DICOM (Digital Imaging and Communications in Medicine) is an interoperability standard that was developed to facilitate the handling, sharing, storage and printing of medical imaging information and allow integration of different devices into a picture archiving and communication system (PACS).
The protocol is mainly the result of collaboration between The National Electrical Manufacturers Association (NEMA), representing hardware manufacturers, and the American College of Radiology (ACR), representing users from the medical community. This standard requires that manufacturers create a statement of conformance when claiming DICOM compliance, including specifically stating supported DICOM classes. The latest version of the DICOM standard, 3.0, runs on top of the TCP/IP stack (the Transport and Network layers of the OSI model) and is compatible across different networks, unlike previous versions which focused on direct connections.
DICOM files are embedded with clinical data as well as imaging content, and include a header that contains various attributes such as patient info and imaging file dimensions. Supported standards under DICOM include SNOMED, JPEG and MPEG.
Unlike HL7, DICOM is an Information Technology standard that promotes interoperability among different medical imaging devices, and is not a comprehensive backbone upon which health care information exchange systems can be built.
Submitted by Jeremy Tran
The DICOM Standard consists of 18 parts, two of which have been retired and are no longer used (see Table 1). Each part of the standard focuses on a different part of the protocol (MergeCOM-3, 2011; Mustra et al., 2008). Part 1 gives an overview of the standard but can be confusing and is somewhat outdated. Part 2 describes the conformance which is the Information Object Definition (Part 3) paired with the Service Class Specification (Part 4). Parts 3 and 4, therefore, define the types of services and information that can be exchanged. Parts 5 and 6 describe how commands and data are encoded and Part 7 describes the structure of the DICOM commands. Part 8 is the Upper Layer Protocol where the transport layer protocols are described (TCP/IP and OSI). Part 9 has been retired but described how the messages were exchanged in point-to-point connections of the first two versions. Part 10 describes the model for storage of information regarding medical imaging on any removable media. Part 11 specifies media format for storage while Part 12 details the characteristics of the media format. Part 13 has also been retired as it relates to the point-to-point connection of versions 1.0 and 2.0. Part 14 standardizes the display function for grayscale image display. Part 15 involves security protocols and Part 16 specifies the Content Mapping Resource that defines the template and context used in the standard. Part 17 describes the use of the standard while Part 18 specifies web-based accessing and presenting services for DICOM objects (MergeCOM-3, 2011). These parts are then combined in the DICOM Standard topology, as seen in Figure 2.
Table 1- Parts of the DICOM Standard (Adapted from Mustra et al., 2008)
PS 3.1 Introduction and Overview
PS 3.2 Conformance
PS 3.3 Information Object Definitions
PS 3.4 Service Class Specifications
PS 3.5 Data Structure and Encoding
PS 3.6 Data Dictionary
PS 3.7 Message Exchange
PS 3.8 Network Communication Support for Message Exchange
PS 3.9 Retired (formerly Point-to-Point Communication Support for Message Exchange)
PS 3.10 Media Storage and File Format for Data Interchange
PS 3.11 Media Storage Application Profiles
PS 3.12 Storage Functions and Media Formats for Data Interchange
PS 3.13 Retired (formerly Print Management Point-to-Point Communication Support)
PS 3.14 Grayscale Standard Display Function
PS 3.15 Security and System Management Profiles
PS 3.16 Content Mapping Resource
PS 3.17 Explanatory Information
PS 3.18 Web Access to DICOM Persistent Objects (WADO)
Figure 2-DICOM topology (See figure 6.2-2 from: http://www.dicomtags.com/dicom-standard/09_10pu.php)
DICOM Working Groups
DICOM is a complicated and complex standard in the fact that it must be relatable to all fields using digital imaging. In order to accomplish this mission successfully and address issues relating to new technologies, security, performance, workflow and structure and coded documents there are 27 working groups and a standards committee (DICOM, 2011; Mustra et al., 2008). Each of these workgroups deals with specific, small, subjects or topics (see Table 2). Therefore, it is each working group that does the main part of work regarding expansion and correction of the Standards. Working groups are commissioned by the committee to work on a particular set of tasks and then execute the work needed. Once a supplement or correction is created by the work group it is submitted to the Base Standards Working Group (WG-06) where it is reviewed. The supplement is then subjected to a public review and approval by DICOM members (DICOM, 2011).
Table 2- Working Groups (adapted from DICOM, 2011) WG-01: Cardiac and Vascular Information
WG-02: Projection Radiography and Angiography
WG-03: Nuclear Medicine
WG-05: Exchange Media
WG-06: Base Standard
WG-08: Structured Reporting
WG-10: Strategic Advisory
WG-11: Display Function Standard
WG-13: Visible Light
WG-15: Digital Mammography and CAD
WG-16: Magnetic Resonance
WG-18: Clinical Trials and Education
WG-19: Dermatologic Standards
WG-20: Integration of Imaging and Information Systems
WG-21: Computed Tomography
WG-23: Application Hosting
WG-25: Veterinary Medicine
WG-27: Web Technology for DICOM
Each of the Working Groups deals with and develops only a small part of the whole standard (DICOM, 2011). Within a given year there will be about 100 proposals for minor corrections, which anyone can submit, 10 supplements from Working Groups, and one consolidated version (Revet, 2011).
DICOM has sought to standardize communication of images as well as the data associated with them. Impressively, every major vendor uses DICOM Standards in their systems. This universality of the standard has led to a cooperative environment, in which vendor work with the committee to enhance the standard. DICOM’s functions are to work with the transmission of images, query and retrieval, performance, workflow management and quality of images. The standards are constantly evolving and remain current with technologies and needs within digital imaging fields. In order to accomplish this, the DICOM committee has Working Groups which handle only a small subset, with supplements and addendums added throughout the year. This standard is complex, complicated and technical in its definitions. However, this is needed when images and the associated data are being transferred, archived or processed. The complexity also arises from the interconnectivity between different systems and vendors. Furthermore, it incorporates and supports all branches that have digital imaging needs, which are vast, from pathology to veterinary medicine. DICOM also defines attributes that should be included, although issues arise when information is entered in the wrong field. Despite some drawbacks to DICOM (Mustra et al., 2008), it is an internationally used product that is supported by all major vendors and allows interoperability with images and associated data. DICOM is also structured so that continuous changes and evolutions can take place within the system, allowing for expansion and new technologies. Despite its complexity, DICOM Standards are extremely important for health care, quality, and research.
- Digital Imaging and Communications in Medicine (DICOM), NEMA Publications (2011) DICOM strategic document Ver. 11.3. Accessed : http://medical.nema.org/dicom/geninfo/Strategy.pdf
- MergeCOM-3, Merge Healthcare Inc (2011) The DICOM Standard. Accessed November 12, 2011:
- Mustra M, Delac K, Grgic M (2008) Overview of the DICOM standard. ELMAR, 2008. 50th International
Symposium , vol.1, no., pp.39-44.
- Revet B (2011) Philips Healthcare What’s New in DICOM. DICOM Workshop @ SPIE MEDICAL IMAGING.