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D

DAS See Direct Attached Storage.

DAT See Digital Audio Tape.

DATA Factual information, usually organised for analysis. It can also be thought of as information which is in a suitable form for processing by a computer.

Data mining A description for a class of database applications that look for hidden patterns in data. Data mining techniques can discover previously unknown relationships within data.

Data warehousing The storage of an organisation's data (e.g. medical imaging data) at a remote site, management of which may be the responsibility of a third party. See Application Service Provider (ASP).

Database A collection of information organised in such a way that a computer program can quickly select desired pieces of data. A database can be constructed using several methods, examples are a relational database and a flat database; a relational database stores data in related tables whereas a flat database stores data in a single table. See Database Management System (DBMS).

Database Management System (DBMS) A collection of programs that enable the user to access a database. See Database.

DBMS See Database Management System.

DDP See Default Display Protocol.

DDS See Digital Data Storage.

Default Display Protocol (DDP) When the images in a PACS are displayed on a workstation for reporting they will be placed in a standard or default format known as the Default Display Protocol. This is also referred to as the hanging protocol.

DES See Device Evaluation Service.

Detailed Statement of Need (DSON) This is a procurement document produced primarily by PaSA with technical input from PACSnet. This gives a framework for the purchaser to detail to the vendor their requirements for the project. See Statement of Need (SON) and Purchasing and Supply Agency (PaSA).

Device Evaluation Service (DES) This is a division of the MDA that deals with the Medical Devices Evaluation programme. See Medical Devices Agency (MDA).

Diagnostic Imaging Review (DIR) An executive summary magazine produced by the DES to highlight the work done by the diagnostic imaging evaluation centres. See Device Evaluation Service (DES) and Medical Devices Agency (MDA).

Diagnostic Medical Equipment (DME) A section in PaSA that deals with the purchase of diagnostic imaging equipment. See Purchasing and Supply Agency (PaSA).

DICOM See Digital Imaging and Communications in Medicine.

DICOM gateway An interface between a modality and PACS. This will allow the transfer of images or data when the PACS and the modalities have DICOM conflicts.

Digital This describes any system that is based on discrete units, e.g. computers. Computers are digital because they operate on a series of discrete units called bits. See bit and byte.

Digital Audio Tape (DAT) A magnetic tape storage device used in the backup of large amounts of data which conforms to the DDS standard. The cartridges can store from 2 to 20 GB of native or uncompressed data with an archiving rate of 2 Mbps. See Digital Data Storage (DDS), Linear Tape Open (LTO), Digital Linear Tape (DLT), Advanced Intelligent Tape (AIT), Digital Versatile Disk (DVD), Jukebox and Magneto Optical Disk (MOD).

Digital Data Storage (DDS) This is the physical recording format adopted as an industry standard for DAT drives. See Digital Audio Tape (DAT).

Digital Imaging and Communications in Medicine (DICOM) The ACR-NEMA standard protocol adopted by all manufacturers of equipment associated with medical imaging. The standard provides a method of linking a series of heterogeneous modalities, workstations and printers without the need for customised hardware to allow them to communicate and transfer images (http://medical.nema.org/dicom.html). See American College of Radiology - National Electrical Manufacturers Association (ACR-NEMA), Health Level 7 (HL7) and Integrating the Healthcare Enterprise (IHE).

Digital Linear Tape (DLT) A magnetic tape storage device used in the backup of large amounts of data. The tape cartridges can store from 20 to 40 GB of data and has a transfer rate of 6 MB/sec. The DLT system was improved to super DLT (S-DLT) which has a maximum storage of 110 GB with a transfer rate of 11 MB/sec. See Advanced Intelligent Tape (AIT), Digital Audio Tape (DAT), Digital Versatile Disk (DVD), Linear Tape Open (LTO), Jukebox, and Magneto Optical Disk (MOD).

Digital Versatile Disk (DVD) This is a form of storage media which uses the same technology as CD-ROM but has a higher density of pits on each layer of the disk. A DVD can be a dual sided media and the technology also allows the DVD to have multiple layers, creating an increase in storage capacity. A DVD has the ability to store large amounts of data up to 4.7 GB per side for a single layer disk. See Advanced Intelligent Tape (AIT), Digital Audio Tape (DAT), Digital Linear Tape (DLT), Linear Tape Open (LTO), Jukebox and Magneto Optical Disk (MOD).

Digitiser A device used to scan a traditional X-ray film to create a digital image data file. There are two types of film digitisers in common use. Both use lasers to scan the film to create the digital image; however one uses photo-multiplier tubes (PMT) to capture the light whereas the other uses charged coupled device (CCD) technology. See Charged Coupled Device (CCD) and Photo Multiplier Tube (PMT).

DIR See Diagnostic Imaging Review.

Direct Attached Storage (DAS) This a term used to describe a storage device (usually a disk) attached to a server which can respond quickly to random requests for data.

DLT See Digital Linear Tape.

DME See Diagnostic Medical Equipment.

DSON See Detailed Statement of Need.

Dumb terminal This is a terminal that has no processing capabilities. The information shown on the screen is taken from a central server where the processing is done.

DVD See Digital Versatile Disk.