<div class="gmail_quote"><div>Hello, </div><div><br></div><div>I've been trying to figure this out but I can't seem to get it right, but I assume this is a very simple problem to solve. I am trying to evaluate noise in CT images using a phantom for which I know the dimensions and positions of 20 spheres of different sizes. My idea was to construct a group of spatial objects (EllipseSpatialObject) and connect it to a high dose reference image which I can use to register other images to, and then apply the transform to the spatial objects to find their positions i the new image. </div>
<div><br></div><div>First I create the EllipseSpatialObjects and connect them to a GroupSpatialObject so that they have the correct positions to each other. I also know the world coordinates of the spheres in the reference image, but I wonder how I can place the GroupSpatialObject to match the spheres in the image. I have a couple of different reference image series, and when I apply the SpatialObjectToImageFilter and put in the reference image's direction, spacing and origin I get very different results for different images, which really confuses me. So, my two questions are:</div>
<div><br></div><div><ol><li>How do I assign world coordinates to the spatial objects?</li><li>What is the difference between SceneSpatialObject and GroupSpatialObject? Which one do you recommend for this problem?</li></ol>
</div><div>Thanks in advance!</div>---<br clear="all"><font color="#888888">Patrik Brynolfsson<br><br><br>
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