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The U.S. Army Medical Command, lead by the Brooke Army Medical Center, has embarked on a visionary project. The U.S. Army Virtual Radiology Environment (USAVRE) is a CONUS-based network that connects all the Army's major medical centers and Regional Medical Commands (RMC). The purpose of the USAVRE is to improve the quality, access, and cost of radiology services in the Army via the use of state-of-the-art medical imaging, computer, and networking technologies. The USAVRE contains multimedia viewing workstations; database archive systems are based on a distributed computing environment using Common Object Request Broker Architecture (CORBA) middleware protocols. The underlying telecommunications network is an ATM-based backbone network that connects the RMC regional networks and PACS networks at medical centers and RMC clinics. This project is a collaborative effort between Army, university, and industry centers with expertise in teleradiology and Global PACS applications. This paper describes a model and simulation of the USAVRE for performance evaluation purposes. As a first step the results of a Technology Assessment and Requirements Analysis (TARA) -- an analysis of the workload in Army radiology departments, their equipment and their staffing. Using the TARA data and other workload information, we have developed a very detailed analysis of the workload and workflow patterns of our Medical Treatment Facilities. We are embarking on modeling and simulation strategies, which will form the foundation for the VRE network. The workload analysis is performed for each radiology modality in a RMC site. The workload consists of the number of examinations per modality, type of images per exam, number of images per exam, and size of images. The frequency for store and forward cases, second readings, and interactive consultation cases are also determined. These parameters are translated into the model described below. The model for the USAVRE is hierarchical in nature. There are three levels to the model: (1) Network model of the Cable Bundling Initiative (CBI) network and base networks (CUITIN), (2) Protocol model, including network, transport, and middleware protocols, such TCP/IP and Common Object Request Broker Architecture (CORBA) protocols, and (3) USAVRE Application layer model, including database archive systems, acquisition equipment, viewing workstations, and operations and management. The Network layer of the model contains the ATM-based backbone network provided by the CBI, interfaces into the RMC regional networks and the PACS networks at the medical centers and RMC sites. The CBI network currently is a DS-3 (45 Mbps) backbone consisting of three major hubs, at Ft. Leavenworth, KS, Ft. Belvoir, VA, and Ft. McPherson, GA. The medical center PACS networks are 100 Mbps and 1 Gbps networks. The RMC site networks are 100 Mbps speeds. The model is very beneficial in studying the multimedia transfer and operations characteristics of the USAVRE before it is completely built and deployed.
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