DICOM Digital Imaging COmmunications in Medicine
Communication Protocols: Key to Connectivity • Layered Model, each layer performs a specific function • Set of Services and Protocols • Connectivity requires sharing a complete protocol • Communication requires a shared Semantic Context
Communication Standards • Protocols are defined by standards • A Standard is an agreement which may be voluntary, Government mandated, or International Law • Protocols may also be proprietary
Who Defines Communication Standards? • User Consortia (e.g., HL7) • Organizations (e.g., NEMA, IEEE) • US Government Agencies (e.g., ANSI, NIST) • Foreign Government Agencies (e.g., CEN) • United Nations (e.g., ISO, CCITT)
ACR-NEMA • 1982 - ACR and NEMA form a joint committee • 1985 - Publication of Version 1.0 • 1988 - Compression and Mag Tape Standards • 1988 - Publication of Version 2.0 • 1989 - Began work on Network Version with HIS/RIS
DICOM • The name was changed to separate the standard from the originating body • 1991 - Release of Parts 1 and 8 of DICOM • 1992 - RSNA demonstration, Part 8 • 1993 - DICOM Parts 1-9 approved, RSNA demonstration of ALL parts • 1994 - Part 10: Media Storage and File Format • 1995 - Parts 11,12, and 13 plus Supplements
The Parts of the DICOM Standard • Part 1 - Introduction and Overview • Part 2 - Conformance • Part 3 - Information Object Definitions • Part 4 - Service Class Definitions • Part 5 - Data Structures & Semantics • Part 6 - Data Element Listing and Typing • Part 7 - Message Exchange Protocol • Part 8 - Network Support for Message Exchange • Part 9 - Point-to-Point Support
The Parts of the DICOM Standard • Part 10 - Media Storage and File Format • Part 11 - Media Storage Application Profiles • Part 12 - Media Formats and Physical Media • Part 13 - Print Management Point-to-Point
LiteBox MAGN ETOM DICOM Application Domain Storage, Query/Retrieve, Study Component Print Management Query/Retrieve Results Management Media Exchange Query/Retrieve, Patient & Study Management Information Management System
Summary of DICOM Features • NETWORK PROTOCOL • DICOM incorporates negotiation to permit nodes to agree on the functions to be performed • MESSAGE ENCODING • DICOM defines 24 data types (V2.0 had 4) • DICOM message encoding includes JPEG compression (17 varients) • DICOM includes encapsulated image and multi-frame syntaxes • DICOM supports multiple character repertoires
Summary of DICOM Features • OBJECT DATA MODEL • DICOM is based on a completely specified data model • DICOM includes a robust UID mechanism • DATA DICTIONARY • DICOM includes a large number of new data elements • SERVICE CLASSES • DICOM defines classes of service for specific applications (e.g. image management, printing) and conformance levels
Summary of DICOM Features • Off-Line Media Support • DICOM defines a directory structure and media profiles • CONFORMANCE • DICOM requires conformance statements and contains detailed conformance requirements
DICOM Terminology • DICOM Message Service Element (DIMSE) - The set of DICOM Application Layer communication services. • DIMSE Service Group (DSG) - A subset of the full DIMSE services which is applicable to a specific IOD. • Information Object Definition (IOD) - A data abstraction of a class of real-world objects. A collection of related attributes (data elements).
DICOM Terminology • Service Class - A set of functionality relating to a single type or real-world activity. Composed of a set of SOP Classes plus rules and associated semantics. • Service-Object-Pair Class (SOP) - The atomic unit of DICOM functionality. Composed of an IOD and a DIMSE Service Group plus restrictions or extensions of the IOD. (Equivalent to an Object Class)
Service-Object Pair Class Data Dictionary DIMSE Service Group Information Object SOP Real-World Object
DICOM Service Classes • Composite • Verification • Storage • Query/Retrieve • Study Content Notification • Normalized • Patient Management • Study Management • Results Management • Basic Print Management
Conformance • DICOM Part 2 specifies the structure of a conformance statement • DICOM does not specify a test suite or a compliance verification mechanism • All DICOM implementations must be supported by a properly constructed conformance statement
DICOM Conformance Statement • Implementation Model which describes the Application Entities in the implementation • Detailed specification of each Application Entity • SOP Classes supported • policies for initiation and acceptance of associations • Presentation Contexts • SOP options • Supported communications protocols • Specializations • Configuration
Purpose of a Conformance Statement • Allow a user to determine which optional components of the DICOM Standard are supported by a particular implementation, and what extensions or specializations an implementation adds. • By comparing the Conformance Statements from two implementations, a knowledgeable user should be able to determine whether or not interoperability is possible.
DICOM Conformance Testing • No Formal Mechanism is Defined in the Standard • Committee for the Advancement of DICOM • Define initial test plan and cross-connect matrix • Future RFP for organization to monitor the process • Problem: How to Map DICOM Conformance Statements into Test Plans
The DICOM Explosion • Joint CEN-DICOM development • Medicom = DICOM • MIPS 95 work is underway with JIRA • IS&C Harmonization is also in progress • HL7 Harmonization continuing interest • New DICOM organization • Companies: NEMA and non-NEMA • ACR, ACC, CAP, ... • individuals
Summary • Networking is a critical component of all medical imaging systems • Support for Open Communication Standards is a MUST • DICOM is here, NOW • DICOM products exist on the market • DICOM is emerging as THE common protocol for medical image communication - WORLD WIDE!