A queueing model of picture archiving and communication system (PACS) with a hierarchy of storage

A queueing model is analyzed for systems with a hierarchy of storage where the access time to all the stored images is not the same. A typical PACS consists of a database of medical images, display stations, acquisition systems, and a communication medium. The proposed model is for the delay analysis of the image database, the communication channels, and the picture viewing stations (PVSs). Performance curves are presented for the delay in retrieving images from the database, in the transmission of images, and in processing them in the image processor. The mean delay (that is, the time it takes for a radiologist to view a medical exam from the moment that a request packet is sent to the image database till the time the images are received) is the sum of all the delays mentioned above. The distributions of these delays can be easily evaluated and plotted by using the inverse of the Laplace transforms. From the curves provided, the end-to-end delay for various amounts of load in the system can be accurately estimated.<>