Analysis of Outside Image Submission to PACS
 
Authors:
Kevin W. McEnery, MD, University of Texas M. D. Anderson Cancer Center; S. Jeff Shepard, MS; Stephan Venable, MBA; Jay J. Patel, MBA; Chuck T. Suitor, MS
 
Background:
With the migration of image interpretation to PACS, there has been an ever growing experience with supplementation of internally acquired images with digital comparison images. In analysis of transfer patterns, we intend to understand the present state of image transfer, with regard to age of image studies and the residual reliance on film-based image transfer. We present analysis of outside imaging studies into PACS at an tertiary oncology referral center.
 
Evaluation:
Outside media importation was analyzed for the period 9/1/2008-8/31/2009, or all outside institution studies imported into institutions PACS archive. During the study period, 101,738 studies were imported. Of the imported studies 78,161 (76.8%) originated on digital media (CD or DVD), and 23,577 (23.2%) originated on film. The percentage of studies on via CD increased during the study period to 82% in August (Figure 1). This represented the largest proportion of CD. Since 2005, the proportion of CD-based imported studies continues to increase. Overall, imported studies represented 21.7% of all studies stored on the PACS archive. Digital studies were transferred directly into PACS, while film-based studies required digitization. For studies imported into PACS, both the dates of importation into PACS, as well as the date of study creation, were recorded in the DICOM metadata. Analysis of time from outside study acquisition to study transfer into our PACS for all studies, revealed 12.3% were less than one month old, 54.0% were 4 months or less in age, and 90% were 40 months or less in age (Figure 2). Digital transferred studies were more recent in age: 15% were less than one month old, 62% less than 3 months old, and 90% were less than 19 months old. For film-based images, 3.3% of studies were less than one month old, 27% less than 3 months old, and 90% were less than 76 months old.

Figure 1

Figure 2
 
Discussion:
The ability to import prior comparison examination into PACS is an essential aspect of the radiologist rendering an accurate interpretation. In our experience, there is an ever-increasing reliance on digital media to enable the transfer of studies between PACS systems. However, despite the presumed widespread availability of PACS-based interpretation, film-based transfer was employed in almost 22% of imported studies. It is clearly acknowledged that image transfer via film and digital media will one day be replaced by direct PACS-to-PACS transfer but, given the persistence of film-based image transfer, this is perhaps many years in the future.

Interoperability of healthcare systems has been the topic of much discussion in Washington. The presumption of seamless transfer of healthcare data results is the reduction of overall healthcare costs through the reduction of unnecessary repeat examinations. In our analysis, 12% of the image studies were less than one month old. In this context, it would appear that an equally important value of outside study availability is to serve as comparison studies, increasing the diagnostic accuracy of subsequent examinations. For PACS administrators, contemplating interoperability projects, the experienced pattern of age of the image transfer would indicate that a significant portion of image transfer requests will require transfer of both recent examinations, as well as historical examinations, in many cases, months or even years old.
 
Conclusion:
Imported image studies into PACS represent both recently acquired image studies, as well as historical image studies. Historical images provide an important context for comparison of subsequent imaging studies. The percentage of studies transferred via digital media continues to increase relative to film. However, film digitization still represents approximately 20% of imported image studies.