Picture Archiving and Communication System (PACS). A medical imaging (MRI, X-RAY, PET, CT and so on) protocol for the storage of medical images and the transmission of those images over a computer network. The images can then be viewed offsite by authorized physicians for the purpose of tele-diagnosis, tele-education or for usage during a medical procedure (for example, in an operating room). Alternatively, a PACS can be used to collect and archive images which are sent from radiology departments. Typically a PACS network consists of a central server which stores a database containing the images. This server is connected to one or more clients via a LAN or a WAN which provide and utilize the images. Client workstations can use local peripherals for scanning image films into the system, printing image films from the system and display of images digitally using an interactive monitor. Additionally client workstations can be used to manipulate the images (crop, rotate, zoom, sharpen and so on). In most cases actual imaging machines can be connected directly to the network so that images taken of a subject are immediately sent to the PACS server.

The medical images are stored in an independent format. The most common format for the storage of the images is the DICOM (Digital Imaging and Communications in Medicine) format. This format is very flexible and allows a single image file to contain multiple "layers" (as in 3D imaging) or "frames" (as in animation). Images can also use a variety of compression and encoding standards including JPEG, LZW or Run-length encoding (RLE).