Calcuation of linear measurement in DICOM - DICOM

This is a discussion on Calcuation of linear measurement in DICOM - DICOM ; Dear ALL In our dicom viewer linear measurement and for calculation of linear measurement we are using imager pixel spacing (0018,1164) and then we convert this pixel value is CM to MM . We got information by calculation of this ...

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Thread: Calcuation of linear measurement in DICOM

  1. Calcuation of linear measurement in DICOM

    Dear ALL

    In our dicom viewer linear measurement and for calculation of linear
    measurement we are using imager pixel spacing (0018,1164) and then we
    convert this pixel value is CM to MM . We got information by
    calculation of this imager pixel spacing the value will be correct. and
    not on the basic of Pixel Spacing (0028,0030). As in most of the cases
    the imager pixel spacing is not there.

    So whether the calculation for tags what we are using is correct or
    not. please help me.

    It is really urgent. Thanks in advance.

    with regards
    DICOM_TESTER


  2. Re: Calcuation of linear measurement in DICOM

    Hi

    Making measurements derived from assumptions about the validity
    of pixel spacing related attributes in projection radiography
    images is fraught with difficulty, and is potentially a significant
    safety issue.

    See the rationale described in DICOM CP 586 for a discussion
    of both the theoretical and historical issues involved:

    ftp://medical.nema.org/medical/dicom/final/cp586_ft.pdf

    In short though, it is vital to make sure that the user of
    the measurement software is warned a) when there are different
    values possible based on Imager Pixel Spacing or Pixel Spacing,
    and b) that unless a calibration object of known size (fiducial)
    is present and used as a reference, then the diverging x-ray
    beam makes any measurement dependent on assumptions about
    geometry (which are not necessarily the same as for similar
    measurements made for film-screen radiography, although
    the user might expect this).

    Same issues apply to "true size" printing - how does one
    reliably establish what is meant or expected as "truth" in
    such cases ?

    David

    DICOM_TESTER wrote:
    > Dear ALL
    >
    > In our dicom viewer linear measurement and for calculation of linear
    > measurement we are using imager pixel spacing (0018,1164) and then we
    > convert this pixel value is CM to MM . We got information by
    > calculation of this imager pixel spacing the value will be correct. and
    > not on the basic of Pixel Spacing (0028,0030). As in most of the cases
    > the imager pixel spacing is not there.
    >
    > So whether the calculation for tags what we are using is correct or
    > not. please help me.
    >
    > It is really urgent. Thanks in advance.
    >
    > with regards
    > DICOM_TESTER
    >


  3. Re: Calcuation of linear measurement in DICOM


    David Clunie wrote:
    > Hi
    >
    > Making measurements derived from assumptions about the validity
    > of pixel spacing related attributes in projection radiography
    > images is fraught with difficulty, and is potentially a significant
    > safety issue.
    >
    > See the rationale described in DICOM CP 586 for a discussion
    > of both the theoretical and historical issues involved:
    >
    > ftp://medical.nema.org/medical/dicom/final/cp586_ft.pdf
    >
    > In short though, it is vital to make sure that the user of
    > the measurement software is warned a) when there are different
    > values possible based on Imager Pixel Spacing or Pixel Spacing,
    > and b) that unless a calibration object of known size (fiducial)
    > is present and used as a reference, then the diverging x-ray
    > beam makes any measurement dependent on assumptions about
    > geometry (which are not necessarily the same as for similar
    > measurements made for film-screen radiography, although
    > the user might expect this).
    >
    > Same issues apply to "true size" printing - how does one
    > reliably establish what is meant or expected as "truth" in
    > such cases ?
    >
    > David
    >
    > DICOM_TESTER wrote:
    > > Dear ALL
    > >
    > > In our dicom viewer linear measurement and for calculation of linear
    > > measurement we are using imager pixel spacing (0018,1164) and then we
    > > convert this pixel value is CM to MM . We got information by
    > > calculation of this imager pixel spacing the value will be correct. and
    > > not on the basic of Pixel Spacing (0028,0030). As in most of the cases
    > > the imager pixel spacing is not there.
    > >
    > > So whether the calculation for tags what we are using is correct or
    > > not. please help me.
    > >
    > > It is really urgent. Thanks in advance.
    > >
    > > with regards
    > > DICOM_TESTER


    Thank you Sir

    I have small confusion also sir.
    Whether for CT and MR whether we can caluclate based on Pixel Spacing
    and CR ,MG etc whether we can calculate throught Imager pixel spacing.

    if i am wrong correct me

    Thanks and regards
    DICOM_TESTER


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