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Digital Imaging and Communications in Medicine (DICOM) is a comprehensive set of standards for handling, storing, printing and transmitting information in medical imaging. It includes a file format definition and a network communications protocol. This protocol is an application protocol, it uses TCP/IP to communicate between systems. DICOM files can be exchanged between two entities that have the capability to receive the information - image and patient data - in DICOM format.

DICOM was developed to enable integration of scanners, servers, workstations,printers and network hardware from multiple vendors into a picture archiving and communication system. The different machines, servers and workstations come with DICOM conformance statements which clearly state the DICOM classes supported by them. DICOM has been widely adopted by hospitals and is making inroads in smaller applications like dentists' and doctors' offices.

DICOM Data Format

The same format is used for all uses, including network and file usage. DICOM differs from other data formats in that it groups information together into a data set. That is, an X-Ray of your chest actually contains your patient ID within it, so that the image is never mistakenly separated from your information.

DICOM files consist of a header with standardized as well as free-form fields and a body of image data. A single DICOM object can only contain one image, but that image may have multiple "frames", allowing storage of cine or other multi-frame data. Image data can be compressed using a variety of standards, including JPEG, JPEG Lossless JPEG 2000, LZW and Run-length encoding (RLE).

DICOM Services

DICOM consists of many different services, most of which involve transmission of data over a network, and the file format below is in fact a later and relatively minor addition to the standard.

Storage

The DICOM Storage service is used to send images or other persistent objects to a PACS or Workstation.

Query/Retrieve

This enables a workstation to find lists of, and then retrieve, images or other such objects from a PACS

Modality Worklist

This enables a piece of imaging equipment (a Modality) to obtain details of the patient and examination electronically, avoiding the mistakes caused by typing.

Printing

The DICOM Printing service is used to send images to a DICOM Printer, normally to print an "X-Ray" film. There is a standard calibration (defined in DICOM Part 14) to help ensure consistency between various display devices, including hard copy printout.

Off-line Media (DICOM Files)

DICOM restricts the filenames on DICOM media to 8 character names (many people wrongly use 8.3, but this is not legal). This is a common source of problems with media created by developers that did not read the specifications carefully. This is a historical requirement to maintain compatibility with older existing systems. It also mandates the presence of a media directory, the DICOMDIR file, that provides index and summary information for all the DICOM files on the media. The DICOMDIR information provides substantially greater information about each file than any filename could, so there is less need for meaningful file names.

History

The first significant DICOM standard is version 3.0, which was developed in 1993. Details of the DICOM specification are available at the NEMA site, and many public domain and open source implementations exist. There is also an ongoing media exchange test and connectathon process for CD media and network operation that is organized by the IHE organization.

Examples of Modalities supported in DICOM are:

Sample

This picture is a sample image. It shows a knee that was examined via magnetic resonance imaging.

See also

External links

Radiology | Medical imaging

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This article is licensed under the GNU Free Documentation License. It uses material from the "Digital Imaging and Communications in Medicine".

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