A?patient’s injuries are precisely diagnosed minutes after an automobile accident. A stroke victim’s brain scan reveals no risk of hemorrhage-and shortly after the episode, he is given the drug that will preserve his quality of life. A worried woman’s tumor is imaged, and immediately the radiologist can reassure her that it is not cancer. The quality of health care will dramatically improve as diagnostic images move with lightning speed across the information superhighway, making real-time radiology a reality. Minutes after an imaging procedure is completed, a radiologist’s opinion will be recorded and delivered throughout the health care system.

Even today a crystal ball is not required to see that Web technology is what is driving picture archiving and communications systems (PACS). In addition to improved diagnostic speed and efficiency, Web-based PACS makes a lot of sense in today’s health care system for another very important reason: cost. The Web allows a far more robust, globally available system at significantly lower price than other communication technologies. High-speed communications cables are already in place, making it possible to stream data along the information superhighway. PACS data can hitchhike a ride to where it needs to be.

Another significant cost-cutting advantage of Web-based PACS is that it allows use of simple, relatively inexpensive personal computers (PCs) for viewing clinical data throughout the hospital, instead of expensive dedicated workstations. Of course, do not expect any desktop PC to perform many of the sophisticated image processing functions that can be done on a dedicated station. Fully featured workstations are still needed in the radiology department for primary reading. But with Internet technology, PCs can be turned into viewing stations enterprise-wide as well as in teleradiology applications.?

Moreover, using JAVA technology, this can happen without the addition of software, on- or off-site, eliminating the need to purchase and tweak software for a large number of system computers when upgrading.?

The JAVA application, or applet, enhances the capabilities of a standard Web browser, turning it into a diagnostic or clinical review application. It automatically downloads PACS software when accessed through a Web browser. PACS runs on the PC but is never actually installed. A perfect service provider, JAVA applets are immediately available when needed and then disappear.

The most important argument for Web-based PACS is that it is the way of the future. Technology is racing forwards at an astonishing pace. Anything purchased today will be outmoded by the time it is installed. Therefore, to make the most of a budget, radiologists must build in maximum upgradeability, compatibility, and open architecture. A Web-based PACS will keep the department poised to upgrade to emerging technologies as the importance of the Internet grows in the medical information field.

The flip side of the story is that today many are still experiencing a slow ride. The Internet bandwidth constantly applies the brakes because of its limited data transmission speed. PACS companies have devised an inventive bag of tricks to deal with the problem, from sophisticated image-specific data compression-lossy, lossless, and adaptive-to automatic prefetching and routing of images with data push technology. Some companies have developed complex algorithms that optimize image compression on the fly so that files of any size can be transmitted and opened without data loss. With push and pull technology, the system analyzes images, determines where they need to go, and sends them there in advance of reading sessions to eliminate file transfer waiting time. The good news, however, is that bandwidth is widening rapidly.

Objectives to fulfill

North York General Hospital, based in Toronto and part of the University of Toronto, recently installed an extensive Web-based PACS. The hospital had gone through two archives during the previous 8 years, and so had several primary objectives to fulfill with this project.

North York General Hospital, a 400-bed facility, is merging with nearby North York Branson Hospital and doubling the size of its imaging department. The move to a filmless diagnostic imaging department is inevitable. Because of the organization’s new, larger size, the project is ambitious. Not all features are up and running yet, but it was necessary to develop a system that would accommodate both present and future needs as they changed.

The separate radiology departments need to function together seamlessly with information flowing from one location to another. PACS also had to move images where needed throughout the hospital, from operating and emergency departments to bedsides. This required a distributed PACS architecture that functioned flawlessly as a unified system. The system also had to be teleradiology-enabled to communicate with physicians off-site as well as to send images to referring physicians and on-call radiologists.

In addition, it was necessary to take advantage of existing technology, including an intranet system connecting key departments in the hospital. With the inadequate Canadian health care budgets, it had to be done extremely cost effectively. This was not an easy project.

The advantages of a Web-based system in all these applications are enormous and would have been impossible as recently as 5 years ago. First, the hospital could utilize the Internet’s significant cost advantages. Web-based technology eliminated any compatibility issues throughout the system, whether communicating with other hospital departments, the second radiology department site, referring physicians, or radiologists at remote locations. All image viewing software was on the main server and sent in JAVA applets to the PC viewing stations.

With respect to PACS reliability, the department had high expectations. Most PACS companies guarantee 98% reliability. That may be acceptable for individual pieces of equipment, but not for the system that drives your whole department and upon which patients’ lives depend. Imagine getting into a commercial airliner with the assurance that such planes have a known uptime of 98%?

System Features

The PACS selected uses a decentralized processing paradigm on several CPUs (central processing units), making it extremely fault-tolerant. If one computer fails, others take over. Short of a hospital-wide network failure, the system is always up and running.

Also on the list of features were sophisticated work-flow management tools, modality work lists, which transmit task lists, images, and other information throughout the department; automatic fetching and routing of prior patient studies to address issues of efficiency and speed limited by bandwidth; referring physician distribution tools; and reliable interface with the general hospital information systems.

The system consists of a Web access engine, high-speed, scalable clinical data repository, HL-7 interface with the hospital’s new health care information system, sophisticated work-flow management tools, and a host of PCs. For primary reading, powerful NT-based workstations will be placed at each major modality. They provide individual display protocols and high-resolution, high-luminance monitors. (Each radiologist has a sophisticated Unix-based workstation on his or her desk.)

These dedicated stations are the only viewing tools that are not yet Web-browser based. All system components are connected via standard Ethernet? cables as they were in the previous proprietary PACS installations. Other than upgrading some hubs into switches, no large investment in networking was necessary.

With the new system, when a technician completes a study, the digital image is stored on the data repository. Work-flow management software has been programmed to know when and where this type of study is read. It is automatically routed, along with all previous relevant patient studies, with data push technology to this workstation and entered on the radiologist’s work list.

Radiologists can take advantage of an array of sophisticated processing tools to examine the image and make a diagnosis. As the radiologist dictates a report, it is automatically attached to the study. A copy of the report is sent to the repository for storage. A copy will also be sent to the radiology information system file in the computerized patient record.

The study is automatically routed via the hospital intranet to appropriate physicians involved, whether a primary care physician, surgeon, or other specialist, again using data push technology. These doctors simply open their Web browsers to access the PACS application, which enables them to view the study. Any physician desiring to see the study can similarly access it by calling it up from the data repository. All they need is a standard Web browser.

The PACS intranet has been designed so that it eventually will operate in both hospitals, allowing them to function in an integrated fashion. Hard copy or CD-ROM copies are available as necessary. Physicians outside the hospital can simply use their Internet browsers to enter the hospital intranet and access studies. All they need is a user ID to pass through the fire wall. With the data push feature, studies can also be sent directly to the referring physician’s personal computer. Implementing this is more a matter of education, acceptance, and high-speed Internet access by referring physicians. From a technology standpoint, there are no barriers.

Optional features

Another option under consideration is an email feature, which will connect the intranet to the Internet and automatically e-mail reports with key thumbnail images to physicians outside the network. Doctors wishing to view the entire study can then click on a link and have the study sent to them along with the required image viewing tool-set through JAVA.

Staff radiologists have a code to enter the hospital intranet through the Internet from their home PCs.

The primary NT and Unix-based reading and reporting workstations provide everything North York’s radiologists need in a single unit. In addition to sophisticated work-flow management tools that eliminate administrative red tape, they have advanced image viewing and analysis tools. These include tools for stack reading, maximum/minimum intensity projection, shaded surface display, thin slab sliding display, volume rendering, and virtual endoscopy. It is important for the primary reading radiologist to have a variety of tools easily available, so that a data-set can be easily and thoroughly explored at one location if possible.

In the future, as the capabilities of JAVA expand, this type of software will also likely reside on the main server and be downloaded for use on a simple high-resolution PC, which will replace the dedicated workstation.

Since bandwidth is still limited today, image compression technology was an important aspect of the system. Adaptive wavelet compression is a particularly compelling solution. It uses smart wavelet technology to assess each image and determine the best compression ratio for it. The user does not need to guess at it. Also, each modality tolerates different ratios of compression, while still providing images of acceptable diagnostic quality. Adaptive compression improves overall efficiency.

With regard to PCs, the hospital replaced some of the older models with newer medium-priced units, which generally are more than adequate for today’s PACS. At the minimum, a 300 to 450 MHz Pentium chip, as well as at least 64MB of RAM, are required for acceptable performance. Increasing to 256MB of RAM boosts performance significantly and is not a major added cost. An 8-16MB videocard, which is standard with most new PCs, is fine. If extra money were to be spent on one item, it would be the monitor. A larger screen makes a tremendous difference. High-resolution, high-luminance monitors are probably needed only for interpretations of plain radiographic examinations.

Network considerations

For Internet connection, modems can function acceptably with an integrated services digital network (ISDN) line, although an asymmetrical digital subscriber line (ADSL) or cable connection is obviously much better. Intranet connections require at least a 10-base T line. The lines are 100-base T and a gigabit Ethernet is now being installed throughout the hospital. The thirst for speed on a network appears to be virtually limitless. The faster, the better.

Technology rushes forward. State-of-the-art CT slices are becoming thinner and multi-detector helical scanners are generating more and more data–as much as eight times more per second-than single-slice scanners. A dual-slice scanner has been used for more than 6 years, and even that device generates very large data-sets. Keep in mind that anything perceived as very fast today will be too slow tomorrow. Install the best that can be afforded.

The system that drives the department is well thought out and functions almost flawlessly. The only aspect that needs to be changed is Internet bandwidth. Today, the capacity of the Internet to handle data-intensive radiology image files is Internet-based PACS’ single most limiting factor.

What is needed is a comprehensive network of commercial fiber-optic cable with wide, flexible bandwidth. More and more, service providers are laying the networks that will revolutionize radiology and hospital information in general. Currently, ISDN lines transmit information at 128kb/per second, but cost more than regular telephone lines, while cable and ASL/DSL lines transmit at speeds between four and 20 times faster but cost more. Fast, dedicated T1 lines move data at a rate of 1.54MB/per second but cost more than $1,000 per month to lease.

Some estimates are that fiber-optic cable is doubling its capacity every 9 months. Service providers are now delivering a per fiber capacity of 400 to 800 gigabits (compared with 45 megabits in 1980). Data transmission speeds of terabits per second are expected. Not too far off are wireless information transmission systems that rely on laser data beamed over short distances, further stepping up the speed of an entire communications network.

Be advised: The technology is right around the corner.


Raziel Gershater, MD, is chief of diagnostic imaging at North York Hospital, University of Toronto, Toronto.