Communications for a picture archiving communications system with a parallel operating image data base

In cooperation with BAZIS (Support Group Hospital Information Systems at Leiden, The Netherlands), we started the design of a Picture Archiving and Communications System (PACS) a few years ago that contains a centralized image data base. By means of system modeling and measuring some performance parameters, we have discovered that such a system cannot provide the required response times. This is mainly because of equipment communications interfaces that are not fast enough and have a throughput that does not generally exceed 16 Mbits/second. By providing a parallel operating image buffer system, the problems related to the limited speed of the communication interfaces can be overcome. Moreover, by splitting the network into a number of subnets connected to each other by means of "bridges," the communications load can be locally reduced, improving in this manner the response times. Our PACS contains a supervisor and one relational data base that relates patient data with image locations. A significant part of the report is concerned with the design of the high speed American College of Radiology-National Electronic Manufacturing Association transmission control protocol/internet protocol (ACR-NEMA TCP/IP) communications interface. The use of such an interface eliminates the need for a Network Interface Unit, reducing in this manner communication delays and complexity. We have developed and have in operation for experimental purposes a small-scale PACS, consisting of a number of workstations, a relational data base and image buffers, all connected to a network that uses the ACR-NEMA TCP/IP protocols. This experimental PACS is used to provide input data to a PACS performance model, to validate this model, and to investigate alternative system configurations.