Within the framework of the integration of medical information environment (MIE), special groupware multimedia services (GMS) should be developed. The application of GMSs to specially designed medical communication networks (MCN) creates an integrated user collaboration scheme for supporting and handling special medical cases. The present paper deals with the study and analysis of the traffic performance of a private multimedia ISDN MCN with a dynamic bandwidth allocation.

In designing a picture archival and communications network, it is necessary to take into account the specific rates of flow of information from source devices (acquisition nodes) to destination devices (diagnostic workstations and clinical review stations) and to archival storage. It is also important to consider variations in the flow of data throughout the day to build an accurate model of network activity. Studying the distribution of data generated per patient for all imaging modalities in a radiology department permits analysis of the potential impact on the radiology PACS network. The Radiology Department at the University of Florida performs approximately 150,000 examinations per year. In this study, we investigated the pattern of data generation for fifteen acquisition nodes based on all examinations performed by the department for a four week period. For each acquisition node, the number of studies, types of studies, and number of films per study for discrete hours during the day were recorded. The size of these images in MBytes were calculated based on current computed radiography and film scanner technology. These data provide valuable insights into both the image data storage and image data flow bandwidth needs within our Radiology Department. These data are also useful for evaluating the feasibility and limitations of possible PACS network designs.

We studied the performance characteristics of the acquisition and display subsystems of a clinical picture archiving and communication system (PACS). The PACS was configured to a centralized model and a distributed model. The performance of each subsystem in the two models were measured and compared. In both models, a control computer was designated to direct the flow of image data from the acquisition subsystem to the display subsystem so that performance of these two subsystems can be separately measured. Two image modalities, magnetic resonance imaging (MRI) and computed tomography (CT), were selected for the performance study. Approximately 100 gigabytes of image data from 3 MR scanners and 3 CT scanners were analyzed. The performance of the acquisition subsystem was measured in terms of the delivery time of an individual image file from an acquisition computer to the control computer. The performance of the display subsystem was measured in terms of the delivery time of an individual image file from the control computer to a display unit. Results showed that the centralized PACS model had better control and required less maintenance than the distributed PACS model. However, the performance of a centralized model degraded significantly when more input (radiologic imaging modalities) or output (display station) devices were encountered.

In this paper we briefly describe the operation of PACS(1), equipped with a central relational data base, which correlates patient identification data with the location where the related images can be found. A performance model of this PACS(1) with response times is presented in this paper. PACS(1) has also been built using as much as possible, standard software and standard protocols, to keep the development costs down. From the standards used we mention: TCP/IP, SQL, X Windows and FTP. The recent development of powerful workstations has now made it possible to eliminate the image servers in PACS(1) and integrate the functions of the image servers into the display stations. This rather simple and elegant design, called PACS(2), is presented in this paper together with a performance model. Although the development of PACS(2) has not yet been completed, we found that the presently available high power workstations are still somewhat too slow to execute, with the required response times, simultaneously the high speed communication functions and the display functions. Special purpose hardware, to implement the TCP/IP protocol functions, is introduced in the display workstation in order to reduce its workload and improve the response times.

The ratio of significant findings to `no significant change' on AP chest x-rays in the ICU environment has been investigated. We reviewed 2,162 cases in seven of our ICUs as a function of type of ICU and acquisition time. The results of this preliminary study clearly indicate that the ratio of significant observations per procedure which may have an impact on patient management increases significantly in the `non-morning round.'

Computer-aided diagnosis is generally dependent on feature detection and identification on digitized images. In this project, we explored the use of a computerized system in which features identified by radiologists for a previous set of mammography cases, in addition to other information on those cases, formed a database of information that provided readers of new cases with statistical probabilities (feedback) for malignancy in similarly rated cases. Although in this preliminary study the feedback system did not improve levels of diagnostic accuracy (which were already high), the results suggest that in certain settings and with certain mammography readers the method may be extremely promising.

A potentially valuable tool in medical imaging is the development, and integration with PACS, of systems which enhance the interpretive accuracy of the user -- his ability, given a set of findings (in the broad sense, including clinical information about the patient as well as characteristics of the lesion being analyzed), to assign the proper disease label, or diagnosis, to them. Such systems, which we call here interpretive tools (IT), contain a variety of types of information about diseases and their radiologic diagnosis. They can contain information about large numbers of diseases, including statistical information (incidence, characteristic anatomical locations, association with age and gender or with other diseases, probabilities of various findings given a disease), textual information (description of diseases, treatment, literature references, lists of other entities that might be confused with the disease of interest, additional diagnostic points that may not be represented, or even representable, within IT), and image-based information (typical and atypical examples for each entity and radiographic finding, examples of normal anatomy). These databases can be used both for teaching purposes and as a tool for improving interpretive accuracy [Swett, 1987]. This paper describes some of the requirements for these databases and then discusses early work on the implementation of DDx, an IT whose domain is neuroradiology.

Since PACS functionality and utility are relatively difficult to demonstrate beyond display capabilities, system developers have concentrated on display functions that do not necessarily address many of the problems PAC systems are expected to solve in the clinical environment. In this paper, minimal functional requirements are reviewed. These are designed ultimately to improve patient care through increased efficiency and improved communications (both within and outside of radiology). End user expectations that should be assessed when considering PACS are also discussed.

This paper describes the functional specifications of the HIS/RIS-PACS interface that is being developed within the scope of the HIPIN topic as part of the European AIM/EurIPACS project. This functional specifications characterizes among other things the generic requirements for the interface, the radiological procedures, the HIPIN data dictionary, and the generic messages across the interface. In this paper, which is based on the first HIPIN deliverable, some features of the technical design of the HIPIN interface also are discussed.

A Meta-analysis was performed on the data reported for observer performance studies comparing plain film and digital hard copy on lung interstitial disease and abnormalities of the bones of the extremities. Spatial resolutions from 512² to 4096² were included. It is concluded that spatial resolution alone is not the determinant of success in observer performance. It is quite possible that an optimum is approached between 1024² and 2048² and that further improvement in performance will depend upon improvements in gray scale rendition.

Teleworking refers to the usage of telecommunication facilities to improve human to human collaboration and enhance performance of work. This paper focuses on the way teleworking affects medicine. In particular, a teleworking platform is proposed to support multimedia medical applications embedded into RISC-based workstations. In order to support the teleworking platform, current commercially available products have to be taken into consideration and a range of new technologies need to be developed and made available. In this paper, we put emphasis on a RISC-based workstation, UNIX^TM operating system, communication protocols capable to support the teleworking platform, and ISDN network capabilities.

A software utility package designed to interface our picture archiving and communication system (PACS) to a Macintosh personal computer (PC) radiologist workstation is presented. The application MACPACS, developed to enable the low cost end-user to access a large-scale PACS, incorporates the following modules: a communication module for image retrieval; an interpretation module for translation of images to a format compatible with the tasks to be performed on the Macintosh; a display module (using the OSIRIS application program) for viewing and manipulating images as well as for the production of documents including images and text; and a module for storing images and reports. The low cost end-user can retrieve, view, manipulate, and store computed tomography (CT), magnetic resonance (MR), and computed radiography (CR) images from our PACS through our MACPACS application program and as a result can utilize our existing large-scale PACS without requiring an expensive display station.

We intend to design a 2K display station which can be used in most of the radiology sections. This paper describes how we collected the basic viewing requirements and defined the criteria for designing the 2K display station. Based on the design criteria, hardware components are selected and software modules are implemented. The hardware components in the display station consist of a SUN 470 computer, two 21' diagonal 2K MegaScan monitors, and a 2.6- Gbyte formatted storage concepts parallel transfer disk. The software modules include a communication software module, a local database module, a local storage management module, and an image display module. The station provides features such as dual-cine, region- of-interest, caliper measurement, image retrieval, and diagnostic report. Four stations have been used in genitourinary radiology, pediatric radiology in-patient and out-patient, and neuroradiology since January 1992. The stations are used for morning and afternoon radiology rounds and frequently for consultations between radiologists and clinicians.

Picture archival and communication (PACS) and teleradiology systems require workstations for image display, however not all clinical areas demand the same functionality and performance. Four workstations designed to fill different needs are compared to demonstrate the wide variation in functional requirements. In addition, the results of a survey conducted at InfoRad '92 during the 1992 annual meeting of the Radiological Society of North America are presented demonstrating that more than 90% of the respondents agreed that the two most important features of a workstation are the ability to review multiple studies for a patient at the same time and fast image display.

Large scale feature searches of accumulated collections of medical imagery are required for multiple purposes, including clinical studies, administrative planning, epidemiology, teaching, quality improvement, and research. To perform a feature search of large collections of medical imagery, one can either search text descriptors of the imagery in the collection (usually the interpretation), or (if the imagery is in digital format) the imagery itself. At our institution, text interpretations of medical imagery are all available in our VA Hospital Information System. These are downloaded daily into an off-line computer. The text descriptors of most medical imagery are usually formatted as free text, and so require a user friendly database search tool to make searches quick and easy for any user to design and execute. We are tailoring such a database search tool (Liveview), developed by one of the authors (Karshat). To further facilitate search construction, we are constructing (from our accumulated interpretation data) a dictionary of medical and radiological terms and synonyms. If the imagery database is digital, the imagery which the search discovers is easily retrieved from the computer archive. We describe our database search user interface, with examples, and compare the efficacy of computer assisted imagery searches from a clinical text database with manual searches. Our initial work on direct feature searches of digital medical imagery is outlined.

A Markov chain model is studied and evaluated in determining the retrieval rates of an analog film library and an electronic grayscale display system in an image management network (PACS). This model provides a reasonable representation of retrieval rates since Markov chains depend only upon the current and previous state of the chain. The model requires identification of the states of the chain, one-step transition probabilities between the states, and the initial probabilities of occurrence of the states. The use of the model is demonstrated with three examples. The results of the model are in agreement with measured data.

We have designed and implemented a distributed system that allows access to text and images that reside in the Teleradiology Archive, from any node in our local area network. The textual data is organized into an SQL database with an X Window based graphical user interface and images are stored in an optical disk. The archive is currently in use in various research projects within the department. Also, in collaboration with industry, it has been incorporated into a multimedia research and development system.

Not the least of the requirements of a workable PACS is the ability to store and archive vast amounts of information. A medium-size hospital will generate between 1 and 2 TBytes of data annually on a fully functional PACS. A high-speed image transmission network coupled with a comparably high-speed central data storage unit can make local memory and magnetic disks in the PACS workstations less critical and, in an extreme case, unnecessary. Under these circumstances, the capacity and performance of the central data storage subsystem and database is critical in determining the response time at the workstations, thus significantly affecting clinical acceptability. The central data storage subsystem not only needs to provide sufficient capacity to store about ten days worth of images (five days worth of new studies, and on the average, about one comparison study for each new study), but also supplies images to the requesting workstation in a timely fashion. The database must provide fast retrieval responses upon users' requests for images. This paper analyzes both advantages and disadvantages of multiple parallel transfer disks versus RAID disks for short-term central data storage subsystem, as well as optical disk jukebox versus digital recorder tape subsystem for long-term archive. Furthermore, an example high-performance cost-effective storage subsystem which integrates both the RAID disks and high-speed digital tape subsystem as a cost-effective PACS data storage/archival unit are presented.

Siemens Gammasonics and Loral Western Development Labs have conducted a series of discrete event simulation models to investigate and evaluate different design concepts of large picture archive and communication systems (PACS). The system model, the communication network model, and the workstation model were all initiated to be able to identify the most efficient system capable of supporting large, fully digital hospitals. Siemens and Loral have delivered the first systems. Continuing modeling activity explores opportunities to enhance the performance of the system by investigating new technologies, ideas and changes throughout the life cycle of the Siemens/Loral PACS. This paper describes the database modeling approach based on the validation of currently installed systems, the performance results, how to improve and tune the system under future data growth conditions with minimum costs, and how it fits in the overall Siemens/Loral Modeling Schema.

The full benefits of a PACS system cannot be achieved by a departmental system, as films must still be made to service referring physicians and clinics. Therefore, a full hospital PACS must provide workstations throughout the hospital which are connected to the central file server and database, but which present `clinical' views of radiological data. In contrast to the radiologist, the clinician needs to select examinations from a `patient list' which presents the results of his/her radiology referrals. The most important data for the clinician is the radiology report, which must be immediately available upon selection of the examination. The images themselves, perhaps with annotations provided by the reading radiologist, must also be available in a few seconds from selection. Furthermore, the ability to display radiologist selected relevant historical images along with the new examination is necessary in those instances where the radiologist felt that certain historical images were important in the interpretation and diagnosis of the patient. Therefore, views of the new and historical data along clinical lines, conference preparation features, and modality and body part specific selections are also required to successfully implement a full hospital PACS. This paper describes the concepts for image selection and presentation at PACS workstations, both `diagnostic' workstations within the radiology department and `clinical' workstations which support the rest of the hospital and outpatient clinics.

This paper describes a new approach for archiving and processing cath procedures in a hospital. An analog optical disc is utilized as a real time video storage device. Combined with powerful image capture and processing hardware and software, a real time image archiving and processing system is provided to the cath lab to record and replay cath procedures. It has been proved that the system provides better archive capability than that of cine film, and helps the doctor's diagnosis. The system requires lower level x ray dose. That means the patient and the cath team receive less exposure to x ray.

It is argued that in the design of a PACS archive in addition to the performance aspects in routine clinical use, the problems to be expected in undesirable circumstances need to be considered. In this paper the possibility to reconstruct the image database after a corruption and to convert the archive to a new storage medium are analyzed. Two different ways to organize the image database are considered: In the first set-up (A) the images are stored in historical sequence, as they are acquired. The storage facility is logically considered as a consecutive range of addresses, separation in volumes is neglected in the storage strategy. In the second set-up (B) the storage facility is considered as a set of volumes; images are assigned to volumes in such a way that in most cases all images of a patient will be found on the same volume. It is found that alternative B, that when looking at operational performance is preferable, has serious disadvantages over alternative A when recovery and conversion are considered. It seems recommendable to select the simple archive organization A and solve the inherent performance problem by applying a sophisticated system of prefetching.

Discrete event simulation is often used to predict the performance of PACS systems. Although detailed models can be developed for the system elements, the image generation workload assumptions can have a significant impact on the results. The selection of a source model is a crucial part of any simulation and should be representative of the real application. If the source model is improperly selected it is possible to reach misleading conclusions. Examples of source models that have been used for the image workload in PACS include Poisson, modulated Poisson, and bursty. In this paper we compare the use of different image generation models and the impact on system simulation results. The BONeS simulation package is used to define a PACS system consisting of medical imaging device sources and destinations (archives and displays) which exchange images over a network consisting of ethernet and token bus subnetworks. All parameters ar identically specified for each simulation experiment with the only difference being the type of traffic generator used. The results illustrate that use of a Poisson model results in an overly optimistic estimate of system behavior. An alternative model is proposed which defines imaging device traffic patterns in terms of bursts of images within `studies.' The parameter sensitivity of this model is also examined.

The Image Interchange Facility (IIF) is being developed by an ISO/IEC joint technical committee as part of the Image Processing and Interchange (IPI) Standard. The IIF has been designed with the goal of enabling data transfer between many imaging application domains. This work concentrates on the definition of a profile of the IIF tailored to the interchange of medical imaging data and capable of representing all of the information contained in ACR- NEMA files. The motivation for this work is to provide a translation facility between ACR- NEMA and the IIF in order to create a link from medical imaging networks to general purpose imaging facilities which use the IIF. Three cases were encountered in the definition of the profile: First, where possible, the work defines a mapping between ACR-NEMA elements and corresponding IIF structures. Second, the definition of the IIF syntax was restricted to eliminate those parts with no corresponding ACR-NEMA structure. Third, other parts of the IIF syntax were extended to enable domain specific data to be encapsulated.

In the European Standardization Committee (CEN), the technical committee responsible for the standardization activities in Medical Informatics (CEN TC 251), has agreed upon the directions of the scopes to follow in this field. They are described in the Directory of the European Standardization Requirements for Healthcare Informatics and Programme for the Development of Standards adopted on 02-28-1991 by CEN/TC 251 and approved by CEN/BT. Top-down objectives describe the common framework and items like terminology, security, more bottom up oriented items describe fields like medical imaging and multi-media. The draft standard is described; the general framework model and object oriented model; the interworking aspects, the relation to ISO standards, and the DICOM proposal. This paper also focuses on all the boundaries in the standardization work, which are also influencing the standardization process.

The ACR-NEMA 2.0 standard has made important strides toward providing a manufacturer- independent interconnection for PACS systems. The DICOM standard now in preparation takes an object-oriented approach to design of software protocols for data base query and image exchange. We have developed an object-oriented class library for accessing an ACR- NEMA 2.0 data dictionary and building ACR-NEMA formatted messages. The library, implemented in both Smalltalk/V and being implemented in C++, provides access to the entire ACR-NEMA 2.0 Data Dictionary and allows a program written in either language to ascertain required fields in messages, default values and allowable values of enumerated value elements. The design of the class hierarchies in the data dictionary is discussed in terms of the ACR-NEMA 2.0 standard and the integration of this design into the DICOM standard. Building a sample SEND_REQUEST message for image transfer is illustrated.

Picker MR images were translated to the Bowman Gray School of Medicine (BGSM) IMACS format using software designed for portability to other modalities. The Siemens PET modality was the first successful test of the software's extensibility. Although the Picker project took nine months to complete, the Siemens project took only about two months. The structures of the Siemens PET images are organized utilizing software constructs which made the translation even easier. In addition, the Siemens PET system used standard Unix workstations with the Network File System (NFS), TCP/IP, and X Windows which greatly facilitated the transport of images. The translation of GE 9800 CT modality images, using a PBT interface allowed images to be sent to the 9-track archive system or the network using a state of the art NFS mount. This permitted using many powerful tools available on most Unix machines such as the qsh software developed by Gerald Q. Maguire Jr. and Marilyn E. Noz for the translation of various modalities into their DICOM-based key-value-pair system. This provided a mechanism for modality data base translation. In this way, it is hoped that modality images can be sent effectively to our IMACS. This paper discusses the transmission and conversion of modality database entries (images and demographics) into the BGSM DICOM format.

The American College of Radiology (ACR) and the National Electrical Manufacturers Association (NEMA) are defining the Digital Imaging and Communications in Medicine (DICOM) V3.0 Standard. Previous authors have investigated the performance of the ACR- NEMA V1.0 and V2.0 Standards in point to point and network applications. This paper describes an early implementation of a subset of the DICOM V3.0 Standard and presents performance results for a combination of workstation types and network technologies.

In creating a higher level ethernet model the important effects of the ethernet bus on a PACS system must be taken into consideration. These effects include the delay in time between the submission of an image for transmission and the time the last packet arrives at the receiving node, and the retransmission of packets due to collisions. A good image-level model should approximate the statistical characteristics of the image delay over a range of network loading. It should also predict the number of packets which will require retransmission and the statistical characteristics of this effect over a range of loading. This paper describes the approach used to create such a model and compares the results obtained when using the BONeS model at the packet and image levels. It is shown that the approximate image-level ethernet model is much faster than the packet-level simulation while also providing accurate results. The impact of packet loading time on ethernet fairness is also discussed.

The American College of Radiology (ACR) and the National Electrical Manufacturing Association (NEMA) in 1982 formed the ACR-NEMA committee to develop a standard to enable equipment from different vendors to communicate and participate in a picture archiving and communications system (PACS). The standard focused mostly on interconnectivity issues and communication needs of PACS. It was patterned after the international standards organization open systems interconnection (ISO/OSI) reference model. Three versions of the standard appeared, evolving from simple point-to-point specification of connection between two medical devices to a complex standard of a network environment. However, fast changes in network software and hardware technologies makes it difficult for the standard to keep pace. This paper compares two versions of the ACR-NEMA standard and then describes a system that is used at the University of Arizona Intensive Care Unit. In this system, the application should specify the interface to network services and grade of service required. These provisions are suggested to make the application independent from evolving network technology and support true open systems.

Medical network traffic is characterized by the mix of modalities and applications on the network. Since different modalities or applications have different characteristics on the network, understanding the mix of traffic loads is important in analyzing network activity. Although many commercial products can analyze network traffic at the packet level, they do not capture higher level modality load characteristics or isolate the impact of large image transfers. More insight can be obtained through a high-level analysis of this packet data in which network traffic is examined at an application level. In this paper we report on data collection and analysis of medical network traffic over a local area network. The measurements of the LAN are made using a raw ethernet packet capture program (tcpdump) running on a Sun workstation, and the analysis was accomplished using a PERL script and the ACE/gr data analysis program. The contribution of each modality is isolated and the network protocol performance is examined in detail.

Many existing local area networking protocols currently applied in medical imaging were originally designed for relatively low-speed, low-volume networking. These protocols utilize small packet sizes appropriate for text based communication. Local area networks of this type typically provide raw bandwidth under 125 MHz. These older network technologies are not optimized for the low delay, high data traffic environment of a totally digital radiology department. Some current implementations use point-to-point links when greater bandwidth is required. However, the use of point-to-point communications for a total digital radiology department network presents many disadvantages. This paper describes work on an experimental multi-access local area network called XFT. The work includes the protocol specification, and the design and implementation of network interface hardware and software. The protocol specifies the Physical and Data Link layers (OSI layers 1 & 2) for a fiber-optic based token ring providing a raw bandwidth of 500 MHz. The protocol design and implementation of the XFT interface hardware includes many features to optimize image transfer and provide flexibility for additional future enhancements which include: a modular hardware design supporting easy portability to a variety of host system buses, a versatile message buffer design providing 16 MB of memory, and the capability to extend the raw bandwidth of the network to 3.0 GHz.

In the frame of the EC-sponsored TELEMED project, remote expert consultation in radiology has been developed and implemented. This environment has been established as a pan- European demonstrator for advanced telecommunication applications in medicine. Five European university hospitals have been interconnected using broadband networks from 2 Mbit/s to 140 Mbit/s. Videoconference was introduced and evaluated in more than 120 sessions. In the experiments, videoconference proved to be a useful tool for teleconsultations, providing a number of requirements identified as indispensable for medical videoconference such as remotely adjustable iris for the document camera are fulfilled.

A dial-up teleconferencing network was implemented between three radiologic educational sites for a 30-day period of evaluation. By means of standard T-1 telephone channels, compressed video and audio signals displayed radiologic images, slides and text, allowing residents and faculty from the three sites to participate in visual and auditory interactions. Each site used compressed video/audio codecs conforming to the Comite Consultatif International de Telegraphique et Telephonique (CCITT) H.261 standard. Four video cameras were used at each site and the audio was run in full duplex mode. A multipoint video bridge was used to telecast codec output signals to the input lines of the other codecs. Although audio quality and spatial resolution need to be improved, the results of this pilot study imply that compressed video conferencing has the potential to become a practical, cost-effective method of sharing educational resources by means of interactive radiologic multisite educational programs.

A global PACS is a national network which interconnects several PACS networks at medical and hospital complexes using a national backbone network. A global PACS environment enables new and beneficial operations between radiologists and physicians, when they are located in different geographical locations. This paper presents three user scenarios which enable remote consultation and diagnosis between radiologists at a local PACS site and a remote PACS site. One scenario, called remote consultation, allows the radiologist to view the same image folder at both local and remote sites so that a diagnosis can be performed. We present performance date based on tests between these two sites and show the feasibility of the operation in a global PACS environment. Future improvements to the system will include real- time voice and interactive compressed video scenarios. This work is sponsored by the National Science Foundation and Toshiba Medical Systems Division.

This paper presents a new medical communication service which supports consultation procedures in the modern tele-radiology. The system's perspectives and requirements are studied and analyzed by considering an interactive communication environment, which consists of geographically distributed entities working together and channels for either synchronous or asynchronous inter-communication.

A multimodality image manipulation and analysis software called OSIRIS was developed at the University Hospital of Geneva. This software package is currently used on different hardware platforms as part of a hospital-wide PACS project. An extension of this software was recently designed to allow cooperative work on remotely located workstations. This extension was developed to allow remote consultations and communications between physicians over local and wide area networks. For teleradiology and cooperative consultations, images are exchanged between the different workstations in an ACR-NEMA based format called PAPYRUS. The interactive session can then take place where the communication protocol between the two remote stations allows for simultaneous manipulation of the same images and a live conversation through a vocal link. A special communication protocol was developed to transmit the different actions performed on one station to the other. The lower level communication protocol is TCP-IP. In addition to the local usage in Geneva, this platform was also adopted as part of a European teleradiology project called TELEMED, regrouping 17 partners from 9 different countries. It is being tested on international broadband networks for remote consultations between different countries in Europe.

A pan-European telemedicine environment has been established in the frame of the EC- sponsored TELEMED project. Remote expert consultation in radiology using digital image communication has been developed and implemented as a demonstrator for advanced telecommunication applications in medicine. Eight European university hospitals have been interconnected using 384 kbit/s ISDN and 2 Mbit/s broadband networks. A set of requirements was derived and software for image and text communication, for image display and manipulation and for synchronization of remote workstations was developed. The benefits of digital image communication were demonstrated in evaluation experiments.

Existing teleradiology systems rely almost exclusively on frame-grabbed images from a video source to input data from a variety of modalities. This report details implementation of a teleradiology system which uses an ACR-NEMA gateway to access imagery from a variety of modalities with the full dynamic range of the original data. Such a system allows the user to use the full capability of window and level control to adjust the gray level of the resulting display. The penalty is that since most teleradiology systems transfer 8-bit data and most existing ACR-NEMA modalities transfer 12-bit data in a 16-bit pixel format, transmission times are potentially longer. This may be addressed to some extent with more sophisticated data compression. Ultimately the availability of faster telecommunications services to remote locations such as a radiologist's home will provide a better solution.

The paper gives an overview of the important components of multi-media developments, their impact and relation to PACS system developments, focusing on media integration, data-base interaction, and open-system needs. An example for voice management is given, allowing primitive multi-media communication.

In the EC project TELEMED (R1086) the feasibility of digital image communication for remote expert consultation in radiology is investigated. For a comprehensive evaluation, an international multicenter communication study has been developed. Forty radiologists from eight European university hospitals participate in this study as `experts.' Matching the fields of expertise offered by these experts, about 200 test cases have been prepared to be discussed during consultation sessions between experts and non-experts. Consultation sessions are supported by dedicated hardware and software as well as a variety of different network connections (2 Mbit/s terrestrial, 2 Mbit/s satellite, 384 kbit/s ISDN). Evaluation is performed to answer questions of applicability of teleconsultation for different types of radiological images and cases, the participants' attitude towards and benefits from teleconsultation, the impact of the technical environment and functional features for routine application.

Teleradiology systems are being developed and implemented around the world. The ultimate success of these systems depends on the acceptance by the end users -- the physicians. From a physician's perspective, several major areas need to be addressed in the ideal situation. The areas include (1) image quality and ease of manipulation of images on a workstation; (2) expert interpretation by a specialist or sub-specialist; (3) good communication between the radiologist, radiology technologist, primary care physician, and the patient; (4) accessibility to images; (5) system reliability; (6) costs and assistance in balancing workloads; and (7) education and research. The Medical Diagnostic Imaging Support (MDIS) System is a large tri-service project to install picture archive and communication systems (PACS) and teleradiology at military medical treatment facilities across the United States and abroad. The first sites primarily involved with teleradiology will be installed in the summer of 1993. Ways in which the MDIS teleradiology system address the physicians' ideal configuration as well as possible future improvements are discussed.

The Medical Diagnostic Imaging Support (MDIS) System is a four-year contract to install large-scale picture archival and communications systems (PACS) and teleradiology in Army and Air Force medical treatment facilities. MDIS specifications were based on the results of three years of tri-service research and development through the Digital Imaging Network Systems Project and the Tactical Air Command Teleradiology Project. At the time of the government's request for proposals, MDIS functional specifications represented the most comprehensive understanding of the requirements for large-scale PACS and teleradiology complied by a composite team of radiologists, physicists, clinical engineers, hospital administrators, technologists, and computer systems engineers. As MDIS sites become operational, a better understanding of the capabilities and limitations of teleradiology is emerging. This paper reviews functions and subsystems common to all teleradiology systems, MDIS specifications for teleradiology, installation planning, and the status of Army and Air Force Teleradiology with special emphasis on early installations that validate routine teleradiology operations.

We present a practical software-based architecture for a low-cost distributed modular image management to support a range of teleradiology applications. In addition, an implementation for this architecture is proposed which would use `object-oriented' messages to communicate between functional processes. Applications may register interest in certain types of messages, and whether they wish to observe messages or handle (respond) to queries. This loose coupling allows individual functions and services to be separated into many small modular processes, thus simplifying the interface and accelerating application development. This type of standardized message interface allows messages to be sent without knowing the details of network locations or service implementations, and in turn allows new technology or services to be accommodated through standardized interchangeable software modules. With both static (compile time) and run-time object definitions possible, on-line extensibility is assured. The advantages of this approach are that it: (1) facilitates different methods of file archive and image transfer, (2) allows the integration of legacy or commercial hardware and software through encapsulation, and (3) is adaptable and scalable to a wide range of site resources, capabilities and needs.

The increasing backbone speeds of Wide Area Networks, along with the growing numbers of users of these networks, have created an opportunity for the development of remotely accessible and highly data-intensive digital libraries. The National Library of Medicine is building a prototype system for the storage of several thousand digital x-ray images, while providing remote access to these images across the Internet. This paper discusses the design factors analyzed for this system, and presents performance statistics collected. The design factors considered include: network protocol selection, endpoint tuning of protocol, image compression, and application data handling. Research toward application data handling includes plans to stage groups of images from an optical archive to memory for the efficient transmission of large numbers of images. To maximize image data transmission speed, experimental protocols are being studied as alternatives to TCP/IP. TCP overhead processing is being researched, and approaches to tuning TCP performance for transmission of large image files are being analyzed. To minimize the storage capacity required and to decrease transmission time, lossy compression techniques are being considered. Research is proceeding toward the selection of a compression technique and optimum compression ratio consistent with the image quality required to produce standardized readings.

Off-hour operations of the modern emergency room presents a challenge to conventional image management systems. To assess the utility of intrahospital teleradiology systems from the emergency room (ER), we installed a high-resolution film digitizer which was interfaced to a central archive and to a workstation at the main reading room. The system was designed to allow for digitization of images as soon as the films were processed. Digitized images were autorouted to both destinations, and digitized images could be laser printed (if desired). Almost real time interpretations of nonselected cases were performed at both locations (conventional film in the ER and a workstation in the main reading room), and an analysis of disagreements was performed. Our results demonstrate that in spite of a `significant' difference in reporting, `clinically significant differences' were found in less than 5% of cases. Folder management issues, preprocessing, image orientation, and setting reasonable lookup tables for display were identified as the main limitations to the systems' routine use in a busy environment. The main limitation of the conventional film was the identification of subtle abnormalities in the bright regions of the film. Once identified on either system (conventional film or soft display), all abnormalities were visible and detectable on both display modalities.

Although several studies have demonstrated the feasibility of teleradiology its cost- effectiveness has not yet been proven but is a prerequisite for wide acceptance and routine use in the medical environment. Thus, our aim is to develop a tool for cost-effectiveness analysis of radiological remote expert consultation and other teleradiological applications. The overall objective of the cost-effectiveness analysis tool is to provide the user with a detailed and comprehensive overview on the costs and benefits associated with the teleradiological application under consideration. A recommendation on the cost-effectiveness of a particular application should be given, and, if possible, an identification of superior alternative(s). The tool comprises several modules for data input, cost analysis, analysis of benefits, cost- effectiveness evaluation, and sensitivity analysis. It is applied in the EC project TELEMED (R1086) for the economic assessment of the pan-European teleradiological application pilot `Remote Expert Consultation.' Simulating costs and benefits of these and other teleradiology applications yields essential information for future routine use of teleradiology.

A PACS system has been implemented at the University of Florida that has eliminated the use of film in Nuclear Medicine. Six acquisition devices, four display devices, three paper printers, and a digital archive comprise the system. Nuclear Medicine images are viewed on display workstations for diagnosis and are printed in color on paper to be placed in the patient's folder or sent to referring physicians. An interface to the medical center's on-line medical records checks the demographic information stored with the images for accurate spelling of the patient's name, valid patient identification number, and ties the study to the radiology information system order (accession) number. The database used for the on-line medical record and for the Nuclear Medicine PACS system is ORACLE. The archive consists of 4 GBytes of mirrored magnetic disk (essentially 2 GBytes of accessible disk), 8 GBytes of non-mirrored magnetic storage, and a tape jukebox with 50 GByte capacity.

An economical and practical digital solution for the replacement of 35 mm cine film as the archive media in the cardiac x-ray imaging environment has remained lacking to date due to the demanding requirements of high capacity, high acquisition rate, high transfer rate, and a need for application in a distributed environment. A clinical digital image library and network based on the D2 digital video format has been installed in the Duke University Cardiac Catheterization Laboratory. The system architecture includes a central image library with digital video recorders and robotic tape retrieval, three acquisition stations, and remote review stations connected via a serial image network. The library has a capacity for over 20,000 Gigabytes of uncompressed image data, equivalent to records for approximately 20,000 patients. Image acquisition in the clinical laboratories is via a real-time digital interface between the digital angiography system and a local digital recorder. Images are transferred to the library over the serial network at a rate of 14.3 Mbytes/sec and permanently stored for later review. The image library and network are currently undergoing a clinical comparison with cine film for visual and quantitative assessment of coronary artery disease. At the conclusion of the evaluation, the configuration will be expanded to include four additional catheterization laboratories and remote review stations throughout the hospital.

In this paper we have present data from pilot studies to estimate the impact on patient care of an intensive care unit display station. The data were collected during two separate one-month periods in 1992. We compared these two different periods in terms of the relative speeds with which images were first viewed by MICU physicians. First, we found that images for routine chest radiographs (CXRs) are viewed by a greater number of physicians and slightly sooner with the PACS display station operating in the MICU than when it is not. Thus, for routine exams, PACS provide the potential for shortening of time intervals between exam completions and image-based clinical actions. A second finding is that the use of the display station for viewing non-routine CXRs is strongly influenced by the speed with which films are digitized. Hence, if film digitization is not rapid, the presence of a MICU display station is unlikely to contribute to a shortening of time intervals between exam completions and image-based clinical actions. This finding supports the use of computed radiography for CXRs in an intensive care unit.

The hospital-wide PACS installation at Hammersmith Hospital is the subject of an independent technology evaluation exercise. This paper focuses on one aspect of the evaluation: the assessment of the impact of PACS on the performance of the radiology department in the intensive care unit (ICU). A quasi-experimental before and after research design has been adopted and initial baseline measurements have been undertaken of the time intervals between the various events from the radiograph request to the initiation of a subsequent clinical action. The results presented suggest that the radiology department at Hammersmith is currently performing well with an interval of about 10 minutes from the radiograph being taken to it being available for viewing in the ICU for non-routine radiographs (taken after 11.00 and before 9.00). The main findings from this study to date relate to the appropriateness of the research methods used, given the disappointing response rates for specific variables, and thus the potential for bias in the results obtained.

The MDIS acceptance test is the government evaluation of the MDIS system availability, performance, and functionality. The test is performed over a period of 30 days and is composed of three test scenarios which are: (1) System/component availability test, (2) component performance test, and (3) system integration test. A test protocol describes each test in detail, as well as describing the actions of the vendor and test teams during the test period. Fifty-six test modules were derived directly from the performance criteria specified in the MDIS contract. These test modules are used by the test team members to evaluate the MDIS system. A database is used to compile the results of the acceptance test for management and comparison of multiple MDIS site results.

In the Accident and Emergency Department (A&E) x-ray images are used to assist in the initial diagnosis and management of the patient. It is therefore expected that the main benefits of PACS in A&E will arise from the ability of clinicians to manipulate the digital image and thus potentially improve their diagnostic performance. In order to evaluate whether this benefit is realized or not a case-study evaluation has been undertaken; this has three components: (a) monitoring the extent of misdiagnosis by A&E clinicians before and after the PACS implementation; (b) an examination of the decision performance of the clinician-image combination for the visualization of the lower cervical spine/upper thoracic spine and of fracture of the head of the radius; and (c) a more general monitoring of the impact of the image archiving and communication aspects of PACS. In this paper the study of the impact of PACS on misdiagnosis by A&E clinicians at the Hammersmith Hospital, London, is described and pre-PACS results for the period 31 March 1992 to 30 September 1992 are presented.

The Medical Diagnostic Imaging Support System (MDIS) is a project to install PACS systems at several medical sites in the military. The configuration calls for links to nuclear medicine in the near future but to date no definite system has been devised. This presentation describes a scenario in which a nuclear medicine department acts as a mini-PACS system with a direct link to the larger parent PACS system. The advantage of this approach is that it allows greater specialization at the workstation than is presently configured into the MDIS PACS system. Also large data sets can be reviewed and manipulated without slowing down the flow of images in the parent PACS. Only processed and formatted images are sent to the parent PACS system. Several problems exist in interfacing a nuclear medicine service with the MDIS PACS system and these are discussed.

There are no existing instruments which can be used to investigate users' subjective valuations of radiology services or the amount of time spent in obtaining and using radiological images. The development and use of an instrument to assess these two variables is described.

This paper describes a software communication architecture for medical imaging services. This work aims to provide to the physician the communication facilities to access and track a patient's record or to retrieve medical images from a remote database. The proposed architecture is comprised of a communication protocol and an application programming interface (API). The implemented protocol, namely the Telemedicine Network Services (TNS) protocol, has been designed in agreement with Open System Interconnection (OSI) upper layer protocols already standardized. Based on this concept an OSI-like interface has been developed capable of providing application services to the application developer, and thus facilitating the writing of medical application. TNS protocol has been implemented on top of TCP/IP communication protocols, by implementing OSI presentation and application services on top of the Transport Service Access Point (TSAP) which is provided by the socket abstraction on top of the TCP.

This paper describes current research in picture archiving and communications system (PACS). A PACS has been developed and implemented using a new approach. The standards TCP/IP (Transmission Control Protocol/Internet Protocol), SQL (Structured Query Language) and X Windows System are the basic elements. Our PACS consists of four major components: display stations, a supervisor, a relational database server and image servers. These components are connected through a communication network. Users on a display station can perform a query for both images and text data, using the SQL-IE query language we developed in this project. The SQL-IE (SQL Image Extension) language is an extension to the standard SQL language and gives users the possibility to display images. Images are stored in a distributed image database. The text data and information related to the images are stored in a central relational database. A general communication interface with a database server has been developed. We designed a supervisor to manage the complete PACS. The TCP/IP is used for communication. A user interface for PACS has been implemented based on the X Windows System. Some performance measurements have been carried out and a brief discussion of these is presented.

One of the aims of the EC subsidized project EurIPACS, is to provide evidence for cost- effectiveness of PACS. To this aim, assessment studies are carried out in three hospitals. These hospitals all implement a partial and/or small-scale PACSystem in the period 1992- 1994. In order to be able to compare the data of the assessments, and to facilitate generation of guidelines, each of the three hospitals uses the same evaluation protocol. This paper describes this evaluation protocol.

Lung cancer cell nuclei light microscopic image storing was performed in a computer database as a 32 bit number in 96 patients operated on for lung cancer in order to characterize the differences among various histological forms, to find out the nuclear feature combinations for them, and to divide the existing heterogeneous cell population into subpopulations displaying variable morphology and sensitivity to anticancer agents.

The accurate prediction of image throughput and delay is a critical issue in planning for and acquisition of any successful picture archiving and communication system (PACS). Bottlenecks or design flaws can render an expensive PACS implementation useless. This manuscript presents methods for predicting and measuring the end-to-end mean delay time (image generation to image display) of a PACS design with successively greater level of resolving power: (1) mean value analysis, (2) Jackson queuing models and (3) computer simulation using the block oriented network simulator (BONeS).

Advances in image processing techniques, databases, workstations, network technologies and communication systems have created great interest in the integration of heterogeneous collections of multimedia data. The success of a medical multimedia information system depends on integration of distributed heterogeneous PACS, RIS and HIS, to provide rapid access to patients' text and image information throughout a hospital. The work presented here adapts a distributed database (DDB) approach to integrating HIS, RIS and PACS in a distributed heterogeneous environment. It is based on previous work on integrating structured (relational) database systems using the `Multidatabase' approach. Integrating distributed heterogeneous HIS/RIS/PACS causes special problems. Two alternative architectural proposals for providing system support to integrate heterogeneous HIS/RIS and PACS in a distributed environment are presented and discussed. One of these architectures provides system support by using a distributed index approach, where the images indexes are held at the local sites. The second proposed architecture uses a global image index. In this approach the global image index provides the list of available images within the network. Advantages and disadvantages of each approach are also discussed.

This paper describes the Center for Imaging Systems Optimization's (CISO) initial efforts to develop a query system that will enhance medical image archive retrieval. As medical archive systems become more commonplace, it is important to examine the system architecture, associate data types, and query support required to effectively take advantage of these systems. Our implementation is a federated system of a relational database, textual database, and image server. The architecture is based on a client-server, extended relational data model. Access is possible through an X window compatible query interface. The data scheme is based on inclusive divisions of the data by patient, study, series, and images. These support patient history, study diagnosis, series protocols, and image observations. This scheme defines four tables in the relational database and four text fields. Acquired images are stored in the image archive, while associated header data is mapped into the relational tables. Dictated readings and other textual information is added and indexed to the image as it is acquired. This system supports a wide range of ad hoc queries based on any or all of the four data categories.

The RSNA's involvement with computerized communications and electronic technology has grown rapidly over the past decade. We recommend the further liaison with SPIE for it fits perfectly with the charge to our Electronic Communications Committee which is, simply stated, to keep the medical specialty of radiology on the cutting edge of electronic communications. A point of history is probably important to note at this time to help explain our involvement. And, to quote one of my favorite educators from college, it is often as important to tell your audience "what not" as it is to explain "what is".

Over the past 10 years, a large number of devoted individuals have worked on a project to develop a standard for the storage and exchange of medical images. Known as the ACR/NEMA standardization effort, this project is jointly sponsored by the American College of Radiology (ACR) and the National Electrical Manufacturers Association (NEMA). Over the years, radiologists and industry representatives alike have supported the standardization effort, but there has been little evidence of actual exchanges of medical images among medical equipment vendors who use the ACR/NEMA standard.

Researchers around the world are developing computer workstations designed to enable radiologists to display and process radiologic images in a single integrated environment. For the first time in 1992, the RSNA Electronic Communications Committee sponsored an infoRAD Workstation Exhibit at RSNA '92, the scientific assembly and annual meeting of the Radiological Society of North America. The purpose of the exhibit was to demonstrate new developments in workstations to attendees of RSNA '92, to offer hands-on experience with a variety of workstation functionalities and user interfaces, and to provide a hands-on refresher course on workstations. The infoRAD workstation exhibit was a noncommercial, educational exhibit comprised of 12 workstation exhibits designed by university-affiliated researchers. Each exhibitor had the opportunity to lecture about his or her research in one of the theaters set up in the infoRAD exhibit area. A questionnaire was distributed to attendees to assess the value of the workstation exhibits.

Ever since 1990, the National Library of Medicine (NLM) has displayed a software program in the infoRAD learning center at RSNA's annual meeting that enables literature searches through the NLM's database. Called GrateFul Med, the software program is a user-friendly front-end program used for searching the NLM's on-line databases.

InfoRAD, a term that stands for informatics in radiology, is a demonstration and learning area set up every year at RSNA's Scientific Assembly and Annual Meeting to showcase applications of computers and other electronic tools in radiologic education, information management, and quality assurance. The learning center had its origins in 1986 when the RSNA Board of Directors established the Electronic Communications Committee (ECC) to study the potential uses of electronics in the practice of radiology. At the 1987 scientific assembly, Anne G. Osborn, MD, from the University of Utah, exhibited a computer-based teaching module in neuroanatomy concerning the sella turcica. This popular scientific exhibit used an interactive videodisc that allowed viewers to choose options displayed on a monitor by touching the screen.

In the health-care industry, medical imaging represents the largest potential application of broadband telecommunications technology. Health care is, of course, an enormous industry that today consumes about 13 % of the nation's gross national product (GNP). Competition in health care is based on service. Patients demand convenient access to medical facilities and prefer outpatient treatment. To facilitate easy access and outpatient care, the health-care industry needs an electronic infrastructure that provides both intraconnectivty and interconnectivity. Electronic local area networks allow imaging equipment to be intraconnected within hospitals and clinics. However, as health- care organizations set up facilities scattered throughout an urban or rural area, such as satellite hospitals, outpatient clinics, health maintenance organizations, and physician offices, these sites need to be electronically interconnected as well. Interconnection can link a specialist in the city with a patient in a rural area, at a military site, in a retirement village, or at a distant hospital or clinic. The infrastructure that provides interconnectivity is based on broadband telecommunications technology, such as frame relay, broadband ISDN (integrated services digital network), SONET/SDH (synchronous optical network/synchronous digital hierarchy), and ATM (asynchronous transfer mode) switches.