For films produced by digital imaging modalities such as CR, CT, and MR, non-linear pixel value look-up tables can be used to present images in a format that is well matched to human visual perception. The use of nonlinear look-up tables typically allows selected elements of dynamic range to be emphasized or de-emphasized within the constraints of the film characteristics. The resulting films may contain more diagnostic information than is achievable using linear look-up tables, thus allowing assessment of individual image features within the overall image context, often without the need for localized adjustment of contrast. Similar benefits may be achievable for softcopy display of digital images from digital modalities such as CT, MR and digital fluoroscopy as well as CR, digitized analog films and mammography images through the implementation of non-linear look-up tables for softcopy image display. A research project based upon the implementation of non-linear display functions within diagnostic-quality PACS workstations is described. A modular, open-architecture application has been implemented to facilitate development and clinical assessment of non-linear display functions and fifteen `standard' non-linear display functions for CR images have thus far been implemented and imbedded into a UNIX-based PACS workstation by means of this application. In addition, a monitor compensation function has been developed to more closely match the characteristics of softcopy image display to those of film. A data histogram feature has also been implemented and a user interface developed to allow viewing of histograms as well as interactive modification of tonal transfer function parameters. The scope of this project also included a preliminary assessment of the diagnostic improvements to radiologic workstations that employ these capabilities.

With the increase in the volume and distribution of images and text available in PACS and medical electronic health-care environments it becomes increasingly important to maintain indexes that summarize the content of these multi-media documents. Such indices are necessary to quickly locate relevant patient cases for research, patient management, and teaching. The goal of this project is to develop an intelligent document retrieval system that allows researchers to request for patient cases based on document content. Thus we wish to retrieve patient cases from electronic information archives that could include a combined specification of patient demographics, low level radiologic findings (size, shape, number), intermediate-level radiologic findings (e.g., atelectasis, infiltrates, etc.) and/or high-level pathology constraints (e.g., well-differentiated small cell carcinoma). The cases could be distributed among multiple heterogeneous databases such as PACS, RIS, and HIS. Content- based retrieval systems go beyond the capabilities of simple key-word or string-based retrieval matching systems. These systems require a knowledge base to comprehend the generality/specificity of a concept (thus knowing the subclasses or related concepts to a given concept) and knowledge of the various string representations for each concept (i.e., synonyms, lexical variants, etc.). We have previously reported on a data integration mediation layer that allows transparent access to multiple heterogeneous distributed medical databases (HIS, RIS, and PACS). The data access layer of our architecture currently has limited query processing capabilities. Given a patient hospital identification number, the access mediation layer collects all documents in RIS and HIS and returns this information to a specified workstation location. In this paper we report on our efforts to extend the query processing capabilities of the system by creation of custom query interfaces, an intelligent query processing engine, and a document-content index that can be generated automatically (i.e., no manual authoring or changes to the normal clinical protocols).

Digital imaging is an evolving technology with significant potential for enhancing medical education and practice. Current teaching methodologies still rely on the time-honored traditions of group lectures, small group discussions, and clinical preceptorships. Educational content and value are variable. Utilization of electronic media is in its infancy but offers significant potential for enhancing if not replacing current teaching methodologies. This report details our experience with the creation of an interactive atlas on neonatal surgical conditions. The photographic atlas has been one of the classic tools of practice, reference, and especially of education in surgery. The major limitations on current atlases all stem from the fact that they are produced in book form. The limiting factors in the inclusion of large numbers of images in these volumes include the desire to limit the physical size of the book and the costs associated with high quality color reproduction of print images. The structure of the atlases usually makes them reference tools, rather than teaching tools. We have digitized a large number of clinical images dealing with the diagnosis and surgical management of all of the most common neonatal surgical conditions. The flexibility of the computer presentation environment allows the images to be organized in a number of different ways. In addition to a standard captioned atlas, the user may choose to review case histories of several of the more common conditions in neonates, complete with presenting conditions, imaging studies, surgery and pathology. Use of the computer offers the ability to choose multiple views of the images, including comparison views and transparent overlays that point out important anatomical and histopathological structures, and the ability to perform user self-tests. This atlas thus takes advantage of several aspects of data management unique to computerized digital imaging, particularly the ability to combine all aspects of medical imaging related to a single case for easy retrieval. This facet unique to digital imaging makes it the obvious choice for new methods of teaching such complex subjects as the clinical management of neonatal surgical conditions. We anticipate that many more subjects in the surgical, pathologic, and radiologic realms will eventually be presented in a similar manner.

Despite over a decade of development, diagnostic radiology workstations have not gained popular acceptance by radiologists. Among the requirements for a clinically acceptable workstation are good image quality, a well designed user-interface, and access to ancillary diagnostic information. The user-interface should reflect radiologists' film reading habits and encourage new reading methods that take advantage of the electronic environment. We documented neuroradiologists' reading habits and used software engineering tools to design interfaces that could provide rapid access to common diagnostic tasks in neuroradiology. We used an embedded configuration tool to prototype layouts for specific clinical cases on a commercial workstation, and database integration and user-interface design tools to develop interfaces for browsing medical records. We then designed an image presentation model using the concept of a `virtual view box' for the rapid browsing and pairwise comparison of images. We used the interface design tools to prototype the `virtual view box' on commercially available hardware and tested it with experienced neuroradiologists.

In a PACS environment, multimedia information is archived and stored. Although PACS has been successfully providing clinical services to radiologists through diagnostic-quality viewing workstations, the expanse of this information has rarely been readily and easily accessible to radiologists after clinical diagnosis and review. It undermines undoubtedly the power and capability of the PACS system, and also creates significant inconveniences and impacts in the teaching and research activities which are often a very vital part in an academic institution. To accommodate these drawbacks, we, at the University of California, San Francisco (UCSF), have developed a pilot project to allow PACS imagery and textual data to be easily transferred and accessed by radiologists in their office. The process of retrieving PACS data should require minimum effort from radiologists and should be cost effective. With these objectives in mind, this paper describes the design and mechanism for a low-cost and easy access system to PACS.

We present a novel image navigation methodology for PACS viewing stations to handle very high volume studies efficiently. This methodology is based on the `customizable folder' concept in which a scaleable electronic worklist is formulated according to the prefetching algorithm based on radiologist's preference and the `virtual panel' concept which provides a virtually unlimited screen space on the station. Furthermore, the `moving strips paradigm' is presented to serve as an efficient `browsing' method to allow rapid and random access to a selection of studies and a `pre-handing procedure' during the formation of an electronic worklist. Finally, the advantages and applications of such methodology are presented.

This paper proposes a multi-decision-tree induction (MDTI) approach to image prehanging and discusses how it can facilitate knowledge acquisition and maintenance through the induction of knowledge embedded in radiological image reading cases which have the characteristics of inconsistent retrievals, incomplete input information, and multiple decision outcome classes. We present empirical comparisons of the MDTI approach with backpropagation network algorithm, and the traditional knowledge acquisition approach using the same set of cases in terms of the recall rate, the precision rate, the average number of prior examinations suggested, understandability of the acquired knowledge, and the required learning time. The results show that the MDTI approach outperforms the backpropagation network algorithm in all performance measures studied.

Existing picture archiving and communication systems (PACS) lack intelligence in managing radiologic images distributed throughout individual PACS components (i.e. the acquisition, archive, and display subsystems), resulting in inefficient access to images. A multi-level storage system within our departmental PACS has been developed which minimizes access time for both current and historical images. The storage management system is based on a composite staging mechanism utilizing multiple storage media: redundant array of inexpensive disks (RAID), magnetic disks, erasable magneto-optical disks, and write-once-read-many (WORM) optical disks. Three levels of access to images at display stations are provided: (1) immediate access to both current and selected historical images via local RAID disks, (2) fast retrieval of images from archive subsystem's cache magnetic disks, and (3) retrieval of any historical images from long-term archive's magneto-optical disks and WORM disks. Mechanisms implemented in the system include: image routing, image stacking, image aging, HIS/RIS/PACS interfacing, image pre-fetching, studies grouping, and platter management. The storage management system for our distributed PACS was evaluated in terms of image access time at the display stations. With its multi-level storage architecture, the system demonstrated a 70% improvement in image access time compared with a centralized storage system. We conclude that fast access to radiologic images in PACS can be achieved through a well-designed, multi-level storage architecture.

Along with the digital radiology environment supported by picture archiving and communication systems (PACS) comes a new problem: How to establish trust in multimedia medical data that exist only in the easily altered memory of a computer. Trust is characterized in terms of integrity and privacy of digital data. Two major self-enforcing techniques can be used to assure the authenticity of electronic images and text -- key-based cryptography and digital time stamping. Key-based cryptography associates the content of an image with the originator using one or two distinct keys and prevents alteration of the document by anyone other than the originator. A digital time stamping algorithm generates a characteristic `digital fingerprint' for the original document using a mathematical hash function, and checks that it has not been modified. This paper discusses these cryptographic algorithms and their appropriateness for a PACS environment. It also presents experimental results of cryptographic algorithms on several imaging modalities.

The rapid advancements in high performance global communication have accelerated cooperative image-based medical services to a new frontier. Traditional image-based medical services such as radiology and diagnostic consultation can now fully utilize multimedia technologies in order to provide novel services, including remote cooperative medical triage, distributed virtual simulation of operations, as well as cross-country collaborative medical research and training. Fast (efficient) and easy (flexible) retrieval of relevant images remains a critical requirement for the provision of remote medical services. This paper describes the database system requirements, identifies technological building blocks for meeting the requirements, and presents a system architecture for our target image database system, MISSION-DBS, which has been designed to fulfill the goals of Project MISSION (medical imaging support via satellite integrated optical network) -- an experimental high performance gigabit satellite communication network with access to remote supercomputing power, medical image databases, and 3D visualization capabilities in addition to medical expertise anywhere and anytime around the country. The MISSION-DBS design employs a synergistic fusion of techniques in distributed databases (DDB) and artificial intelligence (AI) for storing, migrating, accessing, and exploring images. The efficient storage and retrieval of voluminous image information is achieved by integrating DDB modeling and AI techniques for image processing while the flexible retrieval mechanisms are accomplished by combining attribute- based and content-based retrievals.

The challenge to archiving images in the modern radiology department arises from the need to interface heterogeneous modalities. The DICOM 3 standard is an industry-wide attempt to produce a homogeneous solution to this problem. Our initial attempt at a unified archive server (Frost et al., 1994) demonstrated that there were limitations imposed by vendor interpretation of the DICOM standard, and initial DICOM toolkit solutions. More rigorous compliance by the vendors to the adopted DICOM standard has allowed the development of a uniform archive server process. As new DICOM conferment equipment is added to the Department of Radiology, the identical archive server process can be utilized, thus significantly reducing the installation, maintenance, and operational costs.

The DICOM standard, in addition to resolving certain problems with the ACR-NEMA 2.0 standard regarding network support and the clinical data dictionary, added new capabilities, in the form of study content notification and patient, study and results management services, intended to assist in interfacing between PACS and HIS or RIS systems. We have defined and implemented a mechanism that allows a DICOM application entity (AE) to interrogate an HL7 based RIS using DICOM services. The implementation involved development of a DICOM- HL7 gateway which converted between DICOM and HL7 messages to achieve the desired retrieval capability. This mechanism, based on the DICOM query/retrieve service, was used to interface a DeJarnette Research film digitizer to an IDXrad RIS at the University of Maryland Medical Systems hospital in Baltimore, Maryland. A C++ class library was developed for both DICOM and HL7 massaging, with several constructors used to convert between the two standards.

The goal of the DICOM standard is to define a standard network interface and data model for imaging devices from various vendors. It shall facilitate the development and integration of information systems and picture archiving and communication systems (PACS) in a networked environment. Current activities in Oldenburg, Germany include projects to establish cooperative work applications for radiological purposes, comprising (joined) text, data, signal and image communications, based on narrowband ISDN and ATM communication for regional and Pan European applications. In such a growing and constantly changing environment it is vital to have a solid and implementable plan to bring standards in operation. A communication standard alone cannot ensure interoperability between different vendor implementations. Even DICOM does not specify implementation-specific requirements nor does it specify a testing procedure to assess an implementation's conformance to the standard. The conformance statements defined in the DICOM standard only allow a user to determine which optional components are supported by the implementation. The goal of our work is to build a conformance test suite for DICOM. Conformance testing can aid to simplify and solve problems with multivendor systems. It will check a vendor's implementation against the DICOM standard and state the found subset of functionality. The test suite will be built in respect to the ISO 9646 Standard (OSI-Conformance Testing Methodology and Framework) which is a standard devoted to the subject of conformance testing implementations of Open Systems Interconnection (OSI) standards. For our heterogeneous communication environments we must also consider ISO 9000 - 9004 (quality management and quality assurance) to give the users the confidence in evolving applications.

The DICOM (Digital Imaging and Communications in Medicine) standard revision 3.0 defines a `print management service class' which allows a DICOM application to print medical images by accessing a remote `service class provider' (another DICOM application) which controls a printing device. This contribution describes a prototype implementation of the DICOM print management service, consisting of a `service class user' application which constitutes the user interface and a `service class provider' application which creates output on a PostScript device. The peer application communicate over a TCP/IP network using the `DICOM upper layer for TCP/IP' service. Possible fields of application for the prototype are discussed.

This paper describes an approach to aide in the decision-making process for the justification and design of a digital image and information management system. It identifies key technical and clinical issues that need to be addressed by a healthcare institution during this process. Some issues identified here are very controversial and may take months or years for a department to determine solutions which meet their specific staffing, financial, and technical needs.

Today's teleradiology transmits images with telephone lines (from 14400 to 1.5 Mbits/sec). However, the large amount of data commonly produced during an MR or CT procedure can limit some applications of teleradiology. This paper is a progress report of a high speed (155 Mbits/sec) testbed teleradiology network using asynchronous transfer mode (ATM OC 3) technology for neuroradiology. The network connects radiology departments of four affiliated hospitals and one MR imaging center within the San Francisco Bay Area with ATM switches through the Pacific Bell ATM main switch at Oakland, California; they are: University of California at San Francisco Hospital and Medical School (UCSF), Mt. Zion Hospital (MZH), San Francisco VA Medical Center (SFVAMC), San Francisco General Hospital (SFGH), and San Francisco Magnetic Resonance Imaging Center (SFMRC). UCSF serves as the expert center and the ATM switch is connected to its PACS infrastructure, the others are considered as satellite sites. Images and related patient data are transmitted from the four satellite sites to the expert canter for interpretation and consultation.

Unique advantages of satellite communication over fiber-optic communication include on- demand linkage and easy access to remote or mobile sites. These advantages are particularly important in life-critical medical services of teleradiology, distributed treatment planning and medical triage support applications. This paper reports on experiments designed to use the supercomputer power, 3D volumetric modeling technology, and NASA ACTS (Advanced Communication Technology Satellite) Ka-band communication to validate the suite of deployable digital radiography technologies for image-based medical triage as well as remote cooperative delivery of health care. The success of the experiments demonstrates that high speed (giga-bit) satellite communication (particularly, ACTS) providing access (via the steerable antenna) to high performance computation and high resolution 3D visualization are not only practical but also crucial for many medical applications, especially for remote regions or moving populations. This demonstration is expected to stimulate new medical services as well as delivery mechanisms that transcend both time and distance barriers. The availability of remote access to supercomputing via high-speed portable connections will have a profound impact on the provision of image-based medical services, and this certainly bears important implications for future PACS development.

This paper assesses the utility of gigabit speed wide-area networks such as the ACTS (Advanced Communication Technology Satellite) in enabling the delivery of medical expertise and service to remote regions, providing radiation treatment planning with access to supercomputers, and conducting workload redistribution. The first part of this multi- institutional effort between the University of Hawaii, Georgetown University Medical Center (GUMC) and the Ohio Supercomputer Center (OSC) uses a T1-VSAT (very small aperture terminal) for transmitting teleradiology images. The second part of the project uses high data rate (HDR) communications through the ACTS satellite at OC-3 transmission speeds (155 Mbps). This allows 3-D volume rendering of radiation therapy planning images between GUMC and OSC as well as the transmission of high-volume teleradiology loads between Tripler Army Medical Center (TAMC) and GUMC. It is shown that while the bandwidth required to perform 3D interactive radiation treatment planning is around 300 Mbps, OC-3 rates can be adequate. Another important application is workload redistribution either for hospitals that need to reroute a certain percentage of their workload to other institutions of the same magnitude but with different subspecialties or for peak workload leveling. This paper shows that gigabit speed wide area networks such as the ACTS-HDR network are required in order to achieve effective remote treatment planning as well as high volume teleradiology for workload redistribution.

UCLA is beginning teleradiology projects in Latin America, Asian Pacific, and the U.S. The UCLA teleradiology system communicates with remote imaging centers through a T1 based WAN and satellite technology. A network management center, i.e., PACS war room, with graphical user interface allows the system manager to monitor and control different elements of the system through various levels of abstraction from one location. The network manager software can monitor the activities of both hardware and software devices in the remote imaging centers, LAN and WAN performance, telearchiving and teleaccess pattern. Telearchiving can be monitored by graphically indicating large image movements between jukeboxes and over LAN or WAN. Once the teleradiology system is configured, the image flow pattern in a teleradiology center is predictable. Manual intervention of these teleradiology system functions is easily done through menu control in the war room display. A centralized network management with the global view of a teleradiology system has been developed. It can give commands to the elements of the system to tune the system for efficient utilization of the system resources. These managerial functions scale with the teleradiology system which is expandable to include many more potential remote imaging centers.

The Mount Zion Hospital (MZH) in San Francisco, Calif. is associated with the University of California at San Francisco (UCSF) medical center. These hospitals are approximately two miles apart. The UCSF radiology department supports specialty image reading for MZH daily. The major issue involved with this service is the access of patient images. Currently, the patient image access is through two ways: (1) inter-hospital travel, and (2) image delivery. Both methods are neither efficient nor economic. If patient images can be transferred from MZH to UCSF to be viewed in digital form in a reasonable time period, the issue of patient image accession can be resolved. This study attempts to use an available digital communication technology, a T-1 line, to verify this hypothesis. The study is centered on the comparison between the T-1 line and courier service with respect to cost and image delivery performance. This comparison study focuses on CT images with an emphasis on neuroradiology application.

This paper presents the results of surveys that were performed in 1990 and 1994 to assess radiologists' use and opinions of teleradiology. In the time between the two surveys, teleradiology use increased from 30% to 42% of surveyed radiologists. Practices using teleradiology tended to have more radiologists within the group and cover more locations than practices that did not. A number of reasons were cited for not using teleradiology. In 1990, some radiologists did not use teleradiology due to the objections of hospital administrators and/or referring physicians. This reason was not given in the 1994 survey. Eighty percent of users used teleradiology for on-call exams in both years. In each year, just over 50% of users also used teleradiology for the remote, daytime interpretation of exams. Computed tomography was the most common remotely interpreted exam modality in both years. Teleradiology use for remote interpretation of ultrasound, plain film, nuclear medicine and magnetic resonance images increased considerably in the time between the two surveys. By the time of the second survey, image quality was acceptable for all modalities except plain film. Use of laser film digitizers, frame-grabber boards and direct digital acquisition increased between 1990 and 1994.

Teleradiology offers significant improvement in efficiency and effectiveness over current practices in traditional film/screen-based diagnosis. In the context of digital mammography, the increasing number of women who need to be screened for breast cancer, including those in remote rural regions, make the advantages of teleradiology especially attractive for digital mammography. At the same time, the size and resolution of digital mammograms are among the most challenging to support in a cost effective teleradiology system. This paper describes a teleradiology architecture developed for use with digital mammography by GE Corporate Research and Development in collaboration with Massachusetts General Hospital under National Cancer Institute (NCI/NIH) grant number R01 CA60246-01. Experience with a testbed prototype is described. The telemammography architecture is intended to consist of a main mammography diagnostic site serving several remote screening sites. As patient exams become available, they are forwarded by an image server to the diagnostic site over a WAN communications link. A radiologist at the diagnostic site views a patient exam as it arrives, interprets it, and then relays a report back to the technician at the remote site. A secondary future scenario consists of mobile units which forward images to a remote site, which then forwards them to the main diagnostic site. The testbed architecture is based on the Digital Imaging and Communications in Medicine (DICOM) standard, created by the American College of Radiology (ACR) and National Electrical Manufacturers Association (NEMA). A specification of vendor-independent data formats and data transfer services for digital medical images, DICOM specifies a protocol suite starting at the application layer downward, including the TCP/IP layers. The current DICOM definition does not provide an information element that is specifically tailored to mammography, so we have used the DICOM secondary capture data format for the mammography images. In conclusion, experience with the testbed is described, as is performance analysis related to selection of network components needed to extend this architecture to clinical evaluation. Recommendations are made as to the critical areas for future work.

The authors have an in-kind grant from NASA to investigate the application of the Advanced Communications Technology Satellite (ACTS) to teleradiology and telemedicine using the JPL developed ACTS Mobile Terminal (AMT) uplink. This experiment involves the transmission of medical imagery (CT, MR, CR, US and digitized radiographs including mammograms), between the ACTS/AMT and the University of Washington. This is accomplished by locating the AMT experiment van in various locations throughout Washington state, Idaho, Montana, Oregon and Hawaii. The medical images are transmitted from the ACTS to the downlink at the NASA Lewis Research Center (LeRC) in Cleveland, Ohio, consisting of AMT equipment and the high burst rate-link evaluation terminal (HBR-LET). These images are then routed from LeRC to the University of Washington School of Medicine (UWSoM) through the Internet and public switched Integrated Serviced Digital Network (ISDN). Once images arrive in the UW Radiology Department, they are reviewed using both video monitor softcopy and laser-printed hardcopy. Compressed video teleconferencing and transmission of real-time ultrasound video between the AMT van and the UWSoM are also tested. Image quality comparisons are made using both subjective diagnostic criteria and quantitative engineering analysis. Evaluation is performed during various weather conditions (including rain to assess rain fade compensation algorithms). Compression techniques also are tested to evaluate their effects on image quality, allowing further evaluation of portable teleradiology/telemedicine at lower data rates and providing useful information for additional applications (e.g., smaller remote units, shipboard, emergency disaster, etc.). The medical images received at the UWSoM over the ACTS are directly evaluated against the original digital images. The project demonstrates that a portable satellite-land connection can provide subspecialty consultation and education for rural and remote areas. The experiment is divided into three phases. Using the ACTS fixed-hopping beam, phase one involves testing connection of the AMT to medical imaging equipment and image transmission in various climates in western and eastern Washington state. The second phase involves satellite relay transmissions between the Inmarsat satellite and the ACTS/AMT through a ground station in Hawaii for medical imagery originating from either Okinawa, Japan or Kwajalein, in the Pacific. The third phase involves extended use of the ACTS steerable beam in Washington state, Idaho, Montanan and Oregon.

Most rural clinics across the country have limited facilities to provide state-of-the-art medical services. The availability of enabling technologies, such as telecommunication networks, multimedia workstations, and telemedicine systems which provide medical services to patients without requiring them to travel from their cities represents a great step in patient care. In previous work, we have developed a distributed software for remote consultation and diagnosis (RCD) in a Global PACS environment over the Internet. The RCD system has been designed and tested on DEC and SUN workstations. In this paper, we present a Unix-PC based platform to implement the RCD over a standard telephone line and Serial Line Internet Protocol (SLIP). The Unix-PC platform offers an inexpensive option for telemedicine workstations in rural clinics, where no Internet is available. If an Internet connection is available at the rural clinic, full RCD multimedia services are possible. The Unix-PC platform has been developed by using Linux, a Unix-like operating system available from several public sites over the Internet. We call the system PC-PACS. The PC-PACS workstation has been tested from different rural sites by connecting the Unix-PC system to the Internet through SLIP. Once the system is connected, RCD sessions have been performed between the Unix- PC platform and SUN workstations. The tests have included diagnosis on radiology and pathology images. A separate telephone line for voice communications during the RCD session is required. This paper describes performance tests for the PC-based workstation and the RCD system over SLIP and Ethernet interfaces. Results show acceptable performance of the workstation and the RCD software.

Telemedicine is becoming increasingly possible due to the confluence of ongoing technical advances in such areas as telecommunications, imaging, multimedia, computers, and information systems. Project Seahawk is a regional telemedicine program in the Pacific Northwest with Madigan Army Medical Center (MAMC) as the hub connecting various military and other federal hospitals and clinics utilizing the state-of-the-art technologies. The first phase of Project Seahawk successfully connected MAMC in Tacoma, Wash. to the University of Washington in Seattle, Wash. through the Western Washington Local Access Transport Area (LATA) Integrated Optical Network (LION) Sonet Ring using asynchronous transfer mode (ATM) and two MediaStation 5000s as a feasibility demonstration. Several telemedicine scenarios were demonstrated including synchronized image manipulation, real- time transmission of ultrasound and medical images, and video and audio teleconferencing, and remote consultation. The second phase implementation will consist of increasing the number of hospitals and clinics with telemedicine capability, e.g., Bremerton Naval Hospital, Oak Harbor Naval Hospital, Seattle VA, and American Lake VA.

This study was designed to provide a clinically oriented evaluation of a commercially available teleradiology system for remote diagnosis in the family practice setting. We sought a technique to determine if the diagnostic report from interpretation of transmitted digitized radiographs differed from the report rendered following interpretation of the original radiograph. Radiographs taken in our Family Medicine Clinic were digitized and transmitted to a display station. One of two ABR certified radiologists interpreted the digitized images and a report was printed. In keeping with our current practice, the radiographs were transmitted by courier for interpretation. Interpretation of the original radiographs was rendered and entered into the medical record. Reports were compared retrospectively and classified as: Class I -- The reports agree; Class II -- The reports disagree without clinical significance; Class III -- The reports disagree with clinical significance. A total of 197 exams were compared, of which approximately half had positive findings on the radiograph. Of the 197 exams considered, the interpretations of digitized and original radiographs agreed in 183 (93%) of the cases. The 14 clinically significant discordant cases were reviewed to ascertain the reason for disagreement. For all 14 cases, both the electronic image and radiographs were interpreted again independently by both radiologists. This analysis demonstrated only 1 case with a Class III disagreement. Thus the interpretations were in agreement for 99.5% of the cases upon review. We believe this methodology is a viable and robust technique for the clinical evaluation of teleradiology systems. The radiologist performs similar and familiar functions in both domains and the technique can be easily implemented in many practice settings. We are encouraged that our results indicate substantial agreement is possible with a relatively inexpensive, commercially available teleradiology system. An expansion of our current study is underway.

A second generation PACS provides an open architecture allowing a seamless connection to other picture archiving and communication systems (PACS) modules with industrial standards. The open architecture of the UCSF PACS provides the flexibility to use commercial `off-the- shelf' components when needed. This paper describes our experience interfacing a stand-alone commercial ultrasound (US) PACS module to our departmental PACS. US PACS module (Acuson Aegis) links 7 Acuson scanners in 2 buildings. This US PACS module features a network sever with 1.5 GB disk storage used for short-term archiving, with images stored in a compressed format (DICOM compatible). The images must be compressed due to the inherently large size of the full images (640 X 480 X 24 bit/image). The interface consists of a gateway which encodes and decodes US images and related patient data to DICOM standards permitting open communication between the module and the PACS infrastructure over ethernet. The first phase of the implementation is to transmit US images to the departmental PACS optical disk library for long term archiving automatically and to retrieve US images from this archive using workstations in the US module. The second phase is to retrieve selected images acquired by other modalities from the archive for display on the US workstation. The third phase is the integration of a pre-fetch mechanism, initiated by the HIS, that sends archived prior studies of patients with scheduled appointments to the US module. Phase 1 has been completed. US images and reports can be archived and retrieved between the departmental PACS and the US module. Retrieval times for cases are between 45 to 120 seconds depending on the time of day. Performance tests have been taken, and average times for study transfers, average study sizes, and general gateway performance issues have been measured. Phases 2 and 3 will be completed shortly. With open architecture design, the US module and the departmental PACS infrastructure function as an integral image information system.

Picture archiving and communication systems (PACS) have been quite successful at the University of Florida in the areas of CT, MR, and nuclear medicine. In each case, although we have not always been able to provide the optimal level of performance, we have been able to solve a problem and the systems are used extensively. Ultrasound images are required in a number of locations and the multiformat camera print capability was no longer adequate for the growing volume in the ultrasound section. Although we were certain we could successfully implement PACS for ultrasound, new forces in health care dictate that we justify our system in terms of cost. We analyzed the feasibility of a PACS solution for ultrasound and designed a system that meets our needs and is cost effective. We evaluated the ultrasound operation in terms of image acquisition patterns and throughput requirements. An inventory of existing and PACS equipment was made to determine the feasibility of interfacing the two systems. Commercial systems were evaluated for functionality and cost and a system was designed to meet our needs. The only way to achieve our goal of installing a cost effective ultrasound PACS was to eliminate film and use the cost savings to offset the cost of new equipment and development. We designed a system that could be produced using inexpensive components and existing hardware and software to meet our needs. A commercial vendor was chosen to provide the ultrasound acquisition. The Radiology Information System interface used at the University provides the necessary data to build a DICOM header, and an existing DICOM server routes the images to the appropriate workstations, archives, and printers. Additional storage is added to an existing archive to accommodate the ultrasound images and two existing workstations are evaluated for use in ultrasound.

Two approaches were taken to evaluating the potential for productivity improvement that could result from use of a miniPACS in the ultrasound section. First, a time-motion study was carried out on conventional, non-networked ultrasound machines to determine the amount of time that sonographers spend handling film. A component of this was also the darkroom time and was separately measured. Second, a field trial of an ultrasound system that incorporated centralized printing techniques was done. The first study showed a mean film handling time of 28.3 seconds per film (standard deviation: 11.4 seconds) and a darkroom time (not processing time) of 16.3 seconds per film (standard deviation: 4.2 seconds). Expanding these to multiple films per study and multiple studies per sonographer shows that elimination of film handling by `partial PACS' centralized printing or `miniPACS' for ultrasound can result in additional sonographer time available for examinations, or reductions in sonographer overtime.

Urological diagnosis using fluoroscopy images has traditionally been performed using radiographic films. Images are generally acquired in conjunction with the application of a contrast agent, processed to create analog films, and inspected to ensure satisfactory image quality prior to being provided to a radiologist for reading. In the case of errors the entire process must be repeated. In addition, the radiologist must then often go to a particular reading room, possibly in a remote part of the healthcare facility, to read the images. The integration of digital fluoroscopy modalities with clinical PACS has the potential to significantly improve the urological diagnosis process by providing high-speed access to images at a variety of locations within a healthcare facility without costly film processing. The PACS additionally provides a cost-effective and reliable means of long-term storage and allows several medical users to simultaneously view the same images at different locations. The installation of a digital data interface between the existing clinically operational PACS at the University of Virginia Health Sciences Center and a digital urology fluoroscope is described. Preliminary user interviews that have been conducted to determine the clinical effectiveness of PACS workstations for urological diagnosis are discussed. The specific suitability of the workstation medium is discussed, as are overall advantages and disadvantages of the hardcopy and softcopy media in terms of efficiency, timeliness and cost. Throughput metrics and some specific parameters of gray-scale viewing stations and the expected system impacts resulting from the integration of a urology fluoroscope with PACS are also discussed.

The evaluation of a PACS for intra- and inter-departmental utilization is compared to the standard film management system for CT and MRI examinations. This comparison demonstrates that film hardcopy recording can be reduced if the clinical faculty well utilize grayscale monitors in developing diagnostic consultation reporting.

The purpose of this paper is to present the default display protocol (DDP) we have devised for the spatial and temporal organization on PACS monitors of chest images taken in the intensive therapy unit (ITU). The goal is that when a patient has ITU status, his/her images will appear by default automatically ordered and arranged in the configuration most clinically useful and appropriate to the ITU setting. This DDP takes into account features specific to the ITU patient, namely: (1) the comparison of multiple chest images from the same patient in accurate temporal sequence to assess subtle trends in disease course; (2) the ability to display any desired image at maximum resolution for diagnostic purposes, and then quickly revert to displaying the entire image sequence; (3) minimization of the time spent in rearranging images on the display monitor; and (4) adaptation of the DDP to suit 1, 2, or 4 monitor workstations.

Image sources for the medical intensive care unit workstation used to view portable chest radiographs include both digitized screen-film images and phosphor plate images. This study compares usage of image manipulation functions when physicians view the images from different sources on the workstation. The authors hypothesize that the improved image-to- image uniformity afforded by phosphor plate radiography reduces the use of some of these functions; in particular, the controls for image brightness and contrast. The automated workstation logs and analysis of the results from digitized film-based and phosphor plate-based study periods show that this hypothesis is supported. Overall, use of all image manipulation functions decreased, but use of brightness/contrast showed the largest decrease, from 24.5% for digitized film to 7.6% for phosphor plate imaging. The overall workstation usage increased for the phosphor plate period, supporting the idea that this decrease in function usage was not the result of overall decrease in workstation use. This paper further describes the comparison of the workstation usage during these two study periods.

Our purpose is to determine the incremental costs (or savings) due to the introduction of picture archiving and communication systems (PACS) and computed radiology (CR) in a medical intensive care unit (MICU). Our economic analysis consists of three measurement methods. The first method is an assessment of the direct costs to the radiology department, implemented in a spreadsheet model. The second method consists of a series of brief observational studies to measure potential changes in personnel costs that might not be reflected in administrative claims. The third method (results not reported here) is a multivariate modeling technique which estimates the independent effect of PACS/CR on the cost of care (estimated from administrative claims data), while controlling for clinical case- mix variables. Our direct cost model shows no cost savings to the radiology department after the introduction of PACS in the medical intensive care unit. Savings in film supplies and film library personnel are offset by increases in capital equipment costs and PACS operation personnel. The results of observational studies to date demonstrate significant savings in clinician film-search time, but no significant change in technologist time or lost films. Our model suggests that direct radiology costs will increase after the limited introduction of PACS/CR in the MICU. Our observational studies show a small but significant effect on clinician film search time by the introduction of PACS/CR in the MICU, but no significant effect on other variables. The projected costs of a hospital-wide PACS are currently under study.

The purpose of this study was to compare the efficiency of image delivery, the effectiveness of image information transfer, and the timeliness of clinical actions in a medical intensive care unit (MICU) using either conventional screen-film imaging (SF-HC), computed radiography (CR-HC) or a CR based PACS. When the CR based PACS was in use, images could be viewed in the MICU on digital workstation (CR-WS) or in the radiology department as laser printed hard copy (CR-HC). Data were collected by daily interviews with the house-staff, by monitoring computer log-ons and other time stamped activities, and by observing film viewing times in the radiology department with surveillance cameras. The time at which image information was made available to the MICU physicians was decreased during the CR-PACS period as compared with either the SF-HC periods or the CR-HC periods but the image information was not accessed more quickly by the clinical staff. However, the time required to perform image related clinical actions for pulmonary and pleural problems was decreased when images were viewed on the workstation.

The radiological department of Viborg Sygehus, Denmark is one of the very few departments in Europe which has made the conversion from an analog to a digital and almost totally filmless environment. The changes have taken place during the period 1989 - 1993. Experiences with PACS in daily practice for more than two years are presented, with focus on clinical and organizational changes inside and outside the radiological department.

This paper communicates the operational implementation of filmless digital radiology in clinical routine, its feasibility and its effect on the radiology profession, based on the three years clinical experience from the filmless digital radiology department of the Danube Hospital, a major teaching hospital in Vienna, Austria, with currently 850 acute-care beds. Since April 1992 all radiological modalities are reported from the monitors of 16 reporting consoles in the radiology department. Images and reports are distributed by the hospital-wide network (Sienet, Siemens Medical Systems, Erlangen), and can be viewed on 60 display consoles throughout the hospital. Filmless radiology primarily is an efficient hospital-wide infrastructure to deliver radiological services along with other medical information, providing safe and fast access to this information anytime and anywhere, necessary for the conduct of the diagnostic and therapeutic task of patient care. In a comparative study of the Danube Hospital with the film based Rudolfstiftung Hospital in Vienna, we found a significant decrease of the mean patient length of hospital stay (1.99 to 3.72 days) that partially might be attributed to the implementation of filmless radiology.

This paper describes the RETAIN project (radiological examination transfer on ATM Integrated Network), which is supported by the European Community, in the frame of the TEN-IBC program (trans-European networks integrated broad band communication). It links together three European sites in France (Rennes), Spain (Barcelona), and Germany (Oldenburg) and involves a partnership between the public national operators France Telecom, Telefonica, and Telekom. One important reason to explicitly consider asynchronous transfer mode (ATM) for medical imaging is that multimedia applications on such networks allow integration of digital data and person-to-person communication. The RETAIN project includes trials of teleworking sessions between radiologists of Rennes and Barcelona within a clinical and/or scientific context based on ATM equipments performing DICOM transfer on examination, digital remote manipulation within a comprehensive dialogue, and high quality visiophony on ATM adaptation layer (AAL) type 1. The project includes also visiophony trials with Oldenburg and preparation of harmonized regional experimentation within an emergency context. The network used is a full 10 Mbits/s ATM network directly connected to local PACSs.

In many hospitals, radiological examinations are scheduled via a Radiology Information System (RIS) or Picture Archiving and Communication System (PACS) before the imaging is performed. Demographic and examination information is first entered into the PACS database; when the images are later acquired, they have to match up with the correct pre-scheduled exam. This problem is non-trivial because patients may be scheduled for several exams on the same modality on the same day, and older modalities are unable to identify unambiguously the type of examination being performed. The purpose of this work is to develop practical and reliable strategies to assist in matching up the correct exam. Three potential solutions are considered: (1) modifications to imaging hardware and/or software, which force a PACS- generated exam ID into the image headers at acquisition time and thus guarantee a perfect match; (2) profiling algorithms, which attempt to find a match based on information already contained within the image headers; and (3) interactive Modality Examination Terminals (METs), which query the PACS database and assist human operators in manually selecting an appropriate exam. Solution (1) was found to be impractical with our existing digital imaging equipment, therefore solutions (2) and (3) were implemented and evaluated. Configuration files read at start-up time permitted the same hardware to be operated in either profiling or true MET mode. For each digital imaging modality the most appropriate mode of operation was determined, maintaining as far as possible a consistent hardware and software user interface.

Integration of networking and data management technologies such as PACS, RIS and HIS into a healthcare enterprise in a clinically acceptable manner is a difficult problem. Data within such a facility are generally managed via a combination of manual hardcopy systems and proprietary, special-purpose data processing systems. Process modeling techniques have been successfully applied to engineering and manufacturing enterprises, but have not generally been applied to service-based enterprises such as healthcare facilities. The use of process modeling techniques can provide guidance for the placement, configuration and usage of PACS and other informatics technologies within the healthcare enterprise, and thus improve the quality of healthcare. Initial process modeling activities conducted within the Pediatric ICU at Children's Medical Center in Dallas, Texas are described. The ongoing development of a full enterprise- level model for the Pediatric ICU is also described.

This paper recalls the major motivations for developing the MIMOSA model (medical image management in an open system architecture). It gives an overview of the content of this model and focuses on the validation brought by the prototyping activity. The paper describes the functional scenario addressed by the demonstrator developed at the University Hospital of Rennes, France. Emphasis is put on methodology and architectural issues, allowing a portable MIMOSA-based PACS core to be built while addressing the integration of local PACS components by means of an ad-hoc adaptation layer. Openness is also a central issue: the architecture has been designed in such a way that the MIMOSA services can be requested and provided using established standards. The influence of the DICOM standard with respect to this concern is analyzed in detail. Achievements and current limitations are highlighted. Conclusions are drawn concerning the technical assessment of that part of the model involved in the demonstrator. Clinical validation is not discussed here since the system should be introduced in clinical routine in the course of 1995.

Efficiency is crucial to economic viability in the current climate of intense competition in the healthcare industry. The heterogeneity of the information systems, RIS, PACS, HIS, DDS, often found in radiology practices has made it difficult to fully leverage these costly investments in information technology into efficiency gains. An approach to integrating these heterogeneous systems that will make information technology more effective as an efficiency tool, while preserving the separate hardware and software environment of each system, is presented. Based on an integrated information model and automated message passing between the different systems, this approach can be used to support an automated, proactive sequencing of the radiology workflow.

The Department of Veterans Affairs has developed a bidirectional HL7 - ACR-NEMA V 2.0 interface for connecting existing federal government hospital/radiology information systems (HIS/RIS) to commercial picture archive and communication systems (PACS). The interface has been in use since October 1993 at the Baltimore VAMC between the VA's HIS/RIS (DHCP) and a commercial PACS, and handles both text and image transfer. The text-only portion of the interface has been ported to work with a second vendor's PACS, and to work with the Department of Defense HIS/RIS (CHCS). Currently the interface is in production at two VA and three DoD sites. The common benefit experienced at all these sites is that passing patient, order, and report information directly from the HIS/RIS to the PACS greatly improves the flow of work in the Radiology Department. Image transfer to the DHCP Imaging System at the Baltimore VAMC demonstrated the advantage of providing `reference quality' (1K X 1K X 8-bit) radiology images to treating clinicians throughout the hospital. Experience has shown that the gateway must handle transactions between the HIS/RIS and the PACS quickly in order to keep up with the volume, and must provide an audit trail for system diagnostic purposes. Work is underway to construct a HL7 - DICOM gateway built upon the operational experience gathered from the existing interface.

Picture archiving and communication systems (PACS) perform the systematic acquisition, archiving, and presentation of large quantities of radiological image and text data. In the UCLA Radiology PACS, for example, the volume of image data archived currently exceeds 2500 gigabytes. Furthermore, the distributed heterogeneous PACS is expected to have near real-time response, be continuously available, and assure the integrity and privacy of patient data. The off-the-shelf subsystems that compose the current PACS cannot meet these expectations; therefore fault tolerance techniques had to be incorporated into the system. This paper is to report our first-step efforts towards the goal and is organized as follows: First we discuss data integrity and identify fault classes under the PACS operational environment, then we describe auditing and accounting schemes developed for error-detection and analyze operational data collected. Finally, we outline plans for future research.

Asynchronous transfer mode (ATM) switch-based networks can provide high bandwidth for digital video and image data transmission as well as scalability and interoperability between local-area networks and metropolitan or wide area networks. However, migration to ATM is complicated by the limitations of existing radiology networks. Our goal was to develop an effective migration strategy for incorporating ATM into existing radiology networks. We characterized traffic flow for a large-scale, clinical picture archiving and communication system (PACS) with multiple imaging modalities, archives, and display workstations; we then developed a network delay model and, based upon the design criteria, the network delay model, and estimates of future traffic, we designed a switch-based network that uses both Ethernet and ATM switches. Our strategy allows an existing PACS to utilize ATM technology where appropriate, to gain interoperability with wide area networks, and to maximize the investment in an existing PACS infrastructure.

Looking to the medical environment of the 21st Century, this paper describes the use of the signal interchange format (SIGIF) standard to integrate the data collected by biological signal monitoring systems with systems from other parts of a hospital or research facility. This paper covers three parts of this process. The first is the signal archive and communications system (SACS) which collects the data directly from a patient, the second part covers the signal interchange format standard which is used to communicate data from the SACS to a picture archive and communications system (PACS), and the last part covers the changes to a PACS. The concept of a signal archive and communications system was presented at the 1993 IEEE Engineering in Medicine and Biology Conference as part of a paper by Joao Paulo Cunha. This paper attempts to define a specific architecture for a SACS and describe changes to published descriptions of a PACS required to complete the PACS/SACS interface. For over 15 years the use of computerized signal collections systems have been commonly accepted as part of hospital and research environments. Each manufacture has devised a unique, and usually proprietary, method of storing that information. During that time, very little has been done to provide a common standard so this information could be communicated to another computer. This has resulted in millions of miles of hard copy printouts being stored in patient records. The radiology departments have had the same problem; however, they solved the problem with the ACR/NEMA DICOM standard. The SIGIF standard is being presented as an equivalent standard to solve the communications problem for biological signal data. This paper presents a new step in the integration of bio-signal collection systems with other hospital data processing systems. The concept being presented for the first time in this paper is to convent signal information into the DICOM image format. Each pixel of the image will represent one data point from a biological signal. A twelve lead EKG would result in twelve images representing approximately 30 minutes of collected data. Each image would take up less than 2 MBytes of information based on an 8 bit, 1024 samples per second, A/D converter. Once this conversion has been performed the signal data can be integrated into the PACS environment without requiring any additional software. It can be processed, filtered, displayed, and stored using the same algorithms as would be used for an MRI image. The concepts presented in this paper open up the use of the hospitals computational resources to signal data; that, at the present time, are reserved for the processing, display, and storage of radiology department images.

Current infrastructure research in PACS is dominated by the development of communication networks (local area networks, teleradiology, ATM networks, etc.), multimedia display workstations, and hierarchical image storage architectures. However, limited work has been performed on developing flexible, expansible, and intelligent information processing architectures for the vast decentralized image and text data repositories prevalent in healthcare environments. Patient information is often distributed among multiple data management systems. Current large-scale efforts to integrate medical information and knowledge sources have been costly with limited retrieval functionality. Software integration strategies to unify distributed data and knowledge sources is still lacking commercially. Systems heterogeneity (i.e., differences in hardware platforms, communication protocols, database management software, nomenclature, etc.) is at the heart of the problem and is unlikely to be standardized in the near future. In this paper, we demonstrate the use of newly available CASE (computer- aided software engineering) tools to rapidly integrate HIS, RIS, and PACS information systems. The advantages of these tools include fast development time (low-level code is generated from graphical specifications), and easy system maintenance (excellent documentation, easy to perform changes, and centralized code repository in an object-oriented database). The CASE tools are used to develop and manage the `middle-ware' in our client- mediator-serve architecture for systems integration. Our architecture is scalable and can accommodate heterogeneous database and communication protocols.

PACS research and development in the past decade mainly emphasized technical issues such as networking, archiving, data communication standards and image display workstation development. In order to fully realize the benefits of these advanced digital technologies in current and future radiology practice, a discipline for development of next generation PACS must be established and practiced. We devised and applied a development process or life cycle that facilitated PACS system definition, development and operation. With the application of the development process, user requirements and expectations of a PACS can be effectively and accurately transformed into system models, and the implementation and the operation of a PACS can be carried out in a systematic way. The development process also provides a framework for repeatable systems and software engineering.

Our tele-medicine/PACS archive system is based on a three-tier distributed hierarchical architecture, including magnetic disk farms, optical jukebox, and tape jukebox sub-systems. The hierarchical storage management (HSM) architecture, built around a low cost high performance platform [personal computers (PC) and Microsoft Windows NT], presents a very scaleable and distributed solution ideal for meeting the needs of client/server environments such as tele-medicine, tele-radiology, and PACS. These image based systems typically require storage capacities mirroring those of film based technology (multi-terabyte with 10+ years storage) and patient data retrieval times at near on-line performance as demanded by radiologists. With the scaleable architecture, storage requirements can be easily configured to meet the needs of the small clinic (multi-gigabyte) to those of a major hospital (multi-terabyte). The patient data retrieval performance requirement was achieved by employing system intelligence to manage migration and caching of archived data. Relevant information from HIS/RIS triggers prefetching of data whenever possible based on simple rules. System intelligence embedded in the migration manger allows the clustering of patient data onto a single tape during data migration from optical to tape medium. Clustering of patient data on the same tape eliminates multiple tape loading and associated seek time during patient data retrieval. Optimal tape performance can then be achieved by utilizing the tape drives high performance data streaming capabilities thereby reducing typical data retrieval delays associated with streaming tape devices.

Future medical centers will consist of multiple picture archiving and communication systems (PACS) serving local needs of different specialty sections and departments. This distribution of medical image archives will require high performance broadband networks to ensure effective communication and reliable services. One major stumbling block to this distributed PACS environment is the lack of an appropriate networking technology to integrate individual systems and their services seamlessly. Asynchronous transfer mode (ATM) provides a promising solution to this infrastructure problem. ATM is defined as cell-based switching and multiplexing technology designed to be a general-purpose, connection-oriented transfer mode for a wide range of services. This work investigates the suitability of this new technology for distributed medical PACS applications and discusses the user needs and operational issues accompanying the ATM deployment. It also presents with the design and preliminary throughput results of an ATM based hospital-integrated PACS at the University of California, San Francisco.

The practice, training and research of medical image reading or medical sciences involving medical images often require interactions among individuals for expertise/information exchange, sharing and transfer. Examples include diagnosis, case correlation and resident consultations as well as teaching and research conferences. Recently, computer-based consultation and conference support enabling multimedia interactions and precise spatial references on images has been developed. However, the focus has primarily been on interaction support. More research is needed to develop proper query and information management support for before, during and after computer-aided consultations and conferences that are essential to effective interactions and information dissemination. The information management needs of computer-aided consultations and conferences include storage, retrieval, editing, migration and distribution of case-related information. Query support is expected to handle not only predicate-based retrievals but also content-based and similarity-based retrievals in distributed environments. This paper analyzes the requirements of query and information management support for computer-aided consultation and conference systems and presents the design of query and information management functions for before-, during- and after-consultation/conference. The user interface of a computer-aided consultation and conference system along with the architecture of the backend information management system are described. The paper concludes with the implementation status and future directions of this study.

Waiting for images from a PACS archive is frustrating for radiologists whenever images are missing from their workstations. We employ system intelligence into our PACS to estimate the image retrieval time and to notify the radiologist upon image availability. When an image retrieval request is made by a radiologist, our PACS manager software is automatically notified. It then collects archival information and system conditions from various PACS nodes (database, file servers, and workstations) through a trap mechanism. A statistical model is developed to estimate the image retrieval delay based on image size, number of prior requests, network topology, and storage device type. A retrieval time table is then graphically displayed on the workstation. Automatic paging notifies the relevant radiologist if the delay is substantial and catastrophic. A radiologist is much more willing to perform softcopy viewing regularly once he is given a good estimation of image retrieval delay, from which he is able to make better decisions in prioritizing his work list. The implementation of PACS intelligence requires enormous information. The PACS manager makes it possible to collect them anywhere in the network. The retrieval time notification is an important example of applying PACS intelligence to assist clinical practice.

This study extends the survey performed in 1992 by Levine et al., on available standards of data communication and interfacing in the RIS and PACS industry. We sought more detailed knowledge about such interfaces and contacted a greater number of RIS/HIS and PACS vendors. We also wanted to determine if interfaces had changed in the two years since the previous study and in what direction the industry is moving. Sixty vendors of RIS, HIS and PACS were surveyed. We included questions about communications protocols, data format, data integrity checks, etc., and reasons for the vendors' choices. Of responding RIS/HIS vendors, 26% supported ACR-NEMA 2.0 and 21% supported DICOM, compared to none in the previous survey. Support for the HL-7 standard has also grown, from 58% in 1992 to 80% of vendors in 1994. All of the surveyed PACS vendors supported ACR-NEMA 2.0 or DICOM and 50% supported HL-7. The reasons most often cited for supporting certain options were widespread use and robustness, with ease of implementation and cost-effectiveness following closely behind. We found that vendors now offer many more options for interfacing their systems to other systems than two years ago. Also, more vendors are supporting such industry standards as HL-7 and ACR-NEMA/DICOM.