Digital Imaging and Communications in Medicine (DICOM)

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Chapter 10 DICOM Media: Files, Folders, and DICOMDIRs
DICOM committee tip: flexible is better
One practical way to avoid DICOMDIRs would be to add a new M-
INQUIRE-DICOM FILE service. If present, the M-INQUIRE FILE can
query only the file date and time, and an extended M-INQUIRE-DICOM
FILE would be able to support a few DICOM search keys traditionally
listed in DICOMDIRs (patient name, study date, and so on).
As we have just observed, this would be easy to implement with a partial
reading of DICOM data groups by looking for a few first-key elements instead
of reading the files completely. In fact, a few years ago, my company
had to implement a DICOM over FTP protocol using the exact same idea
of searching for DICOM data on any FTP-connected media, which enabled
us to do DICOM searches on virtually anything, cross-platform and crossspace.
Making DICOMDIRs virtual, and building them on demand at the
application layer will substantially enhance the flexibility of DICOM software,
and support for various types of local and remote media.
Moreover, this approach could be taken even further if we extend DIMSE
services (C-Find, C-Store, C-Move, and so on) to DICOM files. In essence,
our hypothetical M-INQUIRE-DICOM FILE already implements C-Find,
and the others would easily follow. This would lead to a very unified and
consistent way of dealing with DICOM data, whether it is networked or
read from DICOM files.
10.4.2
Media Storage
In many ways, the DICOM media storage model (and PS3.12 of the DICOM
standard in particular) attempts to do what DICOM shouldn’t be doing at all:
giving scrupulous details on how DICOM file data must be recorded on various
media (mostly CDs and DVDs). From a practical standpoint, the DICOM
media storage specifications are really overdone. Compare them to the DICOM
data encoding model, which is based on simple and universal rules and has
lasted more than 20 years because it has always stood outside any particular
implementation. DICOM media storage regulations, on the contrary, need to
be rewritten every year or two because they are media-dependent. They attempt
to control many unnecessary details and they occasionally run into obscure
or self-contradicting claims. Moreover, they leave ample space for human
error, which seems to occur almost every time humans get involved with
DICOM files.
Instead of insisting on specific implementation details (such as controlling
boot sectors and file name periods), parts 10, 11, and 12 of the DICOM standard
need to see some refreshing changes to become far more abstract and
functionally oriented.