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Next XDS Release

Publication date: Oct 27, 2016

There has been speculation for a while that the next version of XDS wil be FHIR based. This would have some advantages.


The current release of XDS (XDS.b) is based on Webservices (and the WS* stack in general), the ebRIM metadata format, and on the use of SAML tokens. This works relatively well in settings where one deals with backend integration. People gripe about the obscurity of the ebRIM standard and its complex XML structure, and about the heavyweight nature of the webservices layer, which motovated IHE to define the MHD (Mobile access to Health Documents) profile - based on REST, FHIR and OAuth2. That's the kind of technology stack that's optimized for use in lightweight web aplications as well as apps.

The FHIR resource definitions needed to capture the document metadata as well as the image metadata (a.k.a. the KOS manifest) were created in close coordination between HL7 and IHE, thus ensuring easy metadata mappability between XDS.b and MHD. The MHD profile introduces a couple of new actors/transactions, effectively allowing for the translation between the XDS.b technology stack and MHD.

XDS.b and MHD Actors and Transactions\

During a XDS training course in the UK about a year ago a representative from a healthcare region looked at the above diagram and said "Hmm - so why should I use the webservices stack at all? I might as well use the MHD transactions for everything." - and they're right in that assumption. The transactions already exist in MHD. I did ping some IHE contacts at the time to find out if this had been discussed within IHE and they confirmed that such ideas have been floated in the IHE community as well. One major hurdle is the fact that the FHIR standard is not normative yet (it will be end of 2017, or early 2018), and that they'd like to gain more experience using the MHD profile.

XDS.c and bridging to the old XDS.b

Let's call that version of XDS "XDS.c". Based on MHD transactions, and allowing for the mapping of XDS.b transactions to XDS.c transactions (and vice versa).

FHIR DevDays

During last years FHIR DevDays meeting Keith Boone (a.k.a. MotorcycleGuy) presented an overview (video recording) of the use of FHIR in IHE profiles. The DevDays this year (Nov. 16-18, Amsterdam) is the largest worldwide gathering (200+ attendees) of FHIR experts - Brad Genereaux will hold a "FHIR and DICOMweb" presentation. DICOMWeb is a set of DICOM specifications for a RESTful exchange of DICOM objects, the development of which is nicely intertwined with that of FHIR and MHD.

In Summary

Highly speculative? Definitely. Doable? Definitely.


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