Data Compression

Method to reduce sheer volume of data by more efficient encoding practices, thereby reducing image processing, transmission times, bandwidth requirements, and storage space requirements. Some compression techniques result in the loss of some information, which may or may not be clinically important.

Data Repository

The element of an information system that accepts, files, and stores data from various sources.

DDS

Digital Data System. A system for transmitting telephone traffic in digital format between major switching hubs. This system allows digital transmission of voice and data as a component of the analog telephone system (POTS).

Dedicated Line

A permanent telephone line reserved exclusively for one patient, accessible all hours of the day. These lines usually offer better quality than standard telephone lines, but may not significantly augment the performance of data communications. May also be known as 'leased,' or 'private' lines.

DICOM

Digital Imaging and Communications in Medicine. A set of protocols describing how radiology images are identified and formatted that is vendor-independent and developed by the American College of Radiology and the National Electronic Manufacturers Association. The standard emphasizes point-to point connection of digital medical imaging devices. DICOM 3.0 is the current version.

Digital

Used in both electronic and light-based systems, these signals transmit audio, video, and data as bits. Digital technology allows communications signals to be compressed for transmissions that are more efficient.

Digital Camera

An image producing lens system made up of one or more light-sensitive integrated circuits, a myriad of light sensitive elements, and circuits for timing, nonlinear amplification, and encoding color.

Digital Image

An image formed by independent pixels, each of which is characterized by a digitally represented luminance level. For example, a popular screen size for digital images is a 1024 by 1024 matrix of pixels x 8 bits, representing 256 luminance levels.

Digital Signal

An electrical signal in the form of discrete voltage pulses. These signals transmit audio, video, and data as bits, which are either on or off, differing from analog signals, which are continuously varying. Communications signals may be compressed using digital technology, allowing efficient and reliable transmission rates.

Digitize

The process by which analog, or continuous, information is transformed into digital, or discrete, information. Because most computers are only capable of processing digital information and visual information is inherently in analog format, this process is essential in computer imaging applications.

Direct Capture

A procedure by which image data are formed directly from the original source allowing a high quality image reproduction. In this process, images created from image files are identical to the original, regardless of the device used to capture them, such as a CT or an MRI. In direct video capture, the video signal is digitized from the display, which creates a higher quality image and is more efficient than acquisition through scanning.

Direct Digital Imaging

Involves the capture of digital images so that they can be electronically transmitted.

Dish

An antenna shaped like a parabola that is the essential component of a satellite earth station, or downlink.

Download

The process of transferring files or software from another computer to your computer.

Dpi

Dots per inch. The number of dots or pixels per inch used in film resolution. In conventional radiography resolution is given in line pairs per millimeter (lp/mm).