J. P. J. de Valk

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.

Introduction to Pacs for Those Interested in Image Processing

This paper gives a brief overview of PACS, including the basic components of a PACS system and what operations are or should be provided by it. This includes as well, a discussion of desired response time.

Considerations On An Algorithm For Activation Of Images In A Multi-Layered Storage System Within A PACS

One of the major bottlenecks in realizing a full size PACS is the image storage component. Further technological developments are necessary before sufficient capacity can be realized. It can be expected that a multi-layered storage structure will be necessary where large capacity with relatively long access times will be offered at the lowest level. The higher levels will show decreasing access times combined with decreasing capacity. Both in the judgement of images acquired in the diagnostic study and in the work of the clinician historical images of the patient concerned may be needed. If these images had to be retrieved from the lowest storage level at the moment they are needed, the service time would definitely be unacceptable. So a strategy is necessary for the anticipation of the need of access to images. In this paper a first attempt is made to identify relevant parameters to be used in such a look ahead algorithm for the activation of images to a next level. A simple algorithm is suggested; the need for further study is emphasized.

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.

First experiences with the modelling and simulation packagemiracles 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.

A Layered Storage Structure For Images Confronted With The Use Of X-Ray Images In A Hospital

In modern hospitals the attention paid to the problem of lending and archiving of images is increasing. In almost every (big) hospital complaints are heard concerning missing X-ray images and lack of storage space. The use of the computer and digital storage systems might lead to a solution of these problems. However enormous amounts of data are involved, ranging per image from 128 kbytes for a CT-scan to over 2 Mbytes for a thorax X-ray. For the Leiden university hospital (940 beds) this implies a daily production of about 8000 Mbytes of uncompressed data after digitisation. At this moment, a study is in progress carried out by the central development organisation (BAZIS) of a group of Dutch cooperating hospitals, aiming at a well founded choice of a system framework. During this study extensive use is made of the information available from the existing Hospital Information System (HIS). The acquired data will be used as input to a simulation model, which should give more insight into the behaviour and necessary characteristics of the memory configuration required. This configuration will consist of different layers.

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.

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.

Radiological Information Flow Between Departments And Out-Clinics In The Utrecht University Hospital In The Netherlands

Crucial in the planning of a medical image archiving and communication system is the knowledge of the logistics of diagnostic images in and between departments. On the prerequisite that all requested images should be available at the referring department, knowing the average area (in cm2) of used film per kind of examination, as well as the necessary estimated spatial sampling frequency, an estimate is generated of the necessary intermediate storage buffers and the network capacity to the different departments.

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.