[Insight-users] NoiseImageFilter for 3D images

[Bradley Lowekamp]

Hello Micro,

I don't regularly work with CT, so I don't know for certain. What is the pixel type in your file?

http://www.itk.org/Wiki/ITK/Examples/IO/ReadUnknownImageType

Also why do you say you image is all zeros? Did you inspect it in am image viewer? Perhaps all the values were just too low to be seen?

It may be best to have the output of the filter be at least of float, since its computing the standard deviation will be low in homogeneous regions which may be causing you to thing it's zero.

You are correct that in 3d a radius of 2 aka [2,2,2] will yield a neighborhood with a size of [5,5,5].  This has to do with how the Neighborhood operators and iterator work. You can find some example which may help you understand the behavior better here:

http://www.itk.org/Doxygen/html/examples.html
http://www.itk.org/Wiki/ITK/Examples

Brad


On Aug 16, 2013, at 9:02 AM, Mirco Serra <mirco9091 at hotmail.it> wrote:

> Hello,
> 
> Thanks for your answer!
> 
> I am using unsigned short as image type both for the input and the output image. Is this the correct type for 3D CT images? Also, would you mind explaining me the way the radius for the local region is selected for 3D images? In 2D I know that a radius value of 1 corresponds to a 3x3 region, a radius of 2 is a 5x5 region and so on. Is it the same in 3D, i.e. a value of 1 is a region of 3x3x3?
> 
> Many thanks,
> 
> Mirco
> 
> Subject: Re: [Insight-users] NoiseImageFilter for 3D images
> From: blowekamp at mail.nih.gov
> Date: Fri, 16 Aug 2013 08:48:56 -0400
> CC: insight-users at itk.org
> To: mirco9091 at hotmail.it
> 
> Hello,
> 
> What are your template parameters to the filter i.e. the image types used?
> 
> I just tried this filter in SimpleITK with a couple different images and it seems to work fine.
> 
> Thanks,
> Brad
> 
> On Aug 16, 2013, at 5:05 AM, Mirco Serra <mirco9091 at hotmail.it> wrote:
> 
> Hi guys,
> 
> I am trying to use the NoiseImageFilter class in order to get the local standard deviation of a 3D DICOM/nrrd dataset. The filter works nicely with 2D images, but when I try to use for 3D datasets it does not work properly and it returns an image with only zeros as intensity values. Do you have any idea why this could happen? I struggled with it a lot but I could not find a solution! Is the filter for 3D images too?
> 
> All the best and thank you very much,
> 
> Mirco 
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