DICOM Update: VA issues updated DICOM requirements

VA issues updated DICOM requirementsBy Herman Oosterwijk, president, OTech Inc.

The Department of Veterans Affairs (VA), in cooperation with the Department of Defense, has updated its modality interface DICOM-compliance requirements for new imaging equipment (PNN 6/99). The original version of this specification was developed in 1997 to ensure consistent support of and compliance with the DICOM standard among the medical imaging vendor community. It covers requirements for all digital modalities, including MR, CT, ultrasound, digital radiography, nuclear medicine, film digitizers, digital x-ray systems, and nonradiology imaging.

The final version of this original document was issued on July 17, 1998, with compliance to begin one year later. However, several vendors protested that they could not meet the requirements by the specified deadline. In addition, the VA decided to incorporate into the document the technical framework of the Integrating the Healthcare Enterprise (IHE) initiative developed by the RSNA and HIMSS. Thus, the VA and the DOD determined to review the specification and two workshops were held earlier this year to give all modality vendors the opportunity to discuss the requirements.

The result is version 1.2 of the DICOM-compliance specifications. The most important section specifies the DICOM SOP Classes, which outline functionality for each modality. The most basic of these is storage SOP, which provides the mechanism for sending images from a modality to the PACS. The VA has raised the bar with regard to key attributes in the image header, now requiring patient name, ID, sex, and accession number. In the original DICOM standard, this information could be left blank in order to allow the exchange of images even when patient identifying information is not readily available, such as in emergency cases. However, this creates havoc down the line when these images have to be managed and retrieved.

Another important component of the new DICOM-compliance requirements is the modality worklist, which enables scheduling of specific modalities between the PACS and the information system. Support of this feature is critical because it eliminates dual data entry and ensures data integrity. Early implementations have demonstrated that “orphan” and duplicate images can be almost completely eliminated using this service.

Performed procedure step is the counterpart to modality worklist (PNN 7/98). This new service has yet to be widely implemented by many vendors, but it is essential for tracking how many images were generated within a particular procedure and what procedures were actually performed.

Storage commitment is another required service in the new DICOM-compliance requirements. This service allows a modality to transfer responsibility for its images to another device, such as the PACS. If the receiver commits to storing the images using this service, the images can then be safely deleted outside the PACS. This feature is particularly important for remote connections.

The most significant change in the VA specification, however, is that it now harmonizes with the technical specifications of the IHE initiative (PNN 4/99): The same DICOM services chosen by the group of vendors for the IHE demonstrations have been chosen for the VA specification, which should improve long-term interoperability.

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