W. J. J. Stut

PACS costs: modelling and simulation

The advantages to be expected of full-scale PACS implementation are widely described in the literature. In the decision to introduce such systems, costs will also play an important part. The benefits to be achieved should at least outbalance the costs. In this paper the set-up of a software package for cost assessment is described. The configuration requirements have to be determined based on the workload of the radiology department and a PACS model using results of simulation studies. Of course additional user requirements are important input parameters (e.g. number of workstations, screen resolution, etc.). Data on costs of the various configuration components and the expected future trends in these costs will be used to estimate the costs of a specific PACS configuration as a function of time. Savings to be achieved in the various categories of resources will be input (again with their trends) to lead to an overview of the total savings to be expected. The package will result in a graph of the net annual costs as a function of the timing of PACS introduction. In the package a critique module is foreseen that checks whether the data fed into the system are of reasonable agreement with expert opinions.

Picture archiving and communication system design issues: The importance of modelling and simulation

Picture archiving communication system (PACS) development turns out to be very complex. Due to both the vast amount of data and the complexity of hospital organizations, currently only small-scale systems have been realized. And although the experiences obtained with these systems are essential, there is a risk for underestimating the complexity and requirements inherent in hospital-wide PACS systems. In this paper, it is advocated that modelling and simulation be used as tools to obtain insight into the behavior and structure of future PACS systems. Modelling and simulation can also be used to actively support the design of PACS, especially its software. In order to capture the full complexity of PACS in a simulation model, and to take full advantage of simulation as a design tool, the development of a new modelling method has begun. This method is based on semantic data models and decision processes, and can be used for both system analysis and design. The first systems modelled with this method were imaging procedures in a hospital and a computer network. The resulting simulation models are a direct reflection of reality, and have a high degree of modularity. Consequently, in spite of the complexity of the systems, their models are easy to understand and maintain.

A design for a Picture Archiving Communication System central storage facility

A Picture Archive and Communication System (PACS) as it is to be used in a Hospital will consist of a number of workstations, data acquisition stations and output stations, connected to a central storage facility. In this paper the architecture of the central storage facility is studied, and an implementation is proposed. Simulation studies have been performed on the proposed implementations, showing their feasibility. The simulation studies show that the central storage facility can store over 500 sets on a daily basis, while simultaneously handling the review and output activity associated with such a production. On the average, each set is assumed to consist of 3 images of 4 Mbyte each. Simulation results are presented for a number of alternative systems. Special attention is given to the implications of prefetching on the protocols to be used in the PACS system. It is shown that prefetching, in particular in combination with a pipelined system, can yield significant performance benefits. We believe that prefetching of images is a prerequisite for good system performance. The implementation assumes that a high-speed communication protocol is used to interconnect the PACS components. The paper will not go into details on the network considerations. The central storage facility is designed using a general purpose System/370 machine, with the peripherals commonly used for such machines. This implies that it can be realized with currently available equipment. Several alternative implementations using interconnected workstation based systems are suggested.

Prediction and analysis of PACS performance with the simulation tool MIRACLES

Since the construction of image information systems appears to be extremely difficult in practice, BAZIS has decided to use computer modelling and simulation as decision support tools. In order to support the construction of simulation models, the simulation package and modelling environment MIRACLES (Medical Image Representation, Archiving and Communication Learned from Extensive Simulation) has been developed by BAZIS. This paper describes modelling and simulation techniques in general, as well as the benefits of simulation within the scope of designing Picture Archiving and Communication Systems (PACS). In order to illustrate the theory, results of a concrete yet simple PACS, which has been simulated with MIRACLES, will be described and discussed.

Simulation-based PACS development

The development of picture archiving and communication systems benefits from modeling and simulation. In order to capture the full complexity of PACS in a simulation model, and to take full advantage of simulation as a design tool, the authors have started the development of a new modeling method. This paper illustrates the modeling method by means of simulation models of the Geneva PACS.

Cost Modelling Of PACS

In a contribution to the Medical Imaging,II conference 1988 the design and construction of a package for PACS cost modelling was advocated. In this paper the main features of such a package are described. A first version of the package, called CAPACITY, is ready and experiences are being collected. The package produces as its main results a comparison oftotal cost differences of a PACS configuration and a film-based system as a function of time. The user has to describe the PACS configuration, the technical characteristics of the various components together with the estimated price (as a function of time). Also for the film based system the costs of the various components have to be defined by the user. The production volume of the hospital and the radiology department is input and used in the critique module that checks the input data supplied against a number of rules of thumb (to be defined by experts). At present the package is being used experimentally within our group. At the next EUROPACS meeting (March 1989) it will be demonstrated and other groups will be invited to use it. It is expected that discussions on the results of the package and analysis of the input data supplied will contribute to convergence of the widely varying opinions about the costs of PACS and the moment PACS will be cost justified (both within the radiology department and in the clinic).

Procedures To Study The Impact Of PACS On The Logistics Within A Diagnostic Imaging Department

The Dutch PACS project is a cooperation of the Utrecht University Hospital, BAZIS Hospital Information Systems group, and Philips. In this paper the impact on the organization of logistic procedures within a diagnostic imaging department will be described, as a part of the Dutch PACS project at the Utrecht University Hospital, the clinical evaluation (as described previously in SPIE proc. #767 and #626). A detailed analysis was carried out regarding image logistics, object flow (patients, images, request forms etc.) and working procedures of all personal involved. Goal is to compare the results of these studies with similar data after the introduction of a complete PACS working procedure for the target ward and to find design parameters for the intrinsic image management system. Furthermore, the data are used to establish the efficiency of the new situation. The results of this study are described in detail per parameter.

Modelling and simulation: indispensable tools for PACS development

This paper illustrates the use of PACS simulation. We briefly describe the modelling methodology used. By reporting on a concrete PACS network simulation we show that modelling and simulation are indispensable tools for PACS development.

First experiences with a semantic modeling method to guide simulation-based PACS development

The design of PAC systems benefits from modelling and simulation. Within the scope of the Dutch PACS project several simulation studies have shown that simulation is a powerful tool to evaluate hardware architectures, image management strategies and clinical working methods before they are actually implemented. Besides using simulation techniques for obtaining insight into a PACSs performance and behaviour, they can also be applied to actively support the design of a PACS. In order to capture the full complexity of PAC systems in a simulation model, and to take full advantage of simulation as a design tool, we are currently developing new techniques for model construction. This paper summarizes the underlying principles of our modelling method, and describes our first experiences with it.