Digital Imaging and Communications in Medicine (DICOM)

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Chapter 7 DICOM SOPs: Basic
The Verification SOP Class plays the most fundamental role in controlling the
sanity of any DICOM network. For that reason, it is commonly implemented in
most DICOM interfaces as some kind of “verify connectivity” button that users
can click to make sure the remote device is still available to DICOM. Should
anything go wrong in your DICOM connectivity, start troubleshooting with
the Verification SOP.
Consequently, avoid buying DICOM devices and software that do not implement
the Verification SOP SCP. As this definition implies, they won’t be able
to reply to the DICOM verification requests; in plain words, you will have no
means of verifying the DICOM connectivity to them.
Real case: Verification SCP and security?
On one occasion, we were connecting to a CR unit from a well-known
imaging vendor and we discovered that the unit failed to support the Verification
SOP SCP.
“No wonder”, commented the vendor’s engineer, who was involved in the
installation, “we do not want you to export the image data from the CR.
This is a security feature”.
For all people who make similar statements to mask their ignorance: as
we just learned, the Verification SOP does not transmit image data or any
other confidential information. Consequently, it cannot be used for stealing
any information, proprietary or not.
Never build security on obscurity, and never use security as an excuse to
cover up poor functional design.
7.3
Storage
If C-Echo (the Verification SOP) is important because of its role in DICOM
connectivity checks, C-Store (Storage SOP) is the main DICOM data workhorse
responsible for moving DICOM images (and other data types) between the AEs.
Despite a somewhat misleading name, C-Store sends DICOM data objects from
one AE to another over a DICOM network. Because different objects imply
different processing, DICOM assigns a separate SOP class to each modality or
data type (for example CT Image Storage SOP, MR Image Storage SOP, and so
on). For that reason, DICOM Storage is represented by a family of data-specific
storage SOPs, each with its own UID. You can find all Storage SOPs in Appendix
A.2; for brevity, we show the most frequently used SOPs in Table 25.
Apart from the modality-specific Storage SOP type (UID), everything else
in DICOM storage works the same for all storage modalities. First of all, the
structure of all storage SOP classes is the same (Fig. 38). Here, the DIMSE C-