Richard Robb | PubMed Health

PubMed2003

Interrogative visualization: embedding deformation and Constructive Solid Geometry into volume visualization.

Existing volume visualization algorithms lack sophisticated volumetric modeling capabilities to represent, construct and manipulate objects of interest within a volumetric dataset. Integrating manipulations such as non-linear deformations and constructions similar to those in solid modeling into the visualization process would have significant value in surgical planning and simulation. Interrogative visualization--the ability to extract, enumerate, deform and track objects of interest is also crucial in other visualization tasks. The conventional approach to visualize the volume deformation and construction process is to construct an intermediate volume for each step of manipulation. This is prohibitively time consuming and costly. This paper presents an approach to overcome this constraint. We model the target capture space as octrees. The target octree is adaptively subdivided to efficiently balance the complexity of deformation and visualization. The source volumetric data can either be in octree or conventional 3D array format. Deformations are specified by landmark displacements, and in-between deformation is filled in by scattered data interpolation. Volumetric modeling is supported by a Constructive Solid Geometry (CSG) structure. Spatial Coherency is exploited in the view-dependent node traversal and projection of individual octree nodes.

Algorithms↗

PubMed2002

An immersive simulation system for provoking and analyzing cataplexy.

Cataplexy, a sudden loss of voluntary muscle control, is one of the hallmark symptoms of narcolepsy, a sleep disorder characterized by excessive daytime sleepiness. Cataplexy is usually triggered by strong, spontaneous emotions, such as laughter, surprise, fear or anger, and is more common in times of stress. The Sleep Disorders Unit and the Biomedical Imaging Resource at Mayo Clinic are developing interactive display technology for reliably inducing cataplexy during clinical monitoring. The use of immersive displays may help bypass patient defenses, and game-like "unreality" allows introduction of surprising, threatening, or humorous elements, with little risk of offending patients. The project is referred to as the "Cataplexy/Narcolepsy Activation Program", or CatNAP. We have developed an automobile driving simulation to allow the introduction of humorous, surprising, or stress-inducing events and objects as the patient attempts to navigate a simulated vehicle through a virtual town. The patient wears a stereoscopic head-mounted display, by which he views the virtual town through the windows of his simulated vehicle. The vehicle is controlled via a driving simulator steering wheel and pedal cluster. The patient is instructed to drive his vehicle to another location in town, given initial directions and street signs. As he attempts to accomplish the task, various objects, sounds or conditions occur which may distract, startle, frustrate or cause laughter; responses which may trigger a cataplectic episode. The patient can be monitored by reflex tests and EMG recordings during the driving experience. An evaluation phase with volunteer patients previously diagnosed with cataplexy has been completed. The goal of these trials was to gain insight from the volunteers as to improvements that could be made to the simulation. All patients that participated in the evaluation phase have been under a physician's care for a number of years and control their cataplexy with medication. We believe this is a novel and innovative approach to a difficult problem. CatNAP is a compelling example of the potentially effective application of virtual reality technology to an important clinical problem that has resisted previous approaches. Preliminary results suggest that an immersive simulation system like CatNAP will be able to reliably induce cataplexy in a controlled environment. The project is continuing through a final stage of refinement prior to conducting a full clinical study.

Automobile Driving↗