Hi Mathieu,<br><br>Thanks for the link. A lot of my doubts have been cleared. It seemed I had misunderstood the whole concept.<br><br>I have a couple of questions though that I hope someone could help me with:<br><br>- The patient coordinate system. How is that determined? Is it relative to the scanner?
<br><br>- I saw that the normal along a slice could be determined from the direction cosines as follows:<br><pre>normal[0] = cosines[1]*cosines[5] - cosines[2]*cosines[4];<br>normal[1] = cosines[2]*cosines[3] - cosines[0]*cosines[5];
<br>normal[2] = cosines[0]*cosines[4] - cosines[1]*cosines[3];<br></pre>Can someone explain how this works? I know that the cross product of the unit vector along x axes and the unit vector along y axes willpoint towards the z axes but cannot figure out how the above relationships translate to that. If someone can explain this to me, I would be grateful.
<br><br>Thanks a lot.<br><br>Luca<br><br><div><span class="gmail_quote">On 6/4/07, <b class="gmail_sendername">Mathieu Malaterre</b> <<a href="mailto:mathieu.malaterre@gmail.com">mathieu.malaterre@gmail.com</a>> wrote:
</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Hi Luca,<br><br> I would suggest you to read:<br><a href="http://www.itk.org/Wiki/Proposals:Orientation#Some_notes_on_the_DICOM_convention_and_current_ITK_usage">
http://www.itk.org/Wiki/Proposals:Orientation#Some_notes_on_the_DICOM_convention_and_current_ITK_usage</a><br>and<br>PS 3.3 - 2007, section:<br>C.7.6.2.1.1 Image Position And Image Orientation<br><br>HTH<br>-Mathieu<br><br>
On 6/4/07, Luca Pamparana <<a href="mailto:luca.pamparana@gmail.com">luca.pamparana@gmail.com</a>> wrote:<br>> Hi everyone,<br>><br>> I am pretty new to medical imaging and trying to learn some vector<br>> mathematics behind it. I have a question about the "Image Orientation
<br>> Patient" tag. It says this tag gives the direction cosines for the rows and<br>> colums for the 3 axes.<br>><br>> Now my question is, rows and colums direction cosines wrt to which plane??<br>><br>
> Also, each slice has this tag and a slice is just a 2D image. So, how come<br>> we get 3 pairs of direction cosine values?<br>><br>> I am sorry if these questions are very stupid. I would be really grateful if
<br>> someone can clarify these doubts for me...<br>><br>> Thanks a lot,<br>><br>> Luca<br>><br>> _______________________________________________<br>> Insight-users mailing list<br>> <a href="mailto:Insight-users@itk.org">
Insight-users@itk.org</a><br>> <a href="http://www.itk.org/mailman/listinfo/insight-users">http://www.itk.org/mailman/listinfo/insight-users</a><br>><br>><br><br><br>--<br>Mathieu<br></blockquote></div><br>