Digital Imaging and Communications in Medicine (DICOM)

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Chapter 10 DICOM Media: Files, Folders, and DICOMDIRs
how these pieces were to be connected, and each piece was meaningless by
itself. When this PACS aged to the point of falling apart and had to be replaced
by another system, the entire data-migration process turned into a long nightmare.
Since then, I have worked with a couple of contemporary DICOM devices
that would store their DICOM data in a somewhat similar “piece-wise”
manner. Please remember that the DICOM standard is designed to store pretty
much everything your digital device is acquiring as a well-structured DICOM
object; there is no need to cut or redistribute anything.
Another example was somewhat opposite and was related to a well-known
PACS company that chose to store certain DICOM data in the PACS database
only; never updating the DICOM files (objects). In this case, these were annotations
done by radiologists on the images. Although DICOM provides ample
support for including annotations in DICOM objects, this was not implemented.
Annotations were stored only in the PACS database, and in a very obscure proprietary
format. As a result, the radiologists had to do double work: first placing
annotations on the images on PACS workstations, and then manually retyping
these annotations into the radiology database (a separate tool to track annotation
measurements). From there, they could be easily exported. Needless to say,
the process was time-consuming, annoying, and full of human errors. I have
repeated this countless times, and I will keep repeating it: when looking for any
DICOM software, make sure that it can export all data it collects in a standard,
well-defined format. This will make your life and projects so much easier!
10.5.4
Choice of Internal File Format
The choice of the file format becomes essential for the efficiency and interoperability
of your application, especially if your PACS comes with file-based
DICOM storage. Ideally, this should be DICOM. Moreover, if you have to
compress it (and with current volumes of digital data in radiology, you most
certainly will), please rely on standard lossless DICOM compression (6.2.1)
such as 8-bit and 12-bit lossless JPEG. This will make your PACS-stored files
compatible with nearly any other DICOM application.
Also, avoid overstoring. One popular medical imaging system, for ex ample,
decided to keep its imaging data in two formats: the original DICOM files (for
compatibility), and the proprietary-formatted image files (for optimized processing).
Need less to say, it doubled the size of the required storage and added a
substantial processing overhead for continuously converting the data between
the two formats. When this system was introduced in a busy hospital, its storage
inefficiency was matched only by its slow and unreliable performance, both
resulting from managing twice as much data when one copy would have sufficed.
What started as a relatively small server soon took the entire server rack.
PACS should be smart enough to work with a single internal data format, preferably
DICOM.