OK, I think I get what you're saying. Here's my problem: I'm displaying images that are anisotropic in the X or Y direction.<br><br>This is a consequence of the way the data was acquired -- I'm displaying 3 brainscans, the first which is scanned Coronal (
i.e. back of the head to the front) and the other two are scanned Sagittal (i.e. left ear to right ear). <br><br>When I read the images using ITK I re-orient the Sagittal scans to Coronal. So the first image is spaced
0.9375, 0.935, 1.5, and the second and third are spaced 1, 3, 1.<br><br>What I have been doing is chainging the input to the ImageViewer in order to flip between the 3 images. If I get what you're saying, the images spaced 1,3,1 are displayed incorrectly because the size of a pixel in the XY plane isn't square.
<br><br>This doesn't make sense to me -- if it accounts for anisotropic spacing, shouldn't it do so in all directions?<br><br> <br><div><span class="gmail_quote">
On 3/23/07, <b class="gmail_sendername">Dean Inglis</b> <<a href="mailto:dean.inglis@camris.ca" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">dean.inglis@camris.ca</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hi Kent,<br><br>vktImageActor in vtkImageViewer2 is doing<br>what it should do when you have non-isotropic<br>voxels: the X-Z or Y-Z planes should show<br>elongated voxels in the z-dir if the x-y resolution<br>is isotropic and less the than out of plane (z) resolution.
<br>To really see this, set the image actor's interpolation<br>on and off with SetInterpolate().<br>Unless your MRI data is acquired isotropically there<br>is not much else to do. You can use vtkImageResample to make
<br>your data isotropic, but as you say, this is generally<br>not acceptable.<br><br>Dean<br><br><br>So when I run my program one orthogonal view -- i.e. looking at a slice in<br>the XY plane it is proportioned correctly. But if I look at a different
<br>plane (XZ or YZ) the pixels appear squashed or stretched in either the X or<br>Y direction.<br><br>I attempted to fix this by using the vtkViewport::SetPixelAspect method on<br>the vtkRenderer. This appears to do nothing at all.
<br><br>I spent quite some time with Google trying to figure out if anyone else had<br>solved this problem, with no luck. I read a lot of messages indicating that<br>SetPixelAspect was basically broken in 2003 or 2004, but never saw anywhere
<br>that it was fixed.<br><br>Can anyone give me a clue as to how to fix this? This is radiological data<br>so it isn't acceptable to resample the image data into isotropic voxels.<br>_______________________________________________
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