Cancel C-MOVE following an event?

[djbower]

I'm experienced with python but new to DICOM and pynetdicom. I would like to retrieve only the first instance (image) of a series from PACS. Currently, I've added a hook to the C_STORE service request (EVT_C_STORE, as per some of the code examples) to call cancel_c_move. I then time.sleep(15) to allow time for the C-MOVE to cancel before proceeding (otherwise images continue to download). Of course, having to wait is not optimal, but it seems like the cleanest approach to allow C-MOVE to exit cleanly without leaving orphaned or zombie processes running. Unfortunately, the PACs system I am working with does not support C-GET.

The above approach seems to work, although I'm not sure it is optimal. Any suggestions for improvements? Many thanks.

[stefanoostwegel]

Hi,
We have had a similar usecase in our environment.
How we solved it is that we do a c-find on the series on image level. This gives you a list of all associated instance UID's within that specific series (can de the same for study level). Then you only pic the first item in your list and use that instance UID to perform a MOVE on image level for one UID. This prevents aborting, timeouts etc.

[djbower]

Many thanks for this suggestion - indeed this works for me also.

[lmdulz]

Hey @djbower,

We're having the exact same usecase and problem. But on top, we can't query our PACS on image level as @stefanoostwegel had suggested. Would you be able to share your code for that problem with me? I also have zero experience with pynetdicom unfortunately.

[djbower]

Hi @lmdulz,

I followed the example here for Storage SCP: https://pydicom.github.io/pynetdicom/stable/examples/storage.html

Then I added the following at the end of handle_store:

ds0.save_as(outfilename, write_like_original=False)
logger.info(f"Storing: {outfilename}")
self.cancel_c_move()
time.sleep(16)  # 16 secs is sufficient for only one dicom to be exported
return 0x0000

where cancel_c_move() looks like:

def cancel_c_move(self) -> None:
    """Cancels a C-MOVE request."""
    msg_id = 1  # Default value of send_c_move
    self.association.send_c_cancel(
        msg_id, query_model=StudyRootQueryRetrieveInformationModelMove
    )

That's it. I literally just send a cancel signal and then wait until the request is registered by the PACS. Then control switches back to the main loop over series and the whole process is repeated (export one image, send a cancel request, wait, ...).

It also helps to look at the pynetdicom source code to get clarification on the default message ids for requests.

I hope this helps.

Dan