As DICOM continues to evolve, new functions emerge

November 8, 2002

The DICOM standard is continuously evolving. As a matter of fact, every two or three months, a new part of the standard is typically approved by the DICOM committee and incorporated into the standard. A look at

The DICOM standard is continuously evolving. As a matter of fact, every two or three months, a new part of the standard is typically approved by the DICOM committee and incorporated into the standard. A look at past elements in the evolution and what's likely in the future will give you a sense of how this process works.

Additions to DICOM can be considered as steps to bring the standard up to a new level or expand its functionality within a level. For example, when DICOM was initially implemented, most vendors did not go beyond the basic implementation of exchanging images and retrieving them, as well as being able to print. This image communication is the most basic level.

But in using these basic services, issues involving the integrity of the patient information became apparent: Names and other identifying information could be misspelled and/or mistyped, so that the resulting images from the study could not properly be matched with other procedures from the same patient. The DICOM Modality Worklist attacked this problem by permitting the exchange of patient demographics between the information system and the digital acquisition modalities. It was followed by the Modality Performed Procedure Step to communicate the examination status, number of images, their location, and information about the actual performed study.

The Storage Commitment, transferring responsibility between the modality and PACS for the images, was already defined early on, and customers were starting to demand this functionality. This is the image and information management level.

Another group of DICOM services deals with the image quality and consistency. These standards allow the images to be presented on one workstation in the same way as they appear on another workstation and to also match the printed hard copy. This is referred to as the image quality level.

The most recent level -- integration -- is what the DICOM committee currently spends most of its time on. This is the collection of structured reports that allow the integration of text, annotations, and measurements with images. Examples of these DICOM objects are measurements from an ultrasound device.

Finally, there is the security level, which spans all other DICOM levels. This allows for user authentication, de-identification of certain text attributes, digital signatures, and encryption of the communications and images stored on exchange media such as a CD.

HOW AND WHY CHANGES HAPPEN

New additions to the DICOM standard are mostly made to the top levels such as security and structured reports, although there are also extensions at the other levels. For example, a recent extension to facilitate the new multidetector CT units and MR devices that produce spectroscopy data adds to the basic communication level by specifying a new CT and MR data object. Another recent addition was a standard method to identify "key images" -- the most significant images from a series -- for the convenience of a physician. If a study has a few hundred images, it is hard for a physician to browse through all of them to figure out which are the most significant. Instead of maintaining this information in a proprietary manner, it can be done with a standard DICOM service.

How does a user deal with all these different levels? Unfortunately, some vendors do not package all the DICOM services together, and it is not always quite clear what you get -- or, even worse, what you don't get. A typical example is a workstation that does not have the DICOM print facility included in the standard package. Another example is a modality for which a modality work list must be purchased separately. From my perspective, offering a modality without a work list is similar to selling a car in Texas without air conditioning.

It is important to request a specification of all the DICOM services, preferably in the form of a DICOM conformance statement. It does take some practice to be able to read this specification, but a DICOM working group is crafting a new format for these documents that will include an "executive overview" at the top, specifying all the DICOM services very clearly and unambiguously, including whether they are optional or not.

Some people wonder when the DICOM standardization will stop, whether there will ever be a time when we say "this is enough." I typically answer that I don't think it will happen in my lifetime. First of all, not a single RSNA meeting takes place where I do not spot several new modalities that will require new additions to the DICOM standard. Tight connections between some of the PACS components still require proprietary connections. For example, the connection between workstations and an image archive/image manager are still somewhat proprietary, so that other vendors' workstations might not have access to the folders of images. The image manager, typically containing the database and image location, and the image archive itself, containing the actual images, are also still very tightly connected, and there is no standard for the exchange of information between these devices.

Both users and vendors can only accept the continuous evolution as a de facto given. Just be aware of it and manage it properly. The gØod news is that added functionality will increasingly level the playing field for different vendors.

Herman Øosterwijk is president of OTech Inc, a healthcare technology consulting firm. Questions and concerns can be addressed to herman@otechimg.com. His bØok, "DICOM Basics," available from www.otechimg.com provides more information about DICOM.