Applying REST to DICOM

Chris HafeyFeb 23, 2011

Introduction

• Three Types of Web Services– RPC Based (WS*)– REST– REST/RPC Hybrid

• Pure REST is a great fit for DICOM– Simple– Wide technology support– Many DICOM use cases are CRUDish

Resource Oriented Architecture

• Resources• URIs• Addressability• Statelessness• Representations• Links and Connectedness• Uniform Interface

Resources• Entities

– DICOM Modules• Patient• Study

– UID Based• Study, Series, Instance

– Internals• Image Frame

• Algorithms– Render Image– Search

• Complex Transactions– Merge Studies

URIs• Entites

– Use path to specify where an entity is– E.g – A study

• http://server/study/1.2.3.4.5

• Algorithms– Use Path to specify which algorithm/entity to run– Pass algorithm parameters via http query parameters– E.g. – render a sop instance as a JPEG with a specific window center/window width

• http://server/study/1.2.3.4.5/series/1.2.3/instance/1.2.3?windowWidth=400&windowCenter=40

• Transactions– Use path to specify transactions– The transaction resource can point to other entities that will be affected

Addressability

• Expose interesting aspects of its data set as resources– Allows data to be used in ways not originally

anticipated– E.g. exposing individual DICOM Modules to be

independently accessed

Statelessness

• Each HTTP Request happens in complete isolation– No “session”– Simplifies error conditions– Can send the same web request multiple times

without side effects

Representations

• Leverage MIME Types– Application/XML– Application/JSON– Application/DICOM– Image/JPEG– Image/PNG

• A resource can be returned in multiple representations

Links and Connectedness

• Use HREF to link between resources

• DICOM Examples– Patient to Study– Study to Series– Series to Instance– Presentation State to Image– Structured report to Image

Uniform Interface

HTTP Method Purpose RDBMS Analog

GET Retrieve Select

PUT Update Update

POST Create Insert

DELETE Delete Delete

Reference Books

• RESTful Web Services– Leonard Richardson & Sam Ruby

• RESTful Web Services Cookbook– Subbu Allamaraju

• REST in Practice– Ian Robinson, Jim Webber, and Savas Parastatidis