PACS through the years definitely has been a "lessons learned" experience. This article describes some of the history, and evolution of these systems as well as early experiences. The first large-scale PACS installation was in 1982 at the University of Kansas, Kansas City. As is typical with early experiments, people learned more about how NOT to do it than they did how to do it. The experiences from this installation taught that PACS requires abundant data exchange, and that an Ethernet connection is not necessarily the best method to do this (remember the fastest connection at that time was 10 MBit/sec, and routers and bridges were not really commonplace).
That brings us to one of the big "drivers" in this technology; network standardization. In the early '80s, there was no one single standard. TCP/IP was just one of the several options available. The government was pushing for the OSI standard, and major manufacturers, notably GM, were trying to enforce broadband instead of Ethernet standards. As a matter of fact, the first PACS by Philips used broadband technology. There were also "ad-hoc" developments using inventive solutions in the '80s, such as the one at Michigan State University, whereby images from three CT scanners were sent to the University diagnostic center for reading via the commercial CATV cable system; a predecessor to cable modems! The early versions of DICOM, called ACR-NEMA, only specified a dedicated point-to-point connection, leaving it up to the manufacturer to exchange the data via their network of choice. It took about 10 years for the network standard to emerge, something we take for granted now. Today, everyone uses the TCP/IP as the basis for network communication, making it easy for new developments at the physical level such as gigabit/sec Ethernet to be deployed.
PACS & PIXELS
Display technology has also come a long way. Initially, there were only 1k by 1k monitors, and there was a big question as to whether the resolution was going to be sufficient. It is interesting to note that this discussion is still very valid, not because higher resolution monitors are unavailable, but because there is a definite price trade-off. For example, should one use a 3 Mpixel monitor for reading of chest images, or is a 5 MPixel more efficient? Is it OK for referring physicians to use their high-quality PC monitor, or should they use a medical grade monitor with a special video board? It is not only a question of using the appropriate hardware, but also using the correct display look-up tables to provide a consistent presentation. Another issue is still the appropriate number of viewing monitors. Early PACS viewing stations mimicked the electronic film alternators they were supposed to replace, and most of them therefore had two rows of four monitors stacked above each other. Most institutions now seem to be happy with two monitors, especially since more people like to use "stack view" with digital modalities such as CT and MR. As for chest, there is still the obvious cost factor and limitation of space. Interestingly enough, some institutions use four monitors for all their diagnostic viewing, while others use two. Talking with radiologists from either institution, they both seem to make a convincing story justifying their configuration.
Economically speaking, it is interesting to see that over the years, the question as to whether PACS is cost-justifiable has not gotten any easier. The early work at the Hospital of the University of Pennsylvania, as well as at Washington University in Seattle, provided some early numbers and a framework to use, however, a clear "savings-model" is still difficult to formulate. The challenge is that one cannot just look at how much is saved by eliminating film, but that the true savings lie more in the increases in efficiency. Productivity studies by the VA in Baltimore in the early '90s have helped in this regard. However, one has to realize that, as Dr. Eliot Siegel from the VA in Baltimore strongly advocates, one has to re-engineer a department and its workflow to make use of the advantages of this new technology to really realize the benefits. As you can imagine, the early PAC systems only replaced their film-based operation with a softcopy environment without the emphasizing re-engineering.
One of the true drivers that made PACS technology affordable was the implementation of standards, especially HL7 in the IT domain, and DICOM in the imaging domain. Both were initiated in the late '80s, and enjoyed widespread support in the early '90s. In particular, early demonstrations at the Radiological Society of North America (RSNA) meeting of DICOM brought awareness to the user community. Subsequently, the open-source toolkit, developed by the research lab of the Mallinckrodt Institute of Radiology in St. Louis, gave a big push to the DICOM standard implementation. As of today, PACS and DICOM/HL7 go hand-in-hand having an inter-dependant relationship.
Archiving technology also has come a long way. One of the initial most important benefits of a PAC system was to replace the film room, thereby reducing costs. PACS image storage choices included commercial 12-inch or 14-inch optical disks, as well as various tape options. Many early PACS installations used large jukeboxes with big disks, with probably quite a few still around. Recent developments in consumer electronics have enabled replacement of jukeboxes with CD, DVD or even Magneto Optical (MOD) Read/Write devices. Some institutions actually store everything on magnetic disks. Image storage also has shifted more from a radiology/imaging focus to an IT responsibility, whereby archiving is centralized instead of storing archives at multiple imaging departments.
Viewing stations also have evolved. Early viewing stations had specially built keyboards with buttons for various functions. Many usability studies were conducted at AT&T (who was in the PACS business at that time as a Philips partner), to determine the best user interface. With the advent of the graphical user interfaces (pioneered by Apple, and later taken over by Microsoft) this became less of an issue.
The focus for PACS has truly shifted. It began as a means to eliminate film archiving, i.e. the focus was on the "A" in PACS. Teleradiology definitely addresses the "C"ommunications in PACS, whereby images are sent to another location, such as from a remote clinic to a main hospital, or to a doctor's home during the night. Improvements in image communication have always been a major driving force in PACS development. This was the main reason that the U.S. Department of Defense became involved, and why they sponsored early PACS projects at Georgetown, and the University of Washington. They are responsible for running a large amount of medical facilities, ranging from South Korea to Germany, as well as covering the many bases in the U.S., ranging from Alaska and Hawaii to Nevada. At some facilities, either a civilian radiologist would review images periodically, or they shipped the films to one of their main facilities. The Navy was particularly interested in improved communication, because of the importance of determining whether an injured sailor needed to be picked up from a vessel by a helicopter, posing risks and high costs. The vision of a single, "virtual" department spanning all services, and locations has really helped to propel PACS development.
More and more, the "S" or system aspect in PACS has become critical. A PAC system cannot be implemented through merely connecting a series of boxes; it must be integrated, and able to support a changing workflow environment. The integration aspect has been emphasized by the recent Integrating the Healthcare Environment (IHE) initiatives. (See "A Look Inside IHE," page 60.) Going beyond integration in radiology, the U.S. Department of Veterans Affairs (VA) has one of the best integrated electronic patient record systems. That is what continued innovation, and vision of PAC systems brings: a truly integrated electronic folder, accessible by multiple physicians, across institutions, and ideally by the patients themselves.
Both the Department of Defense and VA are good examples of how a top-down directive and vision can make a major difference in implementing a new technology. It is somewhat surprising that major hospital corporations, some of which have more than 100 hospitals, have not pursued the same ideas with the same vengeance as the U.S. government. In any case, PACS has been instrumental over the past 20-plus years to facilitate the exchange and integration of imaging into mainstream healthcare. However, there is still a long way to go. As a matter of fact, the majority of the U.S. hospitals still do not have a PACS. However, I believe it is only a matter of time given its many benefits.
Herman Oosterwijk is president of OTech, a consulting firm specializing in PACS training, including e-learning. Information about OTech's services, as well as questions/comments on this article can be addressed via www.otechimg.com.