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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.

Solution

  • 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!