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ananth_adroit
ananth_adroit

Reputation: 347

How to query a CT machine - DICOM

I am developing a dicom image archiving and viewer for hospitals. Since 2 weeks have studied and learned what are they ! . Still have a question of how to query the modalities (Syntax). I have the tag sheet but heard something like matching key and response key from SCP and SCU.

Upvotes: 0

Views: 1504

Answers (2)

Michael
Michael

Reputation: 41

there are some rules which query keys (i.e. search keys) must be supported by every PACS; of course it may support more.

Every image (more general, nearly every object) in the PACS is sorted into a hierarchy, so every image belongs to a Series, which again belongs to a Study which again belongs to a patient. On every of those levels, an image carries information to describe that level. For example on Patient level the image has information about the patient name, birth date and sex.

When querying the PACS, the client has to follow a strict query model that corresponds to exactly that hierarchy. There are actually at least 3 models that are interesting for you and that a client has to select when negotiating a connection (association) with the PACS (Study Root/Patient Root/Patient-study Only Models).

According to the very model, you must query the different hierarchy levels seperately one after another, starting with the highest one (usually patient or study in the above models).

Part 4 of the DICOM standard tells for each of the models, which search keys you might query for (i.e. what the server at LEAST supports) and which rules you have to follow by composing your search out of several search keys. You must read part 4 about query/retrieve, otherwise you won't manage to understand how it exactly works.

The terminology of matching keys and return keys is mostly used with regard not to PACS query/retrieve but to Modality Worklist. In general a matching key is a key that you send with a value to search the PACS for. A return key is a key that send empty, ie. you ask the PACS to fill up all responses that you filtered with the matching keys, to also fill in the value for the requested return keys. The mechanism can be used for PACS query the same as in worklist -- the terminology of matching/return is only used for worklist to better describe the server requirements.

HTH, Michael

Upvotes: 1

CharlesB
CharlesB

Reputation: 90496

A viewer workstation doesn't query a modality, but an image archive previously pushed by the modality. Image archive are queried by a viewer with the query/retrieve DICOM service. There may be exceptions, but modalities don't archive the images themselves.

A modality pushes images to an archive with SCU/SCP communication, modality being the SCU, archive the SCP. Modality uses the Storage commitment service.

Also get yourself a book like Oleg S. Pianykh's, since Internet has no really friendly DICOM learning resources.

Upvotes: 2

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