What Tags should the Modality Worklist SCP return?

[enyaw...@hotmail.com]

Hi:

In the DICOM standard 2007, part 4, page 182

K.2.2.1.2 Return Key Attributes
The values of Return Key Attributes to be retrieved with the Worklist
are specified with zerolength
(universal matching) in the C-FIND request. SCPs shall support Return
Key Attributes
defined by a Worklist Information Model according to the Data Element
Type (1, 1C, 2, 2C, 3) as
defined in PS 3.5.

And assume it only has two item tags (0008,0060), (0040,0009).

Scheduled Procedure StepSequence (0040,0100) R 1
> Modality (0008,0060) R 1
> Scheduled Procedure Step ID (0040,0009) O 1

If the SCU only specify the Modality (0008,0060) tag in the request,
should the SCP also return the Scheduled Procedure Step ID (0040,0009)?
This tag has a return key type of "1". But the section K.2.2.1.2
Return Key Attributes says The values of Return Key Attributes to be
retrieved with the Worklist are specified with zerolength (universal
matching) in the C-FIND request. So does that mean the SCU need to
specify the Scheduled Procedure Step ID (0040,0009) tag with a zero
value before the SCP will return it? Otherwise, if not requested,
don't return it.

example: SCU request:

Scheduled Procedure StepSequence (0040,0100) R 1
> Modality (0008,0060) "CT"

should SCP returns:

Scheduled Procedure StepSequence (0040,0100) R 1
> Modality (0008,0060) "CT"

or

Scheduled Procedure StepSequence (0040,0100) R 1
> Modality (0008,0060) "CT"
> Scheduled Procedure Step ID (0040,0009) "stepid1"

Thanks

Wayne Tran

[Hercules Dev.]

The DICOM standard doesn't require the SCU to send the SCP specific
attributes when querying a MWL, it only requires the SCP to support
some attributes for returning if the SCU requested them by giving them
a Type1, on the other hand the IHE requires that the SCU should request
some attributes that are necessary to create the Image SOP and requires
the SCP to support them for returning (refer to IHE 2006 Vol 2 page 61
Table 4.5-3).

So the most important thing when implementing an SCP is to stick to the
DICOM and IHE by supporting all the required attributes for returning
and return only what the SCU requested, and leave validating the SCU
request according to the IHE as an option for the RIS System, so you
can refuse any SCU request that doesn't follow the IHE requirements
if the RIS System chose that.

Thanks,
Zaid H. Safadi

[David Clunie]

Hi Wayne

The SCP has to return it if asked, since it is Type 1.

But it should only return it if asked (present in request
with zero length), and not otherwise.

This is a basic rule for all query SCPs in DICOM - do not
return anything more than asked (unless it is specifically
described in the response description in the standard as
being additionally allowed or required).

David