Introduction

The MediSim system extends virtual environments to represent simulated medical personnel interacting with simulated casualties. Fig. 1 diagrams the major components of the MediSim system.

• Existing human models are being extended to provide close-range simulated casualties. Casualties must show medically significant features such as face, skeletal structures, and internal organs. Wound and injury types are being coupled probabilistically to the simulated battlefield. Casualties must appear sufficiently real in terms of both physical behavior and appearance, in order to motivate the trainee and his avatar to expeditiously but carefully provide medical intervention. The Jack [3] human model is being extended with capabilities for appropriate injury display. A stealth human instructor can create simulated injuries and patient responses to treatment while monitoring the training exercise.

• The semi-automated medical corpsman (SAM) must be able to demonstrate rescue and medical assessment procedures as a model for the trainee or to function as an independent agent during a simulation. The SAM must demonstrate sufficient trauma care skills and practices in conformance with corpsman or EMT protocols to render reasonable and responsible simulated medical care. The Jack human model behavioral set is being augmented with a repertoire of relevant corpsman behaviors such as taking vital signs to confirm and/or augment PSM data, immobilizing suspected fractures, and stabilizing and transporting casualties with signs and symptoms of shock. Task ordering will be determined by established medical corps or EMT protocols [5,20].

• Virtual Environment technology will ensure the feeling of presence in the battlefield environment [22,25] (Fig. 2). A VE embedding (avatar) of a corpsman must be produced, with physical control over navigation and voice control over medical procedures, allowing the corpsman to direct his avatar as if instructing a knowledgeable assistant.

• Evaluation measures will assess both quantitative (timing, amount of movement, change in patient's physiological state) and qualitative (care quality, effectiveness) aspects of interactive corpsman training.

  
Figure 1: Architecture of Proposed MediSim System

MediSim offers a number of significant advances:

• Synthetic generation and visualization of wounds and injuries, along with their concomitant physical, physiological, and behavioral manifestations.

• Model-based visualizations of injuries and vital signs that trigger corpsman decision-making and behaviors implemented as a hierarchy of behavior nets.

• Task-based coordination of either multiple synthetic human figures or combinations of synthetic figures and VR avatars.

• Communication channel between the trainee and the avatar modeled in an effective VE embedding.

• The use of a ``stealth'' instructor to create, monitor, and effect injuries and dictate the outcomes of procedures or treatment response, places the MediSim project within the highly successful paradigm of flight simulation but entails major innovation in the stealth's user interface.

• A system is to be designed from the start with DIS compatibility where possible.

In this paper, we first present an overview of the MediSim System and discuss a prototype real-time implementation, virtual environment embedding, and distributed interactive simulation. Next in Section 3, we discuss our model of the wounded soldier, including the generation of penetrating injuries, casualty simulation and local wound simulation. Section 4 discusses the physics-based modeling needed to support the animated simulation of passive responses to outside forces, including medical procedures. We conclude in Section 5 with a discussion of concurrent work in medical decision support and developments in integrated anatomical and physiological modeling. These appendices are included: (A) which elaborates the NPS component of MediSim, (B) which contains a SCAMC paper on generating penetrating path hypotheses for medical decision support, and (C) which describes a physics-based blood flow model.

  
Figure 2: Scene in the Battlefield Environment