C-FIND Request Identifier content

[Hervé Garfagni]

Hello Everyone,

Although I've been working on DICOM stuff since many years, but not so much on Query/Retrieve matters, I dare asking a question that some readers may find silly, as I need help clarifying or correcting my understanding of a C-FIND Request content.

I've always thought that, when using the Baseline behavior,  a C-FIND Request identifier could not include keys related to levels below the Query/Retrieve Level.
Example, when using the FIND StudyRoot SOP Class, with QueryRetrieve Level set to STUDY, the C-FIND request shall not include Series-Level attributes such as Modality or SeriesNumber, nor Instance-level attributes such as SOP Class UID or SOP Instance UID.

However, looking back into Part 4, I could not find any such requirement and could only find the following (cf. C.4.1.2.1 Baseline Behavior of SCU):

The Identifier contained in a C-FIND request shall contain a single value in the Unique Key Attribute for each level above the Query/Retrieve level. No Required or Optional Keys shall be specified that are associated with levels above the Query/Retrieve level..

The second sentence is quite confusing to me and I wonder whether it should state "No Required or Optional Keys shall be specified that are associated with levels below the Query/Retrieve level.".
But such a typo seems quite unlikely to me after so many years, so I'd love someone further explains what this statement means with a couple examples.

Hervé.

[Jouke Numan]

Hi Herve,

The answer is in the description of HSM where it says that processing stops after the requested level has been processed:

C.4.1.3.1.1 Hierarchical Search Method

Starting at the top level in the Query/Retrieve Information Model, continuing until the level specified in the C-FIND request is reached, the following procedures are used to generate matches:

a. If the current level is the level specified in the C-FIND request, then the key match strings contained in the Identifier of the C-FIND request are matched against the values of the Key Attributes for each entity at the current level. For each entity for which the Attributes match all of the specified match strings, construct an Identifier. This Identifier shall contain all of the Unique Keys at higher levels and all of the values of the Attributes for this entity that match those in the C-FIND request. Return a response for each such Identifier. If there are no matching Keys, then there are no matches, return a response with a status equal to Success and with no Identifier.

So no attributes of lowel levels should be present in the responses.

Regards, Jouke

Op wo 24 sep 2025, 11:14 schreef Hervé Garfagni <garfahe...@gmail.com>:

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[Hervé Garfagni]

Thank you, Jouke.

I'm already clear about the C-FIND response content and how a C-FIND SCP should proceed based on the hierarchical search method.

My question is about the C-FIND request identifier itself, and whether it can include keys from levels below the Query/Retrieve level.

Regards,

Hervé.