Face, content and construct validity of the University of Washington virtual reality transurethral prostate resection trainer.

PURPOSE: We examined the face, content and construct validity of version 1.0 of the University of Washington transurethral prostate resection (TURP) trainer. MATERIALS AND METHODS: Version 1.0 of a virtual reality based simulator for transurethral skills was developed at our laboratory by integrating TURP hardware with our virtual 3-dimensional anatomy, irrigation control, cutting, bleeding and haptics force feedback. A total of 72 board certified urologists and 19 novices completed a pre-task questionnaire, viewed an introductory training video and performed a pre-compiled 5-minute resection task. The simulator logged operative errors, gm resected, blood loss, irrigant volume, foot pedal use and differential time spent with orientation, cutting or coagulation. Trainees and experts evaluated the simulator on a modified likert scale. The 2-tailed Levene t test was used to compare means between experts and novices. RESULTS: Overall version 1.0 content was between slightly and moderately acceptable. Experts spent less time with orientation (p < 0.0001), resected more total tissue (p < 0.0001), had more gm resected per cut (p = 0.002) and less blood loss per gm resected (p = 0.032), used less irrigant per gm resected (p = 0.02) and performed fewer errors (p < 0.0001) than novices. CONCLUSIONS: We established the face, content and construct validity for version 1.0 of the University of Washington TURP trainer to simulate the skills necessary to perform TURP. A predictive validity study showing a translation of skills from the virtual environment to the operating room will complete the validation of this model.

Identifying and reducing errors with surgical simulation.

The major determinant of a patient's safety and outcome is the skill and judgment of the surgeon. While knowledge base and decision processing are evaluated during residency, technical skills-which are at the core of the profession-are not evaluated. Innovative state of the art simulation devices that train both surgical tasks and skills, without risk to patients, should allow for the detection and analysis of errors and "near misses". Studies have validated the use of a sophisticated endoscopic sinus surgery simulator (ES3) for training residents on a procedural basis. Assessments are proceeding as to whether the integration of a comprehensive ES3 training programme into the residency curriculum will have long term effects on surgical performance and patient outcomes. Using various otolaryngology residencies, subjects are exposed to mentored training on the ES3 as well as to minimally invasive trainers such as the MIST-VR. Technical errors are identified and quantified on the simulator and intraoperatively. Through a web based database, individual performance can be compared against a national standard. An upgraded version of the ES3 will be developed which will support patient specific anatomical models. This advance will allow study of the effects of simulated rehearsal of patient specific procedures (mission rehearsal) on patient outcomes and surgical errors during the actual procedure. The information gained from these studies will help usher in the next generation of surgical simulators that are anticipated to have significant impact on patient safety.

The representation of blood flow in endourologic surgical simulations.

An image-based approach has been developed to represent bleeding in a simulator for transurethral resection of prostate (TURP). While previous attempts have simulated bleeding over tissue surfaces or in blood vessels, our approach focused on the macroscopic visualization of bleeding in a fluid environment. TURP is an ideal procedure for simulation-based training because of the dynamic environment and the variety of flow patterns it presents. The first step in the development of the simulator was the generation of blood flow movies which consisted of capturing videos of bleeding vessels in vitro, processing them to separate the actual blood from the background anatomy and organizing the movies into a parametric database. During the running of the simulation, resection of prostate tissue systematically triggers bleeding events and the playback of a blood flow movie. The blood flow movie is texture mapped onto a virtual surface that is positioned oriented, morphed, composited and looped into the virtual scene.

Virtual reality simulators for dermatologic surgery: measuring their validity as a teaching tool.

Surgical simulation is increasingly being considered for training, testing, and possibly credentialing in medicine and surgery. At the University of Washington we have been developing a virtual reality (VR) suturing simulator. In the course of development it must be realized that expensive new technologies should bear the burden of proof of their effectiveness and reliability before they are put into training programs. The purpose of this article is to define the concept of surgical skill and to discuss how it can be measured in the context of validating VR surgical simulators. Specific measures of validity and reliability are reviewed and discussed.

Issues in validation of a dermatologic surgery simulator.

At the University of Washington, we have been developing a suturing simulator using novel finite element model techniques which allow real-time haptic feedback. The issues involved in measuring validity in a suturing model have not been examined in a systematic way. Very few studies exist on the surgical factors that lead to good sutures. We have examined published data on these factors as well as previously studied metrics in suture training. This information has been combined with a review of types of validity (e.g., face, construct, predictive and concurrent) and reliability that must be considered in assessing any surgical simulator.

Laparoscopic surgical simulator and port placement study.

We have developed a virtual laparoscopic surgical simulator and gathered data during student trial runs. The students performed simulated surgical dissections from 3 pairs of port positions with angles between the cutting and grasping instruments set to 60, 90, and 120 degrees. Preliminary data indicates improved performance at the 90 degree angle. Study updates can be found at http:¿www.hitl.washington.edu/research/lss

Creating fast finite element models from medical images.

The procedure for creating a patient-specific virtual tissue model with finite element (FE) based haptic (force) feedback varies substantially from that which is required for generating a typical volumetric model. In addition to extracting geometrical and texture map data to provide visual realism, it is necessary to obtain information for supporting a FE model. Among many differences, FE-based VR environments require a FE model with appropriate material properties assigned. The FE equation must also be processed in a manner specific to the surgical task in order to maximize deformation and haptic computation speed. We are currently developing methodologies and support software for creating patient-specific models from medical images. The steps for creating such a model are as follows: 1) obtain medical images and texture maps of tissue structures; 2) extract tissue structure contours; 3) generate a 3D mesh from the tissue structure contours; 4) alter mesh based on simulation objectives; 5) assign material properties, boundary nodes and texture maps; 6) generate a fast (or real-time) FE model; and 7) support the tissue models with task-specific tools and training aids. This paper will elaborate on the above steps with particular reference to the creation of suturing simulation software, which will also be described.

Virtual reality for dermatologic surgery: virtually a reality in the 21st century.

In the 20th century, virtual reality has predominantly played a role in training pilots and in the entertainment industry. Despite much publicity, virtual reality did not live up to its perceived potential. During the past decade, it has also been applied for medical uses, particularly as training simulators, for minimally invasive surgery. Because of advances in computer technology, virtual reality is on the cusp of becoming an effective medical educational tool. At the University of Washington, we are developing a virtual reality soft tissue surgery simulator. Based on fast finite element modeling and using a personal computer, this device can simulate three-dimensional human skin deformations with real-time tactile feedback. Although there are many cutaneous biomechanical challenges to solve, it will eventually provide more realistic dermatologic surgery training for medical students and residents than the currently used models.

Fast finite element modeling for surgical simulation.

Given the geometric complexity of anatomical structures, realistic real-time deformation of graphical reconstructions is prohibitively computationally intensive. Instead, real-time deformation of virtual anatomy is roughly approximated through simpler methodologies. Since the graphical interpolations and simple spring models commonly used in these simulations are not based on the biomechanical properties of tissue structures, these "quick and dirty" methods typically do not accurately represent the complex deformations and force-feedback interactions that can take place during surgery. Finite element (FE) analysis is widely regarded as the most appropriate alternative to these methods. Extensive research has been directed toward applying the method to modeling a wide range of biological structures, and a few simple FE models have been incorporated into surgical simulations. However, because of the highly computational nature of the FE method, its direct application to real-time force-feedback and visualization of tissue deformation has not been practical for most simulations. This limitation is primarily due to the overabundance of information provided by the standard FE approaches. If the mathematics is optimized to yield only the information essential for the surgical task, computation time can be drastically reduced. Parallel computation and preprocessing of the model before the simulation begins can also reduce the size of the problem and greatly increase computation speed. Such methodologies are being developed in a combined effort between the Human Interface Technology Laboratory (HIT Lab) and the Mechanical Engineering Department of the University of Washington. We have created computer demonstrations which support real-time interaction with simple finite element soft tissue models. In collaboration with the Division of Dermatology, a real-time skin surgery simulator is being developed using these fast FE methods.

Validation of the Madigan ESS simulator.

The Madigan Endoscopic Sinus Surgery (ESS) Simulator, developed by a multi-institution team led by Lockheed Martin, includes force-feedback instrument and virtual endoscope interaction with three-dimensional paranasal anatomy models derived from the Visible Human dataset, supplemented by a variety of graphical and auditory instructional aids embedded in the model. Our formal evaluation of Version 1.2 of the system focused on its validity as an ESS simulator. Run-time and survey data were collected for three groups of subjects on a common protocol progressing through the three basic ESS subtasks: navigation, injection, and dissection. Non-MD subjects performed the tasks on a simplified abstract virtual model with instructional aids (hoops for the navigation path, injection targets, dissection spheres, auditory feedback about task completion, and simulated patient heart rhythm). Non-ENT MDs progressed from this "novice" model to a simulated anterior ethmoidectomy on an "intermediate" model with the aids embedded in the reconstructed and segmented paranasal anatomy. Otolaryngologists ranging from second-year ENT residents through senior staff progressed through both the abstract and intermediate models, and then performed the simulated surgical procedure on an "advanced" model, consisting of the anatomy with no instructional aids. The procedural validity of the simulator is supported by a strong correlation between performance on the simulator and degree of prior ESS experience, by convergent correlation among independent measures of subject task performance, and by subjective evaluations by experienced ESS surgeons.

Virtual reality and tactile augmentation in the treatment of spider phobia: a case report.

This is the first case report to demonstrate the efficacy of immersive computer-generated virtual reality (VR) and mixed reality (touching real objects which patients also saw in VR) for the treatment of spider phobia. The subject was a 37-yr-old female with severe and incapacitating fear of spiders. Twelve weekly 1-hr sessions were conducted over a 3-month period. Outcome was assessed on measures of anxiety, avoidance, and changes in behavior toward real spiders. VR graded exposure therapy was successful for reducing fear of spiders providing converging evidence for a growing literature showing the effectiveness of VR as a new medium for exposure therapy.

New interface metaphors for complex information space visualization: an ECG monitor object prototype.

Wearable augmented reality medical (WARM) interfaces could provide ubiquitous point-of-care decision support and enhance the quality and efficiency of clinicians' efforts. Creation of such systems involves the design and evaluation of new information displays that leverage the representational and presentational capabilities of three-dimensional AR environments. We describe our first efforts in this process: the implementation of interface objects for display of real-time electrocardiographic monitoring information and an evaluation methodology using a simulated clinical environment. Our pilot data confirm the utility of presentation modes that place simultaneous information tasks in close proximity, and highlight issues encountered in designing new representations of medical information.

ENT endoscopic surgical training simulator.

This paper describes work in progress on the design and development of a prototype simulator for minimally invasive otolaryngology surgical training. The anatomy of the paranasal sinuses is geometrically complex and dangerously close to the brain and orbits, making this procedure challenging to practice and difficult to learn. We discuss the potential role of computer simulation to enhance and accelerate acquisition of surgical skills. The design goals of the prototype include high-fidelity simulation of the endoscopic imagery and haptic cues of surgical palpation. The prototype enables endoscopic navigation and limited interactive tissue manipulation and dissection tasks on a virtual patient using realistic replicas of surgical tools. We present an overview of the system architecture with a discussion of the technological challenges, design issues and current status of the efforts.

A resource guide to VR in medicine.

This guide provides a bibliography of many of the most noteworthy contributions to the emerging literature about virtual reality in medicine, along with listings of the most relevant conferences and resources for researchers. This is an abridged version of a continuously updated comprehensive document which is available on-line to the research community.