Retrieve preformatted images over web services - Brief Proposal
1. Proposed Workitem: Retrieve preformatted images over web services
- Proposal Editor: Mark Sinke
- Editor: <Name of candidate Lead Editor for the Profile, if known>
- Date: N/A (Wiki keeps history)
- Version: N/A (Wiki keeps history)
- Domain: Radiology
2. The Problem
With the current XDS-I and XDS-I.b infrastructure, it is not possible in a standard way to obtain JPEG-preformatted images using web services. The main things that break interoperability is that to get to preformatted images, one must use WADO (which is a plain HTTP GET).
This has two consequences
- using XUA to convey user identity and other identifying traits is not possible
- routing the request over XCA-I does not work, as XCA-I only supports RAD-69, not WADO
An optimization of the WADO server might also be possible, if we allow multiple preformatted images to be retrieved at once. WADO only allows one retrieval at a time. I consider this a lucky side effect, not a criterion per se.
The value of this profile or supplement would be that we can use the XDS-I.b RAD-69 service or an extension to use to securely access image information within or across affinity domain boundaries. We avoid a proliferation of non-interoperable private extensions to IHE to make the same thing happen.
3. Key Use Case
A mammography screening program results in images being collected. These images are stored and shared within the mammography screening program using XDS(-I). For follow-up in treatment sites it is necessary to gain access to the images taken. Users in the treatment hospitals are used to sharing information in their region, and they need access to the images in the screening domain. The need is even greater if the treatment hospital is not determined upfront (for example, in the Netherlands, where women have the right to choose the actual treatment site).
The current problem is that it is (a) hard to make this work from a system engineering perspective, as the WADO transaction is not profiled for XCA-I use, and (b) that any user identity is lost, as WADO cannot convey it. Hence, in the current situation, the study needs to be transferred on a CD, or by other proprietary electronic means.
In the new situation the user logs in to their XDS-I enabled system and is able to look at a quick preview of the screening images. Under the hood, this transaction is audited, and access control is applied according to the identity of the user established at login.
4. Standards and Systems
- XCA, XCA-I, XDS-I.b have parts of the solution, but the missing piece is retrieval of preformatted images over XCA-I.
- DICOM has performed work in a transaction like RetrieveImagingDocumentSet that allows for preformatted images. I cannot find the right part of DICOM to point to now. It might still
be work in progress.
5. Discussion
<Include additional discussion or consider a few details which might be useful for the detailed proposal> The current RAD-69 allows for the JPIP transfer syntax, but we see very little uptake of that standard in the field, and the JPIP standard suffers from the same interoperability problems (lack of XUA, no routing over XCA-I), as it is also based on plain HTTP traffic.
<Why IHE would be a good venue to solve the problem and what you think IHE should do to solve it.> It is a gap in the current move from XDS-I to XDS-I.b. We changed everything to support web services, but left WADO/JPEG out.
- <What might the IHE technical approach be? Existing Actors? New Transactions? Additional Profiles?>
My suggestion would be to introduce a new transaction or a version of RAD-69 which allows for preformatted images in JPEG format. Actors can be reused. Logically, this is not a new profile, but it might be an option to XDS-I.b
- <What are some of the risks or open issues to be addressed?>
The state of the DICOM standard regarding this transaction is unknown to me.
<This is the brief proposal. Try to keep it to 1 or at most 2 pages>