WADO – Web Access to DICOM Persistent Objects Partnerships WADO – Web Access to DICOM Persistent Objects Emmanuel Cordonnier ETIAM

DICOM 20th Anniversary Conference / WADO Context Users of medical information systems require rapid and reliable access to reports and images Within computerized environments such access is increasingly based on web technologies Access to relevant DICOM persistent objects is required without the need for duplication of such data objects Clinicians need to have access: either in native DICOM format for advanced use, or rendered into a generic format (e.g. JPEG, PDF) that can be presented with off-the-shelf applications Cordonnier DICOM 20th Anniversary Conference / WADO

DICOM 20th Anniversary Conference / WADO ISO and DICOM effort ISO TC215 (Medical Informatics) / WG2 (Messages and Communication) and DICOM / WG10 (Strategy Advisory) have decided to jointly develop a new standard for defining a « web hook » on DICOM After 2 years of work, a couple of face to face meetings and T-cons involving a douzen of key experts from user and vendor sides, « WADO » is ready for ballot Cordonnier DICOM 20th Anniversary Conference / WADO

DICOM 20th Anniversary Conference / WADO Scope of the Standard New web-based service for accessing and presenting DICOM persistent objects Simple mechanism for accessing a DICOM persistent object from HTML pages or XML documents, through HTTP/HTTPs protocol, using the DICOM UIDs (study, series, instance) NOT a way for searching DICOM images from the web, using parameters such as the Patient ID This standard relates only to DICOM persistent objects (e.g. images, reports, NOT workflow msg) Cordonnier DICOM 20th Anniversary Conference / WADO

DICOM 20th Anniversary Conference / WADO Normative references DICOM PS 3.0 Digital Imaging and COmmunication in Medicine IETF RFC2045 to 2049 Multipurpose Internet Mail Extension (MIME) IETF RFC2396 Uniform Resource Identifiers (URI): Generic Syntax IETF RFC2616 Hypertext Transfer Protocol -- HTTP/1.1 IETF RFC3240 Application/dicom MIME Sub-type Cordonnier DICOM 20th Anniversary Conference / WADO

Retrieving Persistent Objects Store Q/R Print Services Worklist Patient IE Study IE Series IE SOP Image IE Pixels (compressed or not, depending of the TransferSyntax) Image Object Patient IE Image IE Study IE Series IE Image I WADO Objects Cordonnier DICOM 20th Anniversary Conference / WADO

Terms and definitions (1) DICOM Persistent Object An instance of a data object as defined by [DICOM PS 3.3] that has been allocated an unique identifier in the format specified for SOP Instance UID in [DICOM PS 3.3] and has been chosen as an object to be saved securely for some period of time. Within the DICOM Standard, a DICOM Persistent Object is referred to as a Composite Service Object Pair (SOP) Instance. Cordonnier DICOM 20th Anniversary Conference / WADO

Terms and definitions (2) Web Client System A system using Internet technologies (web, e-mail…) interested in retrieving DICOM Persistent Objects from a Web Enabled DICOM Server, through HTTP/HTTPs protocol Web Enabled DICOM Server A system managing DICOM Persistent Objects and able to transmit them on request to the Web Client System Web Access to DICOM Persistent Objects Service enabling Web Client System to retrieve DICOM Persistent Objects managed by Web Enabled DICOM Server, through HTTP/HTTPs protocol. Cordonnier DICOM 20th Anniversary Conference / WADO

DICOM 20th Anniversary Conference / WADO Applications Referencing an image or a report from an electronic patient record (EPR) Including references to images in an e-mail (second opinion, hospital to doctor distribution) Providing access by outside referring doctors to a hospital web server that contains references to reports, images and waveforms Providing access to anonymized DICOM reports, images and waveforms via a web server, for teaching purposes and for clinical trials Cordonnier DICOM 20th Anniversary Conference / WADO

Scenario: form the reference Radiology dept Interpretation Acquisition Modality Image Manager & Archive Images Store Images Retrieve Reference to images Report Store Report Export Report Repository Clinical Documents Repository Clinical dept Cordonnier DICOM 20th Anniversary Conference / WADO

Typical scenario: form the reference The radiologist performs an acquisition creating DICOM images He interprets the images producing a DICOM SR including reference to some significant images He exports the DICOM SR as an HL7 CDA including those references to « external observations » (instance, series and study UIDs as different « id » sets, and « path » of the DICOM System in the « reference ») The CDA is stored into the EMR/EPR/EHR database, using patient information for selecting the right record Cordonnier DICOM 20th Anniversary Conference / WADO

Clinical Documents Repository Scenario: web access Radiology dept Interpretation Acquisition Modality Image Manager & Archive Images Store Images Retrieve Reference to images Report Store Web Access to DICOM Persistent Object Report Repository Report Export Clinical Documents Repository Clinical Document Consultation Clinical dept Cordonnier DICOM 20th Anniversary Conference / WADO

Typical scenario: web access A clinician consults the CDA (the stylesheet builds the « URI » using the « reference » of the « custodian » which provided the CDA, completed by the « Web Access to DICOM Persistent Objects » parameters) The clinician clicks on one « image » link The WADO service, implemented as an HTTP script, build a « DICOM FIND » message using the parameters (studyUID=1.2.32.…&seriesUID=1.2.32….), and retrieve the image form the DICOM server It creates the HTTP response body as a MIME part (either application/dicom, or image/jpeg) Cordonnier DICOM 20th Anniversary Conference / WADO

Examples of implementation Web Client System Web Access to Dicom Persistent Objects Web Access to Dicom Persistent Objects Direct Interface Web Gateway Gateway DICOM Q/R DICOM Interface Web Interface DICOM Q/R DICOM Interface DICOM Objects Database DICOM Objects Database Flexibility for the client to be implemented either as new system or on existing system Cordonnier DICOM 20th Anniversary Conference / WADO

Web Enabled DICOM Server Interaction Diagram Web Client System Web Enabled DICOM Server Object(s) request (HTTP GET) Object(s) send (HTTP response header and body) Cordonnier DICOM 20th Anniversary Conference / WADO

Syntax of the HTTP GET method Syntax defined by the RFC2396 (URI) http://<authority><path>?<query> e.g: http://www.hosp.fr/dicom/wado.asp?studyUID=1… The « Web Access to DICOM Persistent Object » standard defines only the <query> Path of the Web Enabled DICOM Server WADO Parameter(s) Cordonnier DICOM 20th Anniversary Conference / WADO

Consistency with IHE IT Infrastructure Approach « Inspired » by the WADO work, IHE IT Infrastructure has defined a « Retrieve Information for Display (RID) » integration profile, enabling: To retieve a list of « typed » documents available for a patient (thanks to PatientID) To retrieve a document using its UID « Inspired » by the IHE IT Infrastructure work, WADO has defined a requestType(=WADO) parameter for compatibility with extensions Cordonnier DICOM 20th Anniversary Conference / WADO

DICOM 20th Anniversary Conference / WADO Selection Parameters studyUID&seriesUID&objectUID [&frameNumber] studyUID => UID of the study containing the object(s) seriesUID => UID of the series containing the object(s) objectUID => UID of the single object (Service Object Pair SOP) frameNumber => number of the selected frame (multiframe image objects) – if NOT retrieved as application/dicom Cordonnier DICOM 20th Anniversary Conference / WADO

MIME type of return object The MIME type of the object contained in the contentType parameter, compatible the <accept> parameter of the GET method application/dicom for all objects, or a different MIME type for converting the DICOM object, depending of the nature of the object: image/jpeg for still image object text/html or text/plain for text object, or other optional formats Cordonnier DICOM 20th Anniversary Conference / WADO

MIME type of a Structured Report application/dicom application/x-hl7-cda-level-one+xml for converting the SR into CDA (see HL7 Imaging SIG /DICOM WG20) text/plain for « minimal » version of document text/rtf for « Word » version of document application/pdf for « stable » version of document, potentially containing images text/html a priori without the images (to contained into only one file). The reference to the images can used the WADO syntax. Cordonnier DICOM 20th Anniversary Conference / WADO

Parameters when the object is return as application/dicom [transferSyntax][anonymize][charset] transferSyntax => DICOM UID of the transferSyntax to be applied to the image (lossy/lossless compression). Implicit and Big Endian TS shall not be used. anonymize => “=yes” for blanking all the personal healthcare information (patient name, study date…) as described in Sup. 55. Potentially the server can refuse to deliver an object if there are some risk the personal information is burned into the image (secondary capture…) charset => for converting the text fields in a different character set (available also if object return as text/xxx) Cordonnier DICOM 20th Anniversary Conference / WADO

Parameters when the object is return as image/xxx (1) [imageQuality] [presentationUID & presentationSeriesUID |[windowCenter & windowWidth]] imageQuality => controls the level of compression (from 1 to 100) presentation => UIDs of the Presentation State SOP and of its series to be applied on the image (P-values, and display size set to the original size if undefined) windowCenter / windowWidth => controls the luminosity and the contrast of the B&W image Cordonnier DICOM 20th Anniversary Conference / WADO

Parameters when the object is return as image/xxx (2) [region][rows][columns][annotation] region => part of the image to be displayed, in relative coordinates (top left hand corner and bottom right hand extent) rows => maximum number of pixels (vertical) columns => maximum number of pixels (horizontal) annotation => text to be superimposed of the image (“patient” and / or “technique” for demographic information and technical information, respectively) Cordonnier DICOM 20th Anniversary Conference / WADO

DICOM 20th Anniversary Conference / WADO Security aspects It is clear that the information contained within DICOM objects may be considered as protected healthcare information (PHI). The protocol used, that is HTTP, can be replaced by HTTPs, which is its secure extension, for that purpose. Two optional parameters, anonymize and annotation, control respectively the absence of patient identification in a retrieved DICOM object and the presence of patient identification burned in to the pixel data of images. Cordonnier DICOM 20th Anniversary Conference / WADO

Providing a image as image/xxx Select the object studyUID&… Apply the presentation presentationUID&… or windowCenter… Select a region region Build the pixel area rows…&columns… Burn the annotations CT WC-800 WW200 DOE 2003-9-22 annotation Generate the MIME type Content-Type: image/jpeg; name="Image.jpg" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="Image.jpg" /9j/4AAQSkZJRgABAQEASABIAAD/2wBDAAYEBQYFBAYGBQYHBwYIChAKCgkJChQODwwQFxQYGBcU FhYaHSUfGhsjHBYWICwgIyYnKSopGR8tMC0oMCUoKSj/2wBDAQcHBwoIChMKChMoGhYaKCgoKCgo KCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCj/wgARCABkAGQDASIA AhEBAxEB/8QAGwABAQEBAQEBAQAAAAAAAAAAAAUEAwECBgf/xAAYAQEAAwEAAAAAAAAAAAAAAAAA AQIDBP/aAAwDAQACEAMQAAAB/qgAAAAAAABNpnSTVc6Sbpm2lO6RG0a7gAcZWztzcORR8tef9+6a 09xdPZncOjtAfH3Opls+oOrHlq8+Eubfoc3LpfXRn4ZaZUtOTXr0BfVPoKZxud1lzRdFJN5PSklI 8sIjJrNegLXAAAAAAAAAAAAAA//EACEQAAMAAQQCAwEAAAAAAAAAAAECAwQREhMUACAQNFAk/9oA CAEBAAEFAvyksxxl7DILsYJ2GVSyIrXoJVbf6zoKeT+lPscTS48WUWM8lSMQHWSPTs+r42rcI4EG contentType Cordonnier DICOM 20th Anniversary Conference / WADO

DICOM 20th Anniversary Conference / WADO Client flexibility The WADO functionality supports access to Native (un-rendered) DICOM data Associated rendering data e.g. Gray Scale Presentation State “Rendered” information e.g. JPEG image So client design can be Simple, relying on basic features of the web browser Complex, providing advanced functionalities by taking ‘raw’ DICOM data and deciding the processing and rendering to be applied Cordonnier DICOM 20th Anniversary Conference / WADO

DICOM 20th Anniversary Conference / WADO Conclusion A small standard but a precious « missing link » offering the modernity of the Web to DICOM equipement and all the DICOM richness and stability to the (messy) Web Will be implemented largy soon in large and small systems (« where is WADO? ») To be extended (multiple objects retrieval, WSDL definition…) after implementations Thanks to Hidenori Shinoda and Nick Brown for chairing the WADO ad hoc group, as well as to all the contributors of that group Cordonnier DICOM 20th Anniversary Conference / WADO