# N4ITK MRI Bias correction

**URL:** <https://discourse.slicer.org/t/n4itk-mri-bias-correction/1200>\
**Category:** Support\
**Created:** [October 9, 2017, 2:06pm UTC](https://discourse.slicer.org/t/n4itk-mri-bias-correction/1200 "2017-10-09T14:06:01Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![annapbarnes](https://avatars.discourse-cdn.com/v4/letter/a/d26b3c/32.png) [@annapbarnes](https://discourse.slicer.org/u/annapbarnes)\
**Post date:** [October 9, 2017, 2:06pm UTC](https://discourse.slicer.org/t/n4itk-mri-bias-correction/1200/1 "2017-10-09T14:06:01Z")

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Operating system: MacOSX Sierra  
Slicer version: 4.6.2 r25516  
Expected behavior: N4ITK bias correction output  
Actual behavior: nothing

Hi  
I’m a bit of a newbie to this GUI but I have used N3 bias correction before in linux and bash scripts etc. so I know what I want to do and what output I want to get it from it but…

So I’ve loaded my data in to the 3D slicer viewer, I’ve selected N4ITK MRI Bias correction in drop down.

I would like to apply this to the image I have loaded in the GUI but it just says “output volume” as does the next 3 drop down menus.

What I was then expecting would be an output of the corrected image and the bias field.

Feeling a bit of “numpty” can someone send me a “dummies guide” on how to get this module to work in this rather snazzy GUI

thanks  
Anna

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [October 9, 2017, 5:45pm UTC](https://discourse.slicer.org/t/n4itk-mri-bias-correction/1200/2 "2017-10-09T17:45:10Z")

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Hi Anna -

The panel should look something like below.

I just tested like this:

- download MRHead from the SampleData
- go to the N4ITK MRI Bias Correction module
- for the Output volumes, pick Create New from the menu
- select MRHead as the input
- click Apply

(Note that in 4.6 there is a bug that resets the input volume after creating a new volume , which is why the input is selected last in the sequence above. In the recent nightly builds this issue is fixed).

HTH,  
Steve

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/6/6/66fd14fe84a909cae9944f1e2c374caad8f82eb0.png)