Picture Archive and Communication Systems (PACS), which allow the electronic acquisition, storage, transportation, and viewing of medical images, hold the eventual promise of reduced costs, improved image-management logistics, and ultimately, improved patient care. But at what point in the future will PACS really cost less than film-based image management for a given hospital size; and how are these costs affected by the choice of the digital communication network? To address these questions, a static differential cost model has been constructed. Four PAC systems based on different speed networks as well as film, were considered for five different sized hospitals and two time periods. Based on the assumptions outlined, high-speed-network PACS (greater than 150 Mbps) are less costly than those based on low-speed networks for hospitals generating more than 15,000 procedures per year starting in 1995. Further, even though all possible PACS cost savings were not considered, high-speed network PACS appear to be less costly than film for hospitals larger than 30,000 procedures in 1995 and larger than 15,000 in 2000, while low-speed-network PACS should cost less than film for 60,000 and 30,000 procedure hospitals in 1995 and 2000respectively.

We have implemented two high resolution workstations within our pediatric radiology PACS module: a two-monitor 2K x 2K station and a six-monitor 1K x 1K station. The 2K x 2K workstation is under evaluation for primary reading of pediatric radiographs from a computed radiography unit. System implementation and evaluation methods are described. Operational efficiency measures of both film and digital systems are reported. This study is our first attempt to integrate a primary viewing station into a busy clinical environment. The 1K x 1K workstation is available 24-hours a day, 7 days a week for fast reviews by referring physicians. Images from a compated radiography system are available at the workstation in about 8 minutes. A digital voice reporting system is being developed to communicate radiology reports from the 2K x 2K workstation to the 1K x 1K secondary review station.

Seven months experiences of a filmless PACS (named HU-PACS) which covers Radiology, Orthopedic, Internal medicine and General Surgery departments are reported. The PACS has only 20 Image terminals but handles more than 50% of images produced which is about 1000 images per working day. Physicians of the departments have many criticisms and opinions on the PACS but generally speaking it is well accepted and inspiring the physicians to improve the PACS in its image quality and other functions instead of being discarded. Preliminary clinical assessment are performed and reported also.

Since September 1988 a PAC System (CommView by AT&T and Philips) is in operation in the Radiology Department of the University Hospital of Trieste, Italy. A research project is presently in progress aiming at providing factual evidence for the evaluation of this kind of systems as far as operational, technical, clinical and economic aspects are concerned. The general approach to this research consists in implementing and monitoring a PACS in a stepwise way, starting with an "entry-level" system With respect to our actual experience we propose a multi-attribute approach to the problem of justifying PACS, thus classifying attributes into three broad classes: operational, clinical and economic. For each of the relevant problems we distinguish what could be expected in general, what we actually found in practice and what we suppose to do in the future. Justifying PACS turns out to be a difficult task. Within a longer horizon, a horizontalintegration within the Radiology Department and among different Radiology Departments appears to open the more effective perspectives.

The Department of Radiological Sciences at the UCLA School of Medicine is developing an archiving and communication system (PACS) for digitized ultrasound images. In its final stage the system will involve the acquisition and archiving of ultrasound studies from four different locations including the Center for Health Sciences, the Department for Mental Health and the Outpatient Radiology and Endoscopy Departments with a total of 200-250 patient studies per week. The concept comprises two stages of image manipulation for each ultrasound work area. The first station is located close to the examination site and accomodates the acquisition of digital images from up to five ultrasound devices and provides for instantaneous display and primary viewing and image selection. Completed patient studies are transferred to a main workstation for secondary review, further analysis and comparison studies. The review station has an on-line storage capacity of 10,000 images with a resolution of 512x512 8 bit data to allow for immediate retrieval of active patient studies of up to two weeks. The main work stations are connected through the general network and use one central archive for long term storage and a film printer for hardcopy output. First phase development efforts concentrate on the implementation and testing of a system at one location consisting of a number of ultrasound units with video digitizer and network interfaces and a microcomputer workstation as host for the display station with two color monitors, each allowing simultaneous display of four 512x512 images. The discussion emphasizes functionality, performance and acceptance of the system in the clinical environment.

The increasing use of magnetic resonance imaging (MRI) as a clinical modality has put an enormous burden on medical institutions to cost-effectively teach Mill scanning techniques to technologists and physicians. Since MRI scanner time is a scarce resource, it would be ideal if the teaching could be effectively performed off-line. In order to meet this goal, the Radiology Department has designed and developed a Magnetic Resonance Imaging Simulator. The Simulator in its current implementation mimics the General Electric Signa scanner's user-interface for image acquisition. The design is general enough to be applied to other MRI scanners. One unique feature of the simulator is its incorporation of an image-synthesis module which permits the user to derive images for any arbitrary combination of pulsing parameters for spin-echo, gradient-echo, and inversion recovery pulse sequences. These images are computed in five seconds. The development platform chosen is a standard Apple Macintosh-Il computer with no specialized hardware peripherals. The user-interface is implemented in HyperCard. All other software development including synthesis and display functions are implemented under the MPW 'C' environment. The scan parameters, demographics and images are tracked using an Oracle database. Images are currently stored on magnetic disk but could be stored on optical media with minimal effort.

Since October, 1988, a picture archiving and communications system has been our primary means of managing ultrasound images. The ultrasound area was selected because of satisfactory image resolution with PACS, relatively low volume (18-20 cases per day), and minimal clinician request for the images. We have performed over 6,000 examinations, comprising over 50,000 images during this time period. The images and examination reports, stored on optical disks, are available on line for one week before removal to shelf archiving. When shelf archived studies have required de-archiving, most have been retrieved within five minutes. Rapid, reliable image acquisition allowed for decrease in the study performance time. Display monitor illuminance stability eliminates density variation associated with improper exposure of films. Immediate availability of images makes possible on-line monitoring of technologist performed cases. No images have been lost. Technical problems have included image degradation because of pixel shift artifact, hardware and software failure, and duplicate entry of patient demographic data. Despite rapid initial display and review, subsequent image review is 6-10 times slower than with film based studies. If PACS are to succeed, automatic archiving and de-archiving, improved system reliability, and improved speed of display must be developed.

Although trauma has been recognized as the third leading cause of death overall in the United States, it is the leading cause of death in persons less than 40 years of age. There are approximately 150,000 trauma deaths per year. About 50,000 of these occur on the highway, with victims suffering severe multiple system injury. For every death, 2-3 patients suffer major long-term disability. An important estimate states that one in four of these deaths could be prevented1. With this unfortunate fact in mind, trauma systems have been developed across the country over the past decade. A trauma system consists of 1) a sophisticated prehospital system with paramedics initiating resuscitation and rapid transport; 2) on-line communication networks linking prehospital personnel with physicians in trauma centers who provide medical control; and 3) the trauma center, which acts as the hub of the system by coordinating the prehospital efforts and providing definitive trauma care. The trauma center concept has been developed and defmed by the American College of Surgeons, which established three tiers: Levels I, II, and III, with the most severely injured patients being triaged to Level I institutions. Since death and major disability occur within a short time following injury in those patients, diagnosis and therapy must be both simultaneous and expeditious. This is accomplished by having surgeons--trauma surgeons, neurosurgeons, orthopedic surgeons and anesthesiologists--and operating room teams present in the hospital at all times. A level I trauma center recreates, in part or in whole, a hospital environment focused on a limited spectrum of disease. All the problems in medical care related to imaging that are experienced in the trauma center also exist throughout the remainder of the hospital system. However, due to the speed of health care delivery and the concentrated focus of multiple surgical subspecialists and radiologists on the same small number of medical images the problems become severely exacerbated. Virtually all of the most serious problems related to imaging in a level I trauma center can be resolved with digital acquisition and storage of conventional images combined with transmission of already digital images (CT scans) to a central display location. Additional benefits can be expected with the provision of remote access to images from intensive care units and operating rooms and rapid transmission of images to the ShockfTrauma section where the earliest and most intense medical care is administered. Consequently, a PACS system was installed at the Regional Medical Center at Memphis. Installation was completed in the first week of December, 1989 and the system is currently being phased into operation, and evaluated.

A digital image network has been installed in the James Whitcomb Riley Hospital for Children on the Indiana University Medical Center to create a limited all digital imaging system. The total system is composed of commercial components, Philips/AT&T CommView system, and connects an existing Philips Computed Radiology (PCR) system to viewing workstations located in the intensive care unit and the new born nursery. The purpose and design of the system is to input the portable chest images from the PCR system, and to display these images at the remote workstations on high resolution monitors for direct viewing by referring clinicians, thus eliminating some of their visits to the radiology department three floors away. The design criteria includes the ability to centrally control all image management functions on the remote workstations to relieve the clinicians from any image management tasks except for recalling patient images. The principal components of the system are the Philips PCR system, the acquisition module (AM), and the PCR interface to the data management module (DMM). Connected to the DMM are a display workstation (DW), a optical disk drive, and a fiber optic to ethernet gateway. The ethernet link is the network connection to the two results viewing stations (RVS) located approximately 100 meters from the DMM. The DMM acts as an image file server and image archive device. The DMM manages the image database and can load images to both the DW's and the two RVS's. The system has met the initial design specifications and can successfully capture images from the PCR and direct them to the RVS's. Additional studies are beginning to determine the optimal image management procedures such as when to archive and purge images from the DMM.

Experience gained from Siemens PACS installations since 1986 has been of great value and has lead to a continuous upgrading culminating in our today's products. Valuable information not only on technical aspects but also experience in PACS project engineering and operating a PACS has been acquired from a manufacturer's point of view. It might supplement what the PACS users are reporting on their individual results.

As part of a multi-project program, we are conducting a number of studies on the implementation and use of digital radiology in the modern radiology environment. In several of our completed studies, 10 participating radiologists have each been asked to view and interpret 300 or more posteroanterior chest cases, presented on both conventional film and on a high-resolution workstation. Because we believe that radiologists' subjective acceptance of new uses of the digital modalities is important if these techniques are to be more widely utilized, we administered a comprehensive questionnaire to these radiologists to examine their attitudes regarding use of the workstation vs use of film. General adjustment to the digitial modality, personal comfort levels, and perceptions about time required for and resulting accuracy of readings, as well as advantages and disadvantages of the digital system were examined. In general, the radiologists in this study felt slightly less comfortable using the workstation than using film, although they found adjustment to the workstation to be fairly easy. The most important advantage of the workstation was thought to be the ability to control contrast and brightness; the most important disadvantage, that interpreting from the workstation was more tiring than interpreting from conventional film when comparable numbers of images (50) were interpreted in a single reading session.

In a large-scale, multi-reader study to investigate questions surrounding the issue of the implementation of picture archiving and communications systems (PACS) into the modern radiology environment, we examined the effect that the incorporation of a clinical history into the reading process would have on levels of diagnostic accuracy. Because we wanted to test the inclusion of the clinical history in an environment as close to that of the clinical situation as possible, we defined "history" to be a concise, objective, and potentially computer-extractable version of what appears in the patient records, including a statement from the referring physician when this is available. In a series of studies, four radiologists interpreted 247 posteroanterior normal and abnormal chest images on conventional film both with and without accompanying patient histories; five radiologists read the same number of images presented on a high-resolution video workstation with and without clinical histories. There were no significant differences (p = .05) in diagnostic accuracy rates with or without clinical history for either the film or the workstation in cases of interstitial disease, nodules, or pneumothorax. Diagnostic accuracy for the radiologists as a group was not affected by the presence of the clinical history. We concluded that for the interpretation of these abnormalities, the incorporation of clinical history with images in the PACS environment should not be a major goal.

We designed and implemented a high-resolution video workstation as the central hardware component in a comprehensive multi-project program comparing the use of digital and film modalities. The workstation utilizes a 1.8 GByte real-time disk (RCI) capable of storing 400 full-resolution images and two Tektronix (GMA251) display controllers with 19" monitors (GMA2O2). The display is configured in a portrait format with a resolution of 1536 x 2048 x 8 bit, and operates at 75 Hz in a noninterlaced mode. Transmission of data through a 12 to 8 bit lookup table into the display controllers occurs at 20 MBytes/second (.35 seconds per image). The workstation allows easy use of brightness (level) and contrast (window) to be manipulated with a trackball, and various processing options can be selected using push buttons. Display of any of the 400 images is also performed at 20MBytes/sec (.35 sec/image). A separate text display provides for the automatic display of patient history data and for a scoring form through which readers can interact with the system by means of a computer mouse. In addition, the workstation provides for the randomization of cases and for the immediate entry of diagnostic responses into a master database. Over the past year this workstation has been used for over 10,000 readings in diagnostic studies related to 1) image resolution; 2) film vs. soft display; 3) incorporation of patient history data into the reading process; and 4) usefulness of image processing.

Using simulation studies and the data obtained from our clinical investigations, we are comparing some of the techniques commonly employed in ROC analysis. The general areas of our investigation include estimation of the area under the ROC curve and its associated standard error, comparison of the areas under two ROC curves, and simultaneous comparison of the areas under more than two ROC curves. For single ROC curves, maximum likelihood estimation based on the binormal model is being compared to the approximate area obtained using the Wilcoxon Statistic. Standard errors obtained from classical asymptotic theory are being evaluated and compared to standard errors based on jackknifing. With regard to the task of assessing differences in the diagnostic accuracies of two systems, our investigations have compared the maximum likelihood estimation method to a nonparametric method based on the Wilcoxon Statistic, focusing primarily on correlated observations, e.g., from readings of different modalities' images of the same patients. Extensions of existing methodology to the problem of comparing ROC areas from more than two modalities are being addressed as well as problems associated with the incorporation of multiple readers.

In this study, we used a high-resolution workstation (1536x2048) with window width (contrast) and level (brightness) manipulations available to test diagnostic accuracy rates of seven experienced radiologists on 300 posteroanterior chest images in a clinically simulated environment. Observer performance was assessed by receiver operating characteristic analysis, and the results were compared to performance when the same cases were interpreted by the same radiologists using conventional film. Efficiency on the workstation was comparable to, if not better than, that with the conventional film, but accuracy indices (Az) for the detection of interstitial disease and pneumothoraces were lower for the workstation than for conventional film. Since window width and level did not compensate for the lack of resolution, we then examined in a following study the effects of different processing options (reverse mode, unsharp masking) on diagnostic accuracy. These image processing options did not significantly improve readers' performance.

In an ongoing, multi-reader, multi-project program dealing with the interpretation of radiological images, we have examined several issues of methodology which have not as yet been addressed that may impact on the determination of reader performance as measured by receiver operating characteristic (ROC) analysis. Among these are issues associated with the training of observers prior to such studies. We employed three types of observer training that we found to be necessary for the successful performance of such studies: 1) a general instructional session for observers on the study protocol and system operation; 2) practice with an interactive computerized feedback teaching file that demonstrates the imaging systems and familiarized readers with an idea of the types of cases that were used in the study along with their correct diagnoses; and 3) training sessions in which readers were taught the manner in which to distribute answer ratings over an ordinal confidence scale. The possible effect of such types of training on the performance and results of ROC studies should be carefully considered prior to their commencement.

High resolution gray scale displays are being evaluated for the display of 2K x 2K x 12 bit digital images. A comparison has been analyzed for conventional chest radiographs, digitized chest radiographs (2K x 2K x 12 bits) printed on laser film, and a high resolution (2K x 2K x 12 bits) gray scale display. An initial study has been conducted comparing computed radiography laser printed films and an interactive 1K x 1K x 12 bit display.

An Integrated Services Data Network test configuration, developed in collaboration with SBC Technology Resources Inc., has been utilized to gain experience with both hardware and software interface isssues relevant to wide-area extensions of PACS. Example workstations capable of inquiry and display of radiological information have been interfaced to the ISDN trial network and tested. A DEGnet router was used to interface our Ethernet-based PACS to an ISDN network. Average throughput rates of approximately 60Kb/s for the lB (64Kb/s) channel and 120Kb/s for the 2B (l28Kb/s) channel were measured. Results were obtained for both embedded and external ISDN terminal adapters.

In this paper, the PACS network data rate requirement in a radiology department is discussed. The network data transmission rate under real data traffic in a medium-size hospital is evaluated using a simulation study. The network is assumed to be a circuit switching network. A preloading system, in which each workstation has local storage to store the next procedure, is assumed, and the network transmission rate which satisfies the response time of this system is obtained.

There are a number of generic problems that researchers in medical imaging have in common. For example, researchers in MR, CT, PET, SPECT, DSA, and digital radiography all need to display and window digital images. We describe here an integrated network with tools applicable to all of the current areas of medical imaging that enable researchers at Duke to share resources and solve software and hardware problems in a unified effort. We will show examples where efforts in a specific area f imaging research can be readily applied in new ways to different imaging modalities through the facilities provided in this integrated approach. We will point out some of the problems and opportunities in the research environment that are different from those encountered in clinical PACS systems.

The concept of picture archiving and communication systems (PACS) is now widely accepted in the medical community. In order to bring the concept to reality, however, innovative designs and implementations are needed. One such design is a fiber optic star based PACS, conceived by the University of Arizona and Toshiba corporation. This PACS network is based on a multiplexed passive star local area network with wavelength-division multiplexing to provide separate logical channels for transfer of control and image data. The system consists of an Image-Network (INET), for image transfer at a rate of 140 Mbps, and a Control-network (CNET), operating at 10 Mbps, for mediating the flow of image transfers. INET is a circuit switched network where a network supervisor grants users permission to transfer images over it, while CNET employs the CSMA/CD protocol for bus arbitration. Before such a system can be deployed, an accurate evaluation study must be carried out to estimate its performance characteristics. Such evaluations are complicated both by the complexity of the PACS itself and the varied demands that are placed on such a system. An novel approach based on siochastic aciiviiy neiworks, a stochastic extension of Petri nets, is useful in this regard. Stochastic activity networks were used to develop a detailed model of the command and image channels. The performance of the system was then evaluated under realistic workload conditions. In particular, we were able to estimate a number of important performance variables including the image response time, command channel delay, and queue length each type of node and the network supervisor. The results 1) show that stochastic activity networks are an appropriate model type for evaluating picture archiving and communication systems, 2) delineate the workload conditions under which PACS may effectively operate, and 3) show that even when these conditions are exceeded, the command channel load remains extremely light. Results of this type are useful both to designers of other PACS networks and those interested in this particular PACS design.

The PAC system: KIDS (Kyoto University Hospital Image Database and Communication System) has been expanded to include several major digital imaging modalities such as X-ray CT, MRI, DSA and CR. The fiber optic high-speed local area network and the workstation with quick image handling are newly designed. The system (new KIDS) is intended to achieve a film-less environment in the department of radiology and to evaluate the feasibility of a hospital-wide PAC system. The present status of the system at the end of 1989 including a image workstation installed in a lecture hall for clinical education is described.

Victoria General Hospital, which is a part of the Greater Victoria Hospital Society, is a 443 bed community hospital with a full-service medical imaging department that includes MRI. In August 1987, four rooms (chest radiography, GI fluorography, CT, and cardiac angiography) were connected to a Picture Archive and Communications System (PACS). We present the experience gained from two years of study with this prototype PACS and briefly describe its hardware and software configuration. Reported in detail is the measured image transfer performance of the PACS for each of the four image sources. Conventional films require more than 150 seconds from exposure to film availability for reporting. Using PACS, chest and GI images take 77 seconds per image from exposure to viewing, 31 secs for CT, and 40 secs for general angiography. The elapsed times with PACS between the various software processes for each modality, and those needed to set up image archive folders are detailed. The present imaging equipment at VGH, a typical community hospital, is specified and is to be integrated into a department-wide PACS. Required PACS performance levels relative to the clinical demands are described, and compared with the current PACS. The information and experience acquired by testing the VGH PACS has been used in the planning of the full implementation of PACS at VGH (ref. 10. Fisher et al). The next phase (3C) of PACS implementation is described.

In expanding our image management and communications system (IMACS) to include a new machine in the Ultrasound Section, we first modeled the impact of attaching the unit to either of our two acquisition modules (AM). Using the software package available to us, we could predict image queue lengths and average image waiting times (before transmission to the central archive). The AMs have attached a variety of devices with differing image production loads. The modeling allowed us to select the AM which would be least impacted (in terms of resoponse time to the devices sending data to the AM) by the added ultrasound machine. We found that though the input response times would not change much with the ultrasound machine connected to either AM, there was a significant impact on the predicted output queue length, with the more heavily loaded AM suffering larger increases in output queue dwell time if the new machine were connected to it. Based on these results, we elected to redistribute the AM loads, and connect the ultmsound machine so as to maintain a relatively balanced load. We tested certain parameters of the model by measuring input and output response times ofan AM under different, artificially induced, acquisition loading. The changes predicted by the model agreed with those measured in order-of magnitude terms.

A model is presented for evaluating the diagnostic value of an imaging system in clinical use. It is site-specific and includes thedistribution of diagnostic findings, diagnostic accuracy, the importance of the test outcomes to the physician, and the timeliness of information delivery.

Abstract not available.

Picture Archiving and Communication Systems (PACS) represent an enormously expensive technological innovation which has the potential to alter the way in which radiology is practiced. In a 1985 survey of radiologists and radiology administrators, over a quarter of those individu1s expected to have some component of an operational PACS system by 1986. The survey respondants perceived advantages including fast access to files, multiple user simultaneous access to films, and possibly secondary benefits in accuracy in diagnosis and improved communications. Progress in widespread PACS implementation has considerably lagged the rate anticipated in the 1985 study. In order to evaluate the current expectations of PACS and contrast them to the earlier enthusiasm we have undertaken this study of the current perceptions of PACS among both radiologists and clinicians.

Our strategy in studying PACS is to evaluate its clinical implementation working with equipment supplied by an established manufacturer. Fiscal and personnel resources required to design and integrate the hardware components and operational software to develop a functional PACS precluded a bottom up development approach at our institution. Imaging equipment vendors possess more abundant design development resources for this task and therefore can support a more rapid development of the initial components of PACS. For this reason we have chosen to serve as a beta test site to study the viability of the basic PACS components in a clinical setting. Our efforts primarily focus on: (1) image quality; (2) cost effectiveness; (3) PACS/HIS/RIS integration; (4) equipment and software reliability; and (5) overall system performance. The results of our studies are shared with the vendor for future PACS development and refi nement. To attain our investigational goals we have formed an interdisciplinary team of Radiologists, Perceptual Psychologist, Economist, Electrical and Industrial Engineers, Hospital Information System personnel and key departmental administrative staff. For several reasons Pediatric Radiology was targeted as the initial area for our PACS study: a small area representative of the overall operation,tight operational controls and willingness of physicians. We used a step-wise approach, the first step being the installation of PACS exclusively within the physical confines of Pediatric Radiology.

A high-level description of a system to pre-fetch comparison radiographs in an Image Management and Communication System (IMAC) is presented. This rule based system estimates the relevance of previous examinations for comparison to the current examination arid uses this determination to pre-fetch comparison studies. A machine learning module should allow the system to improve its skill in pre-fetching examinations for each individual radiologist. This system could be tailored to fit the desires of individual radiologists.

In this paper we present initial work on the design and implementation of an image database system for medical images. The objective of this project is the development of an environment that will permit the quick and intelligent access of images using their content. An image database is a complex system consisting of many components that must be unified and integrated. These are the image analysis component that derives a representation of the stored images, the database component, and the user interface component. This paper focuses primarily on the justification of the design decisions, an illustration of the major features of such a system, and a requirements definition for its implementation. An object-oriented approach is proposed which meets these requirements. The capabilities of an object-oriented data model are demonstrated and possible extensions, needed to meet the data modeling requirements, are discussed.

We are developing a personal image filing system as an alternative method of archiving radiolOgical images. The system can be configured with three popular computers as host: IBM PC/AT, Macintosh II, and SUN. The images are archived on the 3.5-inch optical disk and can be retrieved by any of the host computers for display.

We conceived a hybrid PACS which combines analogue and digital elements where it is required. We experimented a clinical application of the dynamic image utilizing the analogue element which is a feature of the hybrid PACS. With the analogue optical disk, dynamic image acquisition of 30 frames per second is possible and image recording is also possible with any modality of X-ray fluoroscopy function. In addition, X-ray dose to the patient is one-fifth to one-tenth compared with the conventional cine filming method while its still image is clear and a data acquisition to the PACS is easy. We applied this system to the areas of the otorhinolaryngology, orthopaedics and respiratory disease and could perform a various analysis of the disease status under natural conditions, also we found that this system is useful for judging an effect of a treatment as well as jugding a functional recovery after an operation and an effect of a rehabilitation. We are also planning to extend the application to the areas of the digestive system and the group examination from now on.

An IBM Application System/400 (AS/400) anchors the Mayo Clinic/IBM joint development PACS project. This paper highlights some of the AS/400's features and the resulting benefits which make it a strong foundation for a medical image archival and review system. Among the AS/400's key features are: 1. A high-level machine architecture 2. Object orientation 3. Relational data base and other functions integrated into the system's architecture 4. High-function interfaces to IBM Personal Computers and IBM Personal System/2s' (pS/2TM).

Following our initial investigation of the utility and performance of an AS/400 based token ring network for MRI image archival, we have designed and embarked upon a project to install multiple token ring networks at three physically separated facilities connected with fiber optic communication to archive and display CT and MRI image data. The system design will connect six MRI systems, six CT systems, four optical storage systems, three image display systems, three radiology report scanners, and a foreign archival system. Network communication and archival functions will be managed by an IBM AS/400. Preliminary estimates indicate that savings of media, space, and personnel as well as the additional benefit of online reports with image data will enhance the quality and efficiency of clinical practice. Additionally, we are evaluating a medical image display system (MIDS) to be used for on-demand image review, prefetched image review, and a potential replacement for modality-specific physicians consoles. The MIDS workstation is a promising addition to clinical practice both from the standpoint of an efficient means of image review as well as image interpretation. We consider this joint project to be an important step in the process of understanding the impact and subsequent consequences of electronic image transmission, information communication, and archival within a busy clinical setting. Our performance and design criteria focus upon the impact of this system on the clinical practice within radiology and the subsequent ramifications of PACS throughout the institution.

The first parameter of interest in considering network performance is signaling rate. To understand end-to- end image transfer rate, however, signaling rate is often the parameter of least importance. The basic image transfer in a PACS is disk-to-disk or at best disk-to-memory. The real performance bottlenecks are disk and system bus I/O rates, CPU and operating system efficiency in executing network protocols, and throughput of network interface units. Except for issues of congestion, the end-to-end performance of a 100 Mbps FDDI net may not be significantly different from that of a 10 Mbps Ethernet. The system architecture of workstations and storage nodes is the key to overall PACS network performance. Simulation studies indicate that a high speed disk subsystem combined with an intelligent network interface unit avoids the bottlenecks associated with conventional systems and can make use of high bandwidth media such as broadband ISDN. Experience with a preliminary demonstration of broadband ISDN connectivity as part of the Berlin Communications (BERKOM) project will be presented.

A software package has been developed to aid psychophysical studies on diagnostic image quality. The program, called FEASIBLE, supports all phases of experiments to evaluate the diagnostic quality of PACS components, image acquisition and manipulation methods and display techniques. The software allows the user to design any such an evaluation study, to perform an arbitrary number of psychophysical sessions and to statistically analyze the collected data with the Receiver Operating Characteristics (ROC) technique. Furthermore, the calculated ROC curves can be plotted in graphs to be integrated in publications. Within the scope of the Dutch PACS project, a PACS research project jointly carried out by the Utrecht University Hospital, BAZIS and Philips, FEASIBLE has been used to investigate the diagnostic accuracy of the PACS prototype that was clinically evaluated. The package has been sent - upon request - to more than 20 scientists in the field of radiological imaging. This paper explains the backgrounds and the features of the latest version of the program, and the way to use it in an actual ROC study.

The University of Washington participated, during 1986-89, in a clinical evaluation of commercially available PAC systems under the sponsorship of the MITRE Corporation (Contract N55-200). As part of this work, we developed a general approach to the clinical evaluation of PACS workstations. This paper describes the approach and its application to a specific workstation, the AT&T CommView Diagnostic Workstation.

The functional requirements of a radiological viewing station has been determined by feedbacks from radiologists. In this project, we incorporated all the functional requirements in a custom designed display station with emphasis on affordablility and display speed. Utilization of the open architecture of VME and VSB buses led to expandability of display screens, memory sharing, and availability of off-the- shelf frame buffers.

A major factor in determining the overall utility of a medical Picture Archiving and Communications (PACS) system is the functionality of the diagnostic workstation. Meyer-Ebrecht and Wendler [1] have proposed a modular picture computer architecture with high throughput and Perry et.al [2] have defined performance requirements for radiology workstations. In order to be clinically useful, a primary diagnosis workstation must not only provide functions of current viewing systems (e.g. mechanical alternators [3,4]) such as acceptable image quality, simultaneous viewing of multiple images, and rapid switching of image banks; but must also provide a diagnostic advantage over the current systems. This includes window-level functions on any image, simultaneous display of multi-modality images, rapid image manipulation, image processing, dynamic image display (cine), electronic image archival, hardcopy generation, image acquisition, network support, and an easy user interface. Implementation of such a workstation requires an underlying hardware architecture which provides high speed image transfer channels, local storage facilities, and image processing functions. This paper describes the hardware architecture of the Siemens Diagnostic Reporting Console (DRC) which meets these requirements.

One of the challenges to the PACS workstation designer is to cost effectively fulfill the range of requirements from those of the entry-level system to those of the fully digital hospital. The workstation must therefore support many of the functions of film-based image storage and image information systems. A primary diagnosis workstation must support rapid selection and viewing of patient examination folders. The user must easily and rapidly sequence through a stack of examinations. Activities such as printing films, archiving images, and retrieving older examinations must be initiated easily, without interfering with the diagnostic use of the workstation. Some of these functions are executed by the workstation itself while others are performed by service nodes on the PACS network. The workstation's user interface must make the architecture of the system transparent, providing access to the services while concealing the complexity of their accomplishment. This paper discusses the approach taken to the user interface of a commercial PACS primary diagnosis workstation. This workstation may be configured as an entry-level PACS or as a single workstation in a very complex system. Local image storage, retrieval, archiving and display functions will be described. Networking with modalities, image storage systems and image management systems will also be discussed.

As prototype PACS grow into fully digital departmental and hospital-wide systems, effective information storage and retrieval mechanisms become increasingly important. Thus far, designers of PACS workstations have concentrated on image communication and display functionality. The new challenge is to provide appropriate operator interface environments to facilitate information retrieval. The "Marburg Model" 1 provides a detailed analysis of the functions, control flows and data structures used in Radiology. It identifies a set of "actors" who perform information manipulation functions. Drawing on this model and its associated methodology it is possible to identify four modes of use of information systems in Radiology: Clinical Routine, Research, Consultation, and Administration. Each mode has its own specific access requirements and views of information. An operator interface strategy appropriate for each mode will be proposed. Clinical Routine mode is the principal concern of PACS primary diagnosis workstations. In a full PACS implementation, such workstations must provide a simple and consistent navigational aid for the on-line image database, a local work list of cases to be reviewed, and easy access to information from other hospital information systems. A hierarchical method of information access is preferred because it provides the ability to start at high-level entities and iteratively narrow the scope of information from which to select subsequent operations. An implementation using hierarchical, nested software windows which fulfills such requirements shall be examined.

The clinicians at Shands Hospital at the University of Florida were frustrated by the filmbased system, which served them in taking care of their patients in the Intensive Care Units (ICU). Frequently, they would come to the radiology department three to six floors below their respective ICU only to be stymied by the inability to find a study that was needed for patient care. This led to much consternation and outright animosity towards the personnel in the radiology department. On the other hand, the radiologists were exasperated by the missing films and lack of cooperation of the ICU team of physicians and nurses. The common denominator was an inefficient communications system for sending chest and abdominal films to the ICUs. A solution was proposed, tested, and installed by DuPont. Our initial experience with this system was reported.1 We have now modified and extended this system to all of the ICUs, which represents the basis for this report. The clinical review system (CRS) was initially placed in the medical ICU and very shortly thereafter expanded to serve all six ICUs at Shands Hospital. These include surgical, neurosurgical, cardiothoracic, pediatric and neonatal ICUs. Approximately 30,000 portable examinations are done each year in these areas.

We have evaluated the performance of Ethernet, Fiber Distributed Data Interface (FDDI) and Canstar Super 100 networks in a multimodal Picture Archiving and Communication System (PACS) environmenl image data transfer rates were measured for SUN workstations and PC/ATs running TCP/IP communication protocols. The communication between two computers was on a server-client basis and all transfer rates were measured between computer memories in order to eliminate the bottleneck imposed by storage devices. Four test models were used to evaluate the performance of the three individual networks: bidirectional, centralized parallel and relay models. This paper describes the methods of network throughput evaluation using these four models and presents the resulting performance data for the three networks tested.

The Radiology Department at the Hospital of the University of Pennsylvania is currently expanding its prototype Picture Archiving and Communications System (PACS) into a fully functional clinical system. The first phase of this expansion involves three major efforts: the upgrade of the 10-Mbit token-ring to an 80-Mbit backbone with associated sub-nets, the implementation of a large-scale image archive, and, an interface between the PACS and the Department's Radiology Information System. Upon the completion of this phase, the PACS will serve the storage and display needs of four MRI scanners and four of the Hospital's Intensive Care Units. This paper addresses the implementation of a software suite designed to duplicate and enhance conventional Film Library functions on a PACS. The structure of an electronic 'folder' based upon the ACR/NEMA Digital Imaging and Communication Standard is also introduced.

The effective delivery of health care has become increasingly dependent on a wide range of medical data which includes a variety of images. Manual and computer-based medical records ordinarily do not contain image data, leaving the physician to deal with a fragmented patient record widely scattered throughout the hospital. The Department of Veterans Affairs (VA) is currently installing a prototype hospital information system (HIS) workstation network to demonstrate the feasibility of providing image management and communications (IMAC) functionality as an integral part of an existing hospital information system. The core of this system is a database management system adapted to handle images as a new data type. A general model for this integration is discussed and specifics of the hospital-wide network of image display workstations are given.

The design of workstations for use in picture archival and communications systems (PACS) has received a significant amount of attention; rightfully so, as it is the most noticeable element in such a system. Various aspects of medical imaging workstations have been studied in detail, including feature requirements, user interface, performance requirements, and other human factors considerations. Experience during implementation of the CommView system PACS has shown that it is most important to carefully consider the operational environment in which these workstations will be placed to match the tasks and flow of information to, from, and within the workstation with the tasks and flow of information in the traditional film-based environment. Equally important is the cost of such a workstation. and the well - designed workstation is one that successfully matches the operational environment at a reasonable price. We describe in this paper the process undertaken to optimize a PACS workstation for the operational environment of diagnostic reading and reporting. Operational models have been developed, through interviews with and observations of users at Bowman Gray/Baptist Hospital Medical Center. Duke University Medical Center. San Francisco VA Medical Center, and Georgetown University Hospital. Hardware and software designs of the workstation were optimized to match the workstation to those operational models, including matching the time intervals, and providing easy access to relevant exams and to historical exams to be used for comparison.

The exchange of information between a Radiology Information System (RIS) and a PACS is essential to optimizing the utility of a PACS. Some of the benefits awarded by implementing an interface include a reduction or elimination of repetitious data entry, the availability of more accurate information on the PACS, a reduction in workload for the technologists, registration clerks, transcriptionists, etc, and the availability of more accurate data for automating the PACS. This paper discusses the Georgetown experience of interfacing an HIS/RIS and PACS, by describing the development of the interface and its impact on clinical operations.

Despite the much-discussed advantages of the all-digital radiology department, the speed of electronic display continues to be a major obstacle to its acceptance; physicians generally agree that sophisticated workstation functionality cannot compensate for an interpretation environment that delays diagnosis. Two design schemes have been devised and discussed at length at the Bowman Gray School of Medicine (BGSM) that will improve the efficiency of image transmission significantly. The first of these is image routing and pre-loading. The central archive can use information associated with each exam and a set of rules to predict which workstations will be used to read the exam. The images can thus be sent automatically before the physician arrives at the workstation to interpret a series of exams. The second scheme, which is intimately associated with the first, allows a workstation to manage its own local disk to remove copies of exams so that new ones may be pre-loaded. This disk management algorithm assigns priorities to the exams based on their status in the acquisition/interpretation cycle and performs automatic deletion as the workstation's disk reaches its capacity. The effect is a virtually limitless disk that eliminates the time-consuming task of manual deletion and retrieval of images.

Experience from ten years in Picture Archiving and Communication Systems has led to a clearer understanding of the user, system, and component requirements for PACS, and the evolving market. This paper reports on one manufacturer's considerations and experiences as a PACS supplier.

The Regional Medical Center at Memphis (the MED), including the Presley Memorial Trauma Center (the Trauma Center) is a privately operated, county owned, partially public funded institution that contracts with the University of Tennessee, Memphis (UT,Memphis) for physician clinical services. For approximately the past eight years, the administration of UT,Memphis has encouraged and emphasized the development of "Information Technology". To that end, a number of initiatives were developed on the campus, ranging from the development of a service oriented computer science department and the installation of an extensive broad band cable network to the widespread distribution of personal computers amongst the faculty. More recently, UT,Memphis and Siemens Corporation, the vendor of the UT,Memphis Magnetic Resonance Imaging (MR.I) equipment, collaborated in creating a link between the MRI and a physician workstation located in the Imaging Section of the MED. The MRI is located approximately a half mile from the MED and the link was established over the university broad band cable network. From those beginnings, interest developed within the Department of Raliology in more fully exploring the current PACS technologies. However, a number of resources often associated with the current installation of PACS technologies were lacking at UT, Memphis. No research funds were available from the university or from the Department of Radiology. Until very recently, and well into the final stages of planning for PACS, no significant biomedical engineering resources were available on the campus. The Physics Section of the Department of Radiology was overextended in providing support for a variety of clinical sections of the Department of Radiology. It became apparent that the most appropriate financial support for a PACS system was through the resources of one of the hospitals associated with UT,Memphis and that a major portion of the required technical support would have to come from the vendor and the hospital.

PACS is a topic which has not yet been granted a Seal of Approval by Radiology. One must only count the negative reports published to see that. A change of name from PACS to Image Management, Archival and Communication Systems (IMACS) will also not help the matter at the current stage of development. What is needed are clinical demonstrations of the philosophy behind PACS and of the fact that it works today and is not just an ugly duckling.

In this radiologic communication project two PAC-systems were installed in two locations of one radiologic department of the Rudolf Virchow University Clinic lying about 10 km apart. The realisation of a well-operating PACS-to-PACS communication is related to a fast image- and video- data transfer and a command processing technic. The PACS-workstation has to enable the manipulation and post-processing technics known from CT-, MR- and DSA- imaging.

This session really had its genesis sometime ago when Ed Staab and I had a discussion about the problems of evaluating a PACS. A lot of what we had seen had related to technical evaluation or observer performance studies, and we think those studies are extremely important, but it looked like a lot of the radiology community was interested in going beyond those and looking at PACS as a whole and how it might impact patient care With that thought in mind we began planning the session. We saw a really excellent study by David Gur and his colleagues yesterday on some of the observer performance issues, perhaps the ultimate expression of observer performance studies in terms of evaluating film or digitized film versus CRT displays. As I said, our goal in putting this session together was to try to get some additional insight into clinical evaluation beyond the methodology used for observer performance studies. And perhaps looking at some long range issues that could potentially affect the clinical evaluation of PACS. In that regard I invited, and was happy to receive acceptances from, three speakers. There will be three papers in this session. Unfortunately the last one did not get printed. Harold Kundel and Constantine Gatsonis have their subject titles listed. The third speaker will be David Beard from the University of North Carolina who will be talking about "Is a Work Station as Good as Film?" I think you are in for a very interesting, and I hope thought-provoking session. With that, I would like to introduce Harold Kundel, a radiologist and Professor of Radiology at the University of Pennsylvania, who will speak about the impact of PACS on patient care, efficacy, and outcome studies.