Depends on the metric. Please look at the code of the metric in question. <br><br>For MeanSq its at least 1 sample, as you suspect.<br> Line 110: itkMeanSquaresImageToImageMetric.txx<br> if( !this->m_NumberOfPixelsCounted )<br>
<br>itkMattesMutualnformationImageToImageMetric imposes a 25% overlap threshold.<br> Line 1109 : if( nSamples < m_NumberOfSpatialSamples / 4 )<br><br>Your threshold overlap is metric dependent. Overall a low overlap -> low confidence in metric.<br>
<br>For MI, overlap is quite important, since with MI can increase as overlap reduces, making the optimizer unstable, and driving the registration towards the 0 overlap point. <br><br><br><br>-- <br>Karthik Krishnan<br>R&D Engineer,<br>
Kitware Inc.<br><br><div class="gmail_quote">On Fri, Jul 31, 2009 at 7:42 AM, Gomez Herrero, Alberto <span dir="ltr"><<a href="mailto:alberto.gomez-herrero@philips.com">alberto.gomez-herrero@philips.com</a>></span> wrote:<br>
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<p><span lang="EN-US">Hi,</span></p>
<p><span lang="EN-US"> </span></p>
<p><span lang="EN-US">In the frame of a registration process, I am exploring a metric to get the values for each displacement, something similar to what is done in the example MeanSquaresImageMetric1.cxx.</span></p>
<p><span lang="EN-US">My question is the following:</span></p>
<p><span lang="EN-US"> </span></p>
<p><span lang="EN-US">To compute the metric for a given displacement, the two images have to overlap at least partially. What is the minimum overlap? One may think that any overlap > 0 should work, but my tests make my think that actually
at least one full pixel of the moving image must be fully overlapping the fixed image, otherwise throws exception. Can anyone confirm this please?</span></p>
<p><span lang="EN-US"> </span></p>
<p><span lang="EN-US">Thanks,</span></p>
<p><span lang="EN-US"> </span></p>
<p><span lang="EN-US">Alberto</span></p>
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