DWI support in DICOM - DICOM

This is a discussion on DWI support in DICOM - DICOM ; Hello again, I am currently involved in a group which is working extensively with DWI data (diffusion-weighted image). Their acquisition data is coming in the form of DICOM files. Unfortunately they are currently facing two problems: 1. Each vendors stores ...

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Thread: DWI support in DICOM

  1. DWI support in DICOM

    Hello again,

    I am currently involved in a group which is working extensively with
    DWI data (diffusion-weighted image). Their acquisition data is coming
    in the form of DICOM files. Unfortunately they are currently facing two
    problems:
    1. Each vendors stores the gradient directions differently (if at all!)
    2. Even if you have the directions, you don't have the measurement
    frame(*). As far as I understand the DICOM specification, there is
    currently no way to store this type of information.

    For issue #1 I am currently gathering information about the major
    vendors so that I can add extraction code into gdcm. This would provide
    a function to extract the gradient directions and make invisible to
    user the different way vendors use to store this information. For more
    information see the Wiki at:
    http://www.na-mic.org/Wiki/index.php...or_DWI_and_DTI

    For issue #2, -again correct me if I am wrong- but I could not find
    anything that could represent this measurement frame. Therefore the
    solution we are using is to use an intermediate file format called
    NRRD, see for instance:
    http://wiki.na-mic.org/Wiki/index.ph...TI:Nrrd_format
    Ideally this information should be accessible from a particular
    DICOM tag. Can we request an extension of the DICOM standard to allow
    us to store this information directly in the DICOM file, which would
    greatly simplify the process (avoiding the intermediate NRRD file
    format step).

    Regards,
    Mathieu
    (*)
    "measurement frame": relationship between the coordinate frame in which
    the gradient coefficients are expressed, and the physical coordinate
    frame in which image orientation is defined


  2. Re: DWI support in DICOM

    Hi Mathieu

    Thanks for the very interesting links.

    The proposed standard way to address this problem is with
    the Enhanced MR IOD, which explicitly addresses the
    attributes for encoding diffusion directionality and B-Value.

    There will likely be no extensions of the existing MR IOD to
    address this concern, since by policy, we obviously want
    folks to use the new IOD.

    It would not surprise me if in the interim, vendors started
    to send some of the new Sup 49 attributes in old IOD
    instances, but there will almost certainly be no official move
    to standardize this, and we would certainly not consider
    adding a non-Sup 49 based mechanism.

    If the Sup 49 mechanisms are not sufficient (e.g. for
    tensors), then we need to discuss what the gaps are
    and how to fill them.

    We would not, by the way, ever "encapsulate" the NRRD
    header, but it would nice if there was a clear mapping between
    the DICOM Sup 49 attributes and the relevant NRRD
    attributes, though these are probably obvious.

    David

    Mathieu Malaterre wrote:
    > Hello again,
    >
    > I am currently involved in a group which is working extensively with
    > DWI data (diffusion-weighted image). Their acquisition data is coming
    > in the form of DICOM files. Unfortunately they are currently facing two
    > problems:
    > 1. Each vendors stores the gradient directions differently (if at all!)
    > 2. Even if you have the directions, you don't have the measurement
    > frame(*). As far as I understand the DICOM specification, there is
    > currently no way to store this type of information.
    >
    > For issue #1 I am currently gathering information about the major
    > vendors so that I can add extraction code into gdcm. This would provide
    > a function to extract the gradient directions and make invisible to
    > user the different way vendors use to store this information. For more
    > information see the Wiki at:
    > http://www.na-mic.org/Wiki/index.php...or_DWI_and_DTI
    >
    > For issue #2, -again correct me if I am wrong- but I could not find
    > anything that could represent this measurement frame. Therefore the
    > solution we are using is to use an intermediate file format called
    > NRRD, see for instance:
    > http://wiki.na-mic.org/Wiki/index.ph...TI:Nrrd_format
    > Ideally this information should be accessible from a particular
    > DICOM tag. Can we request an extension of the DICOM standard to allow
    > us to store this information directly in the DICOM file, which would
    > greatly simplify the process (avoiding the intermediate NRRD file
    > format step).
    >
    > Regards,
    > Mathieu
    > (*)
    > "measurement frame": relationship between the coordinate frame in which
    > the gradient coefficients are expressed, and the physical coordinate
    > frame in which image orientation is defined



  3. Re: DWI support in DICOM

    Thanks again David for your help !

    Anyway to close the subject (hopefully!). It's great that DICOM has a
    standard for this information, but until private vendors actually use
    it... it's not that usefull

    Also for future references:
    #1 If the DICOM-recommended tags are used as defined, the measurment
    frame is the identity matric
    #2 Therefore the only deficiency is that you cannot record the full
    B-matrix when it is known.

    Mathieu


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