WADO “wah-doh”

The Web Access to DICOM persistent Objects (WADO) extension to the DICOM standard was defined jointly with the European Standardization Organization. WADO provides a standardized way to access DICOM images in a web-friendly format. Clinicians can access the data in it’s native DICOM format, or access the in a generic format, such as JPEG or PDF.

WADO specifies the means by which a request for access to a DICOM-persistent object can be expressed as an HTTP URL/URI request. The request includes a pointer to a specific DICOM-persistent object in the form of its instance UID, and specifies the format of the result to be returned in response to the request.
Examples include:

(MIME) Content-type (i.e. application/dicom or image/jpeg for images, application/dicom or application/rtf or xml for reports)
Content-encodings
Reports encoded as HL7/CDA

The parameters of the query URL, as defined in WADO, are sufficient for the HTTP server to act as a DICOM SCU to retrieve the requested object from an appropriate DICOM SCP using baseline DICOM functionality.

To retrieve DICOM-persistent objects using WADO, the web-based system must know the UID (study, series, SOP Instance) of the object it needs to retrieve. This may be obtained through a number of different methods, including reception of a standardized message containing a document referencing the DICOM objects, and a query of other systems.