DICOM Transfer Syntax - Image Forwarding

[johnc]

Hi,

My Pacsone server is working pretty well. However, when I receive from Orex, the transfer syntax received is JPEG Lossless. When I try to forward the exam received from the Orex, the destination does not accept it because it doesn't like the format.

Is there a way to force a different syntax when receiving from the Orex system? When I send from Orex directly to the final destination, the transfer is fine as it doesn't send JPEG Lossless.

Any help is much appreciated!

--John

[pacsone]

You may try the following:

1. Force the source AE of the images to always use uncompressed transfer syntaxes.

2. If Orex supports translation from JPEG lossless transfer syntax to an uncompressed transfer syntax, you may be able to force Orex to always use uncompressed transfer syntaxes when sending images to the destination AE.

[johnc]

Thanks for your response. When you state "Force the source AE of the images to always use uncompressed transfer syntaxes", is that done on my PacsOne server? If so, how do I go about doing that? Or are you suggesting that the forcing is done on my Orex workstation?

Thanks again,

John

[pacsone]

The source AE in #1 above means the input modalities from which PacsOne is receiving the images. From your previous post, I think your traffic flow is as follows:

source AE->PacsOne->Orex->dest AE

If the source images are JPEG lossless compressed, but the dest AE does not support it, then somewhere along the above chain the source images must be translated into an uncompressed transfer syntax that can be accepted by the dest AE.

Since PacsOne does not currently perform any translation of transfer syntaxes (see the PacsOne Server Conformance Statement http://www.pacsone.net/conformance.htm), the translation must be done either at the source AE or Orex.

Suggestion #1 in my previous post is to make the source AE perform the translation, so that neither PacsOne nor Orex needs to perform any translation before forwarding the images to the dest AE.

Suggestion #2 above is to have Orex perform the translation, if Orex supports it. You can find out whether Orex supports translation from the JPEG lossless transfer syntax into one of the uncompressed transfer syntaxes by checking its Dicom Conformance Statement.

[johnc]

Thanks again for your response. I guess I wasn't clear on my question and background.

The traffic flow would be:

OREX -> PacsOne -> Dest AE

When OREX sends to PacsOne, it is sending JPEG Lossless
When I try to forward that, it fails as the Dest AE won't accept JPEG Lossless.

If I bypass PacsOne and send from OREX -> Dest AE, OREX sends uncompressed and the transfer functions properly.

When OREX communicates with PacsOne, is there some sort of negotiation that takes place to determine the transfer syntax? For some reason, when OREX sends to PacsOne it is changing the format to JPEG Lossless. I somehow need to prevent that from happening. Is there something I can set on the Pacs?

I spoke with OREX support and they are saying that there is nothing on my OREX machine to specify how to transfer. That it must be the PacsOne requesting JPEG Lossless.

Hope this helps to clarify. Thanks again!

John

[pacsone]

Yes, it's true that the sender (Orex) provides a list of transfer syntaxes and the receiver (PacsOne) gets to choose which transfer syntax to accept.

In the case of multiple supported transfer syntaxes, PacsOne chooses the first supported transfer syntax from the list presented by the sender. So in your case, Orex must have listed the JPEG Lossless transfer syntax first, followed by the uncompressed transfer syntaxes, so PacsOne just selects the first supported transfer syntax, which happens to be the JPEG lossless.

In order for PacsOne to select the uncompressed transfer syntax instead, you'd need to configure the sender (Orex) to list the uncompressed transfer syntax first, followed by the JPEG lossless transfer syntax. That way, when PacsOne picks the first supported transfer syntax from the list, it'll be the uncompressed transfer syntax instead. But you'd need to check with Orex if they support changing the order of the presented transfer syntax list when they send the association request to a remote AE (PacsOne). If so, you can configure Orex to list the uncompressed transfer syntaxes before the JPEG lossless transfer syntax, then PacsOne will pick the uncompressed transfer syntax instead.

[johnc]

Thank you for the clarification.

I talked to OREX support...the guy is going to check into whether or not changing the list order is viable.

If they are unable or unwilling to change the order, and PacsOne can't be changed to not provide Compression as an option, then I'll have to find an alternative to PacsOne.

I will know more from OREX sometime in the middle of next week (Wenesday or Thursday).

Thanks! I really appreciate all your help.

[pacsone]

It may be possible to configure a preferred transfer syntax for PacsOne when receiving images, so that PacsOne will always accept this preferred transfer syntax instead of choosing the first supported transfer syntax from the list presented by the sender (Orex).

But there's still a pre-requisite though: The sender (Orex) must send a single presentation context with a list of transfer syntaxes for PacsOne to choose from, instead of sending a list of presentation contexts each with a single transfer syntax.

If you can confirm with the sending application (Orex) that they've implemented the first option above (single presentation context with a list of transfer syntaxes) instead of the second, then we can modify PacsOne Server to always select a preferred transfer syntax (configurable from registry) from the list of transfer syntaxes presented by the sender. You can then send an email to mailto:pacsone@pacsone.net so that we can send you the updated PacsOne Server with this preferred transfer syntax implementation.