[Insight-users] Heads up on HessianRecursiveGaussian bug fix

[Luca Antiga]

Hi all,
  this is a heads up message on a bug that Oleksandr Dzyubak has found  
in itkHessianRecursiveGaussianImageFilter
(bug 0008990 in Mantis, http://public.kitware.com/Bug/view.php? 
id=10599) and for which I recently submitted a fix.

The bug affected the behavior of the filter when NormalizeAcrossScale  
is set to true with dimensions > 2, and it has effects on multi-scale  
vesselness filters or multi-scale shape-detection filters in general  
(e.g. those using itk::MultiScaleHessianBasedMeasureImageFilter), and  
vessel-enhancing diffusion filters.

The bug caused incorrect normalization of the Hessian across scale- 
space, and, for instance, lead to a poor performance of vesselness  
filters when spanning several scales (vessels at smaller scales were  
washed out compared to how they appear after the fix).

The fix has been committed after 3.18 was released, hence it will be  
in for ITK > 3.18. There is now a test  
(itkHessianRecursiveGaussianImageFilterScaleSpaceTest) that tests the  
scale-space behavior of the class quantitatively.

So, for whoever was using multi-scale Hessian-based filters in 3D and  
higher, please rerun your tests, since there's a very good chance  
(100% ?) that the results will have changed (most likely for the  
better).

I'm here for any clarification. Again, kudos to Oleksandr Dzyubak who  
highlighted the misbehavior through lots of testing.

Best regards


Luca



--
Luca Antiga, PhD
Principal Scientist, OROBIX Srl
via L.A. Muratori 3, 24123 Bergamo, Italy

web: www.orobix.com
mobile: +39.347.43.16.596

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