Larry S. Davis

Dynamic superimposition of synthetic objects on rigid and simple-deformable real objects

A current challenge in augmented reality applications is the accurate superimposition of synthetic objects on real objects within the environment. This challenge is heightened when the real objects are in motion and/or are nonrigid. In this article, we present a robust method for realtime, optical superimposition of synthetic objects on dynamic rigid and simple-deformable real objects. Moreover, we illustrate this general method with the VRDA Tool, a medical education application related to the visualization of internal human knee joint anatomy on a real human knee.

Predicting accuracy in pose estimation for marker-based tracking

Tracking is a necessity for interactive virtual environments. Marker-based tracking solutions involve the placement of fiducials in a rigid configuration on the object(s) to be tracked, called a tracking probe. The realization that tracking performance is linked to probe performance necessitates investigation into the design of tracking probes for proponents of marker-based tracking. A challenge involved with probe design is predicting the accuracy of a tracking probe. We present a method for predicting the accuracy of a tracking probe based upon a first-order propagation of the errors associated with the markers on the probe. Results for two sample tracking probes show excellent agreement between measured and predicted errors.

A method for designing marker-based tracking probes

Many tracking systems utilize collections of fiducial markers arranged in rigid configurations, called tracking probes, to determine the pose of objects within an environment. In this paper, we present a technique for designing tracking probes called the viewpoints algorithm. The algorithm is generally applicable to tracking systems that use at least three fiduciary marks to determine the pose of an object. The algorithm is used to create an integrated, head-mounted display tracking probe. The predicted accuracy of this probe was 0.032 /spl plusmn/ 0.02 degrees in orientation and 0.09 /spl plusmn/ 0.07 mm in position. The measured accuracy of the probe was 0.028 /spl plusmn/ 0.01 degrees in orientation and 0.11 /spl plusmn/ 0.01 mm in position. These results translate to a predicted, static positional overlay error of a virtual object presented at 1m of less than 0.5 mm. The algorithm is part of a larger framework for designing tracking probes based upon performance goals and environmental constraints.

Web-based 3D planning tool for radiation therapy treatment

One of the biggest concerns in external treatment planning is the collision avoidance of the treatment Linear Accelerator (LINAC®) components such as gantry (G), table (T), collimator (C), and any other auxiliary components such as fixation devices etc, with the patient. Some external treatment plans require complex components of the above GTC combinations.We are presenting a preliminary design and implementation of a 3D-graphical tool for the detection of potential gantry-collimator-couch collisions in external treatment planning. The graphical tool uses the Virtual Reality Modeling Language (VRML) to model the exact geometry of any treatment machine by reading its manufacturers CAD design files. Unlike other anti-collision methods developed so far in the literature, our tool would be able to model the details of the treatment linac and add-on devices for patient-specific setups. Hence, the tool will create patient-specific realistic collision map for any external treatment scenario. The tool can be used as a stand-alone program or embedded in the Eclipse treatment planning system.

Visualization of tumor-influenced 3D lung dynamics

A framework for real-time visualization of a tumor-influenced lung dynamics is presented in this paper. This framework potentially allows clinical technicians to visualize in 3D the morphological changes of lungs under different breathing conditions. Consequently, this technique may provide a sensitive and accurate assessment tool for pre-operative and intra-operative clinical guidance. The proposed simulation method extends work previously developed for modeling and visualizing normal 3D lung dynamics. The model accounts for the changes in the regional lung functionality and the global motor response due to the presence of a tumor. For real-time deformation purposes, we use a Greens function (GF), a physically based approach that allows real-time multi-resolution modeling of the lung deformations. This function also allows an analytical estimation of the GFs deformation parameters from the 4D lung datasets at different level-of-details of the lung model. Once estimated, the subject-specific GF facilitates the simulation of tumor-influenced lung deformations subjected to any breathing condition modeled by a parametric Pressure-Volume (PV) relation.

Technologies for Augmented Reality: Calibration for Real-Time Superimposition on Rigid and Simple-Deformable Real Objects

A current challenge in augmented reality applications is the ability to superimpose synthetic objects on real objects within the environment. This challenge is heightened when the real objects are in motion and/or are non-rigid. Yet even more challenging is the case when the moving real objects involved are deformable. In this article, we present a robust method for calibrating marker-based augmented reality applications to allow real-time, optical superimposition of synthetic objects on dynamic rigid and simple-deformable real objects. Moreover, we illustrate this general method with the VRDA Tool, a medical education application related to the visualization of internal human knee joint anatomy on a real human knee.

3D visualization and imaging in distributed collaborative environments

The Optical Diagnostics and Applications Laboratory (ODALab) is investigating methods and technology for 3D visualization and imaging. Specifically, were integrating and assessing systems driven by real-world applications that can benefit from or enhance distributed collaborative environments. Although optics is at the core of the research program, the research involves extensive knowledge from various science and engineering fields. Students in the ODALab can pursue graduate degrees in optics, engineering, physics, computer science, or modeling and simulation. The article surveys the research the ODALab program is doing in optical system design, fabrication, and assessment of innovative head-mounted displays (HMDs); the design of optical tracking probes for integration in HMDs; the development of mathematical methods and applications for augmented reality (AR); the physics-based modeling of anatomical joint motion and optical special effects for augmented environments; and 3D biomedical optical imaging.

Merging augmented reality and anatomically correct 3D models in the development of a training tool for endotracheal intubation

Augmented reality is often used for medical training systems in which the user visualizes 3D information superimposed on the real world. In this context, we introduce a augmented reality tool to train the medical practitioner hand-eye coordination in performing critical procedures such as endotracheal intubation.

Head-mounted projective displays for creating distributed collaborative environments

In this paper, we shall present an overview of research in augmented reality technology and applications conducted in collaboration with the 3DVIS Lab and the MIND Lab. We present research in the technology of head-mounted projective displays and tracking probes. We then review mathematical methods developed for augmented reality. Finally we discuss applications in medical augmented reality and point to current developments in distributed 3d collaborative environments.

A New Paradigm for Head-Mounted Display Technology: Application to Medical Visualization and Remote Collaborative Environments

Today advanced 3D virtual environments are mostly based on either a technology known as the cave or head-mounted displays. A new type of head-mounted display, which consists of a pair of miniature projection lenses and displays mounted on the helmet and retro-reflective sheeting materials placed strategically in the environment, has been proposed as an alternative to eyepiece optics types of displays. The novel concept and properties of the head- mounted projective display (HMPD) suggests solutions to part of the problems of state-of-art visualization devices and make it extremely suitable for multiple-user collaborative environments. In this paper, we first review the concept of the HMPD and present the latest prototype developed. We then discuss its application to medical visualization and remote collaborative environments.