represents a model-based approach using variational shape interpolation and Laplacian mesh optimization techniques. It is independent of training data, requires limited user interactions and is robust to a variety of pathological cases. Further, it was designed for compatibility with both CT and MRI examinations. We evaluated the repeatability, agreement and efficiency of our semiautomated method in two retrospective cross-sectional studies. The results of our validation studies suggest that semiautomated liver segmentation can provide strong agreement and repeatability when compared to manual segmentation. Further, segmentation automation significantly shortens interaction time, thus making it suitable for daily clinical practice. Future studies may incorporate liver volumetry to determine volume-averaged biomarkers of liver disease, such as such as fat, iron or fibrosis measurements per unit volume. Segmental volumetry could also be assessed based on subsegmentation of vascular anatomy