[Insight-developers] DiffusionTensor3DReconstructionWithMaskImageFilter enhancement question.

[Williams, Norman K]

The MaskImageFilter makes the assumption that I'm trying to avoid, that the mask and the input image are identically oriented in space, have the same spacing and the same size.

If it is OK to make this an implicit precondition for the mask image for the DiffustionTensor3DReconstructionImageFilter,  it would make the code much simpler, but since there's no (simple) way to enforce this, we'd just be crossing our fingers and hoping for the best.

As it happens the overhead of working in physical space is probably less than that of calling the solver for voxels of no interest.

On Jan 27, 2011, at 9:12 AM, Magnotta, Vincent A wrote:

> Kent,
>
> My lazy solution would be to use the MaskImageFilter and then just iterate
> though the image. I am not sure how it handles the size correspondence
> between the mask and image, but would allow us to potentially implement a
> solution and only one filter that could be reused many places.
>
> Vince
>
>
> --
> Associate Professor
> Department of Radiology
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> E-mail: vincent-magnotta at uiowa.edu
> Phone: 319-356-8255 Fax: 319-353-6275
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>
>
>
>
>
> On 1/27/11 8:58 AM, "Williams, Norman K" <norman-k-williams at uiowa.edu>
> wrote:
>
>> I am in the process of adding a mask input to
>> itk:DiffusionTensor3DReconstructionWithMaskImageFilter.
>>
>> Currently, there is a threshold parameter, so that it ignores voxels in
>> the reference image with values below the threshold.  What I'm adding is
>> some code at the same point to look up the corresponding voxel in a mask
>> image.
>>
>> The problem is that at that point in the filter, it's stepping through
>> the image with an ImageRegionConstIterator.  I could use an
>> ImageRegionConstIterator to step through the mask at the same time, but
>> the filter can't no for a fact that the mask and the reference image are
>> congruent in space.  So I'm doing this:
>>
>>       ItIndexType index(it.GetIndex()); // get index from reference
>> image iterator
>>       MaskImageType::PointType pt;
>>       refImage->TransformIndexToPhysicalPoint(index,pt); // find
>> physical point for index
>>
>>       MaskImageType::IndexType maskIndex; // find index in mask from
>> physical point
>>       this->m_MaskImage->TransformPhysicalPointToIndex(pt,maskIndex);
>>       MaskImageType::PixelType pix =
>>         this->m_MaskImage->GetPixel(maskIndex);
>>
>> This seems to be the right thing to do, but it has to add considerable
>> overhead compared to a ImageRegionConstIterator. Is there a better way to
>> do this?
>>
>>
>>
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