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The infrastructure build of a PACS (Picture Archiving and Communication System) certainly varies from large hospitals to small hospitals to radiology centers. Aside from defining the parameters of physical allocation, and assuming that every build has cost optimization as the ultimate decision maker, the driving force of how a PACS is designed is an assessment of purpose.

PACS requires storage of not only image data but also indexing data. Even though the two different types of data take up storage, the type of storage is of great importance. Image data requires an enormous amount of storage space, especially with the use of more advanced imaging modalities, like a multi-slice CT (Computed Tomography) or an MR (Magnetic Resonance) imager. The demand is ever increasing, somewhere in the vicinity of two to five terabytes per year, depending on the hospital and the demand of the hospital’s workflow, and that is after applying reversible compression. In years back, the cost of storage took up the largest part of a PACS budget, and if the demanding growth, percentage-wise, of today’s storage needs were superimposed to earlier needs, the cost would be astronomical.

Fortunately, prices of storage space has decreased so significantly, the main component of the overall PACS investment has now shifted to be the lesser, and especially initially, as hospitals can defer the purchase of storage on a “pay per need” basis. Once image data is written, the data is hardly ever changed, viewed by more than one person at any given time, or even accessed more than several times before it is archived. Therefore, this type of data does not require high speed disk access – the least expensive kind, especially considering that the system is only as fast as the system’s slowest constituent – network speed. Conversely, indexing data does require fast access. Data is constantly being updated, backed up, changed, queried, and accessed not by one but multiple workstations concurrently, demanding the fastest and most robust “stuff” out there. Obviously, the cost is significantly higher, but the amount of storage needed for indexing data, comparatively, is much smaller.

An assessment of purpose can affect the ultimate functionality of PACS workstations. Monitor quality, the use of simple web browsers rather than sophisticated PACS software, and strategic locations and surroundings—to name a few, all have cost savings implications. If a workstation in an outpatient clinic will be used to review imaging studies as a reminder of imaging findings, the megapixels requirements in such views are not as demanding as, let us say, a workstation used by a radiologist, to generate a diagnostic report. Determination of when it is necessary to view an image at maximum resolution on a high resolution monitor and when such a need is not deemed indispensable provides the resolve.

Similarly, the use of proprietary software, typically very expensive, by radiologists, issuing diagnoses and final reports, or searching for specific features of studies, or even preparing patient or multipatient folders for multidepartmental team meetings or conferences, necessitates the manipulation of images via tools that enhance things like density values, contrast levels, and grayscales or control image orientation and magnification. Inversely, the use of a web browser, like Internet Explorer, using a typical computer, is free and can be used by anyone to display images primarily for review.

Certainly, the choice of where to set up PACS workstations is important for optimization of workflow. Ambient light is a consideration one might not immediately recognize as important. Lighting, or the lack thereof, where monitors will be placed, must be optimized. High monitor luminance and dimmable lights to achieve a good viewable atmosphere are just as important as the use of a quality, high resolution screen.

An assessment of purpose in all the aforementioned areas can greatly enhance PACS cost savings. Luckily, image and indexing costs are going down by the minute and a good question to ask when considering workstation setup is “Why am I looking at the image in this particular location?”

References:

• Meenan C, Daly B, Toland C, Nagy P: Use of a thin-section archive and enterprise 3D software for long-term storage of thin-slice CT data sets. J Digit Imaging 2006; 19(suppl 1):84-88.
• Brem MH, Bohner C, Brenning A, et al: Evaluation of low-cost computer monitors for the detection of cervical spine injuries in the emergency room: an observer confidence-based study. Emerg Med J 2006; 23:850-853.
• Strickland NH: PACS (picture archiving communications systems): filmless radiology. Arch Dis Childhood 2000; 83:82-86.
• Mathie AG, Strickland NH: Comparison between 'stack' and 'tile' mode CT image display on PACS. Radiology 1997; 203:207-209.
• Luo H, Luo J: Robust online orientation correction for radiographs in PACS environments. IEEE Trans Med Imaging 2006; 25:1370-1379.