[Insight-users] Problem with position of dicom image !!

[Luis Ibanez]

Hi Circass,

Please take a look at the diagrams in
http://www.itk.org/Wiki/Proposals:Orientation#C.7.6.2.1.1_Image_Position_And_Image_Orientation

This orientation information is included in the DICOM
header, and you get access to it in ITK via the
"Direction" matrix of the image.


You will see that the Direction cosines that
you get from:

           image->GetDirections();

are defined with respect to an LPS system,
in which the:

+X direction is going from Right to Left of the Patient
+Y direction is going from Anterior to Posterior
+Z direction is going from Inferior to Superior


In order to properly visualize your object with VTK,
you must place the camera in the position of the
physician:
http://www.itk.org/Wiki/Proposals:Orientation#DICOM_LPS_Differences_in_Visualization_presented_to_Radiologist_and_NeuroSurgeons


Normally, you DO NOT need to reverse an image.
Just need to take the Direction matrix into account
when you are performing the visualization.

You must be very careful in this process, since there it
is very easy to invert the left-right sides of the patient
by accident.

In order to do this properly you must think in terms
of the coordinate system of the scan, DO NOT think
in terms of the screen coordinates system (that's a
common mistake).

For an example on how to do this correctly, please
look at the source code of the Image Guided Surgery
Toolkit (IGSTK). (http://www.igstk.org),

in particular to the igstkView class
http://public.kitware.com/IGSTK/NightlyDoc/classigstk_1_1View.html

and the View2D class
http://public.kitware.com/IGSTK/NightlyDoc/classigstk_1_1View2D.html


IGSTK is based on ITK and VTK.


    Regards,


         Luis


---------------------------------------------------------------
On Wed, Apr 7, 2010 at 9:12 AM, circass <circass at gmail.com> wrote:
>
> Is there any header tag specifically that i can take the position of
> patient's head or legs ?
>
> For example;
>
> If scanner takes the images from legs to head and write the reference image
> with that order, the image must be reverse ! right ? how can i know the
> right position of image ?
>
> Or there is nothing like that ?
>
> It is some kind of weird for me cause i think that information is not
> included into dicom header...
>
> --
> View this message in context: http://old.nabble.com/Problem-with-position-of-dicom-image-%21%21-tp28163343p28164802.html
> Sent from the ITK - Users mailing list archive at Nabble.com.
>
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