What is a DICOM Data Set?
A Data Set is a collection of Data Elements stored in a DICOM file. Each DICOM file may or may not include a header consisting of a Preamble and a Prefix. Each DICOM file represents a separate class of information. For example, one DICOM file may represent the Computed Tomography Image class, and another DICOM file may represent the Radiotherapy Structure Set class. DICOM Standard defines a vast numbers of Class Information Object Definitions as standard classes. LEADTOOLS supports user-defined classes in addition to the standard classes.
For each class supported by DICOM there are certain modules contained in each class. Each module consists of a number of Data Elements, each Data Element having its own tag. These Data Elements can be mandatory or optional, depending on the module and the class. In addition to the standard modules and data elements supported by DICOM, user-defined modules and data elements are also supported by LEADTOOLS.
LEADTOOLS maintains the Data Set internally as a tree structure and provides functions to evaluate the Data Set as a tree or as a list. The developer can create the data set object with all the appropriate elements for the specified class in one function call. LEADTOOLS Medical Imaging toolkit provide a number of functions for maneuvering through the Data Set, getting and setting Data Set information, getting and setting Data Element values, searching the Data Set, and creating, loading and saving Data Sets. LEADTOOLS provides functions to delete individual items, delete entire modules, delete all items and delete one or more images in a Data Set.
To retrieve and store values in the Value Field of the Data Element in a Data Set, LEADTOOLS provides low-level and High-level functions.
What are Value Representations (VR's)?
The value representation of a data element indicates the type of data that can be stored in the value field of the data element. There are a number of value representations that are standard for the DICOM. In addition to the standard value representations, user-defined value representations may also be added using LEADTOOLS.
LEADTOOLS maintains a table (or list) internally along with the code, name, length, restrictions and unit size of all available standard and user defined value representations. LEADTOOLS also provides functions to get, set, delete, and rename the value representations in the table.
What are Data Elements and Tags?
The tag of a data element consists of an ordered pair of 16-bit values that represent a Group number and an Element number. The tag indicates the type of information stored in the value field of the data element. There are a number of tags that are standard in DICOM. In addition to the standard tags, user-defined tags may also be added using LEADTOOLS.
LEADTOOLS maintains a table (or list) internally of all available standard and user-defined tags, including the tag's code, name, value representation and value multiplicity information. LEADTOOLS provides a number of functions for maneuvering through, adding, deleting and modifying the Data Element Tag table. Also Data Element table allows the developer to add support for future Data Elements in DICOM without having to receive an upgrade from LEADTOOLS.
What do Unique Identifiers (UIDs) identify?
A unique identifier identifies items such as Service-Object Pair Classes and images. There are a number of unique identifiers that are standard for the DICOM file format. In addition to the standard unique identifiers, user-defined unique identifiers may also be added using LEADTOOLS.
LEADTOOLS maintains a table (or list) internally of all available standard and user-defined unique identifiers, with the UID's name, value and type information. LEADTOOLS provides a number of functions for maneuvering through, adding, deleting and modifying the UID Table.
What is an Information Object Definition?
An Information Object Definition (IOD) is an abstract data model that specifies information about Real-World objects. It provides a means of standardizing information exchanged between applications. There are a tremendous number of IODs that are standard in DICOM. In addition to the standard IODs, user-defined IODs may also be added using LEADTOOLS.
LEADTOOLS maintains a tree internally of all available standard and user defined Information Object Definitions (IODs). LEADTOOLS' functions allow you to evaluate the internal IOD Structure as a tree or as a list.
LEADTOOLS provides a number of functions for maneuvering through and modifying the IOD Structure such as GetRoot, GetParent, GetChild, GetFirst, GetLast, GetCountModule, etc... The toolkit provides several functions for searching the IOD Structure to insert new items, delete individual items and change the name or the description of an IOD already in the IOD Structure. A developer can use the IOD Structure to validate a DICOM Data Set. Additionally, the IOD table Structure allows user to add support for future IODs in DICOM with the current version of LEADTOOLS.
What are DICOM Basic Directories (DICOMDIR)?
In order to identify a DICOM file-set and to facilitate accessing the information stored in the DICOM files of the file-set, the DICOM standard has defined the Basic Directory IOD. A DICOM file-set contains one or more DICOM files. One of the files contained in the file-set is the DICOMDIR file. The DICOMDIR file contains DICOM Directory information, making it easier to access the information contained in the other DICOM files in the file-set. The DICOM files in the file-set are assigned File IDs; so, they can be referenced by the DICOMDIR File, which itself, is identified by a File ID of DICOMDIR.
DICOM Dir data sets may contain special data element called key elements. A Key element is a data element that also contains special information about other key elements in the data set and their relative location within the data set. The specialized information included in a key element maintains information on key element children, non-key element children, parent key elements, and the logical relationships between the elements.
LEADTOOLS maintains the DICOMDIR data set as a tree; however, all key elements are stored at the same level of the tree. LEADTOOLS provides special functions for searching the DICOM Dir data set, maneuvering through the data set, inserting and deleting key elements, and manipulating key elements.
LEADTOOLS also provides high-level functions to create or update DICOMDIR by adding DICOM files or DICOM Data Set loaded in the toolkit.
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