The quest to implement filmless radiology systems encounters the significant problem of electronic image archival. Over the years, radiology departments have developed and efficiently managed film file room libraries. These film file rooms consist of a significant number of patient film jackets which contain analog films and possibly copies of consultation reports and pathology reports. To organize and maintain these files, film file room libraries are staffed by radiology personnel, requiring on average 15 to 18 full time equivalent staff members for a department conducting 230,000 examinations per year. As can be imagined, such analog archival systems are people intensive and often come under fire, especially when a particular patient's film jacket cannot be found. Bar codes affixed to the film jackets assist with their management, but this does not lessen the burden on available personnel.

The radiology film file library is distributed into several files, consisting of the immediate film file room section (film jackets for patients whose examinations have been conducted in the past 15 to 30 days), the intermediate film file room section (those film jackets that contain the examinations that occurred within 30 days to 2 years past the last examination date), and the long-term film file room section (film jackets that are more than 2 years past the last examination date). Anytime an examination occurs on a patient who has had a previous examination, for any reason, the film jacket is reinserted into the immediate film file room section.

Radiology departments generally are proud of the performance of their film file room library staff. The average retrieval rates are the following: Seventy-three percent of all retrievals are requested from the immediate film file room selection (2,500 to 3,000 film jackets), 24% are from the intermediate film file library (over 250,000 archived film jackets), and 3% are from the long-term film file libraries (over 470,000 archived film jackets). Due to the high volume, once analog films are separated from the film jacket, it is difficult to properly reinsert them.

Achieving successful electronic archival requires a lot of work just to change the analog film library paradigm. In analog image archival strategies, there is a general understanding of the existing technology, so the level at which the archival is managed is high. For electronic image archival, the radiology department has to move past the work of selecting the technology, to the harder work of figuring out how to make the electronic archival serve the operational environment. Otherwise the technology becomes yet another barrier the physician has to hurdle to effect care.

It is critical to recognize that changes in the technical environment require greater changes in the operational environment. In light of all the potential advantages of an electronic-based archiving system, these changes seem worth the necessary adjustments in systematic operations. The advantages of electronic archival are: 1) no loss of examination data; 2) savings in work hours and cost due to elimination of physical handling of analog films; 3) the simultaneous availability of images (and patient records) to many users; 4) easy retrieval of examinations and patient data; and 5) the provision of security levels to archived images and patient records.

There are, however disadvantages to implementing the electronic image archive. These include: 1) the need for reprocess engineering, such as use of workflow engines, to obtain the benefits of electronic image archival; and 2) the requirement of cost analysis of the increased level of additional technology (acquisition, networking, soft-copy reading on workstations, database operation, DICOM standards, image compression engines, selected hard-copy generation, and throughput analysis).

Archival device media

The choice of an archival device medium is an important issue in respect to cost and throughput of the archiving system. Magnetic disks provide a fast medium with less than 50 msec access times. But these systems are expensive, even in spite of their declining costs. Redundant Array of Inexpensive Disks (RAID) systems are best for the requirements of immediate file section (15 to 30 days) archiving. These add redundancy in that one disk of the five that are online could fail and the image data can still be recovered. Optical disks and magneto-optical disks provide high capacity, (100GB-10TB) but are slower in accessing and retrieving image data. Automated magnetic tape units offer higher capacity, throughput, and cost effectiveness, and are excellent alternatives to optical storage. These units are now being offered to radiology departments for archival of image and patient record data. Data transfers from magnetic tape units can achieve 5M bits-per-second (sustained). Also, such units, with the addition of wavelet video compression engines, can offer a library of video-recorded patient examinations.

Data management software

A software system is required for managing the image and patient archival function. While many software systems are available, it is best to acquire a software package that has been implemented as a Hierarchical Storage Management (HSM) system. This type of software system has to be able to move data in an HSM fashion and perform the network backups. When choosing management software, it may be useful to visit sites where the archival system under consideration is currently operational.

Additionally, a DICOM database is essential to the operation of the archival system. It is also important to look to the future and consider that an upgrade path for increasing archival capacity be provided which does not greatly impact the operation of the system and is not prohibitively expensive.

There are significant reasons to explore the use of one large, enterprise-wide archive to meet the needs of administrative data processing, research storage, cardiology, pathology, and the electronic medical record. By sharing the electronic data repositor's needs of all these services, the single data archive warehouse can be enhanced to provide many features that no single department could justify cost wise, such as data security engines, workstations that display images and text, etc.

Conclusion

The implementation of an electronic image management archival system is necessary to achieve a completely filmless radiology operation. Additional technologies will be required in this endeavor, including the acquisition of image and patient data, intra- and inter-networks, acceptable grayscale workstations for soft-copy reading, selected hard-copy recording, DICOM standards, and HL 7 interfaces. Implementation conducted in phases (first the ER, then ICUs, the radiology department, etc) should allow for smoother transition. Parameters of throughput, cost, image quality, and diagnostic accuracy should be measured. If image data compression is to be utilized, then these parameters also should be carefully recorded. AR

Dr. Dwyer is a Professor in the Department of Radiology at the University of Virginia Health Sciences Center in Charlottesville, VA. He is also a member of the editorial advisory board of this journal.