CODEWITHSUNDEEP
dicom
Joe.wang
Joe.wang

Reputation: 11791

In what case the DICOM should be build with SQ VR type attribute

All, Forgive me I am a Newbie of the DICOM. And I was just learning the DICOM standard right now. I just knew there has an attribute named SQ (Sequencing Data Sets) in the DICOM standard. Basically, It can be used to describe a DICOM object like a tree. I am just curious about in what particular case we should use this kind of structure to build a DICOM object? Thanks.

Upvotes: 1

Views: 843

Answers (2)

Markus Sabin
Markus Sabin

Reputation: 4013

One relevant thing is missing in the excellent answer by Gabriel IMHO: It is not the implementor's choice, when to use a sequence to encode data in DICOM. DICOM datasets are structured in modules which constitute from attributes. So there is a list of attributes allowed for a particular type of DICOM object (such as ultrasound image, CT image,...). The attribute has a "type" (in DICOM terms: Value Representation - VR) - string, number, person name or sequence - where the items allowed in the sequence are also well defined. So the answer to "when to use a sequence" is: When the DICOM standard requires you to.

References:

DICOM Part 3 - which attributes are required/allowed for which type of DICOM object

DICOM Part 6 - which attributes are encoded with which value representation

Upvotes: 1

user6320679
user6320679

Reputation:

The dicom sequence is type of nested structure to define some complex tag and consist in a set of datasets, like a structured report. The image above can exemplify:

Schematic of dicom sequence

Currently I'm working in ultrasound images and I use the dicom sequence to specify a region of a image, for example:

Ultrasound image with priority regions

The region 'A' have a specific tag: (0018,6011) Sequence of Ultrasound Regions, and this region have nested tags like:

  • (0018,6018) Region Location Min x0
  • (0018,601A) Region Location Min y0
  • (0018,601C) Region Location Max x1
  • (0018,601E) Region Location Max y1
  • (0018,6024) Physical Units X Direction
  • (0018,6026) Physical Units Y Direction

These tags is used for a instance of a region, the region 'B', 'C' or whatever may have the same tags. To exemplify better see the image above Example of ultrasound image

For more information, in this link (http://dicom.nema.org/dicom/2013/output/chtml/part05/sect_7.5.html) have a standard associated with nesting structures, and in this link(http://dicom.nema.org/medical/dicom/2014c/output/chtml/part03/sect_C.8.5.5.html) have specific use for ultrasound image to use with example.

Good luck in your Dicom studies!

Upvotes: 5

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