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<TITLE>RE: [Insight-users] How to calculate displacement from deformation field</TITLE>
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<P><FONT SIZE=2>Thank you for your help pinpress. I tried to read it with float32 and now the numbers make sense. Just another question, is the unit of the displacement values here in millimeters or pixels? I need to calculate the strains from them. Thanks!<BR>
<BR>
Yufei<BR>
<BR>
<BR>
-----Original Message-----<BR>
From: insight-users-bounces@itk.org on behalf of pinpress<BR>
Sent: Tue 25.11.2008 15:12<BR>
To: insight-users@itk.org<BR>
Subject: Re: [Insight-users] How to calculate displacement from deformation field<BR>
<BR>
<BR>
Hi,<BR>
<BR>
I have used demons registration recently, but in my case, I have<BR>
M-by-N-by-P-by-3 double values of the displacement, that means 3<BR>
displacement values (e.g., vector) at each and every voxel.<BR>
<BR>
My wild guess: you read in the displacement file in Matlab as a sequence of<BR>
one-byte (e.g., uint8) integer, but you really should have read in the file<BR>
as a sequence of 4-byte double value. Then you will also get 3 displacement<BR>
values at each voxel, instead of 12.<BR>
<BR>
Also be cautious here, Matlab uses column major, whereas VTK files from ITK<BR>
are row major. So you need to switch the first two dimensions of the<BR>
deformation matrix in Matlab.<BR>
<BR>
<BR>
Li Yufei wrote:<BR>
><BR>
> Hi all,<BR>
><BR>
> I have been working with some deformation fields generated from my demons<BR>
> registration. I am able to view the field in paraview with no problem.<BR>
> What I really want is to quantify the displacement (max, min, average<BR>
> displacement) and subsequently the strains.<BR>
><BR>
> I tried to read the field to matlab and I found that for an image size of<BR>
> 300*300*100, there are 300*300*100*12 elements in the field. so I guess<BR>
> for each pixel, there are 12 numbers specifying the deformation. Can<BR>
> someone tell me what are these 12 elements? or anyone has an idea how to<BR>
> calculate the displacement? Thank you very much.<BR>
><BR>
> Best regards<BR>
><BR>
> Yufei<BR>
><BR>
<BR>
--<BR>
View this message in context: <A HREF="http://www.nabble.com/How-to-calculate-displacement-from-deformation-field-tp20677817p20681978.html">http://www.nabble.com/How-to-calculate-displacement-from-deformation-field-tp20677817p20681978.html</A><BR>
Sent from the ITK - Users mailing list archive at Nabble.com.<BR>
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