This installment describes the advantages and disadvantages of an electronic-based image archiving system, and its accompanying acquistion and implementation challenges.
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
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
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.
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