# how to speed up the n4 bias correction

**URL:** https://discourse.itk.org/t/how-to-speed-up-the-n4-bias-correction/4276
**Category:** Uncategorized
**Tags:** simpleitk
**Created:** [July 17, 2021, 9:50am UTC](https://discourse.itk.org/t/how-to-speed-up-the-n4-bias-correction/4276 "2021-07-17T09:50:43Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![asmaharry](https://discourse.itk.org/user_avatar/discourse.itk.org/asmaharry/32/2177_2.png) [@asmaharry](https://discourse.itk.org/u/asmaharry)
#### Post date: [July 17, 2021, 9:50am UTC](https://discourse.itk.org/t/how-to-speed-up-the-n4-bias-correction/4276/1 "2021-07-17T09:50:43Z")

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I am using SimpleITK bias field correction for my NIFIT images  
corrector = sitk.N4BiasFieldCorrectionImageFilter()  
It takes too much time. Is there any way to speed up this process.

Thanks.

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### Author: ![zivy](https://discourse.itk.org/user_avatar/discourse.itk.org/zivy/32/1726_2.png) [@zivy](https://discourse.itk.org/u/zivy)
#### Post date: [July 17, 2021, 10:34pm UTC](https://discourse.itk.org/t/how-to-speed-up-the-n4-bias-correction/4276/2 "2021-07-17T22:34:15Z")

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Hello @asmaharry,

The computation speed depends on the number of control points specified with the `SetNumberOfControlPoints` method. Possibly reduce the number of control points to the minimum which still gives sufficiently good results.