storescp + findscu for series assoication??

[gnchen]

Hi! All,

Since there is no so-called " series level association" in SOP class, I wonder if it is possible to use storescp + findscu to make sure you know how many slices in that series. My plan is:

1. have an storescp server running
2. After got a dicom image, I use findscu to query the server who sent the image and find out how many slices in that series.


Is this durable? If it works, I think it is better than a time-out option. Any comment on this will be welcomed..

Gen

[Marco Eichelberg]

In principle it would be possible to have a tool like storescp open a second association to the archive and query for the number of objects in a given series. This can be done with a Study Root Q/R model, where one could directly take the Study and Series Instance UIDs from the incoming image and issue an INSTANCE level query. However, this approach has at least three problems:

• First of all, there is no guarantee that the archive will accept storescp as a valid query client, unless configured appropriately. What do you do if the archive does not "talk" to you?
• Secondly, this will greatly slow down communication because it will cause at least as many messages as there are SOP instances to be exchanged, thereby increasing the total latency of the transmission by at least 50%.
• Finally, there is no guarantee that the archive will actually send all images of that series. The client could as well have instructed the archive to only send selected images out of one series. In that case your storescp will wait forever for images that never arrive.

[gnchen]

Thanks! Marco.

My post image processing stream really needs a whole 3D MR series. Another solution will be using movescu. But that means I need to know which series I should query by using some key, such Series Instance UID.
But I am not so sure how can I get that from DICOM's point of view.

What's your recommendation on this? Is timeout still the best option here??

Gen

[Marco Eichelberg]

If you need to be sure that you receive a complete series (which at least means all objects of that series that are actually stored in the archive), then you should indeed use you own Q/R SCU (such as movescu) and make sure that you initiate retrieve transactions on SERIES level. Once such a transaction is complete, the final C-MOVE-RSP message will provide you with counters telling you how many objects from that series were successfully transmitted and, maybe more important, how many objects of that series were not transmitted successfully (for whatever reason). If that latter counter is zero, this means you have received the series as complete as it will ever be.

[gnchen]

Thanks! Marco,

In fact, that is what I think. But since I have no way yo know which series I should retrieve, is there any dicom related communication which can be used to notify me which series I should retrieve??

Or I might need to use other protocol to do that...


Gen

[Marco Eichelberg]

No.