Hi Seth,<div><br></div><div>Thank you for the comment. </div><div><br></div><div>I double-checked my code, and found that before calling MattesMutualInformationImageToImageMetric::Initialize(), I called MattesMutualInformationImageToImageMetric::ReinitializeSeed(76926294). After debugging into the code, I am sure that ImageToImageMetric::SampleFixedImageRegion() was called. But, still, it is observed that the samples were different for different runs. Do I miss anything else?</div>
<div><br></div><div>With the same code, if I do NOT apply <span style="background-color:rgb(255,255,255);color:rgb(34,34,34);font-family:arial,sans-serif;font-size:14px">ImageMaskSpatialObject for both the fixed and moving images, I do see consistent result. However, it was no good than the better ones I got by chance with </span><span style="background-color:rgb(255,255,255);color:rgb(34,34,34);font-family:arial,sans-serif;font-size:14px">ImageMaskSpatialObject applied.</span></div>
<div><br></div><div><br><br><div class="gmail_quote">2013/2/26 Seth Gilchrist <span dir="ltr"><<a href="mailto:seth@mech.ubc.ca" target="_blank">seth@mech.ubc.ca</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div>Hi Lien,</div><div>You may be seeing the effects of the sampling of the registration region to create the mattes histogram.</div><div><br></div><div>If you check the doxygen for the MattesMutualInformationImageToImageMetric and expand the section "public member functions inherited from itk::ImageToImageMetric" you will find a few functions that concern sampling (SetUseAllPixels, SetUseFixedImageIndexes, SetUseSequentialSampling). Importantly, one of these is called ReinitializeSeed(). Take a look at the documentation for that function and it may help answer your question. Briefly:</div>
<div><br></div><div>"<span style="line-height:19px;font-size:12px;font-family:'Lucida Grande',Verdana,Geneva,Arial,sans-serif">By nature, this metric is not deterministic, since at each run it may select a different set of pixels. By initializing the random number generator seed to the same value you can restore determinism."</span></div>
<div><span style="line-height:19px;font-size:12px;font-family:'Lucida Grande',Verdana,Geneva,Arial,sans-serif"><br></span></div><div><span style="line-height:19px;font-size:12px;font-family:'Lucida Grande',Verdana,Geneva,Arial,sans-serif">Hope this helps,</span></div>
<div><span style="line-height:19px;font-size:12px;font-family:'Lucida Grande',Verdana,Geneva,Arial,sans-serif">Seth</span></div></div>
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