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Actually, as far as I can tell, ITK does not use DICOM orientation.<br>
<br>
Encoded in the DICOM tag "Image Orientation (Patient)" are two 3D
vectors. The first gives the orientation in 3D space if the first
row of the image and the second gives the orientation of the first
column. (If the image is 3D, the third axis, which is normal to the
plane of the other two, is calculated as the cross product of the
first two vectors). Because a 2D image is embedded in 3D space, it
needs the 3D vectors for correct orientation.<br>
<br>
The orientation (direction in ITK) in ITK is given as a 3x3x3 matrix
in a 3D image which is correct. However, a 2D image contains only a
2x2 direction matrix instead of the 2x3 matrix implied by the DICOM
tag. The orientation is lost when extracting a slice from a 3D image
using the itk::ExtractImageFilter regardless of the direction
collapse strategy.<br>
<br>
Please let me know if my analysis is incorrect.<br>
<br>
Thanks,<br>
Tim<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 13-06-19 06:37 PM, Bill Lorensen
wrote:<br>
</div>
<blockquote
cite="mid:CADZJ4hMa386pk2-UB-pm+g54FZmzhEAN0+Ly8xgeRNDDMmf9dA@mail.gmail.com"
type="cite">
<div dir="ltr">ITK uses the DICOM orientation information.<br>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Wed, Jun 19, 2013 at 2:13 PM, Tim
Allman <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:dr.tim.allman@gmail.com" target="_blank">dr.tim.allman@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">I have
been trying to make sense of both systems of describing
orientation but without success. Is there a function or some
documentation somewhere that describes how to convert one to
the other?<br>
<br>
Thanks,<br>
Tim<span class="HOEnZb"><font color="#888888"><br>
<br>
-- <br>
Tim Allman, Ph.D.<br>
35 Margaret Street,<br>
Guelph Ontario N1E 5R6<br>
Canada<br>
<br>
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<pre class="moz-signature" cols="72">--
Tim Allman, Ph.D.
35 Margaret Street,
Guelph Ontario N1E 5R6
Canada
</pre>
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