Each data type has a unique VR. If the VR is not included in the file ("implicit VR transfer syntax"), it must be obtained from a dictionary. The dictionary included with Scan2MCNP---
Dicom.dic---was prepared by copying descriptions of the data elements from the NEMA1 documents ("Part 6: Data Dictionary"). The dictionary consists of 1881 entries. Some entries required changes to be consistent with our parser. A typical entry is:
(0008,0022) Acquisition Date DA 1
The tag ((0008,0022)) consists of a group (8) and element (22) number. The description (Acquisition Date) is not required for use in the program. The Dictionary submenu of the File menu contains an option to not store the definitions. The penultimate field (DA) is the VR. The last field is ignored; it specifies the number of required entries.
The dictionary parser recognizes a line beginning with "!" as a comment. The dictionary includes descriptive information from the NEMA document as comments. Data items marked as "Retired" in the documentation are included but are commented.
A lookup function returns the VR given the tag.
1 National Electrical Manufacturers Association (NEMA; 1300 N. 17th Street, Rosslyn, Virginia 22209); the 2003 version of the documents were downloaded from http://www.dclunie.com/.
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