<span>Dear all,</span><div><span>i have some questions about level set methods as itk</span>ShapeDetectionLevelSetImageFilter, itkGeodesicActiveContourLevelSetImageFilter, itkThresholdSegmentationLevelSetImageFilter </div>
<div>and I think i have some problems with the setting of parameters (propagationScaling, curvatureScaling, advectionScaling , number of iterations).</div><div>I work on CT data dicom of chest (volume 512x512x300 with pixel in hounsfield unit ) to segment trachea and bronchi using approaches describing in section of 9.3 in itkSoftwareGuide.</div>
<div>I place 15 seeds inside my object and create map of distance (initial level set) -> at this point i have my first little problem: </div><div><br></div><div>1) Fast marching used to create map of distance takes biblical times if i don't set stopping value or if i set stopping value at 60,70 (seeds value for initial distance are -5,-10,-15). Is it normal???</div>
<div>To overcome this obstacle i use stopping value = 5, 10 (luckily trachea has a diameter of 20-25 pixel).</div><div><br></div><div>2) My real problem is when i run level set 's filters : i get resulting volumes very strange; i get 15 spheres not connected (each sphere grows where i placed each seed) and these spheres overlap and exceed boundaries too.</div>
<div>I have tried many combinations of parameters (propagation [-1, 0.5 , 1], curvature[0.05 , 0.5 , 1 ] and advection [0.1 , 1] ) but no major improvements!!!</div><div>What's wrong? Is it possible have a explanation of how best to use the parameters of these filters?</div>
<div><br></div><div><br></div><div>3) I get the best result using only the simple itkFastMarchingImageFilter (as described in itkSoftwareGuide). Is this not absurd? :></div><div>In this case i have my third problem or question : i get my object segmented inside my real object (trachea) or rather my object segmented doesn't include the edges.</div>
<div>I have to apply a morphological operator as dilate to obtain approximately my real object. Is there anything I can do to improve this aspect???</div><div><br></div><div>Thanks for interest and any hints in advance.</div>
<div><br></div><div>Daniele</div><div><pre style="background-color: rgb(255, 255, 255); "><br></pre></div>