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Letters |
Beth Israel Deaconess Medical Center &
Harvard Medical School
Boston, MA 02215
The article by Schueller et al. [1] in the January 2006 issue of AJR compares hard-copy image reproductions of full-field digital mammograms (FFDMs) made with wet laser printers and paper printers. Importantly, but not surprisingly, the authors concluded that "images obtained from a wet laser printer show superior objective and subjective image quality compared with a paper printer" [1].
Schueller et al. [1] state (italics added) that "hard copies for FFDM are routinely generated by wet laser printers which have also become state-of-the-art equipment for other imaging techniques such as CT, MRI, and sonography." Nowhere in the article do the authors mention dry laser printers that, in the United States and, I suspect, in Europe, have long been the industry standard for rendering hard copies of digitally generated images in radiology, including FFDM.
Fuji and Kodak have discontinued the manufacture of wet laser printers and, I believe, only Agfa continues to manufacture a wet laser model. This is sold primarily outside the United States and is the model used by Schueller et al. [1]. As the authors point out, "wet laser images require chemical development, which is expensive, contributes to environmental pollution, and needs careful handling to obtain image quality" [1]. In Massachusetts, the environmental water pollution laws, mandating high levels of silver extraction, threaten to make the use of wet printers prohibitory.
Both wet and dry laser printers can produce detailed images with 40- to 50-µ resolution. Both printers are expensive (generally > $60,000), but wet printing is more expensive because it requires purchase of a processor in addition to the camera. Film for wet processing is slightly cheaper than dry film ($0.92 vs $1.10 per sheet).
New purchasers of an FFDM unit may not be aware that laser printers are an important added expense—over and above the costs of the mammographic unit, high-resolution monitors, and computers. Even when images are interpreted from the monitor and stored digitally, some will still need to be converted to hard copy for viewing at other facilities and offices. It is my understanding that all printers used for copying digital mammograms in the United States are required to meet Mammography Quality Standards Act (MQSA) standards [2]. Eventually, expensive laser copiers may be less necessary if digital images are conveyed to other sites via discs or the Internet. However, the required compatibility and widespread availability of equipment from different manufacturers are not yet a reality.
In summary, I believe dry, rather than wet, laser printers are the state-of-the-art equipment for producing hard-copy images of FFDMs and other high-resolution digital images in medicine. They are currently used by most radiology departments in the United States.
References
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