In the early 1980s it was almost impossible for anyone, other than manufacturers of computed tomography or Magnetic Resonance Imaging devices to decode the images that the machines generated. Radiologists and medical physicists wanted to use the images for dose-planning for radiation therapy. There was a clear demand for specifying a standard that is capable of storing the images from different sources; patient data, history of treatment etc. together and is general and extensible enough for long-term usage.
The first steps were taken around 1985, when the first standard (ACR/NEMA 300) was released. Soon after its release, it became clear that improvements were needed. In 1993 the third version of the standard was released. Its name was then changed to DICOM to improve the possibility of international acceptance as a standard.
Digital Imaging and Communications in Medicine (DICOM) became a standard for handling, storing, printing, and transmitting information from medical imaging. It includes a file format definition and a network communications protocol. The communication protocol is an application protocol that uses TCP/IP to communicate between systems. DICOM files can be exchanged between two entities that are capable of receiving image and patient data in DICOM format. The National Electrical Manufacturers Association (NEMA) holds the copyright to this standard. It was developed by the DICOM Standards Committee, whose members are also members of NEMA.
DICOM enables the integration of scanners, servers, workstations, printers, and network hardware from multiple manufacturers into a picture archiving and communication system (PACS). DICOM has been widely adopted by hospitals and is making inroads in smaller applications like dentists' and doctors' offices.
DICOM data format, groups information into data sets. This means that a chest X-Ray image, for example, actually contains the patient ID within the file. This means the image can never be separated from the information. This is similar to the way that image formats such as JPEG can also have embedded tags to identify and describe the image.
A DICOM data object consists of a number of attributes, including items such as name, ID, etc., and also one special attribute containing the image pixel data. It can contain not only single image but multiple "frames", allowing storage of cine loops or other multi-frame data. For example, a NM image by definition is a multi-dimensional multi-frame image. In this case, three- or four-dimensional data can be encapsulated into a single DICOM object. Pixel data can be compressed using a variety of standards, including JPEG, JPEG Lossless, and Run-length encoding (RLE).
For more information about DICOM format see: http://medical.nema.org.