PACS mini refresher course. Local area network topologies, media, and routing.

Picture archiving and communication systems (PACS) use local area networks (LANs) for the transfer of images and image-related data. There are several aspects of LANs that are used to describe and categorize them: topology, the media used for transmission, and the medium access control (MAC) protocols. The four basic topologies are the bus, tree, ring, and star; the four primary types of media used for LANs include coaxial cable, twisted-pair wire, fiberoptic cables, and wireless. The wireless LANs that use infrared and radio frequencies are new but promising. Of the three MACs presently being used--Ethernet, fiber distributed data interface (FDDI), and UltraNet--Ethernet is the most common. LANs can be interconnected by means of the repeater, bridge, router, and gateway internetworking devices. The future of LAN development lies in increased standardization and increased connectivity in order to make teleradiology a reality.