[Insight-users] Compute metric for subregion of image?

[motes motes]

I have two 512*512 images (fixed, moving). Now I would like to compute
the metric for a subregion between those two images, something like:

    metric->SetFixedImage(imageF);
    metric->SetMovingImage(imageM);
//    metric->SetFixedImageRegion(imageF->GetBufferedRegion());
    metric->SetFixedImageRegion(UserSpecifiedRegion);

Is this possible somehow using a UserSpecifiedRegion?