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.

EuroPACS: a catalyst for PACS in Europe.

The EuroPACS organization and its intended role in PACS development in Europe is briefly described. EuroPACS was initiated at Braunlage FRG, August 1984. Its aim is to stimulate mutual contacts between various groups in Europe being active in the PACS field. Its main activities are: organization of EuroPACS conferences (once or twice per year), publication of a newsletter and organization of special sessions in larger congresses.

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.

Diagnostic evaluation of a PACS subsystem using mammographs. An ROC analysis.

The objective of this study was to compare the diagnostic accuracy of digitized mammographs with the original conventional films. The criterion was the detectability of small calcifications in the female breast. Four skilled radiologists read 100 films, conventional as well as digitized. The results were analysed using ROC methodology, and showed much lower diagnostic accuracy of digitized images (average AUC 0.67) compared to conventional films (average AUC 0.89). One of the problems with digitized images was to recognize and ignore film artifacts, which were hard to discriminate from small calcifications. The experiment was prepared, carried out and analysed with the FEASIBLE software package.

FEASIBLE (I): The PC software package for feature evaluation and system inspection by logged experiments.

FEASIBLE is an MS-DOS software package which can be used for the evaluation of: Picture Archiving and Communication System (PACS) components; diagnostic image quality; and image manipulation and representation techniques. The FEASIBLE software allows the user to design any psychophysical study in detail in the fields mentioned above, to execute an arbitrary number of sessions and to statistically analyse the results by way of the Receiver Operating Characteristic (ROC) technique. FEASIBLE consists basically of three modules: DESIGN, which allows the user to set up an experiment; EXECUTION, which allows the user to execute the experimental sessions based on the design entered in the DESIGN module and stored in the program's database; and, STATISTICS, which allows various statistical analyses on the data collected during the psychophysical sessions (including the calculation of ROC curves and related parameters) and can provide a graphical presentation of the results. FEASIBLE has been designed to support experts and those who have little knowledge of psychophysical experiments. This paper discusses the background, structure and possibilities of the FEASIBLE package at this point (version 1.2, May 1988).

FEASIBLE (II): Its use in an actual PACS evaluation study.

The software package FEASIBLE is a tool for carrying out observer performance studies. The structure, background and possibilities of the program are described in paper I of this series. Observer performance studies can be used to evaluate the diagnostic quality of Picture Archiving and Communication System (PACS) components. This paper summarizes the general features of such an evaluation. It states the specific characteristics of a diagnostic evaluation of a prototype PACS. The examples of the use of FEASIBLE presented here originate from the study that has recently been conducted within the Dutch PACS project, a cooperation between the BAZIS project IMAGIS (IMAGe Information System), the Utrecht University Hospital and Philips Medical Systems. Furthermore, this paper demonstrates how FEASIBLE is used to carry out an observer performance study. It is shown step-by-step how experiments on the evaluation of PACS components can be executed in an easy, reliable and quick way, by means of the FEASIBLE package.

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)

HIS-PACS coupling: BAZIS/ZIS and Philips/MARCOM on speaking terms.

Nowadays a growing number of experts in the PACS field agree on the necessity of having an integrated HIS-PACS combination available in modern hospitals in order to manage the enormous amounts of patient data, both textual, numerical and image information, in an effective way. Since 1986 BAZIS (the Development and Support Group of the Hospital Information System), Philips Medical Systems and the University Hospital of Utrecht (AZU) are partners in the so-called Dutch PACS Project in the development and evaluation of a fully integrated image information system. The first phase of the coupling (sub)project consists of establishing a communication link between the BAZIS/ZIS and the Philips/MARCOM system with the following restrictions: the only data sent concerns the inpatients of one ward; data will only flow one way, from BAZIS/ZIS to Philips/MARCOM. In the second phase two-way communication will be realized and more departments can be part of the experiment. In phase 3 a more general HIS-PACS interface will be developed, independent of the manufacturers of HIS and PACS. In this paper the technical solution chosen for the first phase coupling, the format of the messages being transferred, and the events which result in sending the messages, will be described. Also, reference is made to the demonstration of the working HIS-PACS link, given during the 6th EuroPACS meeting in Utrecht and Leiden on 25-26 April 1988.

Top-down design of a picture archiving and communications system (PACS) by means of simulation.

The development of picture archiving and communications systems (PACS) for medical applications can be regarded as a challenging field in medical informatics. Since 1982, several projects have been started into this direction worldwide. The Dutch IMAGIS (Image Information System) project, started in 1984, is one of them. Within this project, a top-down design strategy is chosen, with the following first steps: (1) A thorough information analysis for a Radiology Department, in which both qualitative and quantitative aspects are included. Such an analysis can be used to estimate the workload on a future PACS system. (2) The construction of a flexible performance prediction tool, based on discrete even simulation. Such a tool can be used to predict the performance of a certain computer system configuration under a certain workload. Based on the information analysis, and using the performance prediction tool, a PACS system is drafted for the thorax section of the Diagnostic Radiology Department of the Leiden University Hospital. In this first design attempt, the assumption was made that current working procedures concerning images will be maintained as much as possible.