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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Hi Emma,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-GB
style='font-size:12.0pt'>A mean square error of 958 over a scale of 0-255 says
that, in the mean, the difference is about 31. You will receive this solution
if you just take the root, you still have the squares.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-GB
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-GB
style='font-size:12.0pt'>Regards,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-GB
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-GB
style='font-size:12.0pt'>Daniel</span></font><font size=2 color=navy
face=Arial><span lang=EN-GB style='font-size:10.0pt;font-family:Arial;
color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>---</span></font><font color=navy><span
style='color:navy'><o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'> <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Dipl.-Inform. Med. Daniel Stein<br>
German Cancer Research Center<br>
Div. Medical and Biological Informatics (E130)<br>
Im Neuenheimer Feld 280<br>
D-69120 Heidelberg, Germany<br>
Phone: (+49) 6221/42-3547<br>
Fax: (+49) 6221/42-2345<br>
<a href="http://www.dkfz-heidelberg.de/de/mbi/">http://www.dkfz-heidelberg.de/de/mbi/</a><br>
Homepage: <a
href="http://www.dkfz-Heidelberg.de/de/mbi/people/Daniel_Stein.html">http://www.dkfz-Heidelberg.de/de/mbi/people/Daniel_Stein.html</a></span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'> </span></font><o:p></o:p></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>Von:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
insight-users-bounces+d.stein=dkfz-heidelberg.de@itk.org
[mailto:insight-users-bounces+d.stein=dkfz-heidelberg.de@itk.org] <b><span
style='font-weight:bold'>Im Auftrag von </span></b>Emma Ryan<br>
<b><span style='font-weight:bold'>Gesendet:</span></b> Donnerstag, 16. August
2007 15:20<br>
<b><span style='font-weight:bold'>An:</span></b> insight-users@itk.org<br>
<b><span style='font-weight:bold'>Betreff:</span></b> [Insight-users] Fw: Mean
Squares Metric Computation does not match</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Hi,<br>
<br>
I posted this a few days ago and did not get response. I was
wondering if anyone tried the same experiments on their data ?<br>
<br>
Essentially, if you have any results of final metric values from synthetic
tests using registration/optimizations algorithms and by using direct matrix
computations of known transforms,<br>
please let me know. <br>
<br>
Thank you,<br>
Emma<o:p></o:p></span></font></p>
<div>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>----- Forwarded Message
----<br>
From: Emma Ryan <eryanvtk@yahoo.com><br>
To: insight-users@itk.org<br>
Sent: Tuesday, August 14, 2007 2:01:58 PM<br>
Subject: Mean Squares Metric Computation does not match<o:p></o:p></span></font></p>
<div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Hi,<br>
<br>
I use versor-based 3D rigid registration and gradient descent
-based affine registration algos to register two 3D volumes.<br>
<br>
The metric is mean squares and interpolator type is linear.<br>
<br>
To perform a cross-check on the final metric received after registration, I
-recompute the metric values as follows :<br>
<br>
1. Grayscale images<br>
MetricType::Pointer
metricOrig =
MetricType::New(); <br>
TransformType::Pointer transformOrig =
TransformType::New(); <br>
<br>
metricOrig->SetInterpolator(interpolator);<br>
metricOrig->SetTransform(transformOrig);<br>
metricOrig->SetFixedImage(fixedImageOrig);<br>
metricOrig->SetMovingImage(movingImageOrig); <br>
metricOrig->SetFixedImageRegion(fixedImageOrig->GetBufferedRegion());<br>
MetricType::TransformParametersType finalParam =
registration->GetLastTransformParameters();<br>
metricOrig->Initialize(); <br>
std::cout<<"MetricOnOriginalImage =
"<<metricOrig->GetValue(finalParam)<<std::endl;<br>
<br>
<br>
For the above code, I get metric values like 50 and 90 (for two different
datasets )whereas the bestValue = optimizer->GetValue() returned by
the optimizer (after registration) is 0.70 and 1.70 respectively.<br>
How does one explain this ? Especially when the Mean Square Error is the MEAN
and not the total error ?<br>
<br>
<br>
<br>
2. If the volumes sent to the registrator were binary, and the resultant
transform is to be applied to binary moving image.<br>
<br>
MetricType::Pointer
metricBin =
MetricType::New(); <br>
<br>
metricBin->SetInterpolator(interpolator);<br>
metricBin->SetTransform(transformOrig);<br>
metricBin->SetFixedImage(fixedBinImage);<br>
metricBin->SetFixedImageRegion(fixedImage->GetBufferedRegion());<br>
metricBin->SetMovingImage(movingBinImage); <br>
metricBin->Initialize();<br>
std::cout<<"MetricOnBinImage =
"<<metricBin->GetValue(finalParam)<<std::endl;<br>
<br>
<br>
<br>
Then I get values of metric = 958 and 220 (for two different datasets) when the
optimizer returns a value of 32 and 90 respectively. <br>
<br>
So my questions are :<br>
<br>
a) How does one explain a MEAN square error of 958 over a scale of 0-255
?<br>
b) For the binary images, when I compute the mean square error using other
softwares, I get a value of 5. Whereas ITK optimizer returns the final metric
value at 32. Both softwares use linear interpolator. I dont think I should get
such huge differences even if I were to uses nearest neighbor .<br>
c) In an earlier itk posting,<br>
<a
href="http://public.kitware.com/pipermail/insight-users/2005-July/014045.html"
target="_blank">http://public.kitware.com/pipermail/insight-users/2005-July/014045.html</a>,
Lydia mentions that this would be due to roundoff errors, but it does not
explain large differences.<br>
<br>
Any clues ?<br>
<br>
Emma<o:p></o:p></span></font></p>
</div>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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