Kevin Montgomery

A multiparameter wearable physiologic monitoring system for space and terrestrial applications

A novel, unobtrusive and wearable, multiparameter ambulatory physiologic monitoring system for space and terrestrial applications, termed LifeGuard, is presented. The core element is a wearable monitor, the crew physiologic observation device (CPOD), that provides the capability to continuously record two standard electrocardiogram leads, respiration rate via impedance plethysmography, heart rate, hemoglobin oxygen saturation, ambient or body temperature, three axes of acceleration, and blood pressure. These parameters can be digitally recorded with high fidelity over a 9-h period with precise time stamps and user-defined event markers. Data can be continuously streamed to a base station using a built-in Bluetooth RF link or stored in 32 MB of on-board flash memory and downloaded to a personal computer using a serial port. The device is powered by two AAA batteries. The design, laboratory, and field testing of the wearable monitors are described.

Real-time knot-tying simulation

The real-time simulation of rope, and knot tying in particular, raises difficult issues in contact detection and management. Some practical knots can only be achieved by complicated crossings of the rope, yielding multiple simultaneous contacts, especially when the rope is pulled tight. This paper describes a graphical simulator that allows a user to grasp and smoothly manipulate a virtual rope and to tie arbitrary knots, including knots around other objects, in real time. A first component of the simulator computes the global configuration of the rope based on user interactions. Another component of the simulator precisely detects self-collisions in the rope as well as collisions with other objects. Finally, a third component manages collisions to prevent penetration, while making the rope slide with some friction along itself and other objects, so that knots can be pulled tight in a realistic manner. An additional module uses recent results from knot theory to identify, also in real time, which topological knots have been tied. This work was motivated by surgical suturing, but simulation in other domains, such as sailing and rock climbing, could also benefit from it.

Real-time simulation of deformable objects: tools and application

Presents algorithms for animating deformable objects in real time. We focus on computing the deformation of an object subject to external forces and detecting collisions among deformable and rigid objects. The targeted application domain is surgical training. This application relies more on visual realism than exact, patient-specific deformation, but requires that computations be performed in real time. This is in contrast with pre-operative surgical planning, where computations may be done offline but must provide accurate results. To achieve real-time performance, the proposed algorithms take advantage of the fact that most deformations are local, human-body tissues are well damped, and motions of surgical instruments are relatively slow. They have been integrated into a virtual reality system for simulating the suturing of small blood vessels (microsurgery).

Lifeguard - a personal physiological monitor for extreme environments

Monitoring vital signs in applications that require the subject to be mobile requires small, lightweight, and robust sensors and electronics. A body-worn system should be unobtrusive, noninvasive, and easy-to-use. It must be able to log vital signs data for several hours as well as transmit it on demand in real-time using secure wireless technologies. The NASA Ames Research Center (Astrobionics) and Stanford University (National Center for Space Biological Technologies) are currently developing a wearable physiological monitoring system for astronauts, called LifeGuard, that meets all of the above requirements and is also applicable to clinical, home-health monitoring, first responder and military applications.

A survey of interactive mesh‐cutting techniques and a new method for implementing generalized interactive mesh cutting using virtual tools‡

In our experience, mesh-cutting methods can be distinguished by how their solutions address the following major issues: definition of the cut path, primitive removal and re-meshing, number of new primitives created, when re-meshing is performed, and representation of the cutting tool. Many researches have developed schemes for interactive mesh cutting with the goals of reducing the number of new primitives created, creating new primitives with good aspect ratios, avoiding a disconnected mesh structure between primitives in the cut path, and representing the path traversed by the tool as accurately as possible. The goal of this paper is to explain how, by using a very simple framework, one can build a generalized cutting scheme. This method allows for any arbitrary cut to be made within a virtual object, and can simulate cutting surface, layered surface or tetrahedral objects using a virtual scalpel, scissors, or loop cautery tool. This method has been implemented in a real-time, haptic-rate surgical simulation system allowing arbitrary cuts to be made on high-resolution patient-specific models. Published in 2002 by John Wiley & Sons, Ltd.

A Microsurgery Simulation System

Computer systems for surgical planning and training are poised to greatly impact the traditional versions of these tasks. These systems provide an opportunity to learn surgical techniques with lower costs and lower risks. We have developed a virtual environment for the graphical visualization of complexsu rgical objects and real-time interaction with these objects using real surgical tools. An application for microsurgical training, in which the user sutures together virtual blood vessels, has been developed. This application demonstrates many facets of our system, including deformable object simulation, tool interactions, collision detection, and suture simulation. Here we present a broad outline of the system, which can be generalized for any anastomosis or other procedures, and a detailed look at the components of the microsurgery simulation.

Simulated Medical Learning Environments on the Internet

Learning anatomy and surgical procedures requires both a conceptual understanding of three-dimensional anatomy and a hands-on manipulation of tools and tissue. Such virtual resources are not available widely, are expensive, and may be culturally disallowed. Simulation technology, using high-performance computers and graphics, permits realistic real-time display of anatomy. Haptics technology supports the ability to probe and feel this virtual anatomy through the use of virtual tools. The Internet permits world-wide access to resources. We have brought together high-performance servers and high-bandwidth communication using the Next Generation Internet and complex bimanual haptics to simulate a tool-based learning environment for wide use. This article presents the technologic basis of this environment and some evaluation of its use in the gross anatomy course at Stanford University.

Surgical simulator for hysteroscopy: a case study of visualization in surgical training

Computer-based surgical simulation promises to provide a broader scope of clinical training through the introduction of anatomic variation, simulation of untoward events, and collection of performance data. We present a haptically-enabled surgical simulator for the most common techniques in diagnostic and operative hysteroscopy-cervical dilation, endometrial resection and ablation, and lesion excision. Engineering tradeoffs in developing a real-time, haptic-rate simulator are discussed.

The forcegrid: a buffer structure for haptic interaction with virtual elastic objects

Real-time surgical simulation often requires computing the deformations of visco-elastic human-body tissue and generating both graphic and haptic renderings. As human users are more sensitive to small haptic discrepancies than visual ones, good force rendering requires a refresh rate of 500 Hz or more, which is far beyond the capabilities of current simulators. Moreover, if the simulator runs on a remote server, limited bandwidth, network latency and variance further compromise the quality of haptic rendering. To address these problems, a new interpolation-extrapolation data structure called the forcegrid is proposed, which makes it possible to approximate forces at rates greater than 500 Hz, regardless of the complexity of the simulated object. The forcegrid is designed for haptic interaction with continuous contact. It is a regular grid defined over the virtual workspace, in which every vertex contains a force. An extrapolation algorithm updates this force at every simulation cycle, while an interpolation algorithm computes the force to be rendered on the haptic device at the desired rate. The forcegrid has been successfully tested on various virtual deformable objects.

A Web-based, integrated simulation system for craniofacial surgical planning.

Background: Advances in computing over the last 10 years have rapidly improved imaging and simulation in health care. Implementation of three-dimensional protocols and image fusion techniques are moving diagnosis, treatment planning, and teaching to a next-generation paradigm. In addition, decreasing cost and increasing availability make generalized use of these techniques possible. Methods: In this article, the authors present a Web-based, integrated simulation system for craniofacial surgical planning and treatment. Image fusion technology was utilized to create a realistic virtual image that can be manipulated in real time. The resultant data can then be shared over the Internet by distantly located practitioners. Results: Initial use of this system proved to be beneficial from a planning standpoint and to be accurate as to the reliability of landmark identification. Additional case studies are needed to further document the results of actual surgical simulation. Conclusion: This technology presents significant advantages in surgical planning and education, both of which can improve patient safety and outcomes.