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At least 271 records · Page 15Linked to original sources

PubMed2006

Context conditioning and behavioral avoidance in a virtual reality environment: effect of predictability.

BACKGROUND: Sustained anxiety can be modeled using context conditioning, which can be studied in a virtual reality environment. Unpredictable stressors increase context conditioning in animals. This study examined context conditioning to predictable and unpredictable shocks in humans using behavioral avoidance, potentiated startle, and subjective reports of anxiety. METHODS: Subjects were guided through three virtual rooms (no-shock, predictable, unpredictable contexts). Eight-sec duration colored lights served as conditioned stimuli (CS). During acquisition, no shock was administered in the no-shock context. Shocks were paired with the CS in the predictable context and were administered randomly in the unpredictable context. No shock was administered during extinction. Startle stimuli were delivered during CS and between CS to assess cued and context conditioning, respectively. To assess avoidance, subjects freely navigated into two of the three contexts to retrieve money. RESULTS: Startle between CS was potentiated in the unpredictable context compared to the two other contexts. Following acquisition, subjects showed a strong preference for the no-shock context and avoidance of the unpredictable context. CONCLUSIONS: Consistent with animal data, context conditioning is increased by unpredictability. These data support virtual reality as a tool to extend research on physiological and behavioral signs of fear and anxiety in humans.

Adult↗

PubMed2002

Development of a virtual speaking simulator using Image Based Rendering.

The fear of speaking is often cited as the world's most common social phobia. The rapid growth of computer technology has enabled the use of virtual reality (VR) for the treatment of the fear of public speaking. There are two techniques for building virtual environments for the treatment of this fear: a model-based and a movie-based method. Both methods have the weakness that they are unrealistic and not controllable individually. To understand these disadvantages, this paper presents a virtual environment produced with Image Based Rendering (IBR) and a chroma-key simultaneously. IBR enables the creation of realistic virtual environments where the images are stitched panoramically with the photos taken from a digital camera. And the use of chroma-keys puts virtual audience members under individual control in the environment. In addition, real time capture technique is used in constructing the virtual environments enabling spoken interaction between the subject and a therapist or another subject.

Computer Simulation↗

PubMed1995

A virtual reality environment for enhanced oral implantology.

The quality of clinical decision making is limited by the performance of human cognitive processing of complex visual information. In the field of oral implantology, treatment planning is still based on the holistic interpretation and mental reconstruction of cross sectional 2d-image data. This surpasses widely human cognitive competence and hampers treatment planning in three dimensions that are essential in implantology. To overcome these problems, a virtual reality environment for enhanced treatment planning in oral implantology is presented, which provides a fully three-dimensional perception of an individual clinical situation. It enables the clinician to perceive and handle the objects of her work in a virtual world as needed for the task of diagnosis and treatment. Human visual decoding effort is thus reduced, and estimating the real position and orientation of implants during planning is enabled in any direction. Immersive three-dimensional perception is achieved by hybrid stereoscopic rendering techniques combined with large screen projections. The virtual world in which treatment planning takes place allows the clinician to move and interact with the individual anatomy simultaneously with three degrees of freedom. A set of virtual tools enables the clinician to perform a virtual treatment "in advance." The design and placement of implants, as it is interactively controlled by the clinician, is simulated in real-time. Thus the results of actions become immediately visible and provide visible feedback for interactive adjustment. In addition, the presented virtual reality environment for oral implant treatment planning includes algorithms for detection of inappropriate treatment in the concerned bone regions, according to the current design of the implant. These algorithms take both the individual properties of a patient's bone and the type of implants used into account.

Computer Simulation↗

PubMed2005

Virtual reality training improves students' knowledge structures of medical concepts.

Virtual environments can provide training that is difficult to achieve under normal circumstances. Medical students can work on high-risk cases in a realistic, time-critical environment, where students practice skills in a cognitively demanding and emotionally compelling situation. Research from cognitive science has shown that as students acquire domain expertise, their semantic organization of core domain concepts become more similar to those of an expert's. In the current study, we hypothesized that students' knowledge structures would become more expert-like as a result of their diagnosing and treating a patient experiencing a hematoma within a virtual environment. Forty-eight medical students diagnosed and treated a hematoma case within a fully immersed virtual environment. Student's semantic organization of 25 case-related concepts was assessed prior to and after training. Students' knowledge structures became more integrated and similar to an expert knowledge structure of the concepts as a result of the learning experience. The methods used here for eliciting, representing, and evaluating knowledge structures offer a sensitive and objective means for evaluating student learning in virtual environments and medical simulations.

Adult↗

PubMed2006

Virtual reality simulation of fluoroscopic navigation.

Surgical navigation systems assist surgeons by tracking targets attached to the patient's bones and to the surgical tools. Fluoroscopic navigation is a technology that adds "live" imaging to surgical navigation. In order to identify the limitations and potential sources of errors in fluoroscopic navigation, a virtual environment is created in which all the key steps of fluoroscopic navigation can be rehearsed. This provides a low-cost, highly portable, and radiation-free training environment with the ability of instant accuracy validation and reliable measurement of trainee progress. This virtual environment also is suitable for comparing different fluoroscopic registration techniques and protocols. Although the imaging component of the navigation is simulated, physical interaction with the environment can be modeled at different levels; from a fully virtual environment, to miniature models, to life-size dummies and cadavers. Each of these options satisfies different specific training needs, such as the need for portability and easy setup to the need for a completely realistic simulation of the entire clinical environment and operating procedure. In this study, we present the example of a system based on a scaled-down model with a specific focus on analyzing and training bony landmark localization using fluoroscopic navigation.

Computer Simulation↗

PubMed2002

Virtual reality in Latin American clinical psychology and the VREPAR project. Virtual Reality Environments for Psycho-Neuro-physiological Assessment and Rehabilitation.

Starting with the excellent collective work done by the European Community (EC)-funded Virtual Reality Environments for Psycho-Neuro-physiological Assessment and Rehabilitation (VREPAR) projects, I try to indicate some possible pathways that would allow a better integration of this advanced technology into the reality of Latin American psychology. I myself use analyses that I did in my master's degree in the PUCSP-Catholic University in São Paulo, Brazil. I also include a brief description of the CD-ROM Clinical Psychology Uses of Virtual Reality (CPUVR) that accompanies my thesis. I point out the importance of collaboration between psychology and other disciplines, including computer science. I explain the method that I used to work with digital information, important for the formation of a critical mass of people thinking in Portuguese and Spanish to accelerate a technological jump.

Computers↗

PubMed1999

[Networked robotics: its present status and future prospect].

One of the most promising technologies today is the integration of virtual reality and robotics on a network. This is called network robotics in general and R-cubed (real-time remote robotics) in particular. R-cubed is a Japanese national R&D scheme to realize augmented telexistence (tele-existence) through various kinds of networks including the Internet. Telexistence is a concept named for the technology that enables people to have a real-time sensation of being present at a location other than the place where they actually exist, and to interact with a remote and/or virtual environment. They can thus "telexist" in a real environment that the robot is present or in a virtual environment that a computer has generated. It is also possible to telexist in a mixed environment of real and virtual which can be called augmented telexistence. The concept of telexistence, i.e., virtual existence in a remote or computer-generated environment, has developed into the national R-cubed R&D scheme to create an advanced and comfortable life for the network society of the 21st century. Based on the national R&D scheme of R-Cubed, the Humanoid Robotics Project (HRP) was launched in April 1998. This is an effort to integrate telerobotics, network technology, and virtual reality into networked telexistence, and significant results are expected.

Forecasting↗

PubMed2003

CAREN (computer assisted rehabilitation environment): a novel way to improve shoe efficacy.

A new technical system, CAREN (computer assisted rehabilitation environment), is described, which makes it possible to do a total body movement analysis in a virtual environment. The virtual environment is reproducible and as close to natural environment as possible. In a case study it proved possible with this system to test different shoes and get insight in the movement problems. The importance of whole body analysis is demonstrated in this case study. The adjustments made in the shoes could be tested for their efficacy.

Adult↗

PubMed2000

Student test scores are improved in a virtual learning environment.

This study evaluates the effectiveness of delivering the core curriculum of an introductory neuroscience course using a software application referred to as a virtual learning interface (VLI). The performance of students in a virtual learning environment (VLE) is compared with that of students in a conventional lecture hall in which the same lecturer presented the same material. This study was not designed to determine whether grades are improved by augmenting a lecture with other information. The VLI takes advantage of audio, video, animation, and text in a multimedia computer environment. Our results indicate that raw average scores on weekly examinations were 14 percentage points higher for students in the VLE compared with those for students in a conventional lecture hall setting. Moreover, normalized test scores were over 5 points higher for students in the VLE. This analysis suggest that a core curriculum can be effectively presented to students using the VLE, thereby making it possible for faculty to spend less class time relaying facts and more time engaging students in discussion of scientific theory.

Data Collection↗

PubMed2005

Cardiovascular, hormone, and lipid responses to stress induced by virtual crane handling.

OBJECTIVES: The aim of the study was to test whether a mixed-mock-up-simulator (MMU-simulator) is suitable for on-the-job training by measuring stress reactions induced by handling a crane in a virtual environment in subjects not experienced in crane operation. MATERIALS AND METHODS: A MMU-simulator in a virtual environment was developed. Twenty three individuals were randomly divided into Group 1 (n = 13) and Group 2 (n = 10). They had the task of transporting a weight over barriers with a virtual crane twice in two 15-min intervals with a 15-min break in between. Acoustical and optical disturbances were generated as an additional strain for Group 1 in the second interval and for Group 2 in the first interval. Heart rate (HR) and blood pressure (BP) were measured consecutively in both groups, blood sampling was performed in Group 1. Plasma concentrations of stress hormones and lipids were analyzed. Data were calculated as the percentage of baseline values. RESULTS: Compared to rest courses, strain led to a significant increase in HR and BP except diastolic BP in Group 2. Apart from an increased systolic BP under additional stress in Group 2, no significant differences were found between the two strain courses. Concentrations of epinephrine showed the highest increase under strain with a mean of 67%. The mean increase in norepinephrine and cortisol was 23% and 7%, respectively, whereas a 4% increase was observed for total cholesterol and high density lipoprotein cholesterol. These differences between "Rest" and "Strain" were significant. After adjusting for total plasma protein concentration, stress hormones, but not lipids, were still significantly higher during strain. CONCLUSIONS: The elevation in lipids during acute stress could be interpreted as an effect of hemoconcentration due to vasoconstriction by catecholamines. The significant increase in cardiovascular parameters and stress hormones during the tasks demonstrate that working in a virtual environment generates mental strain and that the developed MMU-simulator appears to be a promising device for on-the-job training. However, further research is necessary to validate the usefulness of virtual training by means of a comparative study of virtual and real-world training.

Adult↗

PubMed2000

Common object request broker architecture (CORBA)-based security services for the virtual radiology environment.

The US Army Great Plains Regional Medical Command (GPRMC) has a requirement to conform to Department of Defense (DoD) and Army security policies for the Virtual Radiology Environment (VRE) Project. Within the DoD, security policy is defined as the set of laws, rules, and practices that regulate how an organization manages, protects, and distributes sensitive information. Security policy in the DoD is described by the Trusted Computer System Evaluation Criteria (TCSEC), Army Regulation (AR) 380-19, Defense Information Infrastructure Common Operating Environment (DII COE), Military Health Services System Automated Information Systems Security Policy Manual, and National Computer Security Center-TG-005, "Trusted Network Interpretation." These documents were used to develop a security policy that defines information protection requirements that are made with respect to those laws, rules, and practices that are required to protect the information stored and processed in the VRE Project. The goal of the security policy is to provide for a C2-level of information protection while also satisfying the functional needs of the GPRMC's user community. This report summarizes the security policy for the VRE and defines the CORBA security services that satisfy the policy. In the VRE, the information to be protected is embedded into three major information components: (1) Patient information consists of Digital Imaging and Communications in Medicine (DICOM)-formatted fields. The patient information resides in the digital imaging network picture archiving and communication system (DIN-PACS) networks in the database archive systems and includes (a) patient demographics; (b) patient images from x-ray, computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US); and (c) prior patient images and related patient history. (2) Meta-Manager information to be protected consists of several data objects. This information is distributed to the Meta-Manager nodes and includes (a) radiologist schedules; (b) modality worklists; (c) routed case information; (d) DIN-PACS and Composite Health Care system (CHCS) messages, and Meta-Manager administrative and security information; and (e) patient case information. (3) Access control and communications security is required in the VRE to control who uses the VRE and Meta-Manager facilities and to secure the messages between VRE components. The CORBA Security Service Specification version 1.5 is designed to allow up to TCSEC's B2-level security for distributed objects. The CORBA Security Service Specification defines the functionality of several security features: identification and authentication, authorization and access control, security auditing, communication security, nonrepudiation, and security administration. This report describes the enhanced security features for the VRE and their implementation using commercial CORBA Security Service software products.

Artificial Intelligence↗

PubMed2002

The UFRJ-UERJ group: interdisciplinary virtual reality experiments in neuropsychiatry.

This paper describes the research lines of an interdisciplinary group composed by two government universities in Rio de Janeiro. The first research line, a Virtual Environment for testing the acceptance of Virtual Reality equipment by schizophrenia patients, has stimulated a growing interest in this area in the country and abroad. The second research line, in progress now, develops a virtual environment to improve the learning abilities of children with Attention-Deficit and Hyperactivity Disorder (ADHD). Another study is related to the use of Virtual Reality in the cognitive treatment of common city phobias, beginning with the reproduction of some tunnels of our city to treatment of claustrophobic patients. The last of the research lines in progress in this group develops a virtual square for stimulating autistic patients.

Adult↗

PubMed1999

Virtual management of radiology examinations in the virtual radiology environment using common object request broker architecture services.

In the Department of Defense (DoD), US Army Medical Command is now embarking on an extremely exciting new project--creating a virtual radiology environment (VRE) for the management of radiology examinations. The business of radiology in the military is therefore being reengineered on several fronts by the VRE Project. In the VRE Project, a set of intelligent agent algorithms determine where examinations are to routed for reading bases on a knowledge base of the entire VRE. The set of algorithms, called the Meta-Manager, is hierarchical and uses object-based communications between medical treatment facilities (MTFs) and medical centers that have digital imaging network picture archiving and communications systems (DIN-PACS) networks. The communications is based on use of common object request broker architecture (CORBA) objects and services to send patient demographics and examination images from DIN-PACS networks in the MTFs to the DIN-PACS networks at the medical centers for diagnosis. The Meta-Manager is also responsible for updating the diagnosis at the originating MTF. CORBA services are used to perform secure message communications between DIN-PACS nodes in the VRE network. The Meta-Manager has a fail-safe architecture that allows the master Meta-Manager function to float to regional Meta-Manager sites in case of server failure. A prototype of the CORBA-based Meta-Manager is being developed by the University of Arizona's Computer Engineering Research Laboratory using the unified modeling language (UML) as a design tool. The prototype will implement the main functions described in the Meta-Manager design specification. The results of this project are expected to reengineer the process of radiology in the military and have extensions to commercial radiology environments.

Algorithms↗

PubMed2001

Manipulation of volumetric patient data in a distributed virtual reality environment.

Due to increases in network speed and bandwidth, distributed exploration of medical data in immersive Virtual Reality (VR) environments is becoming increasingly feasible. The volumetric display of radiological data in such environments presents a unique set of challenges. The shear size and complexity of the datasets involved not only make them difficult to transmit to remote sites, but these datasets also require extensive user interaction in order to make them understandable to the investigator and manageable to the rendering hardware. A sophisticated VR user interface is required in order for the clinician to focus on the aspects of the data that will provide educational and/or diagnostic insight. We will describe a software system of data acquisition, data display, Tele-Immersion, and data manipulation that supports interactive, collaborative investigation of large radiological datasets. The hardware required in this strategy is still at the high-end of the graphics workstation market. Future software ports to Linux and NT, along with the rapid development of PC graphics cards, open the possibility for later work with Linux or NT PCs and PC clusters.

Computer Communication Networks↗

PubMed2006

Visual distance estimation in static compared to moving virtual scenes.

Visual motion is used to control direction and speed of self-motion and time-to-contact with an obstacle. In earlier work, we found that human subjects can discriminate between the distances of different visually simulated self-motions in a virtual scene. Distance indication in terms of an exocentric interval adjustment task, however, revealed linear correlation between perceived and indicated distances but with a profound distance underestimation. One possible explanation for this underestimation is the perception of visual space in virtual environments. Humans perceive visual space in natural scenes as curved, and distances are increasingly underestimated with increasing distance from the observer. Such spatial compression may also exist in our virtual environment. We therefore surveyed perceived visual space in a static virtual scene. We asked observers to compare two horizontal depth intervals, similar to experiments performed in natural space. Subjects had to indicate the size of one depth interval relative to a second interval. Our observers perceived visual space in the virtual environment as compressed, similar to the perception found in natural scenes. However, the nonlinear depth function we found can not explain the observed distance underestimation of visual simulated self-motions in the same environment.

Adult↗

PubMed2005

Modeling of driver's collision avoidance maneuver based on controller switching model.

This paper presents a modeling strategy of human driving behavior based on the controller switching model focusing on the driver's collision avoidance maneuver. The driving data are collected by using the three-dimensional (3-D) driving simulator based on the CAVE Automatic Virtual Environment (CAVE), which provides stereoscopic immersive virtual environment. In our modeling, the control scenario of the human driver, that is, the mapping from the driver's sensory information to the operation of the driver such as acceleration, braking, and steering, is expressed by Piecewise Polynomial (PWP) model. Since the PWP model includes both continuous behaviors given by polynomials and discrete logical conditions, it can be regarded as a class of Hybrid Dynamical System (HDS). The identification problem for the PWP model is formulated as the Mixed Integer Linear Programming (MILP) by transforming the switching conditions into binary variables. From the obtained results, it is found that the driver appropriately switches the "control law" according to the sensory information. In addition, the driving characteristics of the beginner driver and the expert driver are compared and discussed. These results enable us to capture not only the physical meaning of the driving skill but the decision-making aspect (switching conditions) in the driver's collision avoidance maneuver as well.

Accidents, Traffic↗

PubMedDate not supplied

Training in virtual and real environments.

Transfer of training between real and virtual environments was examined using a pick-and place task with two different difficulty levels. The task was to minimize the time to move cans from one color coded location in the first row to the same color coded location in the back row and then to reverse the process. In the first task, the front and back disk colors were aligned, and in the second disk order, the front and back disk colors were randomly placed on the table. Subjects trained in one environment were then tested in the other and their performance compared with that of subjects being trained in that environment. Some virtual world-trained subjects showed small but significant improvement in performance compared with the untrained subjects for the real world task for both disk arrangements. The differences in performance between the two groups decreased with trial number until no difference was seen at the end of the sessions. None of the real world-trained subjects showed any significant improvement when performing the task in the virtual world compared with the untrained subjects. These results suggest that transfer-of-training from virtual to real world tasks can take place under certain conditions.

Adult↗

PubMed2004

Methods of bronchial tree reconstruction and camera distortion corrections for virtual endoscopic environments.

The use of three-dimensional visualization of anatomical structures in diagnostics and medical training is growing. The main components of virtual respiratory tract environments include reconstruction and simulation algorithms as well as correction methods of endoscope camera distortions in the case of virtually-enhanced navigation systems. Reconstruction methods rely usually on initial computer tomography (CT) image segmentation to trace contours of the tracheobronchial tree, which in turn are used in the visualization process. The main segmentation methods, including relatively simple approaches such as adaptive region-growing algorithms and more complex methods, e.g. hybrid algorithms based on region growing and mathematical morphology methods, are described in this paper. The errors and difficulties in the process of tracheobronchial tree reconstruction depend on the occurrence of distortions during CT image acquisition. They are usually related to the inability to exactly fulfil the sampling theorem's conditions. Other forms of distortions and noise such as additive white Gaussian noise, may also appear. The impact of these distortions on the segmentation and reconstruction may be diminished through the application of appropriately selected image prefiltering, which is also demonstrated in this paper. Methods of surface rendering (ray-casting, ray-tracing techniques) and volume rendering will be shown, with special focus on aspects of hardware and software implementations. Finally, methods of camera distortions correction and simulation are presented. The mathematical camera models, the scope of their applications and types of distortions were have also been indicated.

Algorithms↗