Douglas Ross

Virtual interactive presence and augmented reality (VIPAR) for remote surgical assistance.

BACKGROUND: Surgery is a highly technical field that combines continuous decision-making with the coordination of spatiovisual tasks. OBJECTIVE: We designed a virtual interactive presence and augmented reality (VIPAR) platform that allows a remote surgeon to deliver real-time virtual assistance to a local surgeon, over a standard Internet connection. METHODS: The VIPAR system consisted of a “local” and a “remote” station, each situated over a surgical field and a blue screen, respectively. Each station was equipped with a digital viewpiece, composed of 2 cameras for stereoscopic capture, and a high-definition viewer displaying a virtual field. The virtual field was created by digitally compositing selected elements within the remote field into the local field. The viewpieces were controlled by workstations mutually connected by the Internet, allowing virtual remote interaction in real time. Digital renderings derived from volumetric MRI were added to the virtual field to augment the surgeons reality. For demonstration, a fixed-formalin cadaver head and neck were obtained, and a carotid endarterectomy (CEA) and pterional craniotomy were performed under the VIPAR system. RESULTS: The VIPAR system allowed for real-time, virtual interaction between a local (resident) and remote (attending) surgeon. In both carotid and pterional dissections, major anatomic structures were visualized and identified. Virtual interaction permitted remote instruction for the local surgeon, and MRI augmentation provided spatial guidance to both surgeons. Camera resolution, color contrast, time lag, and depth perception were identified as technical issues requiring further optimization. CONCLUSION: Virtual interactive presence and augmented reality provide a novel platform for remote surgical assistance, with multiple applications in surgical training and remote expert assistance.

RefMoB, a Reflectivity Feature Model-Based Automated Method for Measuring Four Outer Retinal Hyperreflective Bands in Optical Coherence Tomography

PURPOSE To validate a model-driven method (RefMoB) of automatically describing the four outer retinal hyperreflective bands revealed by spectral-domain optical coherence tomography (SDOCT), for comparison with histology of normal macula; to report thickness and position of bands, particularly band 2 (ellipsoid zone [EZ], commonly called IS/OS). METHODS Foveal and superior perifoveal scans of seven SDOCT volumes of five individuals aged 28 to 69 years with healthy maculas were used (seven eyes for validation, five eyes for measurement). RefMoB determines band thickness and position by a multistage procedure that models reflectivities as a summation of Gaussians. Band thickness and positions were compared with those obtained by manual evaluators for the same scans, and compared with an independent published histological dataset. RESULTS Agreement among manual evaluators was moderate. Relative to manual evaluation, RefMoB reported reduced thickness and vertical shifts in band positions in a band-specific manner for both simulated and empirical data. In foveal and perifoveal scans, band 1 was thick relative to the anatomical external limiting membrane, band 2 aligned with the outer one-third of the anatomical IS ellipsoid, and band 3 (IZ, interdigitation of retinal pigment epithelium and photoreceptors) was cleanly delineated. CONCLUSIONS RefMoB is suitable for automatic description of the location and thickness of the four outer retinal hyperreflective bands. Initial results suggest that band 2 aligns with the outer ellipsoid, thus supporting its recent designation as EZ. Automated and objective delineation of band 3 will help investigations of structural biomarkers of dark-adaptation changes in aging.

A Hole-filling Algorithm Using Non-uniform Rational B-splines

A three-dimensional (3D) geometric model obtained from a 3D device or other approaches is not necessarily watertight due to the presence of geometric deficiencies. These inadequacies must be repaired to create a valid surface mesh on the model as a pre-process of computational engineering analyses. This procedure has been a tedious and labor-intensive step, as there are many kinds of deficiencies that can make the geometry to be nonwatertight, such as gaps and holes. It is still challenging to repair discrete surface models based on available geometric information. The focus of this paper is to develop a new automated method for patching holes on the surface models in order to achieve watertightness. It describes a numerical algorithm utilizing Non-Uniform Rational B-Splines (NURBS) surfaces to generate smooth triangulated surface patches for topologically simple holes on discrete surface models. The Delaunay criterion for point insertion and edge swapping is used in this algorithm to improve the outcome. Surface patches are generated based on existing points surrounding the holes without altering them. The watertight geometry produced can be used in a wide range of engineering applications in the field of computational engineering simulation studies.

Development of an efficient aerodynamic shape optimization framework

Although many efforts have been made to develop an aerodynamic shape optimization (ASO) framework, iterative grid generation of the complex configuration within the optimization loop has still been a critical barrier. In this paper, an efficient ASO framework is developed by integrating a parametric grid generator, an optimization toolkit, and a flow solver. A geometry-grid template toolkit is developed to address the need to produce a large number of grids in a timely manner for the parametric design study. An object-oriented optimization toolkit that allows a flexible and extensible interfacing with user-specific codes is used. An in-house full Navier-Stokes flow solver is developed and used in the framework. Code integration is achieved using a black-box interface with script files. Two ASO applications and their optimum solutions are presented to demonstrate the success of this framework.

Structured Grid Generation over NURBS and Facetted Surface Patches by Reparametrization

This paper deals with structured grid generation using Floater’s parametrization algorithm for surface triangulation. It gives an outline of the algorithm in the context of structured grid generation. Then it explains how the algorithm can be used to generate a structured grid over a singular NURBS surface patch. This is an alternate method to the known carpeting method of reparametrization for structured grid generation over a NURBS surface patch. The paper also explains how to generate a structured grid over a four sided trimmed patch of a facetted surface using the parametrization algorithm. All the procedures are explained using examples.

Mesh Generation Transfer Based on Topology Matching

This paper describes a method to automatically generate a mesh by transferring the mesh generation parameters from a standard geometry to an equivalent one. This allows the geometry and mesh generation systems to be separate. The new geometry may be a parametric version of the previous geometry or a new geometry. The requirement is that the geometries have the same topology. The transfer is accomplished by finding the best correspondence between the two topologies.