'Code Sequence Macro' Table 8.8-1 - DICOM

This is a discussion on 'Code Sequence Macro' Table 8.8-1 - DICOM ; The Code Sequence Macro comes up quite a few times in the DICOM standard, particularly in part 3. I read the documentation on it three or four times, but it reads to me like codes are code for coding codes... ...

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  1. 'Code Sequence Macro' Table 8.8-1

    The Code Sequence Macro comes up quite a few times in the DICOM
    standard, particularly in part 3. I read the documentation on it three
    or four times, but it reads to me like codes are code for coding
    codes... and it just keeps going in circles.

    I'm sure this is something simple, and I'm just overly complicating it,
    but could someone please spend just a minute describing just what the
    heck this is all about?

    Thanks!

    -Kelly


  2. Re: 'Code Sequence Macro' Table 8.8-1

    > The Code Sequence Macro comes up quite a few times in the DICOM
    > standard, particularly in part 3. I read the documentation on it three
    > or four times, but it reads to me like codes are code for coding
    > codes... and it just keeps going in circles.
    > I'm sure this is something simple, and I'm just overly complicating it,
    > but could someone please spend just a minute describing just what the
    > heck this is all about?


    There are many places in DICOM where you would like to use machine
    readible codes that are not necessarily defined within the DICOM
    standard itself - think of ICD 10 codes, SNOMED codes, codes identifying
    certain procedures or drugs etc.
    DICOM uses a rather generic encoding for such machine readable codes
    taken from dictionaries, lexicons, controlled vocabularies - whatever
    you would like to call it. Basically, a code is described by three
    attributes:
    - Code Value: the machine readable code itself, e.g. "T-D4000"
    - Coding Scheme Designator: An identifier for the dictionary where
    this code was taken from, e.g. "SRT" for the SNOMED Referenced
    Terminology. Only the coding scheme designator makes the code really
    machine readable because there could be multiple coding schemes using
    the same coded number for different purposes
    - Code Meaning: a human readable text string explaining the meaning
    of the code, usually in English language. This is helpful for example if
    the reading application does not know the coding scheme. In this case
    there is at least some explanation of what this code means.

    Additionally there may be a "Coding Scheme Version" attribute describing
    from which version of a certain dictionary the code was taken. And
    there is a so-called "enhanced encoding mode", which is rarely used but
    provides a number of additional attributes for a machine readible code.

    In any case, each machine readible code is stored inside a Sequence Item
    in DICOM that contains the attributes described above, called the "Code
    Sequence Macro" in DICOM. There are various Sequences that contain the
    code sequence macro, depending on what exactly the machine readible code
    actually describes.

    Regards,
    Marco Eichelberg

  3. Re: 'Code Sequence Macro' Table 8.8-1

    Hello,

    "DICOM uses a rather generic encoding for such machine readable codes
    taken from dictionaries, lexicons, controlled vocabularies - whatever
    you would like to call it."

    What do you mean by machine here? Is it a modality or anything? How the
    conecpt of maching comes in DICOM standard.


  4. Re: 'Code Sequence Macro' Table 8.8-1

    Some background behind Marco's explanation: the committee got tired of
    repeatedly creating an identifical set of text and table entries
    whenever a coded entry needed to be inserted into a IOD definition.
    Essentially the code sequence was identitified as an archeotype whose
    structure could be documented in one place and then simply inserted as
    a "macro invocation" whenever a new code entry was needed. This was
    done to improve the maintainability of the standard. This became
    especially relevent when it was determine that the old definition of
    code, coding scheme designator, and code meaning in code sequence
    entries needed to be enhanced with additional attributes documenting
    the version and update date of coding scheme. Rather than inserting the
    new, optional attributes into the umpteen instances of code sequences
    in various IODs, the editors added the new attributes to the definition
    of the macro at the start of DICOM Part 2 and then replaced all the
    instances of code sequences with a macro invocation. Similarly, other
    common structures, like the names of personnel acting in various
    specific healthcare roles which get captured in IODs, were also
    replaced with macro invocations.

    Something else you should take note of with the code sequence macro
    invocation. In many cases, the set of codes which can be used in a
    particular sequence are constrained to a subset of the total set of
    codes available in a particular coding scheme. For these cases, you
    will also see a context Id (CID + some number) following the macro
    invocation. If you go look up that CID number in DICOM part 16, you'll
    find a listing of the constrained set of codes which can be used in
    that particular code sequence.


  5. Re: 'Code Sequence Macro' Table 8.8-1

    I think the macro thing is a very good idea. It makes the standard much
    more maintainable. Many of the macros seem to be used in just one
    place... is there a history there?

    -Kelly

    eric.good...@gmail.com wrote:
    > Some background behind Marco's explanation: the committee got tired

    of
    > repeatedly creating an identifical set of text and table entries
    > whenever a coded entry needed to be inserted into a IOD definition.
    > Essentially the code sequence was identitified as an archeotype whose
    > structure could be documented in one place and then simply inserted

    as
    > a "macro invocation" whenever a new code entry was needed. This was
    > done to improve the maintainability of the standard. This became
    > especially relevent when it was determine that the old definition of
    > code, coding scheme designator, and code meaning in code sequence
    > entries needed to be enhanced with additional attributes documenting
    > the version and update date of coding scheme. Rather than inserting

    the
    > new, optional attributes into the umpteen instances of code sequences
    > in various IODs, the editors added the new attributes to the

    definition
    > of the macro at the start of DICOM Part 2 and then replaced all the
    > instances of code sequences with a macro invocation. Similarly,

    other
    > common structures, like the names of personnel acting in various
    > specific healthcare roles which get captured in IODs, were also
    > replaced with macro invocations.
    >
    > Something else you should take note of with the code sequence macro
    > invocation. In many cases, the set of codes which can be used in a
    > particular sequence are constrained to a subset of the total set of
    > codes available in a particular coding scheme. For these cases, you
    > will also see a context Id (CID + some number) following the macro
    > invocation. If you go look up that CID number in DICOM part 16,

    you'll
    > find a listing of the constrained set of codes which can be used in
    > that particular code sequence.



  6. Re: 'Code Sequence Macro' Table 8.8-1

    None that I know of. Probably just the result of over-excitement with
    the macro idea


  7. Re: 'Code Sequence Macro' Table 8.8-1

    I wonder why they didn't use it more when they put in the stuff for
    Clinical Studies... seems that would have made sense...

    -Kelly

    eric.good...@gmail.com wrote:
    > None that I know of. Probably just the result of over-excitement with
    > the macro idea



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