Virtual Rounds: Simulation-based education in procedural medicine

Virtual Rounds: Simulation-based Education in Procedural Medicine

David Shaffera, Dwight Meglan", Margaret Ferrellc, Steve Dawson'

a Harvard University, bMitsubishi Electric Research Labs-ITA, Massachusetts General Hospital

ABSTRACT

Computer-based simulation is a goal for training physicians in specialties where traditional training puts patients at risk.Intuitively, interactive simulation of anatomy, pathology, and therapeutic actions should lead to shortening of the learningcurve for novice or inexperienced physicians. Effective transfer of knowledge acquired in simulators must be shown for suchdevices to be widely accepted in the medical community. We have developed an Interventional Cardiology TrainingSimulator which incorporates real-time graphic interactivity coupled with haptic response, and an embedded curriculumpermitting rehearsal, hypertext links, personal archiving and instructor review and testing capabilities. This linking of purelytechnical simulation with educational content creates a more robust educational purpose for procedural simulators.

Keywords: Medicine, Simulations, Learning, Training, Education, Interventional Cardiology

1. INTRODUCTION

1. Simulations and Learning

The first patent for a "flight simulation device" was granted to Edward Link in 1929, originally for a coin-operatedamusement ride. By 1949, Link's trainers were widespread in military and commercial aviation, and the use of simulatorshad cut training time in the flight industry in half. Today, Federal Aviation Administration regulations mandate the use offlight simulators for training and certifying pilots [1].

Right simulators succeeded as a training tool because of their ability to make a complex and difficult process safer, lessexpensive, and more effective. A flight simulator recreates critical aspects of aircraft control and performance. In a simulator,pilots learn how to operate sophisticated insiruments, learn the consequences of possible mistakes, and learn about seriousproblems that can occur during aircraft operations—all while they, and their airplanes, are safely on the ground.

In many arenas, simulations are powerful tools for learning. They are particularly attractive in disciplines such as aviationand medicine, where margins for error are small, and the costs of training are high.

2. The Challenges of Medical Simulation

Creating simulated learning environments for medical and surgical applications is challenging. There are some commerciallyavailable devices that simulate simple medical procedures for medical students and residents, allowing them to learn basictechnical skills such as knot-tying or needle insertion [2-4]. Recent computing advances now make it possible to recreatemuch more complex procedures, such as laparoscopy, endoscopy, and catheterization. Intuitively, interactive simulation ofanatomy, pathology, and therapeutic actions should both shorten the learning curve of inexperienced physicians, and providea tool to assess the skills of experienced practitioners.

One problem for simulation designers is that it is not possible to recreate every aspect of a procedure in a simulation.Determining what features are required for a successful training in a simulator is thus ultimately as much a pedagogicalquestion as it is a clinical and technical issue. Perhaps more fundamental, educating physicians in more complex domainsrequires more than just "re-creation" of a procedure. Because a physician's or surgeon's expertise lies not only in thedevelopment of perceptual and fme motor skills, successful educational tools must also develop complex cognitive processes,including the physician's ability to build a mental model of the patient's anatomy and pathology, and his or her ability toexercise clinical judgement in complex situations. For these reasons, we argue that educational issues must be consideredfrom the very first stages of the design of a simulation.

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3. OvervIew of this paper

This paper presents a new model for medical training in computer simulation environments. First we present the model ingeneral terms, outlining the underlying assumptions and key features of simulation-based learning. Following these"principles" of learning through medical simulation, we present a "case study" of one environment—currently underdevelopment—that embodies these principles.

2. PRINCIPLES OF LEARNING IN MEDICAL SIMULATIONS1. Medicine as a learningdomain

As described above in the introduction, learning in simulated environments is well established in the aviation industry.Piloting military and civilian aircraft requires substanthl training, demands a high level of skill, and imposes significantconsequences for even small mistakes. As a result, flight simulators provide a safe and inexpensive alternative to trainingpilots in the air, and there is a substantial body of work the conditions that lead to maximum skill transfer from flightsimulators to real cockpits (see, e.g., [1, 5]).

Theparallel between aviation and medicine is thus a tempting one to draw as computing power rises and medical simulationsbecome more realistic. However, we believe that this parallel—while clearly useful—needs to be drawn with great caution.

"Expert domains" like both aviation and medicine are characterized by unstructured problems where a potentially unlimitednumber of possibly relevant features are related in unclear and complex ways. Theorists such as Dreyfus and Dreyfus [6]argue that skill development in such domains requires practical experience rather than abstract "book learning." To functioneffectively in their respective fields, pilots and physicians must develop finely-tuned perceptual and motor skills, the abilityto analyze complex situations quickly and accurately based on limited information, and the ability to make sound decisionsabout how to proceed based on their assessment of the tactical or clinical situation.

Flight simulators have historically (though not exclusively) focused on the development of the "precognitive" and"postcognitive" skills that pilots require—that is, on the development of pilots' perceptual and motor skills. Pilots learn toread information from a dazzlingly large number of displays and to coordinate their responses on a complex array of controls.Outcome measures for pilot learning tend to focus on reaction times, awareness of critical parameters that indicate dangerousconditions, and on deviance from ideal flight paths and procedures [7]. In a sense, flight simulators focus on the me well-defined (that is, the more highly structured) portions of aviation.

It is, of course, true that physicians—and particularly surgeons—also require fine motor skills and perceptual abilities. Butfar more important are physicians' cognitive abilities, particularly their ability to create a robust model of a complex clinicalsituation based on limited information, and their ability to exercise clinical judgement and act appropriately based on theiranalysis of the situation.' To make a significant impact on medical training, simulators have to address the full range of skillsused by a physician: perceptual, motor, analytical, and judicial.

Our work has been guided by the idea that this range of skills is not developed in a simulator, but in a "simulation system," ofwhich the technical simulation is but one part (see Figure 1). As in flight simulation, perceptual and motor skills aredeveloped through visual and haptic interactions with the hardware and software of the "simulation engine"—the part of thesimulation system that actually recreates clinical experience. However, this simulation engine is situated in a larger context ofinformation and activities that provide the features and functionality needed to turn experience with the simulation engineinto analytic or diagnostic skill.

1 Failures of these skills are described respectively as errors in diagnosis and errors in judgement in routine morbidity andmortality debriefings among hospital staff.2 Herewe mean "diagnostic" not only in the sense of the cognitive skills of observation and interpretation, but also the activeskills of taking steps to gather additional information to confirm or refute possible interpretations of clinical information.

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Feature 0' 192.! , Outcome

Conviviality — Simulation System .. Judgement

Context — Simulation Curriculum — Analysis

Interaction — —[b 1— Motor SkillsI Simulation Engine I

Recreation —v 1— Perception

Figure 1: An overview of features and outcomes of a simulation "system"

Finally, we believe that a physician's most important skill is his her wisdom. The ability to make sound clinical decisionsultimately involves a wide range of medical, social, moral, and psychological factors. While some decision-making abilitycan clearly be developed through interaction with a simulation curriculum, true clinical wisdom is developed only throughinteractions with experienced physicians as meimxs. Only a full simulation system, including a high-fidelity simulationengine, a well-developed simulation curriculum, and a robust set of interactions with other physicians can develop the mostsubtle and important parts ofa physician's skills.3

2. A pedagogical theory

Exactly what criteria and features make a simulation system (in the sense described above) into a successful learningenvironment is an open question at this point in the field of educational research. However, based on work done in othercontexts and other disciplines—including, but not limited to, work on flight simulation—we believe that we can identifysome characteristics that make a simulation useful as a training tool.

In the section that follows, we discuss properties of the simulation engine itself, properties of the surrounding curriculum, andproperties of the full simulation system that support learning in virtual environments. There is not space here to sununarize indetail the research that supports each of the characteristics. However, in the brief descriptions below we indicate the generalresults that suggest these characteristics play an important role in learning through simulation.

1. THE SIMULA11ON ENGINE

Recreation. Research on learning suggests that authentic contexts for learning are the most effective way to both engagelearners and to help them transfer their skills and understanding from the learning environment to the "real world" (see,e.g., [8-13]). By "recreation" in this context we mean the functionally accurate simulation of the technical features of thelearning situation: in the case of medical simulation, relevant anatomy and pathology, instruments, medications, reports,information, and devices, as well as responses to thereputic actions.

Reach. Simulations not only recreate features of a real environment; they can also provide auginentations that make iteasier to develop skills and understanding. [1, 7, 14] We use the term "reach" in a metaphorical sense to suggest that aneffective simulation engine not only recreates a setting where learning takes place, but also includes enhanced featuresthat extend beyond what is possible in real clinical settings. These might include collection and presentation of dataabout a procedure that is not ordinarily available, alternate visualizations or viewpoints that are not possible in thephysical world, or even simply the ability to freeze a simulation and discuss various options before proceeding.

Rehearsal. "Practice makes perfect" is a well-known adage of learning. Research suggests, however, that except in thecases of simple skill acquisition it is not enough to simply repeat the same actions over and over—more complex skills

3 In saying this, we recognize, of course, that a physician's interactions with other health care providers, patients, and patients'families are also crucial to developing clinical wisdom, and a robust simulation system would take these roles into account asneeded. We also note that while there have been efforts to capture clinical judgement (and other complex reasoning) in "expertsystems," the results of such efforts have been disappointing (see [6] for a more complete discussion). There appears to be noviable replacement in the foreseeable future for interaction with real people in the development ofkey aspects of clinicalexpertise.

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require revisiting situations from multiple perspectives rather than merely repeating the same challenges. [8, 15-17] As inthe mcre usual theatrical context in which the term rehearsal is used, rehearsal here means having the ability to revisitproblem situations, either in whole or in part, under a variety of conditions. Rehearsal in a simulation means the ability totry procedures multiple times, to change tools, to take new approaches, to view from different angles—in short, to learnby exploring, by making mistakes, and by responding to feedback in the safety of a simulated environment.

2. ThE SIMULATION CURRICULUM

Recreation. As described above, research describes the importance of authentic contexts for learning. Thus, it isimportant that a simulation provide a functionally accurate recreation of the technical features of the learning situation.In the context of the simulation curriculum, it is also important to simulate the pedagogical context in which thesetechnical features are situated. So, for example, in most medical training, the simulation curriculum should recreate thecontext in which training and practice take place: a patient case with a medical history such as a physician experiencesduring rounds.

Replication. One of the problems of the "case-based" learning model, as practiced in medical education, is that students,residents, and fellows typically learn from whatever patients happen to come through the door during their time intraining. There is no guarantee that this will provide a sufficient variety or even sufficient number of cases during a givenphysician's residency and fellowship (see, e.g., [18]). By allowing the duplication of real cases and/or continuedreplication of virtual cases, simulations make it possible to choose (and later modify or expand) a set of standard casesfor training.

Reconfiguration. The ability to experience a standardized set of authentic cases is clearly an advantage of learning in asimulation curriculum. But research suggests that perhaps equally important is the ability to customize cases in order todemonstrate particular pedagogical points, and in order to explore unique and challenging cases (see [19, 20]). Thisability to reconfigure existing cases and to create new cases makes it possible to adjust a standard simulation curriculumto varying levels of skill, to changing clinical circumstances, and especially to the interests and needs of diverse learners.

3. THE SIMULATION SYSTEM

Reference. In expert domains such as medicine, learning takes place through experience—both through the directexperiences of the individual, and through the reported experiences of others [6, 21, 22]. The ability to refer to expertsand peers for advice is thus a critical part of the simulation system. This advice may come in the form of real-timeconversations (in person x mediated at a distance). It may come asynchronously through annotations r other messagesthat can be posted for reply. And collected wisdom may come in the form of a library of references from publishedjournal articles and other sources which a learner can consult during his or her work with the simulation system.

Review. Perhaps an even more important role of "others" in the learning process is through feedback. The simulationengine itself can, of course, provide direct feedback on the results of therapeutic actions—and as describe above, caneven provide information not usually available in a clinical setting. But the development of the full range of clinicalabilities, particularly analytical skill and clinical judgement, requires more sophisticated feedback that only other expertscan provide (see [6, 21-24] on expert feedback in learning). This feedback may come as comment on a learner' s actions,or as a response to a learner' s own descriptions, explanations, or discussion of his or her work. As described above in thediscussion of reference, this interaction may be synchronous or asynchronous.

Reflection. The notion that understanding develops through thoughtful consideration and examination of one's ownactions is one of the basic principles of learning theory dating back to the seminal work of Piaget, and supported by thework of many subsequent researchers. This body of work suggests in particular that making the examination of thoughtsand actions an explicit and public process supports the development of understanding [20, 23-27]. In some ways, theability to support reflection—both public reflection through the process of presentation and discussion, and more privatereflection through annotations and review of cases—is ultimately one of the most important features of a simulationsystem. Simulation systems support reflection when they provide the means and motive for learners to think about theiractions in the simulated environment and to record this reflective thinking for review by others or by the learner at a latertime.

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3. Generalcomments on virtual learning

Before closing this general discussion of learning in simulation systems it is worth making a comment on our approach to thequestion of how to best structure such virtual learning environments.

In every field, new technologies challenge old learning paradigms. In medicine, the traditional method of 'see one, do one,teach one" may be less than ideal when simulators make it possible to learn in mxe efficient ways. Simulators make itpossible (and we believe necessary) to think about creating a standard curriculum, about developing benchmarks forperformance (technical performance as well as clinical judgement), and about new methods for practice, review, andassessment. To take advantage of these possibilities, we need to develop a sound theoretical and practical framework forlearning through medical simulation. This framework must incorporate the overlapping disciplines of technical engineering,clinical practice, and educational psychology.

The challenges in developing such a framework will be to retain the best elements of medical training as it currently exists, torecognize that some practices can and should change in the light of new training tools and techniques, and to implement newsystems for learning consistent with the needs and constraints of sound medical practice.

3. AN INTERVENTIONAL CARDIOLOGY TRAINING SYSTEM

The remainder of this paper gives an overview of an Interventional Cardiology Training System (ICTS) currently underdevelopment. Our intent in providing this overview is not to describe the system in all of its technical detail, but rather to useit to illustrate one way in which we have tried to create a full simulation system of the kind described above.

1. Why Interventional Cardiology?

There were a number reasons for choosing interventional cardiology as a domain for a training simulation system.Interventional cardiology is one of a number of relatively new "minimally invasive" therapies. In interventional cardiology acardiologist inserts a catheter into a distal vessel (usually, though not exclusively, a femoral artery). This catheter is runthrough the aorta and into the coronary ostium. The catheter is then used as a channel through which guidewires, balloons,stents and other devices can be used to remove or expand stenoses or other pathoanatomy in the heart and coronary arteries.

As a minimally invasive procedure, the number and type of inputs to and outputs from a simulation of interventionalcardiology are limited. The cardiologist manipulates a set of coaxial tools (catheter, guide wire, interventional device) withwhich he or she carries out therapeutic actions and injects contrast material. A flouroscope provides the only visual feedbackabout the progress of the procedure. A simulation engine for interventional cardiology does not have to provide a wide rangeof haptic feedback or 3-D visual representations of tissues as would be the case in a traditional surgical procedure. Thismeans that the technical requirements for creating a high-fidelity simulation engine for interventional cardiology are lowrelative to other procedures.4

As is true for many procedures, interventional cardiology training is currently done exclusively on real patients in clinicalsettings.5 Although the overall risks of interventional cardiology are relatively low, there are clearly risks and costs associatedin any patient-based training [28, 29]). As a rapidly growing field, the devices and techniques of interventional cardiology areconstantly changing and improving, requiring continual retraining and skill development. In some more remote areas,cardiologists may not see enough cases in a year to meet the minimum number suggested by the American College ofCardiologists (ACC) for skill maintenance. And fmally, there is currently no formal certification procedure for interventionalcardiology.

There is thus significant incentive for developing and using a simulation system for training and assessment of interventionalcardiology.

4 This is, of course, true for minimally invasive procedures in general, where the range of tools and tool motions is limited, andexcept for relatively small amounts ofhaptic feedback, information about the progress ofthe procedure comes in mediatedform—such as two-dimensional flouroscopic or endoscopic images—and EKG and other graphic displays.

Some very early training is performed on animals, but this is both expensive and for some also morally troubling.

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2. RequIrements and assumptions

The technical requirements for an interventional cardiology simulation engine are:

Anatomic model. That it models cardiac and vascular anatomy, as well as other relevant thoracic structures.

Device motion. That it provides a model of device motion and interaction with tissue.

Coronary function. That it simulates the physiology of cardiac function (particularly heart motion, blood pressure, andheart rate).

Fluid dynamics. That it simulates fluid flow through the coronary vessels.

Haptic Interface. That it provides a realistic haptic interface for controlling interventional devices.

Flouroscope. That it provides a realistic rendering of a flouroscopic image based on anatomy, tool and tissue motion,and fluid dynamics.

Our assumptions for usage of the simulation engine were:

Users. The system would be used for training diagnostic and interventional cardiology fellows, as well as for a range ofcontinuing medical education applications in interventional cardiology, including training experienced cardiologists onnew devices and procedures.

Mentoring. The system could be used by a single physician for "solo" training, as well as under the supervision of anattending physician "guide." Further, this supervision could be direct (synchronous), either in person or over a computernetwork from a remote site, or indirect (asynchronous), where the trainee's actions and reflections would be recorded forlater review.

Skill development. The system would develop cognitive as well as sensorimotor skills.

Assessment. The system could be used for both training and assessment of performance.

Extensibility. The system would be expandable, so as to accommodate new devices and procedures, as well as otherchanges in the field of interventional cardiology.

Cost. The system would be inexpensive enough so as to be widely available.

3. Simulation system implementation

Given the above constraints and requirements, we brought together a design team of engineers, clinicians, and educationalpsychologists (represented by the authors of this paper) to design the technical specifications for the simulation system bothfrom the perspective of clinical requirements, and from the perspective of pedagogical requirements. It is beyond the scopeof this paper to describe in more detail the clinical issues in the design specifications, but the remainder of this sectiondescribes how particular design features of the simulation system address the issues in the theoretical framework describedabove. Our goal here is not to be comprehensive, but rather illustrative. That is, we hope that providing specific examples ofthe features of the Interventional Cardiology Training System will make more concrete the framework described above.

Our approach was to embed the "virtual procedure" (that is, the simulation engine) in a larger context of "virtual rounds" (seeFigure 2). In current training in a cardiac catheterization lab, trainees learn by performing procedures on real patients,examining a case history and comorbidities, deciding on a treatment protocol, completing the procedure, and following upwith the patient's attending physician. In virtual rounds, trainees work with virtual patients with full case histories,comorbidities, and other clinical details. Trainees select and using virtual devices, complete virtual procedures, and follow upthe procedure with discussions (synchronously or asynchronously) with colleagues.

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As we implemented the idea of virtual rounds, we tried to flesh out the theoretical framework above with particular featuresof the system. That is, we designed specific technical functionality to support not only the clinical specifications, but also thepedagogical demands of a simulation training system.

1 . THE SIMULATION RG!NE

Full Case (recreation). Perhaps it goes without saying that we strove to design the simulation engine with a high degreeof technical (i.e., clinical) fidelity. More important, however, was the fact that we consciously designed a simulationengine that could handle full cardiac catheterization cases from start to fmish, rather than picking specific parts ofinterventional procedures and simulating them with separate modules (e.g., accessing the coronary ostia, crossinglesions, placing stents, inflating balloons).

Enhanced Clinical Features (reach). We extended the functionality of the system beyond the limits of a real cath labby providing "enhanced clinical features," such as a "contrast freeze." In a cath lab, the flouroscope shows coronaryanatomy only when the cardiologist injects contrast material into the coronary arteries. The image moves in real time asthe heart beats and the contrast material flows through the vessels; the viewpoint is fixed for any one contrast injection,giving the operator a two-dimensional projection of the coronary anatomy in ooe slice of time. Typically, some (or afew) frames from this time slice are selected to make a "roadmap" of the coronary vessels. With the simulator, however,it is possible to freeze a moment in time along some—but not all—dimensions. Thus, the contrast material can bestopped in place while the viewing angle of the flouroscope is changed, making it possible to view the same image of theanatomy from multiple perspectives. In this way, it is possible for trainees to quickly determine optimum viewing angles,and to understand why multiple images are essential to understanding the characteristics of coronary pathology.

Undo (rehearsal). One of the most fundamental and powerful augmentations we included in the simulation engine wasthe ability to roll time forward and (especially) backward. This makes it possible to "skip ahead" in a pre-recordedprocedure to focus on the most interesting and complex parts of a procedure. But more important, the ability to movebackward and forward through time in a simulation means that trainees can easily learn from their mistakes. The abilityto "undo" a poorly-chosen or poorly-executed therapeutic action makes it possible to experiment freely and safely in thesimulation system, learning through trial and error and ultimate success what techniques work and where the edge of the"clinical envelope" lies.

2. T SIMULATION CURRICULUM

Virtual Patients (recreation). In addition to recreating the technical details of full cardiac catheterization cases, we alsorecreated the clinical context of the cases by conceptualizing individual simulation modules as actual patients rather thanas collections of anatomical and physiological features and pathologies. The ICTS system provides patient charts and

6 Strictly speaking, we did not simulate complete procedures because we did not simulate catheter insertion and other pre-andpost-operative features of catheterization. However, the ICTS does replicate a procedure from the point at which the catheter isin the vessels until it is withdrawn for the last time.

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Figure 2: Virtual Rounds


other background information that inform a cardiologist's interpremtion offluoro images in the simulation, as well asguide his or her judgment about possible treatment options.

Virtual Curriculum (replication). The individual virtual patients are organized so as to form a curriculum of standardcases for trainees. In this way, every trained interventional cardiologist would have a chance to perform (on a virtualpatient, if not on a real one) a number of procedures on both typical and atypical cases, using standard and specializeddevices. We imagine, of course, that such a curriculum would require updating as new techniques and procedures aredeveloped and new pathologies discovered—and that this task would be overseen by organizations charged withoversight of the field of interventional cardiology.

Edit Anatomy (reconfiguration). In addition to providing a set of standardized patients, the ICTS makes it possible tochange patient anatomy and physiology. This can be done using a stand-alone case-editing tool, or it can be done duringthe procedure to "experiment" with the effects of changing conditions on therapeutic actions. A guide or ment can alsochange parameters and introduce complications "on the fly" while a trainee is performing a simulated procedure, makingit possible to create simulated crisis situations for training purposes.

3. Tu€ SiMULATION SYSTEM

Links (reference). Access to information in the ICTS is provided through an innovative system of links to adjunctivematerial. This material is connected directly to individual patients, and where appropriate directly to specific features ofa patient's anatomy. For example, a highly eccentric ostiat lesion in a tortuous vessel might be linked to deviceinformation about balloon compliancy. Information of this kind might also include relevant journal articles, case notesand comments from experts, attending physicians, and previous trainees about the patient on the virtual table, as well aspre-run simulations of successful and unsuccessful procedures performed on the patient. This information makes itpossible for a trainee to benefit from accumulated clinical wisdom—and from specific examples—relevant to the case heor she is working on.

Guides (review). Our vision of the full simulation system is that, when possible and appropriate, attending physicianswould act as guides for trainees. This would include watching over their shoulder and making appropriate comments andsuggestions about the procedure—just as happens now during training in the cardiac catheterization lab. This reviewfunction could take place in person and in real time, or in real time at a distance using network communication featuresof the simulation engine. The simulation engine also makes it possible to record a procedure from start to finish for laterreview and comment. In addition, the simulation includes an "assessment mode" where the enhanced clinical features aredisabled and the procedure automatically recorded—thus making it possible to evaluate a trainee's performance in asimulation of a "real" (i.e., unaugmented case).

Logbook (reflection). Finally, the simulation system supports review and reflection by providing an augmented versionof the logbook that all cardiologists keep as a record of procedures they perform. The logbook allows a trainee to makenotes about a case and to include flouro sequences from the procedure along with text comments and other annotations.Logbook entries can automatically include relevant information such as time, date, total time, tools used, and so forth,and can be linked to the virtual patient for later reference by guides or by subsequent trainees. (Logbooks can, of course,also be kept private or linked anonymously.) The goal of the logbook is to provide trainees with an opportunity to reflecton the procedures they have performed—and to give attending physicians a means to review quickly their trainees' workwith the simulation system.

4. Design trade-offs

It is worth noting here that creating the system with these features required a number of design trade-offs. In general, wemight say that in most (though not all) cases, the demands of a robust simulation system of the kind outlined in theframework above meant that we took the more difficult and complex approach from a technical point of view when decisionpoints were reached. For example, it is much harder to create synthetic flouroscopic images that look realistic than it is to usereal flouro images and superimpose tool motion on top of them. However, the simpler technical solution makes it impossibleto offer alternate views, to reconfigure anatomy, or to perform any therapeutic action not envisioned by the designer of thespecific case. Similarly, it is much simpler technically to save only "flouro loops"7 (as is done in the real cath lab) rather than

Flouro loops are digitally recorded excerpts recorded by the fluoroscope that are used to document the progress of a case. Themost significant loops are saved permanently in digital form as a record of the procedure, or on cine film for the same purpose.

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record the full history of the procedure in progress. But saving only loops makes it impossible to rewind a procedure, andimpossible to review a case in full at a later time.

Of course, in some cases, it was possible to make a design choice that simplified the technical development. For example, wedecided that it was important to include a flouro pedal (to control the timing of flouro images), but not essential to include thecontrol manifold that exchanges contrast material and other fluids in the catheter. The flouro pedal serves a cognitivefunction: the cardiologist uses it to mark for him or herself, as well as for outside observers, the "salient" conditions, eventsand outcomes of the procedure. The manifold did not have the same significance in the procedure and so was not included inthe simulation.

The larger point is that it is clearly impossible—and probably not desirable—to recreate absolutely every feature of aprocedure in a simulation engine. Rather, the choice of specific features depends on the pedagogical demands of thesimulation system—even though this sometimes makes the technical challenges of simulation more difficult. Perhaps mostimportant, the consequences of this design rationale are that the educational aspects of the simulation system have to beconsidered and built in from the start. The alternative of building a "clinically accurate" simulation and then designing atraining program around it is not only difficult in practice, but theoretically unsound.

5. Validation

The Interventional Cardiology Training System described here is not yet complete, and thus we can not present data on itsuse as a training tool. In this sense the description here is prospective rather than definitive. Our plan is to valithte thissimulation system—and with it the simulation system framework—through clinical trials. The problem in formulating suchtrials is that there is currently no "gold standard" for expertise in interventional cardiology; thus there is no clear evaluationmetric by which to judge the efficacy of training in the simulator (either on its own terms or in contrast to traditional trainingmethods). We plan to convene an expert panel of interventional cardiologists, educational psychologists, and otherresearchers to design effective assessment instruments upon which to build a clinical trial of the simulation system

4, CONCLUSIONThe Interventional Cardiology Training System described here—and the "simulation system" framework upon which it wasdesigned—are clearly works in progress. We present them because we believe that they outline and exemplify a soundapproach to training through medical simulation. The simulation system approach we describe represents the beginning of anew paradigm in medical education, taking the strengths of traditional training and augmenting them with features and"scaffolds" for learning that new media make possible.

Fundamental to creating a new approach to medical training through simulation is the notion that learning is a systemicphenomenon. The environments for learning through simulation need to build in pedagogical issues "from the ground up"rather than as afterthoughts to an already designed simulation engine, no matter how clinically accurate.

Moving to a new paradigm in any field requires mce than merely tinkering with old methods. In the domain of medicalsimulation and training it requires simultaneous and coordinated work among engineers, clinicians, and psychologists oflearning. Our hope is that the work described here presents a compelling model for such endeavors.

5. ACKNOWLEDGEMENTS

This research was funded in part by the US Army, under Cooperative Agreement No. DAMD17-99-2-9001. This publicationdoes not necessarily reflect the position the policy of the Government, and no official endorsement should be inferred.

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