With approximately 900 digital mammography units now operating throughout the U.S., much has been presented and published about the challenges and opportunities this modality brings to the clinical setting.
While digital mammography offers opportunities for greater patient throughput, reduced recall rates, improved interpretation tools, and elimination of film and chemical processors, the modality also presents significant challenges, especially with workflow, variable learning curves, and system integration, as well as the difficulty in working simultaneously with film.
Challenge for the radiologist
For the radiologist, perhaps the greatest challenge has been the additional time required for interpreting digital mammograms compared to film mammograms. Current estimates are that digital mammograms take two to three times longer, so digital mammography's impact on workflow, productivity, and accuracy merits further discussion.
First and foremost, we must keep in mind that interpretation routines and methods for film mammography are well understood across breast imaging. The process of hanging films on a lightbox, preferred hanging protocols, and the individual search patterns of the radiologist are standard operating procedure at each facility.
Digital mammography shouldn't be seen as merely an extension of the current methods, or as a minor change from a film to a digital receptor that fits easily into the current workflow. Digital mammography is a major change in how images are acquired, hung, viewed, manipulated, and stored for future comparison.
A portion of digital mammography's additional interpretation time can be attributed to the learning curve of working with a new digital workstation and capitalizing on the ability to manipulate or customize the interpretation process. This has been shown to improve over time and should balance out as staff members become more proficient with the technology, but it is far from the only culprit.
The inability to show all images in full resolution simultaneously, applying proprietary image processing algorithms, annotating images, communicating with the technologist at the acquisition station for additional views, rearranging nonstandard hanging protocols, and delays in retrieving images from an archive or PACS are a few factors adding to longer interpretation times. While these issues are not immediately resolvable, they are expected to improve over time as manufacturers upgrade or automate both software solutions and user interfaces.
Comparison with previous films
Another contributor to the additional time required for digital mammography interpretation is a standard component of every mammography interpretation: comparing the current image to previous films.
As compared to the film-only environment, it is here that we come face to face with a true mismatch and conflict between analog and digital technologies (films on lightboxes and digitals on high-resolution displays). Using both together creates a suboptimal reading environment, as the lightbox creates glare on the soft-copy workstation, as well as potential eye strain from side-by-side viewing of different light outputs. Further interpretation difficulty and time consumption is caused by the size difference of the two formats, making it difficult to make a size comparison of subtle features from the prior film to the current digital image.
Several radiologists have described this film/digital mismatch as "reading mammograms in purgatory" and "a very painful place to be." In addition to the increased interpretation time, some feel it contributes to fatigue and the potential for interpretation errors.
Minimizing a pitfall
Unfortunately, the comparison of previous films to current digital images cannot be eliminated in the short term, even if the facility elects to upgrade entirely to digital units, eliminating analog systems altogether. This, of course, stems from the fact that it takes several years of repeat visits to build a completely digital library for returning patients and new patients arriving with prior films.
However, this pitfall can be substantially minimized and the move to a digital library accelerated by digitizing film studies in advance of acquiring digital mammography or while gradually phasing out film. In the past this required the acquisition of a suitable scanner/digitizer and a secure reliable storage method such as a PACS or other solution, as well as the labor necessary to accomplish the various tasks.
The costs associated with this process are often seen as monumental, while the value and payback are seen as minimal or simply misunderstood. Therefore few facilities have been willing to undertake the task. This is quite remarkable since the economic and workflow benefits are substantial when digital images can be electronically called to the workstation on demand and films need not be fetched, hung, or returned to storage after being used for comparison (estimated to cost $5 to $7 per patient per year).
A painless solution
The leading computer-aided detection (CAD) companies now offer the ability (with software upgrades or a new equipment purchase) to capture digitized images at the time CAD is performed and apply a DICOM header, thus allowing them to be stored for electronic retrieval at any time to any DICOM-compliant workstation. This solution eliminates any additional labor costs by using existing CAD labor, and reduces equipment acquisition cost (purchase of a separate scanner/digitizer) with the added benefit of current CAD reimbursement. Secure, reliable image storage can be accomplished with an existing PACS or a suitable alternative.
If a PACS is not available, a very suitable alternative is a storage service provider (SSP). SSPs provide storage and retrieval of digital images on a fee-per-study basis, eliminating the purchase and maintenance of storage devices as well as removing the risk of technology obsolescence. Some SSPs offer onsite storage for immediate study access, long-term offsite storage for the life of the patient, and disaster recovery/backup that can be configured to meet the needs of individual facilities, thus allowing implementation of advanced technology solutions without requiring IT staffing.
For facilities creating a digital library prior to acquiring digital mammography, long-term offsite storage would be economical as the images would not be required for immediate viewing for some time. As the facility adds digital mammography the studies would then be "streamed" back to a PACS or other onsite storage. The SSP is a painless solution as it doesn't require a large capital investment, yet can be easily incorporated with future requirements, including PACS.
Economic and workflow benefits
As stated previously, there are substantial economic and workflow benefits when images are readily available in an electronic format, and previous films do not have to be fetched, hung, and returned to storage. While there are indeed up-front costs for initiating and maintaining a digital mammography library, they are immediately offset by savings (a portion of the $5 to $7 per patient per year, depending on the library depth for each patient) when digital mammography is implemented.
Additionally, numerous hidden costs are associated with workflow and productivity when a facility has to operate in both the digital and analog environments simultaneously. Consider only the productivity of the radiologist and its economic impact. At average volumes an additional minute or two per case equates to days of reduced productivity. Higher volumes would reduce productivity by weeks. Will additional radiologist resources be required to handle the same number of cases in a mixed analog/digital environment? Is there an effect of longer hours and potential fatigue on interpretation accuracy?
Easing the transition
Digital mammography requires an increase in interpretation time by the radiologist. A contributor to this additional time requirement is the comparison of previous analog films with the current digital ones. The conflict of these two technologies in the reading environment negatively impacts workflow and productivity, and could contribute to fatigue and affect accuracy of interpretation.
In the short term, previous films cannot be eliminated, but their impact can be minimized by digitizing them and creating a digital mammography library of comparison studies. Utilizing a CAD system, digitized images with DICOM headers can now be captured as the CAD is performed and sent to a PACS or alternative storage solution for archiving and future retrieval. This solution is cost-effective as it requires no additional labor, and the CAD procedure is reimbursable and pays for itself.
If a PACS or other solution is not available, a storage service provider (SSP) is an excellent and economical alternative as a repository for the library. The SSP is a painless solution as it does not require a large capital investment, yet can be easily incorporated with future requirements, including PACS. There are economic and workflow benefits when images are readily available in an electronic format. Therefore, creating a digital mammography library makes practical sense for all mammography facilities, and minimizes a recognized challenge to the implementation of digital mammography.
By John Neugebauer
AuntMinnie.com contributing writer
October 26, 2005
John Neugebauer has been involved in the introduction and widespread clinical use of products for the early detection of breast cancer for the past 25 years. He is director of breast imaging at dealer/distributor Vasant of Hamden, CT, a distributor for storage service provider InSiteOne of Wallingford, CT. He provides consulting services to various clients, including InSiteOne.
Related Reading
Do DMIST results underestimate FFDM's impact? October 24, 2005
Harnessing technology, training to make the most of FFDM, October 3, 2005
DMIST study: Younger women may benefit most from digital mammo, September 16, 2005
Digital mammography presents PACS challenges, July 8, 2005
Digital mammo with CAD requires sharp eye for false negatives, June 30, 2005
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