DICOM ¿ë¾îÁ¤¸®Abstract Syntax - Generic term, by DICOM 3.0 implemented as SOP syntax ACR - American College of Radiology Access Control - Traffic rules to establish association and avoid collision AE - VR of type Application Entity ACSE - Associated Control Service Element used to establish an association ANSI - American National Standards Institute Application Context - Identifies the overall communications context Application Entity (AE) - A DICOM-conformant agent on the network Application Entity (AE) Title - The name of an Application Entity. The name consists of printable ASCII characters and is limited to a length of 16. The AE Title is not the same as the host name. Application Model - See DICOM Application Model. Application Profile - A Media Storage Application Profile defines a selection of choices at the various layers of the DICOM Media Storage Model which are applicable to a specific need or context in which the media interchange is intended to be performed. AS - VR of type Age String Association - A network connection AT - VR of type Attribute Tag Attribute - A property of an Information Object (IO). An Attribute has a name and a value which are independent of any encoding scheme. Attribute Tag - see Tag Basic Offset Table - A table of pointers to individual frames of an encapsulated multi-frame image. Bits Allocated - see Image Attributes Bits Stored - see Image Attributes Byte Ordering - see Endian Byte Swapping - see Endian Called AE Title - The AE Title of the SCP that an SCU is attempting to start an Association with. Calling AE Title - The AE Title of the SCU that is attempting to start an Association with a SCP. CAT - Computed Axial Tomography. Now called simply Computed Tomagraphy CEN TC 251 - Comite Europeen de Normalisation Technical Committee 251 Center - see Window Cine - A series of image frames that can be displayed one after the other to produce a movie loop. Client Server - Network terms for specific roles, equivalent to SCU and SCP Command - A generic means to convey a request to operate on Information Objects (IO) across an interface or network Command Element - An encoding of a parameter of a command which conveys this parameter's value. Command Stream - The results of encoding a set of DICOM Command Elements using the DICOM encoding scheme. Composite Object - Representing more than one real world object Composite Information Object Definition (C-IOD) - An Information Object Definition which represents parts of several entities in the DICOM Application Model. Such an IOD includes attributes which are not inherent in the Real World object that the IOD represents but rather are inherent in the related Real World objects Computed Axial Tomography (CAT) - Now called simply Computed Tomagraphy Conformance Statement - A formal statement associated with a specific implementation of the DICOM Standard. It specifies the Service Classes, Information Objects, and Communication Protocols supported by the implementation. The requirements of a Conformance Stantment can be found in PS 3.2 CS - VR of type Code String DA- VR of type Date Data Dictionary - Part 6 of the DICOM standard. This part contains a registry of the DICOM Data Elements which assigns a unique tag, a name, value characteristics, and semantics to each Data Element. Also included in this part is a Registry of DICOM Unique Identifiers (UID). Data Element - A subunit of an information object as defined by a single entry in the DICOM Data Dictionary (PS 3.6). An encoded Information Object Definition (IOD) Attribute that is composed of, at minimum, 3 fields: a Data Element Tag, a Value Length (VL), and a Value Field. For some specific Transfer Syntaxes, a Data Element also contains a Value Representation (VR) field. The description of the Data Element can be found in PS 3.5. Each Data Element holds an Attribute of a real world object.
Data Element Tag - The first part of any Data Element. This is a 32-bit value that identifies the Data Element. It is made up of 2 16-bit values. The first is the Group Number and the second is the Element Number. The DICOM specification uses the following notation for a Data Element Tag: (0010:0030). This example is for the Patients Birthday. Data Element Type - Used to specify whether an Attribute of an Information Object Definition or an Attribute of a SOP Class Definition is mandatory, is mandatory only under certain condition, or optional. The DICOM specification defines several levels of these types.
Data Set - A structured set of Attributes directly or indirectly related to Information Objects. That is an organized collection of Data Elements that contain data about a specific Real World Object. The Data Elements are sorted in a Data Set by increasing Group Numbers. See also Nested Data Set. Data Stream - A series of data items that is placed one after another. The result of encoding a Data Set using the DICOM encoding scheme. Defined Term - The value of a Data Element is a Defined Term when it is selected from a finite set of possibilities. A Defined Term is different from an Enumerated Value in that a Defined Terms range can be expanded by an application. Derived Image - An image that contains pixel data that was constructed from the pixel values of one or more other source images. A Derived Image is constructed from a set of image. An example would be a 3-D rendering of a series of CT slices. DICOM - Digital Imaging and Communication in Medicine. A public standard jointly developed by the American College of Radiology (ACR) and the National Electronics Manufactures Association (NEMA). DICOM Application Model - an entity-relationship diagram used to model the relationships between real-world objects which are within the area of interest of the DICOM specification. DICOM File - Formally a DICOM file is one that is formatted according to PS 3.10 of the DICOM Specification. It contains a File Meta Information Header followed be a properly formated DICOM Data Set. Informally, a DICOM file may be a Data Set missing the File Meta Information Header. DICOMDIR - see DICOMDIR File. DICOMDIR File - A unique and mandatory DICOM File within a File Set which contains the Media Storage Directory SOP Class. This File is give an single component File ID, DICOMDIR. DICOM File Format - The DICOM File Format provides a means to encapsulate in a File the Data Set representing a SOP Instance related to a DICOM Information Object. DICOM Information Model - an entity-relationship diagram which is used to model the relationships between the information object definitions representing classes of real-world objects defined by the DICOM Application Model. DIMSE - DICOM Message Service Elements, functionality capable of generating type 4 PDUs. Domain - An Internet zone of authority, part of the address structure DS- VR of type Decimal String DT- VR of type Date Time Element Number - the second 16-bit piece of the Data Element Tag. The Element Number identifies which Data Element the Tag represents in the Data Element Group. Endian - Defines the byte ordering. There are 2 method of ordering multi-byte data values in a computer. Once is called Little Endian and the other is Big Endian. In order
for DICOM Application Entities to communicate with one another they must either use the same Byte Ordering or be able to Negotiate which byte ordering to use and then
have one communication partner Byte Swap to match the other. Enumerated Value - the value of a Data Element is an Enumerated Value when it is selected from a finite set of possibilities. An Enumerated Values different from a Defined Term in that an Enumerated Values range can not be expanded by an application from the standard defined in the DICOM specification. ES - Modality of type Endoscopy Explicit VR - see Value Representation. FD - VR of type Floating Point Double FDDI - Fiber-distributed data interface, high speed network File - An ordered string of zero or more bytes. Files are identified by a unique File ID and may be written, read, and/or deleted. File ID - A unique identifier that references a file in a File Set. A set of ordered File ID Components (up to 8) forms a File ID. File ID Components - A string of one to 8 characters of a defined character set. File Meta Information Header - see Part 10 Image. File Service - see DICOM File Service. File Set - A collection of DICOM Files (and possibly non-DICOM Files that share a common naming space within which File Ids as are unique. File Set Creator - An Application Entity that creates the DICOMDIR File and zero or more DICOM Files. File Set Reader - An Application Entity that accesses Files, create additional Files or deletes existing File in a File Set. File Set Updater - An Application Entity that make appropriate alterations to the DICOMDIR file reflecting the additions or deletions. File Set User - An Application Entity that accesses one or more Files in a File Set. FL - VR of type Floating Point Single Film Session - A group of films Frame - A data packet Gateway - Device and conversion method between heterogeneous networks or systems Group Number - The first part of a Data Element Tag. It is a 16-bit value that identifies the Group that the Data Element falls in to. All Standard DICOM PS 3.6 Group Numbers are even. Odd group numbers are reserved for Private Data Elements and are defined by a specific application. Starting with DICOM 3.0 that Group Number has no significance and should not be considered to Group any Tags even though similar Tags continue to share the same Group Numbers. See also Repeating Group. High Bit - see Image Attributes. HISPP - Health Care Informatics Standards Planning Pannel HL7 - High Level 7, an ANSI member, dealing with HIS development. IE - see Information Entity IEEE - Institute of Electrical and Electronic Engineers Image Attributes - descriptions of the format of a image. Items like width, height, and bits per pixel are all attributes.
Implicit VR - see Value Representation. Information Entity (IE) - That portion of information defined by a composite IOD which is related to one specific class of real-world object. There is a one-to-one correspondence between information entities and the entities in the DICOM Application Model. Information Entity (IE) Module - A number of logically related elements that are grouped together. Patient Module is an example. It contains Data Elements like Patient Name (0010,0010), Patient ID (0010,0020), Referenced Patient Sequence (0008,1120) etc. In DICOM 3.0 the Group Number has no particular significance. An IE ma consist of Data Elements from different Groups. Various IE Modules can then be grouped in to IOD Modules. Information Objects (IO) -An abstraction of a Real World Information Entity (e.g. CT Image, Study, etc) which is acted upon by one or more DICOM Commands. See also Composite Information Objects and Normalized Information Objects. Information Object Definition (IOD) Module - A number of logically related IE Modules are grouped together to form a IOD Module. For instance a CT Image IOD Module consists of a Patient Module, Study Module, Image Module, etc. Information Object Instance - A representation of an occurrence of an Real World entity, which includes values for the Attributes of the Information Object Class to which the entity belongs. Information Model - see DICOM Information Model. Internet - A collection of networks and gateways, including ARPnet, NSFnet, MILnet, and others. Instance - A representation of class. IOD - see Information Object. IP - Internet Protocol addresses and instructs routers on what to do with the data. IS - VR of type Integer String ISO - International Standards Organization Item - A component of the Value of a Data Element that is of Value Representation (VR) Sequence of Items (SQ). Item Delimitation Data Element - Used to mark the end of an Item of Undefined Length in a Sequence (SQ) of Items. This is the last Data Element in an Item of Undefined Length. JIRA - Japanese Industry of Radiology Apparatus LO - VR of type Long String LT - VR of type Long Text Magnetic Resonance (MR) - A method or modality used to create images of the internal structure of an object that used a very strong magnetic fiels and radio frequencies (RF) instead of ionizing radiation. In a very strong megentic field the hydrogen atoms in the object to be images will resonate with detectable energy when a control radio frequency is applied. MR images can look very similar to CT images but the physics used is very different and the types of structures that can imaged are also different. Media Format - Data structures and associated policies which organize the bit streams defined by the Physical Media in to Data File structures and associated file directories. Media Storage - The storage of DICOM Files on a Physical Medium. MEDICOM - Medical Image Communication Message - A structured data unit for communication, divided into PDUs according to part 8 of the DICOM standard (for network communication). A data unit of the Message Exchange Protocol exchanged between two cooperating DICOM Application Entities. A Message is composed of a Command Stream followed by an optional Data Stream Meta Service Object Pair Class (Meta SOP Class) - A predefined set of SOP Classes that may be associated under a single SOP for the purpose of negotiating the use of the set with a single item. MI-MEDICOM - Media Interchange for Medical Image Communication Modality - Modality is used to describe the various classes of imaging devices used to image the internal structures of object. The modality is mostly differentiated by the physics used to create the image. For example Magnetic Resonance and Computed Tomogrphy are different modalities. Modality LUT - Describes the transformation of manufacturer dependent pixel value into pixel values which are manufacturer independent. (i.e. Hounsfield Units for CT and Optical Density for film). The Modality LUT is applied before the VOI LUT. Module - A set of Attributes within an Information Entity or Normalized IOD which are logically related to one another. MONOCHROME1 - see Image Attributes. MONOCHROME2 - see Image Attributes. MR - Modality of type Magnetic Resonance Multi-Frame Image - an image than contains multiple 2-dimentional image. See also Basic Offset Table. NEMA - National Electrical Manufacturers Association. Along with the American Collage of Radiology (ACR) is the standards organization that developed and controls the DICOM Specification. Nested Data Set - A Data Set contained within a Data Element of another Data Set. Data Sets can be nested recursivly. Only Data Elements with Value Representation (VR) of Sequence of Items (SQ) may contain Data Sets. Normalized Information Object Definition (N-IOD) - An Information Object Definition which represents a single entity in the DICOM Application Model. Such an IOD includes Attributes which are only inherent in the Real World Object that the IOD represents. Nuclear Medicine (NM) - A method or modality used to create images of a living object. Radioactive elements are used to tag compounds that are injected into, or ingested by the patient. The labeled compounds are preferentially absorbed by different organs. As the compounds are accumulated the radioactive material is measured creating a 2-dimensional image that spatially indicates the varying concentrations. OB - VR of type Other Byte OW - VR of type Other Word OSI - Open System Interconnection (Model developed by the ISO). An international standard that comprises of a layered model of the communication protocols. DICOM allows for communications over Point to Point, TCP/IP and OSI protocols. Packet - Structure data sets usually between 1 and 1,500 characters in length. PAD - Packet assembler/disassembler, an X.25 term. Papyrus - A DICOM compatible medical imaging format. Part 10 Image File - This refers to a DICOM image that has been saved to disk using the Part 10 section of the DICOM Standard. These files contain a File Meta Information Header at its beginning. This header contains information about the way the DICOM Data Set included in this file was encoded. PDU - Protocol data unit, the transported structure of information. Photometric Interpretation - see Image Attributes. Physical Media - Meterial with recording capabilities for storing streams of computer data. Pixel Data - The part of a DICOM Data Set that contains the actual image intensity values. This is encoded using the OW or OB Value Representations (VR). PN - VR of type Patient Name. Point to Point - A communication channel that consists of a physical wire of short distances. Mostly used for connecting peripherals like printers. DICOM allows for communications over Point to Point, TCP/IP and OSI protocols. Port - Computer ports are I/O channels of communication (i.e., serial or parallel ports); Internet ports are protocol types. Presentation Context - Consists of abstract syntax and transfer syntax. Private Data Element - see Data Element. Protocol - A set of rules that allow Applications of various levels to communicate with one another. PS 3.x - Each part of the DICOM 3.0 specification is numbered. When referring to part 2 you will see PS 3.2. Radiology - The branch of medicine that is concerned with the use of various forms of radiation for diagnostic and therapeutic uses. Real World - A term used to differentiate between an abstract entity and the actual object it self. That is, the concept of a horse is an abstract entity, but the actual horse that I am sitting on is a Real World horse. In DICOM a CT Image is an Abstract Entity while the CT Image I have on a floppy disk of an actual patient is a Real World Information Object or Instance. Real World Object - That which exists in the Real World upon which operations may be performed which are within the area of interest of the DICOM Standard. Such a Real World Object may be represented through a computer information metaphor called a SOP Instance. Repeating Group - Standard Data Element within a particular range of Group Numbers where elements that have identical Element Numbers have the same meaning within the Group. Repeating Groups shall only exist for Curves and Overlay Planes. Retired Data Element - see Data Element. Routers - Path switches of computer networks. SCP - see Service Class Provider. SCU - see Service Class User. Secondary Capture - A general catch all Modality that is used for images that did not originate as a DICOM image. Image that were stored as TIFF or BMP that are converted to DICOM are given this Modality. Service Class - A structured description of a service which is supported by cooperating DICOM Application Entities (AE) using specific DICOM Commands acting on a specific class of Information Object. Service Class Provider (SCP) - A role that an AE that corresponds to a Server in a Client / Server Pair. Service Class User (SCU) - A role that an AE that corresponds to a Client in a Client / Server Pair. Service Object Pair (SOP) - The combination of a specific set of DICOM Message Service Element (DIMSE) and one related Information Object (IO) Definition. A collection of SOP Classes and / or Meta SOP Classes which are related in that they are described together to accomplish a single application. Service Object Pair (SOP) Class - The union of a specific set of DIMSE Services and one related Information Object Definition (as specified by a Service Class Definition) which completely defines a precise context of communication. Service Object Pair (SOP) Instance - A concrete occurrence of an Information Object and a communication context. SH - VR of type Short String. SMTP - Simple mail transfer protocol, usually part of TCP/IP. SOP - Service-Object Pair combining command and data information.
SQ - VR of type Sequence of Items. See also Value Representation. SQL - Structured Query Language SS - VR of type Signed Short. Stack - A set of lower OSI layer protocols (i.e., TCP/IP or OSI). Tag - A unique identifier for an Attribute or Data Element. A DICOM Tag is made up of 2 parts. A Group Number and Element Number. The DICOM specification used the following notation when referring to a Tag: (0010:0030). The first 2 byte hexadecimal value is the Group Number and the second is the Element Number. These can be looked up in the Data Dictionary (PS 3.6). The example give above is for the Patients Brith date. TCP/IP - Transmission Control Protocol divides the PDUs into sequences of packets and, at the receiving end, reassembles these packets into PDUs. This set of Protocols allows various networks to connect to other networks. TCP/IP is implemented through the concept of Sockets. DICOM allows for communications over Point to Point, TCP/IP and OSI protocols. Teleradiology - The electronic transmission of radiologic images from one location to another for interpretation and/or consultation. Telnet - A terminal emulation program of TCP for remote log-in. TM - VR of type Time Tomography - A method of producing a 3-D image of internal objects by comparing the energy (usually x-rays) that is absorbed at various angles about the outside of the object. See also Computed Tomography. TPSQ - Top Parent Sequence Data Element Transfer Syntax - The description of the encoding method used by a DICOM Data Set. Such things are Data Element Structure, Byte Ordering, and Image Compression are defined in the Transfer Syntax. The Transfer Syntax must be known or discovered before a Data Set can be de-coded. UI - VR of type Unique Identifier UID - Unique Identifier Ultra Sound (US) - A method or modality that uses high frequency sound waves to create a 2-dimensional image of the internal structure of an object. US images tend to be low resolution but because they use harmless sound waves instead of radiowaves or ionizing radiation they are used mostly for neo-natal imaging. Unique Identifier (UID) - A string of characters from the set decimal digits 0-9 and the period. These strings provide a method to encode unique codes for a wide variety of items. The coding is based on the OSI Object Identification (numeric form) as defined bt the ISO 8824 Standard. A UID is made up of 2 parts: a root and a suffix. The root is registered by an organization with NEMA. No one else will be authorized to use this root. The usage of the suffix is then the responsibility of that organization. The root "1.2.840.10008" is reserved for DICOM and may UIDs using this root can be found in the DICOM Data Dictionary. A UID is limited to 64 characters. A UID should not be coded as to contain data in it self but should be treated as a whole and reference a single interpretation. UL - VR of type Unsigned Long. Undefined Length - The ability to specify an unknown length for a Data Element Value (of Value Representation (VR) SQ, OW, or OB) or Item. Data Elements of Undefined Length are delimited with a Sequence Delimitation Items and Item Delimiter Data Elements. US - VR of type Unsigned Short Value - Aa component of a Value Field. A Value Field many consist of one or more Values. Value Field - The last component of a Data Element. The Value Field is always made up of an even number of bytes. The data held in this field is padded if needed to make it have an even length. The data held in this field must conform to the rules given by the VR for the Data Element. Value Length (VL) - A mandatory component of a Data Element that give the length of the Value Field. Value Multiplicity (VM) - Specifies the number of Values contained in the Value Field of a Data Element. Value Of Interest LUT (VOI) - Describes the transformation of Modality pixel values into pixel values which are meaningful for print of display. This transformation is applied after any Modality LUT. Value Representation (VR) - An optional component of a Data Element. The VR is the data type of the information in the Value Field of the Data Element. DICOM defines many of these data types and defines them in PS 3.5 of the DICOM standard. Each VR is enumerated by a 2 character code. The codes are: AE, AS, AT, CS, DA, DS, DT, FL, FD, IS, LO, LT, OB, OW, PN, SH, SQ, SS, ST, TM, UI, UL, US (Each of these is defined else where in this glossary). Each VR has a list of rules regarding what is a legal Value and what is not. The use of the VR in the Data Elements depends on the negotiated Transfer Syntax for the Data Set. The VR can be either Explicit or Implicit.
VL - see Value Length or Visible Light. VM - see Value Multiplicity. VOI - see Value Of Interest. VOI LUT - see Value Of Interest. VR - See Value Representation Width - see Window. Window - The display of 16-bit grayscale on an 8-bit display requires that a range of pixel value be selected at a time. This range is often called the window. The window can be adjusted so that the item of interest is display with the maximum contrast that the display adapter can provide. Pixels in the original below this range are displayed a full black. Pixels above this are saturated to full white while the pixels in the range are given the full range of display intensities.
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