Digital Imaging and Communications in Medicine (DICOM)

4.1 How Did This All Get Started? 21
DICOM 3.0 has never been replaced by a DICOM 4.0 and such. Instead, the
same 3.0 standard is reviewed annually by the designated DICOM WGs, publishing
the updated DICOM 3.0 versions and new supplements. The volumes of
the standard revisions are numbered as PS3.X-YYYY, where 3 is the standard
number, X represents the volume number, and YYYY represents the year of the
edition. For example, PS3.5-2008 identifies DICOM 3, part 5, revision 2008,
and supersedes the earlier versions of PS3.5. Nevertheless, each new revision
still refers to the standard as DICOM 3.0. “Plus ça change, plus c’est la même
chose”, as my French colleagues would say. “The more it changes, the more it
remains the same.”
This naming approach, by the way, can lead to confusion between the revision
and the standard numbers. Once I was asked about the software my
company was developing: “Do you support DICOM 2003?” Well, there is no
DICOM 2003 per se. There was, however, a 2003 edition of DICOM 3.0. Nevertheless,
this and similar questions are very common, and should be seen in the
same context of DICOM evolution:
1. All DICOM devices you have to deal with are essentially snapshots of DICOM
editions used at the time of their development. They can be quite different.
2. DICOM units must work together. Therefore, keeping new DICOM devices
backward compliant with the previous models is more important than chasing
the most recent DICOM features. For this reason, DICOM manufacturers
do not really get excited about the most recent DICOM editions, and
they certainly do not hurry to replace older DICOM protocols with more
efficient, recent ones. Even most of the currently produced DICOM units
will have the mid-1990s set of functions.
3. If you have to implement a DICOM solution in a complex environment, always
choose the most compatible over the flashiest, which is not the same
thing. For example, recent DICOM editions have adopted many advanced
image-compression protocols, allowing equipment to transmit and store
medical images much more efficiently. However, in the DICOM world it always
takes two to make it work, and transmitting these newly-compressed
images to an older device simply won’t work when the old devices default to
a basic, non-compressed format.
This does not mean that you have to stay with the old devices; on the contrary,
you need to seriously consider buying newer units without a doubt! But if you
still have a few older ones around, you must make backward compatibility with
them your priority.
The level of a DICOM unit’s compatibility (as always) is reflected in its
DICOM Conformance Statement (as has already been pointed out and will
mention more). DICOM devices can support many optional and semioptional
features, and a wider range of these features is worth thousands of new DICOM
additions.