[Insight-developers] N3/itkBSplineScatteredDataPointSetToImageFilter problems

[Nicholas Tustison]

Hi Richard,

First, are you using the class itkN4MRIBiasFieldCorrectionImageFIlter or itkN3MRIBiasFieldCorrectionImageFIlter?  If it's the latter, how many levels are you using?  Either way, the error that is being thrown occurs when the B-spline object (in this case the scalar bias field estimate) is evaluated at the boundary maximum.  I tried to account for this in the code by generating a use-specific epsilon value which doesn't always work.  A quick fix would be to go to line 267 (after the following code)

  while ( static_cast< RealType >( maximumNumberOfSpans ) ==
          static_cast< RealType >( maximumNumberOfSpans ) - this->m_BSplineEpsilon )
    {
    this->m_BSplineEpsilon *= 10.0;
    }

and add

  this->m_BSplineEpsilon = 0.0001;  

I didn't put that in the code as it was a bit inelegant but perhaps it's time I revisited that.

However, having said all that, with your specific error, it would seem that you're using a mesh size of 21 in at least one dimension which is probably too high for a typical bias correction scenario.  Also, I would switch over to N4 if you haven't already done so as, in my experience, it works much better.

Nick






On Nov 30, 2010, at 5:40 AM, Richard Beare wrote:

> Hi,
> I'm using the N3 bias correction contribution to Insight Journal and
> having problems when setting the number of control points to 6. The N3
> filter uses itkBSplineScatteredDataPointSetToImageFilter. The error
> message when debug is turned on is:
> 
> itk::ExceptionObject (0x20e9210)
> Location: "void itk::MultiThreader::SingleMethodExecute()"
> File: /home/richardb/Build/InsightToolkit-3.20.0/Code/Common/itkMultiThreader.cxx
> Line: 475
> Description: itk::ERROR: MultiThreader(0x342b8f0): Exception occurred
> during SingleMethodExecute
> /usr/local/ITK/ITK-3.20_static/include/InsightToolkit/Review/itkBSplineScatteredDataPointSetToImageFilter.txx:530:
> itk::ERROR: PointSetToImageFilter(0x20e1b20): The reparameterized
> point component 24 is outside the corresponding parametric domain of
> [0, 24].
> 
> 
> The default setting of 4 control points works, as does 8. Is there a
> requirement for number of control points being a power of 2? If not,
> then it appears that there must be some sort of rounding error in how
> the bounds are figured out. I hope to submit a more detailed report
> soon, but thought I'd check to see whether this problem is familiar to
> anyone.
> 
> Thanks
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