# Save a custom attribute in header of Nifti

**URL:** <https://discourse.itk.org/t/save-a-custom-attribute-in-header-of-nifti/7178>\
**Category:** Engineering\
**Tags:** simpleitk, python\
**Created:** [August 16, 2024, 7:53am UTC](https://discourse.itk.org/t/save-a-custom-attribute-in-header-of-nifti/7178 "2024-08-16T07:53:38Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Karol-G](https://discourse.itk.org/user_avatar/discourse.itk.org/karol-g/32/4339_2.png) [@Karol-G](https://discourse.itk.org/u/Karol-G)\
**Post date:** [August 16, 2024, 7:53am UTC](https://discourse.itk.org/t/save-a-custom-attribute-in-header-of-nifti/7178/1 "2024-08-16T07:53:38Z")

</div>

Hey,

I want to indicate to my python code if a Nifti image is an image or a segmentation.

To accomplish that I want to store a single attribute in the Nifti header in one of the more flexible Nifti header fields such as a specific int in the `intent_code` field or a specific string in the `intent_name` field or the `ITK_FileNotes` field.

However, as it turns out SimpleITK deduces the header fields from the image data and is not so flexible in modifying specific header fields. See here: [[Python] Nifti metadata cannot be modified · Issue #2177 · SimpleITK/SimpleITK · GitHub](https://github.com/SimpleITK/SimpleITK/issues/2177)

For example in this code, I can modify the header in memory, but all changes are ignored when saving the image as Nifti. So this code does not solve my problem:

```python
import SimpleITK as sitk

load_filepath = "image.nii.gz"
save_filepath = "new_image.nii.gz"

print("Load image...")
image_sitk = sitk.ReadImage(load_filepath)
# Change some header fields
print("intent_code: ", image_sitk.GetMetaData("intent_code"))
print("ITK_FileNotes: ", image_sitk.GetMetaData("ITK_FileNotes"))
print("pixdim[1]: ", image_sitk.GetMetaData("pixdim[1]"))
image_sitk.SetMetaData("intent_code", "1002")
image_sitk.SetMetaData("ITK_FileNotes", "Test")
# Save the image (All header modifications are ignored by SimpleITK)
sitk.WriteImage(image_sitk, save_filepath)

# New image will have only unmodified header
print("Load new image...")
image_sitk = sitk.ReadImage(save_filepath)
print("intent_code: ", image_sitk.GetMetaData("intent_code"))
print("ITK_FileNotes: ", image_sitk.GetMetaData("ITK_FileNotes"))

```

Are there any Nifti header fields that I can modify with SimpleITK or is there some other way to indicate in the header that the image is a segmentation?

Best,  
Karol

---

<div class="post-metadata">

**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:** [August 20, 2024, 1:33pm UTC](https://discourse.itk.org/t/save-a-custom-attribute-in-header-of-nifti/7178/2 "2024-08-20T13:33:34Z")

</div>

Hello @Karol-G,

Per our [previous discussion](https://github.com/SimpleITK/SimpleITK/issues/2177#issuecomment-2293016018), this is an ITK issue and should have been opened on that toolkit’s issue tracker, not here.

In any case, [this PR](https://github.com/InsightSoftwareConsortium/ITK/pull/4809) adds support for writing the nifti `descrip` (exposed as `ITK_FileNotes`) field which should address your issue. Note that this will take some time till it is included in an official SimpleITK release (you can always access the [latest version from GitHub](https://github.com/SimpleITK/SimpleITK/releases/tag/latest)).