Cross-Community Access for Imaging XCA-I.b

1. Proposed Work Item: XCA-I.b

• Proposal Contributors: Andrei Leontiev, Charles Parisot
• Profile Editor: Andrei Leontiev
• Domain: Radiology

Summary

The continuous development of Healthcare Information exchanges and their expansion to regional and multi-country settings, along with significant improvements in network technologies and the security of cloud deployments, create strong demand for standards-based exchange of imaging studies (consisting of images and other non-image objects) across affinity domains.

Existing Cross-Community Access for Imaging (XCA-I) profile has been developed to address this need. Acceptance of the XCA-I profile has been timid in the past, as its only retrieval options are based on outdated technology (SOAP/MTOM Web-services). With several projects now underway and IHE MCWG's strong interest and support, it is expected that the proposed XCA-I.b profile, especially in conjunction with the MHD profile deployed on top of XCA infrastructure, will gain significant acceptance in a short period of time.

2. The Problem

The XCA-I profile includes one transaction between the Imaging Initiating Gateway and the Imaging Responding Gateway to retrieve DICOM instances: RAD-75 Retrieve Imaging Document Set that uses SOAP-based Web-service for image retrieval. Since this transaction was defined many years back, the DICOMweb specification has been extended with a REST-based image retrieval, WADO-RS. Furthermore, the cross-domain access infrastructure has been extended by the ITI domain to use modern RESTful Webservice definitions (i.e., using an MHD profile for document retrieval). In Radiology, the WIA profile has been defined to use the WADO-RS for image retrieval using transaction [RAD-107]. The technical committee reviewed the initially proposed CP to add the RAD-107 transaction to the current definition of the XCA-I to be used alternatively to RAD-75; however, that would require the Imaging Responding Gateway to still support outdated SOAP-based communication just for the purpose of compliance with the profile, as it is not expected that any deployment will be including Imaging Initiating Gateways using one or the other option. Similarly, it is expected that in preferred deployment will be RESTful based within the domains. Thus it is proposed to create the next-generation XCA-I.b profile that will use the RAD-107 transaction within and across affinity domains.

3. Key Use Case

The key use cases of XCA-I.b are the same as those for XCA-I. Recently formed IHE Multi-country Working Group (MCWG) [1] has expressed very strong interest in implementing the approach where RESTful services are used in conjunction with XCA infrastructure for cross-domain access, using both MHD and WIA as the retrieval mechanism for documents and images, respectively.

4. Standards & Systems

DICOM (Digital Imaging and Communications in Medicine):

• Specifically, set of RESTful web services defined for retrieval of DICOM objects (WADO-RS)
• Version: Current version.
• Support: Many systems support WADO-RS as method for access to DICOM objects (see also WIA profile recently incorporated into IHE Radiology technical framework

Systems involved:

• PACS system in the initiating Affinity Domain
• Initiating Imaging Gateway
• Responding Imaging Gateways in the remote Affinity Domains
• PACS or VNA systems in the remote Affinity Domains

5. Technical Approach

The proposed solution is to revise the WADO-RS Retrieve [RAD-107] transaction so that it can be used between Imaging Document Consumers and Initiating Imaging Gateways (by including the homeCommunityId into the webservice endpoint path.

Also, the new transaction similar to RAD-107 to be defined for use between the Imaging GAteways.

Actors

• Imaging Document Consumer (from XCA-I)
• Imaging Document Source (from XCA-I)
• Initiating Imaging Gateway (from XCA-I)
• Responding Imaging Gateway (from XCA-I)

Transactions

• WADO-RS Retrieve [RAD-107]:
  • Define use of homeCommunityId.
• Cross-Community Wado Retrieve [RAD-X1]:
  • Similar to RAD-107
  • Define specific requirements to WADO-RS request redirect and routing of response (if any)

Profile

Profile text is expected to be significantly similar to existing XCA-I.

Decisions/Topics/Uncertainties

• Packaging:
  • Confirm that separate profile is better than extending the existing XCA-I
  • Profile naming - rather than XCA-I.b, should we adopt something like Web-Based Image Access Cross Communities (WIA-XC)?
• Transactions:
  • What are the considerations for traversing multiple gateways with Web-service requests that may be different for RESTful WS?
  • Is the [RAD-X1] necessary or can the specifics of inter-gateway communication be incorporated into the [RAD-107]?

8. Tech Cmte Evaluation

<The technical committee will use this area to record details of the effort estimation, etc.>

Effort Evaluation (as a % of Tech Cmte Bandwidth):

• 18% for MUE
• 20% for MUE + optional

Editor:

Andrei Leontiev