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

WADO – Web Access toDICOM Persistent Objects

WADO – Web Access toDICOM Persistent Objects

Emmanuel CordonnierETIAM

Emmanuel CordonnierETIAM

PartnershipsPartnerships

Cordonnier DICOM 20th Anniversary Conference / WADO page 2

ContextContext

• 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


ISO and DICOM effortISO 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


Scope of the StandardScope 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)


Normative references 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


Patient IE

Image IE

Patient IE

Study IE

Series IE

Study IE

Series IE

Image I

Patient IE

Study IE

Series IE

Retrieving Persistent ObjectsRetrieving Persistent Objects

Patient IE

Study IE

Series IE

SOP Image IE

Pixels (compressed or not,

depending of the TransferSyntax)

Image Object

Objects

Store Q/R PrintServices WorklistWorklist

WorklistWorklist

WADO


Terms and definitions (1)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.


Terms and definitions (2)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.


ApplicationsApplications

• 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


Scenario: form the referenceScenario: form the reference

Images Store

Image Manager& Archive

Report Export

ReportRepository

AcquisitionModality

Images Retrieve

ReportStore

Radiology dept

Referenceto imagesReferenceto images

Clinical Documents Repository

Clinical dept

Interpretation


Typical scenario: form the referenceTypical 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


Scenario: web accessScenario: web access

Images Store

Image Manager& Archive

Report Export

ReportRepository

AcquisitionModality

Images Retrieve

ReportStore

Radiology dept

Referenceto imagesReferenceto images

Clinical Documents Repository

Clinical dept

Interpretation

Clinical Document Consultation

Web Access to DICOM Persistent Object


Typical scenario: web accessTypical 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)


Examples of implementationExamples of implementation

DICOM Objects Database

DICOM Interface

Web Interface

DICOM Q/R

Web Access to Dicom Persistent

Objects

DICOM Objects Database

DICOM Interface

Web Gateway

DICOM Q/R

Web Access to Dicom Persistent

Objects

Web Client System

DirectInterface

Gateway

Flexibility for the clientto be implemented eitheras new system or on existing system

Flexibility for the clientto be implemented eitheras new system or on existing system


Interaction Diagram Interaction Diagram Web Enabled

DICOM Server

Object(s) request (HTTP GET)

Object(s) send(HTTP response header and body)

Web ClientSystem


Syntax of the HTTP GET methodSyntax 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)


Consistency with IHE IT Infrastructure ApproachConsistency 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


Selection ParametersSelection 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


MIME type of return objectMIME 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


MIME type of a Structured ReportMIME 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.


Parameters when the object is return as application/dicom

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)


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




[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)


Security aspects 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.


Build the pixel arearows…&columns…

Select the objectstudyUID&…

Apply the presentationpresentationUID&…or windowCenter…

Providing a image as image/xxxProviding a image as image/xxx

Select a regionregion

Burn the annotations

CT WC-800 WW200

DOE 2003-9-22annotation

Generate the MIME typeContent-Type: image/jpeg;

name="Image.jpg"Content-Transfer-Encoding: base64Content-Disposition: attachment;

filename="Image.jpg"

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

contentType


Client flexibilityClient 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


ConclusionConclusion

• 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

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

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