Are negative values of physical delta x/y allowed in the US FRAME OF REF MOD? - DICOM

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Thread: Are negative values of physical delta x/y allowed in the US FRAME OF REF MOD?

  1. Are negative values of physical delta x/y allowed in the US FRAME OF REF MOD?

    We are having a problem with calibration of US images from Toshiba
    Aplio US units when reading on a Philips/Sectra PACS review stations
    (version 9).

    Calibration and making measurements works fine as long as all values of
    "Physical Delta X 0018,602C)" and "Physical Delta Y 0018,602E)" are
    positive. The review stations can handle multiple regions on one image
    properly, each having its own pixel size.

    The problem occurs when one of the physical delta values (either x or
    y) is negative. The Sectra review software states the image is not
    calibrated. If I change the sign of the tag value, resend to the PACS
    system, measurements can be made.

    The standard defines the value as:
    Physical Delta X (0018,602C) 1, The physical value increments per
    positive X pixel increment. The units are as specified in the Physical
    units data element.

    What is not clear in the standard is if these tags can contain a
    negative value. Why would I have a negative value from the scanner?
    What is proper intpretation of a negative value, if allowed?

    I am getting finger pointing at the moment. Toshiba stating negative
    is allowed, Philips/Sectra stating it is not.

    Could someone shed some light on this please?

    Thank-you

    Gary Muswick
    University Hospitals of Cleveland
    muswick@uhrad.com
    216-844-7793


  2. Re: Are negative values of physical delta x/y allowed in the US FRAME OF REF MOD?

    Also from the standard,

    C.8.5.5.1.17 Physical Delta X And Physical Delta Y
    The Physical Delta X (0018,602C) is the physical value increment per
    positive X pixel increment,
    which is left to right. The Physical Delta Y (0018,602E) is the physical
    value increment per
    positive Y pixel increment which is top to bottom.
    Note: When displaying Doppler data, ultrasound applications typically
    display the Doppler strip
    horizontally, with data sweeping (moving time origin) from left (oldest) to
    right (newest) or
    scrolling (static time origin) from right to left. The default display of
    positive velocity values
    normally indicates flow toward the transducer; negative velocity values
    indicate flow away from
    the transducer. In this case a negative Physical Delta Y is required to
    specify that the direction
    of positive velocities or frequencies is upward.

    Indicating that negative values are permitted at least for the Y value.

    Jim



    wrote in message
    news:1106155726.456543.308070@z14g2000cwz.googlegr oups.com...
    > We are having a problem with calibration of US images from Toshiba
    > Aplio US units when reading on a Philips/Sectra PACS review stations
    > (version 9).
    >
    > Calibration and making measurements works fine as long as all values of
    > "Physical Delta X 0018,602C)" and "Physical Delta Y 0018,602E)" are
    > positive. The review stations can handle multiple regions on one image
    > properly, each having its own pixel size.
    >
    > The problem occurs when one of the physical delta values (either x or
    > y) is negative. The Sectra review software states the image is not
    > calibrated. If I change the sign of the tag value, resend to the PACS
    > system, measurements can be made.
    >
    > The standard defines the value as:
    > Physical Delta X (0018,602C) 1, The physical value increments per
    > positive X pixel increment. The units are as specified in the Physical
    > units data element.
    >
    > What is not clear in the standard is if these tags can contain a
    > negative value. Why would I have a negative value from the scanner?
    > What is proper intpretation of a negative value, if allowed?
    >
    > I am getting finger pointing at the moment. Toshiba stating negative
    > is allowed, Philips/Sectra stating it is not.
    >
    > Could someone shed some light on this please?
    >
    > Thank-you
    >
    > Gary Muswick
    > University Hospitals of Cleveland
    > muswick@uhrad.com
    > 216-844-7793
    >




  3. Re: Are negative values of physical delta x/y allowed in the US FRAME OF REF MOD?

    Ralph's response is correct.
    Negative values are essential for scaling, though unfortunately,
    some product have neglected to account for this.

    By the way, DICOM recently added significant detail
    to clarify the many ultrasound scenarios involving scaling.
    See ftp://medical.nema.org/medical/dicom/final/sup84_ft.pdf
    or the corresponding text and figurers in DICOM 2004.

    - Doug


    wrote in message news:1106155726.456543.308070@z14g2000cwz.googlegr oups.com...
    > We are having a problem with calibration of US images from Toshiba
    > Aplio US units when reading on a Philips/Sectra PACS review stations
    > (version 9).
    >
    > Calibration and making measurements works fine as long as all values of
    > "Physical Delta X 0018,602C)" and "Physical Delta Y 0018,602E)" are
    > positive. The review stations can handle multiple regions on one image
    > properly, each having its own pixel size.
    >
    > The problem occurs when one of the physical delta values (either x or
    > y) is negative. The Sectra review software states the image is not
    > calibrated. If I change the sign of the tag value, resend to the PACS
    > system, measurements can be made.
    >
    > The standard defines the value as:
    > Physical Delta X (0018,602C) 1, The physical value increments per
    > positive X pixel increment. The units are as specified in the Physical
    > units data element.
    >
    > What is not clear in the standard is if these tags can contain a
    > negative value. Why would I have a negative value from the scanner?
    > What is proper intpretation of a negative value, if allowed?
    >
    > I am getting finger pointing at the moment. Toshiba stating negative
    > is allowed, Philips/Sectra stating it is not.
    >
    > Could someone shed some light on this please?
    >
    > Thank-you
    >
    > Gary Muswick
    > University Hospitals of Cleveland
    > muswick@uhrad.com
    > 216-844-7793
    >




  4. Re: Are negative values of physical delta x/y allowed in the US FRAME OF REF MOD?

    Jim (Ralph) and Doug,

    Thank-you so much for your responses. Also, thank-you for the
    reference of the Sup 84. It clarifies alot.

    Had I kept up with the supplements, I would not have needed to post the
    question. I guess it is time to upload a new group of files.
    I am still looking at the 2003 documents.

    Gary.


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