Standards Watch | IHE elevates CD exchange to a new level of compatibility

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The Integrating the Healthcare Enterprise joint activity by HIMSS and RSNA, which defines profiles based on standards such as DICOM and HL7, just released the new PDI (Portable Data for Imaging) integration profile as one of several supplements in their draft for trial implementation.

This integration profile specifies how images and related information can be exchanged among imaging devices using CDs. In addition, there is an invitation for vendors to participate in an RSNA demonstration. The interesting part of this demo is that attendees of RSNA 2004 will receive a sample IHE-conformant CD with sample medical images and patient information. Vendors participating as so-called IHE Integration profile Media Creator actors also will be able to generate sample CDs on site in their exhibit booths to show their capabilities to create IHE-conformant media. Vendors participating as Media Reader actors will be able to show their capabilities to import IHE-conformant media. RSNA will truly show IHE in action.

The creation of CDs for the exchange of images in a standard, DICOM manner, has been defined for many years. Initially, this was mostly used for niche applications, such as to store cardiology runs, or for cine loops from portable ultrasound. However, this application has become suddenly very popular. The reason is simple: cost reduction. If you have the images available in digital format, burning a CD costs very little, and you can easily train your file room personnel to do it. For example, a major hospital in the Dallas-Fort Worth area will gladly provide a copy of an exam for the patient to take with him or her for $85. However, if they opt for the CD option, it is free, which encourages them to use the latter option - therefore providing savings for the institution.


Writing images on CD is definitely less expensive than printing yet another film. In addition to the film and labor savings, there is another, often overlooked advantage, i.e. mailing cost. I visited with the Mayo clinic in Rochester a month ago, and they told me that they send out about 100 CDs a day. Postage for a CD mailer is less than a dollar; postage for a film jacket is about $10. They save close to $5,000 a week on shipping costs, which results in a quarter of a million dollars saved per year!

One of the risks with writing images to a CD is potential incompatibility. Imagine a patient who has traveled from his hometown, which could be thousands of miles away, to the Mayo clinic with his images on a CD, and the images cannot be viewed, or are of an unacceptable image quality because of the degradation in the storage process. The latter can happen, for example, if a chest CT image, with a very wide contrast range, is stored as an 8-bit JPEG image, basically clipping off all of the lung or bone tissue information. To prevent these situations, the DICOM standard has been very specific and limited the number of options for the images and related information to be stored in DICOM format in the form of a well-defined Application Profile, to increase the chance for interoperability.


However, what has happened over the past few years is that several of the top PACS vendors have been storing images in a proprietary format, which is unacceptable. Imagine an institution needing to have a copy of each vendor's PACS software available to read these? Ridiculous. To address this issue, most vendors package a copy of their viewer on the same CD. However, this poses two problems. First of all, any time you exchange an executable file, there is a heightened chance of spreading a virus. As a matter of fact, many institutions have very strict guidelines about installing non-validated software on their PCs. Secondly, this does not allow the proprietary images to be imported into the PACS for comparison, allowing them to be viewed using their software on their own workstation for 3D or other processing. Even if the images are claimed to be stored in a DICOM format, vendors are not always quite following the DICOM standard. There was actually a poster presentation at the recent SCAR conference in May in Vancouver from the Yonsei University Medical Center in South Korea, demonstrating how they had to validate each and every incoming CD for potential issues. Remember, once you write a CD with information that is not quite stored in a compatible way, it is out there forever.

So why is this new PDI IHE profile so significant? In the first place,