15 research outputs found
Design and Evaluation of Neurosurgical Training Simulator
Surgical simulators are becoming more important in surgical training. Consumer smartphone technology has improved to allow deployment of VR applications and are now being targeted for medical training simulators. A surgical simulator has been designed using a smartphone, Google cardboard 3D glasses, and the Leap Motion (LM) hand controller. Two expert and 16 novice users were tasked with completing the same pointing tasks using both the LM and the medical simulator NeuroTouch. The novice users had an accuracy of 0.2717 bits (SD 0.3899) and the experts had an accuracy of 0.0925 bits (SD 0.1210) while using the NeuroTouch. Novices and experts improved their accuracy to 0.3585 bits (SD 0.4474) and 0.4581 bits (SD 0.3501) while using the LM. There were some tracking problems with the AR display and LM. Users were intrigued by the AR display and most preferred the LM, as they found it to have better usability
Technological competence is a precondition for effective implementation of virtual reality head mounted displays in human neuroscience:A technological review and meta-analysis
International audienceImmersive virtual reality (VR) emerges as a promising research and clinical tool. However, several studies suggest that VR induced adverse symptoms and effects (VRISE) may undermine the health and safety standards, and the reliability of the scientific results. In the current literature review, the technical reasons for the adverse symptomatology are investigated to provide suggestions and technological knowledge for the implementation of VR head-mounted display (HMD) systems in cognitive neuroscience. The technological systematic literature indicated features pertinent to display, sound, motion tracking, navigation, ergonomic interactions, user experience, and computer hardware that should be considered by the researchers. Subsequently, a meta-analysis of 44 neuroscientific or neuropsychological studies involving VR HMD systems was performed. The meta-analysis of the VR studies demonstrated that new generation HMDs induced significantly less VRISE and marginally fewer dropouts. Importantly, the commercial versions of the new generation HMDs with ergonomic interactions had zero incidents of adverse symptomatology and dropouts. HMDs equivalent to or greater than the commercial versions of contemporary HMDs accompanied with ergonomic interactions are suitable for implementation in cognitive neuroscience. In conclusion, researchers' technological competency, along with meticulous methods and reports pertinent to software, hardware, and VRISE, are paramount to ensure the health and safety standards and the reliability of neuroscientific results
TOWARDS EFFECTIVE DISPLAYS FOR VIRTUAL AND AUGMENTED REALITY
Virtual and augmented reality (VR and AR) are becoming increasingly accessible and useful nowadays. This dissertation focuses on several aspects of designing effective displays for VR and AR.
Compared to conventional desktop displays, VR and AR displays can better engage the human peripheral vision. This provides an opportunity for more information to be perceived. To fully leverage the human visual system, we need to take into account how the human visual system perceives things differently in the periphery than in the fovea. By investigating the relationship of the perception time and eccentricity, we deduce a scaling function which facilitates content in the far periphery to be perceived as efficiently as in the central vision.
AR overlays additional information on the real environment. This is useful in a number of fields, including surgery, where time-critical information is key. We present our medical AR system that visualizes the occluded catheter in the external ventricular drainage (EVD) procedure. We develop an accurate and efficient catheter tracking method that requires minimal changes to the existing medical equipment. The AR display projects a virtual image of the catheter overlaid on the occluded real catheter to depict its real-time position. Our system can make the risky EVD procedure much safer.
Existing VR and AR displays support a limited number of focal distances, leading to vergence-accommodation conflict. Holographic displays can address this issue. In this dissertation, we explore the design and development of nanophotonic phased array (NPA) as a special class of holographic displays. NPAs have the advantage of being compact and support very high refresh rates. However, the use of the thermo-optic effect for phase modulation renders them susceptible to the thermal proximity effect. We study how the proximity effect impacts the images formed on NPAs. We then propose several novel algorithms to compensate for the thermal proximity effect on NPAs and compare their effectiveness and computational efficiency.
Computer-generated holography (CGH) has traditionally focused on 2D images and 3D images in the form of meshes and point clouds. However, volumetric data can also benefit from CGH. One of the challenges in the use of volumetric data sources in CGH is the computational complexity needed to calculate the holograms of volumetric data. We propose a new method that achieves a significant speedup compared to existing holographic volume rendering methods
Augmented Reality Assistance for Surgical Interventions using Optical See-Through Head-Mounted Displays
Augmented Reality (AR) offers an interactive user experience via enhancing the real world environment with computer-generated visual cues and other perceptual information. It has been applied to different applications, e.g. manufacturing, entertainment and healthcare, through different AR media. An Optical See-Through Head-Mounted Display (OST-HMD) is a specialized hardware for AR, where the computer-generated graphics can be overlaid directly onto the user's normal vision via optical combiners. Using OST-HMD for surgical intervention has many potential perceptual advantages. As a novel concept, many technical and clinical challenges exist for OST-HMD-based AR to be clinically useful, which motivates the work presented in this thesis.
From the technical aspects, we first investigate the display calibration of OST-HMD, which is an indispensable procedure to create accurate AR overlay. We propose various methods to reduce the user-related error, improve robustness of the calibration, and remodel the calibration as a 3D-3D registration problem. Secondly, we devise methods and develop hardware prototype to increase the user's visual acuity of both real and virtual content through OST-HMD, to aid them in tasks that require high visual acuity, e.g. dental procedures. Thirdly, we investigate the occlusion caused by the OST-HMD hardware, which limits the user's peripheral vision. We propose to use alternative indicators to remind the user of unattended environment motion.
From the clinical perspective, we identified many clinical use cases where OST-HMD-based AR is potentially helpful, developed applications integrated with current clinical systems, and conducted proof-of-concept evaluations. We first present a "virtual monitor'' for image-guided surgery. It can replace real radiology monitors in the operating room with easier user control and more flexibility in positioning. We evaluated the "virtual monitor'' for simulated percutaneous spine procedures. Secondly, we developed ARssist, an application for the bedside assistant in robotic surgery. The assistant can see the robotic instruments and endoscope within the patient body with ARssist. We evaluated the efficiency, safety and ergonomics of the assistant during two typical tasks: instrument insertion and manipulation. The performance for inexperienced users is significantly improved with ARssist, and for experienced users, the system significantly enhanced their confidence level. Lastly, we developed ARAMIS, which utilizes real-time 3D reconstruction and visualization to aid the laparoscopic surgeon. It demonstrates the concept of "X-ray see-through'' surgery. Our preliminary evaluation validated the application via a peg transfer task, and also showed significant improvement in hand-eye coordination.
Overall, we have demonstrated that OST-HMD based AR application provides ergonomic improvements, e.g. hand-eye coordination. In challenging situations or for novice users, the improvements in ergonomic factors lead to improvement in task performance. With continuous effort as a community, optical see-through augmented reality technology will be a useful interventional aid in the near future
Immersive virtual reality methods in cognitive neuroscience and neuropsychology: the Virtual Reality Everyday Assessment Lab (VR-EAL).an immersive neuropsychological test battery of everyday cognitive functions
In cognitive neuroscience and neuropsychology, the collection of cognitive and
behavioural data is predominantly achieved by implementing paper-and-pencil and
computerized (i.e., 2D and 3D applications) assessments. However, these
psychometric tools in clinics and/or laboratories display several limitations and
discrepancies between the observed performance in the laboratory/clinic and the actual
performance of individuals in everyday life. The functional and predictive association
between an individual's performance on a set of neuropsychological tests and the
individual's performance in various everyday life settings is called ecological validity.
Ecological validity is considered an important issue that cannot be resolved by the
currently available assessment tools. Virtual reality head-mounted displays (HMD)
appear to be effective research tools, which may address the problem of ecological
validity in neuropsychological testing. However, their widespread implementation is
hindered by virtual reality induced symptoms and effects (VRISE) and the lack of
skills in virtual reality software development.
In this PhD, a technological systematic literature review of the reasons for adverse
symptomatology was conducted and suggestions and technological knowledge for the
implementation of virtual reality HMD systems in cognitive neuroscience provided.
The review indicated features pertinent to display, sound, motion tracking, navigation,
ergonomic interactions, user experience, and computer hardware that should be
considered by researchers. Subsequently, a meta-analysis of 44 neuroscientific or
neuropsychological studies involving virtual reality HMD systems was performed.
The meta-analysis of the virtual reality studies demonstrated that new generation
HMDs induce significantly less VRISE and marginally fewer dropouts. Importantly, the commercial versions of the new generation HMDs with ergonomic interactions had
zero incidents of adverse symptomatology and dropouts. HMDs equivalent to or
greater than the commercial versions of contemporary HMDs accompanied with
ergonomic interactions are suitable for implementation in cognitive neuroscience.
Another aim of this PhD was to devise a brief tool to appraise and report both the
quality of software features and VRISE intensity quantitatively; such a tool does not
currently exist. The Virtual Reality Neuroscience Questionnaire (VRNQ; Kourtesis et
al., 2019) was developed to assess the quality of virtual reality software in terms of
user experience, game mechanics, in-game assistance, and VRISE. Forty participants
aged between 28 and 43 years were recruited (18 gamers and 22 non-gamers) for the
study. They participated in 3 different virtual reality sessions until they felt weary or
discomfort and subsequently filled in the VRNQ. The results demonstrated that VRNQ
is a valid tool for assessing virtual reality software as it has good convergent,
discriminant, and construct validity. The maximum duration of virtual reality sessions
should be between 55 and 70 min when the virtual reality software meets or exceeds
the parsimonious cut-offs of the VRNQ, and the users are familiarized with the virtual
reality system. Also, gaming experience does not affect how long virtual reality
sessions should last. Furthermore, while the quality of virtual reality software
substantially modulates the maximum duration of virtual reality sessions, age and
education do not. Finally, deeper immersion, better quality of graphics and sound, and
more helpful in-game instructions and prompts were found to reduce VRISE intensity.
The VRNQ facilitates the brief assessment and reporting of the quality of virtual reality
software features and/or the intensity of VRISE, while its minimum and parsimonious
cut-offs may appraise the suitability of virtual reality software for implementation in research and clinical settings. However, the development of virtual reality software is
predominantly dependent on third parties (e.g., freelancers or companies) with
programming and software development skills. A solution that will promote the
adoption of immersive virtual reality as a research and clinical tool might be the in-house development of virtual reality research/clinical software by computer science
literate cognitive scientists or research software engineers.
In Chapter 4, guidelines are offered for the development of virtual reality software in
cognitive neuroscience and neuropsychology, by describing and discussing the stages
of the development of Virtual Reality Everyday Assessment Lab (VR-EAL), the first
neuropsychological battery in immersive virtual reality. Techniques for evaluating
cognitive functions within a realistic storyline are discussed. The utility of various
assets in Unity, software development kits, and other software are described so that
cognitive scientists can overcome challenges pertinent to VRISE and the quality of the
virtual reality software. In addition, VR-EAL is evaluated in accordance with the
necessary criteria for virtual reality software for research purposes. The virtual reality
neuroscience questionnaire (VRNQ) was implemented to appraise the quality of the
three versions of VR-EAL in terms of user experience, game mechanics, in-game
assistance, and VRISE. Twenty-five participants aged between 20 and 45 years with
12â16 years of full-time education evaluated various versions of VR-EAL. The final
version of VR-EAL achieved high scores in every sub-score of the VRNQ and
exceeded its parsimonious cut-offs. It also appeared to have better in-game assistance
and game mechanics, while its improved graphics substantially increased the quality
of the user experience and almost eradicated VRISE. The results substantially support the feasibility of the development of effective virtual reality research and clinical
software without the presence of VRISE during a 60-min virtual reality session.
In Chapter 5, validation of VR-EAL as an assessment of prospective memory, episodic
memory, attention, and executive functions using an ecologically valid approach is
examined. Performance on the VR-EAL, an immersive virtual reality
neuropsychological battery, is examined against an extensive paper-and-pencil
neuropsychological battery. Forty-one participants (21 females) were recruited: 18
gamers and 23 non-gamers who attended both an immersive virtual reality and a paper-and-pencil testing session. Bayesian Pearson correlation analyses were conducted to
assess construct and convergent validity of the VR-EAL. Bayesian t-tests were
performed to compare virtual reality and paper-and-pencil testing in terms of
administration time, similarity to real life tasks (i.e., ecological validity), and
pleasantness. VR-EAL scores were significantly correlated with their equivalent
scores on the paper-and-pencil tests. The participantsâ reports indicated that the VR-EAL tasks were considered significantly more ecologically valid and pleasant than the
paper-and-pencil neuropsychological battery. The VR-EAL battery also had a shorter
administration time. The VR-EAL appears to be an effective neuropsychological tool
for the assessment of everyday cognitive functions, and has enhanced ecological
validity, a highly pleasant testing experience, and does not induce cybersickness.
In the final part of this thesis, the preparatory attentional and memory (PAM) and the
multiprocess theories of prospective memory are examined by attempting to identify
the cognitive functions which may predict the individualâs performance on
ecologically valid prospective memory tasks in the same group of participants
described in Chapter 5. Bayesian t-tests were conducted to explore the differences among different prospective memory tasks (e.g., event-based and time-based) and
prospective memory tasks with varying delays between encoding and the recall of the
intended action (e.g., short-delay versus long-delay). Bayesian linear regression
analyses were performed to examine the predictors of VR-EAL scores. The results
revealed that the type of prospective memory task does not play a significant role in
everyday prospective memory functioning, but instead the length of delay between
encoding and retrieving the prospective memory intention plays a central role. Support
for the PAM and MP frameworks was found in non-focal and focal event-based tasks
respectively. However, the findings, inferring a dynamic interplay between automatic
and intentional monitoring and retrieval processes, agree with the inclusive approach
of the multiprocess framework. Also, the role of executive functions appears crucial
in everyday PM. Finally, everyday PM is predominantly facilitated by episodic
memory, visuospatial attention, auditory attention, and executive functions.
In conclusion, this PhD thesis attempted to show how immersive virtual reality
research methods may be implemented efficiently without the confounding effect of
cybersickness symptomatology in order to enhance the ecological validity of
neuropsychological testing and contribute to our understanding of everyday cognitive
ability
Abstracts on Radio Direction Finding (1899 - 1995)
The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography).
Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM.
The contents of these files are:
1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format];
2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format];
3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion
Laser Systems for Applications
This book addresses topics related to various laser systems intended for the applications in science and various industries. Some of them are very recent achievements in laser physics (e.g. laser pulse cleaning), while others face their renaissance in industrial applications (e.g. CO2 lasers). This book has been divided into four different sections: (1) Laser and terahertz sources, (2) Laser beam manipulation, (3) Intense pulse propagation phenomena, and (4) Metrology. The book addresses such topics like: Q-switching, mode-locking, various laser systems, terahertz source driven by lasers, micro-lasers, fiber lasers, pulse and beam shaping techniques, pulse contrast metrology, and improvement techniques. This book is a great starting point for newcomers to laser physics