[ITK] InvertDisplacementFieldImageFilter in SimpleITK

[Timothee Evain]

Hi Christian,

Physical space only depend of your data. The unit will be the one in the header or meta-data.
I don't know what data you're using, but mms are rather common indeed.

HTH,
Tim

----- Mail original -----
De: "Gustafsson Christian K" <Christian.K.Gustafsson at skane.se>
À: "Bradley Lowekamp (NIH/NLM/LHC) [C]" <blowekamp at mail.nih.gov>
Cc: community at itk.org, "Fredrik Nordström" <fredrik.nordstrom at vgregion.se>
Envoyé: Mercredi 1 Juin 2016 11:05:13
Objet: Re: [ITK] InvertDisplacementFieldImageFilter in SimpleITK



Hi! 

Thanks for your reply. I can not find out any more from the code. If it is physical space, what unit is used? 

Default seems to be 

m_MaxErrorToleranceThreshold(0.1), 

m_MeanErrorToleranceThreshold(0.001), 



so I guess this is not meters, but rather mm (?). 




Från: Lowekamp, Bradley (NIH/NLM/LHC) [C] [mailto:blowekamp at mail.nih.gov] 
Skickat: den 31 maj 2016 16:03 
Till: Gustafsson Christian K <Christian.K.Gustafsson at skane.se> 
Kopia: community at itk.org 
Ämne: Re: [ITK] InvertDisplacementFieldImageFilter in SimpleITK 




Hello, 





My assumption would be that the error is in physical space and not pixels as this is standard ITK practice. While the documentation is rather sparse you can look at the source code to gain insight into these types of questions [1]. 





Also note that there is the InverseDisplacementFieldImageFilter. I don’t recall the difference and if one is generally preferred of the other. 





HTH, 


Brad 





[1] https://github.com/InsightSoftwareConsortium/ITK/blob/1257b0468c147ba2b1a65bae67169bdf35f4fa50/Modules/Filtering/DisplacementField/include/itkInvertDisplacementFieldImageFilter.hxx#L215-L248 








On May 31, 2016, at 8:40 AM, Gustafsson Christian K < Christian.K.Gustafsson at skane.se > wrote: 





Hello! 





What is the unit of measurement that is used in the criterias MeanErrorToleranceThreshold and MaxErrorToleranceThreshold 





/* Set/Get the mean stopping criterion */ 


itkSetMacro( MeanErrorToleranceThreshold, RealType ); 


itkGetConstMacro( MeanErrorToleranceThreshold, RealType ); 








/* Set/Get the max stopping criterion */ 


itkSetMacro( MaxErrorToleranceThreshold, RealType ); 


itkGetConstMacro( MaxErrorToleranceThreshold, RealType ); 





in InvertDisplacementFieldImageFilter in SimpleITK? 





Is it amount of pixels? 





Best regards 


________________________________________ 


Christian Gustafsson 


Medical Physicist, MRI, PhD candidate 





Department of Radiation Physics 


Klinikgatan 5 


Skåne University Hospital 


SE 221 85 Lund 


+46 46 177647 


Christian.K.Gustafsson at skane.se 





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