MIMOSA: a functional model of the management of medical images.

The concept of picture archiving and communication system (PACS) appeared in 1982. Twelve years later most PACS prototypes still do not satisfy the medical community requirements: too much emphasis has been put on technical solutions and little effort devoted to the management of images itself. A common approach to this problem is needed more than ever to allow cost-effective systems to be developed. Modelling is a way to reach this objective, and the MIMOSA topic within the AIM/EurlPACS project aims at defining such a model of medical image management. This paper presents the MIMOSA approach with the three underlying constraints, i.e. genericity, implementation independence and performance. The MIMOSA group is building three interrelated models: a data model, a functional model and a dynamic model. However, in this report we focus only on the functional model, and explain how it was abstracted from various clinical scenarios in the first phase of the project. The availability level concept is introduced as a customizable and implementation independent solution to the problem of managing the delay of access to the information. The so-called contextual diagram and the acquisition of a new examination which are two representative parts of the model are detailed. The validation aspects and the relationships to projects working on the management of patient records are addressed as a conclusion.

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.

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.

First experiences with the modelling and simulation package MIRACLES applied to a picture archiving and communication system (PACS) in a clinical environment.

Since the construction of picture archiving and communication systems (PACS) appears to be extremely difficult, computer modelling and simulation are used as decision support tools. The package MIRACLES (Medical Image Representation, Archiving and Communication Learned from Extensive Simulation) has been developed at BAZIS in order to support the construction of simulation models of image information systems. This article discusses the application of MIRACLES to a prototypical PACS as being installed in a clinical environment. Attention is focussed to the required system analysis and difficulties which arose during the construction of the simulation model. The emphasis is on the presentation of the results of the simulation study, which show that simulation can be fruitfully used to predict, to analyse and to assist in solving performance problems. The simulation study confirmed assumptions and suppositions concerning both the system performance itself and strategies to improve the performance. The study also resulted in a number of concrete recommendations which might be useful for the set-up of the prototypical PACS.

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.

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.

Background of the demonstrated IMAGIS activities and future expectations.

In The Netherlands a national PACS development programme has been started, supported by the Dutch Society of Radiology and funded by the Dutch Department of Health because of the national character of the project. Three main partners are cooperating in this development: the Utrecht University Hospital (AZU), BAZIS and Philips International (Product Division Medical Systems), with the Delft University of Technology as the main BAZIS subcontractor. The non-profit foundation BAZIS, developing and supporting the ZIS Hospital Information System (in use in some 30 Dutch hospitals, over 15,000 acute beds), initiated its current IMAGe Information System (IMAGIS) projects in 1984. The activities were later integrated into the Dutch PACS project started in 1986. The final goal of the project is to achieve a PACS which is fully integrated with already existing hospital information systems (HIS). The development and operation of a HIS-PACS include many aspects of technical and clinical. The current efforts of BAZIS are concentrated on three main issues: diagnostic image quality evaluation (e.g. effects of data compression); modelling, software simulation and technology assessment of a prototype PACS (both general and detailed aspects); and coupling and integration of PACS and HIS (e.g. the BAZIS ZIS). Philips, Hamburg, is supplying equipment, particularly prototype components. A systematic clinical evaluation will take place at the Utrecht University Hospital.2+ We outline the background of the intermediate results as demonstrated during the 6th EuroPACS Conference:the psychophysical software package for Feature Evaluation And System Inspection By Logged Experiments (FEASIBLE); the modelling and simulation software package for Medical Image Representation, Archiving and Communication, Learned by Extensive Simulation (MIRACLES); and first results of the coupling experiments.(ABSTRACT TRUNCATED AT 250 WORDS)