Modeling and performance analysis of image transfer in PACS.

Performance simulation plays an important role in the design of picture archiving and communication systems (PACS). This paper presents simulation models of a PACS in a context of outpatient clinical workflow. Models, which are discussed focusing on shared facilities are resources of the system, consist of two levels. One is the workflow level and the other is the physical level. Patients medical staffs and images are picked up as the important system resources in the workflow level. A network, hard disks and network interface buffers of PACS components are mainly described in the physical level. Models are described with Petri Nets in both levels. Two examples of performance evaluation are also presented. Both of them estimate transfer time of computed radiology images for outpatient consultation. In the first example, both the data transfer rate of hard disks and network speed are varied under fixed system loads. While in the second example, system loads are varied against given system components. From the simulation results, following points are summarized. If physicians want to get a set of images in 5 seconds, both high performance hard disks or disk arrays and high speed network such as 100 Mbps networks are required. And it is effective for high speed network to be used in the acquisition phase. If we have to use the Ethernet and ordinary workstations, the PACS should be used in a single clinic. In conclusion this modeling method makes models simple and is quite useful for the performance evaluation of PACS in the early design phase.