Материал: part03

The Directory

Files containing Objects referenced by the Directory

Referenced

Referenced

Referenced

Image Object

Figure F.2-2. Example of a Directory Organization and Content​

F.2.2.2 Example of a DICOMDIR File Structure​

BasedontheexamplediscussedinSectionF.2.2.1,theinternaldatastructureusedbytheBasicDirectoryIODisdepictedinFigureF.2-​ 3. It shows a set of Directory Records where each Directory Record is linked by three different types of "referencing" mechanisms:​

a.​The chaining of Directory Records to form a Directory Entity. In particular, this facilitates the addition of new Directory Records​ at the level of any Directory Entity by placing them at the end of the DICOMDIR File. On Figure F.2-3, this chaining is shown by​ yellow lines:​

1.​#1 shows the chaining of the Directory Records forming the root Directory Entity​

2.​#2 shows the chaining of the Directory Records for the Directory Entity related to Patient A​

3.​#3 shows the chaining of the Directory Records for the Directory Entity related to Study 1​

4.​#4 shows the chaining of the Directory Records for the Directory Entity related to Series 1​

b.​Green lines depict the reference by a Directory Record to a lower level Directory Entity​

c.​Blue lines depict the reference by a Directory Record to a stored file containing a SOP Class​

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This example of a DICOMDIR File structure shows one example of a specific order of the Directory Records. Other orderings of Dir-​ ectory Records could result in a functionally equivalent directory.​

End of File

Figure F.2-3. Example of Data Structure for the DICOM Directory Information​

F.3 Basic Directory IOD​

ThisIODisbasedontheDirectoryInformationorganizationintroducedinSectionF.2.ThemodelforthisBasicDirectoryIODisdescribed​ Section F.2.1 by the Entity/Relationship model in Figure F.2-1. The rules specified in Section F.2.1 apply to this Information Object​ Definition.​

F.3.1 Module Table​

The Basic Directory IOD includes the Modules specified by Table F.3-1.​

Table F.3-1. Basic Directory IOD Modules​

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Note​

The Directory Information Module is optional. This Directory​ Information Module should be present in all but primitive​ environments where a directory is not needed. In this case,​ only the File-set Identification Information is present.​

F.3.2 Modules of the Basic Directory Information Object​

Attributes of the Basic Directory IOD are defined with a Type designation that indicates if a specific Attribute is required for all Media​ Storage Operations (see Chapter 5).​

F.3.2.1 File-set Identification Module​

Table F.3-2. File-Set Identification Module Attributes​

Note​

Every File-set is assigned a File-set UID when created. The File-set UID need not be duplicated as a Type 1 Attribute of the​ File-set Identification Module. It is conveyed as the SOP Instance UID of the Basic Directory IOD. It is included in the​ DICOMDIR File Meta Information (see PS3.10)​

F.3.2.2 Directory Information Module​

This Module contains a Sequence of Directory Records forming one or more Directory Entities. This Module defines at least one​ Directory Entity, the Root Directory Entity (which may be empty). Each Directory Record is composed of Directory Elements (marked​ by a ">"). They include:​

a.​an offset pointer to another Directory Record of the Same Directory Entity​

b.​an offset pointer to a lower level Directory Entity​

c.​a Referenced File pointed to by the Directory Record​

d.​a set of keys representative of the information contained in the Referenced File​

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Page 1674​ DICOM PS3.3 2020a - Information Object Definitions​

Table F.3-3. Directory Information Module Attributes​

Formerly, this Attribute was intended to facilitate the deletion of files, with​ a value 0000H signally an inactive record. This usage has been retired.​ See PS3.3-2008.​

Other Values are reserved and shall not be set by File-set Creators, but if present​ shall be interpreted as FFFFH by File-set Readers or Updaters.​

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When no lower-level Directory Entity (containing at least one Directory Record) is​ referenced, this Attribute shall have a Value of 00000000H.​

Note​

This offset includes the File Preamble and the DICM Prefix.​

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