WEB DISTRIBUTION
KEITH J. DREYER
At the heart of the digital radiology department are two main computa- tional systems, the radiology information system (RIS) and the picture archiving and communication system (PACS) (Figure 19.1). Although these technologies continue to converge, their functions within an enterprise remain unchanged. The RIS encompasses many text-based computing func- tions including transcription, reporting, ordering, scheduling, tracking, and billing. The PACS deals with image-based computing functions such as acquisition, interpretation, storage, and local image distribution. The proper use of these automated systems dramatically reduces the use of film and paper within a radiology department. However, removing film and paper removes the conventional method for distributing radiology information throughout the hospital. Because the goal of any radiology department is to deliver timely and accurate interpretations to requesting clinicians, the digital department needs a digital method to deliver its results. Enter the Internet.
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C H A P T E R
T H E I N T E R N E T
An introduction to the emerging world of enterprise image distribution requires a basic understanding of the terminology and jargon associated with the Internet and the World Wide Web. For some, this is new and funda- mental information; for others, a review.
The Internet (Figure 19.2) is a collection of computers (i.e., a network) communicating over a variety of transmission lines throughout the world, using a single common protocol known as transfer communication proto-
FIGURE 19.1
The digital radiology department.
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FIGURE 19.2 Advantages of the Internet.
col/Internet protocol, or TCP/IP. This low-level protocol essentially allows all the computers in the world to communicate. It allows computer users and programs to communicate with each other using higher-level protocols such as SMTP (simple mail transport protocol, i.e., e-mail) (Figure 19.3). Hyper- text transport protocol (HTTP) allows the distribution of text and images (and a variety of other media types) and is commonly referred to as the World Wide Web (or the Web for short). It is easy to see why the idea of using a universal way to transmit and receive text and images—the Web—to dis- tribute radiologic information is becoming so generally accepted. Essentially, it is the process of turning your digital radiology department into a Web site.
And, as with all successful Web businesses, the Web does not change your business (radiology) or your customers (clinicians), it just changes the way you deliver your business to your customers. If done correctly, Web distri- bution can offer great efficiencies to you and your clinicians.
Of note, on top of the HTTP protocol sit several languages that define the details of the Web pages. Hypertext markup language (HTML) is the Web’s basic language and has been in place since 1994. Extensible markup language (XML) is a newer language gaining steam in the Web world due to its ability to separate data from display parameters, thus preserving the structure of all data fields. What does this mean? It means, for example, that even if a patient’s medical record number is deeply buried in the middle of a Web page written in XML, a computer program reading that page (yes, they can read Web pages, too) could find it easily and use it to access more information on the patient from a different Web site. Extensible markup lan- guage is becoming the de facto standard for electronic data interconnect
SMTP—Simple Mail Transport Protocol
FTP—File Transport Protocol
HTTP—Hypertext Transport Prot Protocol - HTML—Hypertext Markup Language - XML—Extensible Markup Language
FIGURE 19.3
Common protocols available over the Internet.
(EDI), a way for computer programs (running on different computers) to reference each other through Web services, such as a radiology Web image server connecting to a hospital EMR (electronic medical record).
H O S P I TA L - W I D E I M A G E D I S T R I B U T I O N
With the installation of PACS at many institutions around the United States, the task of distributing images to referring clinicians becomes a challenge.
In the legacy system, physicians who wish to view their images rely on obtaining their films from the radiology department’s film library. Often, these films are used to communicate with patients, family members, and con- sultants for patient education and patient management. The advent of PACS eliminates this classic film-based workflow. The use of preexisting intranet to distribute images is a well-accepted practice within hospitals due to its ubiquity, portability, and reasonable cost (Figure 19.4). (The intranet is the part of the Internet that is behind your hospital’s firewall. See Chapter 14,
“Networking Fundamentals,” for more detail.) The Internet, and associated hospital intranets, has increasingly become the technological basis for both image management within the radiology department and image distribution to the enterprise (Figure 19.5). For hospitals with legacy PACS installations that have not been designed around Web technology, vendors are able to add Web-based solutions with relative ease. Central to the appeal of Web- based distribution is the ability for any physician, anywhere, whether at home
FIGURE 19.4
Typical components of a PACS intranet.
or within the clinical setting, to use a personal computer as a virtual light box and view radiologic images and reports.
Early in the process, visionaries in the PACS arena predicted that the problem of image management and distribution should be approached from an enterprise point of view—creating a digital imaging architecture in radiology that would be integrated into the electronic medical record.
The guiding principle in system design should be that images go wherever alphanumeric medical information goes, a task best achieved by a flexible, integrated Web-based solution. The various protocols available allow this flow of information with guaranteed connectivity (Figure 19.6).
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You Own It
Variety of Pipes with Guaranteed Speed
Good for Short Runs
FIGURE 19.5
Advantages and disadvantages of an intranet.
HL7—RIS and HIS
DICOM—PACS
HTTP—World Wide Web
FIGURE 19.6
Common hospital intranet protocols.
C O S T S
Many PACS vendors still charge high prices for their primary interpretation workstations and thus do not offer a viable alternative for referring physi- cians who need to review their ordered examinations. The current ubiquity of the desktop PC is a resource that obviates the need for software-only primary interpretation clients deployable via the Web. For example, Part- ners HealthCare System Inc., Boston, the parent corporation of Massachu- setts General Hospital, currently has more than 32,000 PCs on its intranet.
Utilizing this resource for image distribution adds essentially no additional cost, provided there is a software-only site-licensed client available over the intranet for primary interpretation.
There remains a confusion of pricing of Web-based PACS solutions within the industry. The alternatives include cost per user, cost per view (or click), cost per maximum users, cost per concurrent users, cost per studies stored, and a one-time cost in annual licensing. This range of pricing struc- tures often creates confusion when comparing products using a price per- formance analysis. In their selection process, hospitals should always require vendors to converge on the same pricing model. It is the opinion of the author that the ideal pricing model is one that results in a one-time capital expense for a perpetual software-only license with a 10% to15% recurring annual software maintenance fee that secures all future upgrades. All hard- ware for the Web-based PACS, archive, and enterprise distribution system should be purchased directly from the hardware vendor to achieve maximum savings and direct customer support.
I N F R A S T R U C T U R E
Inherent in standard Web protocol is a client-server relationship. Whereas the Web server is a computer that contains the images to be distributed for viewing, the client, in this example, is basically the clinician’s PC. The fol- lowing paragraphs describe the requirements for both the server and client systems of a typical radiology distribution system.
S E R V E R
A Web server used for radiology image distribution needs to perform several functions, as follows:
◗ Accept images from a variety of DICOM sources.
◗ Compress images in either a lossy or lossless format (or both).
◗ Store compressed images in a local, fast access device (e.g., redun- dant array of inexpensive disks [RAID]).
◗ Archive all image data to a removable media archive (e.g., linear tape open [LTO])
◗ Act as an HTTP server waiting for Web requests over TCP/IP.
Typically, Web servers for radiology are Wintel-based PC servers, available from a variety of vendors, with a range of performance specifications. Sizing the system for this function requires several factors to be evaluated to provide optimum performance throughout the enterprise. These factors include cost, speed, number of concurrent users, reliability, and support. If the hospital distribution workflow calls for more than one Web server, it should be deter- mined whether each server should have its own archive or if one archive should be shared among all servers. In most circumstances, a single archive should be shared, with each Web server accessing a common, compressed RAID. As demand increases from clinicians for Web access, more powerful servers may be needed to maintain performance. One way to accommodate this growing need is by increasing the server’s processing power and RAM.
Another way is simply to increase the number of servers available for the task. Beware, some vendors’ software architectures will allow for these levels of upgrades, but others may run only as a single server, resulting in a much more expensive and limited upgrade path.
C L I E N T
The client device is quite variable (i.e., it can be any form of computer with access to the Internet—PDA, Tablet PC, or wireless laptop). In fact, pos- sibly the only commonality necessary among clients is that they contain an HTTP browser to access the server. Further, the browser can be from a variety of manufacturers (Netscape Navigator and Microsoft Explorer are the most common). Because of the large file sizes and video requirements for display of medical images and because the most common client in the hospital setting is an IBM-compatible PC, minimum configurations for PC- based client machines accessing radiology images should be defined by the hospital and supported by the software provider. Again, there is a wide variety among Web PACS vendors regarding minimum configurations. Hos- pitals need to be certain that any potential Web PACS software provides
functionality to as many existing PCs as possible within their current infra- structure.
This is one of the most challenging aspects of ubiquitous Web distri- bution. Because any computer on the intranet can access the radiology Web server, it is often difficult to enforce a minimum client requirement. There- fore, performance is unpredictable. For a new institution, it is simple to recommend the purchase of a certain level of PC. But for most of us, there is an existing fleet of PCs throughout our institutions that would probably require upgrades to meet the core requirements. For a large institutional deployment of clients, it is best to evaluate users’ needs individually to assess the intent of specific clinical access. Typically, some client computers are dedicated to specific clinicians while other systems are common and avail- able to several users (ideally with individual logons and passwords).
E X A M P L E : T H E W E B E X P E R I E N C E AT M A S S A C H U S E T T S G E N E R A L H O S P I TA L
A Web-based primary interpretation client (Figure 19.7) and server solution were installed for image distribution (Figure 19.8) as a film alternative that would allow the hospital to cost-effectively distribute radiology images to all
FIGURE 19.7
Web-based enterprise solution. CR indicates computed radiography;
MRI, magnetic resonance imaging; US, ultrasound; CT, computed tomography.
clinicians. The growing popularity of the Web guaranteed a degree of famil- iarity with the client software (a browser), which was easy to use and install with low support costs from the hospital information services department.
It was felt that a Web server solution would layer onto any basic security system, such as firewalls, token-delivered coded access numbers, passwords and usernames, secure sockets layers (SSLs), and virtual private networks (VPNs) (Figure 19.9); and that these technologies, as they evolved, would enable the radiology department to ensure security and patient confiden- tiality regardless of the referring physician’s access method and location.
Further, integration with the institution’s EMR has provided easy access to the enterprise for Health Insurance Portability and Accountability Act (HIPAA) tracking, central help-desk support, and integration with other departmental result-reporting applications. Incorporated into the Web- based solution is a JPEG2000 wavelet image compressor/decompressor that rapidly distributes compressed images throughout the enterprise with secondary access to lossless image data upon request. (No one, to date, has requested any.) The system is in its tenth year of deployment and continues to provide real-time image access to more than 5000 users with tremendous reliability.
PCT—Private Communication Technology SET—Secure Electronic Transaction
S-HTTP—Secure Hypertext Transfer Protocol SSL—Secure Sockets Layer
VPN—Virtual Private Networks
FIGURE 19.8 Internet security options.
C O N C L U S I O N
Converting from film-based radiology to filmless radiology is challenging, to say the least. Many of these challenges exist outside the department of radiology. Replacing film means providing clinicians with another distribu- tion mechanism. While there is great momentum within hospitals to keep the status quo, Web distribution offers many advantages over film. The successful deployment of Web servers and client viewers throughout the hospital enterprise will prove critical for the conversion to a truly digital radi- ology environment.
FIGURE 19.9
Sample client Web image viewer for computed tomography with selected features from text depicted.
