# NaN values in FA Map

**URL:** <https://community.mrtrix.org/t/nan-values-in-fa-map/8806>\
**Category:** Uncategorized\
**Created:** [August 3, 2026, 9:20am UTC](https://community.mrtrix.org/t/nan-values-in-fa-map/8806 "2026-08-03T09:20:13Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![nschalkx](https://community.mrtrix.org/letter_avatar_proxy/v4/letter/n/6f9a4e/32.png) [@nschalkx](https://community.mrtrix.org/u/nschalkx)\
**Post date:** [August 3, 2026, 9:20am UTC](https://community.mrtrix.org/t/nan-values-in-fa-map/8806/1 "2026-08-03T09:20:14Z")

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I have created some FA maps using the MRTrix suite, but after closer inspection of the images there are multiple ‘holes’ in the map, where the value is NaN / ?. I have attached some screenshots of the ‘holes’ in question. What could these ‘holes’ be? They only appear in the FA map, the original image & mask image do not have anything that could resemble these holes.

The commands I used to create the map are as follows:  
`dwi2tensor input_file output_name_fa -mask mask_file_name`

`tensor2metric input_file (output of the dwi2tensor command) -fa output_fa_map -adc output_md -mask mask_file_name`

 ![Screenshot 2026-08-03 at 11.13.44](https://community.mrtrix.org/uploads/default/original/2X/e/e8ee16e1bd95d633695b0e018798b40eed95fad4.jpeg)

 ![Screenshot 2026-08-03 at 11.13.33](https://community.mrtrix.org/uploads/default/original/2X/6/63f67df09aae3b839efc5e3ea0979a7bcacff7d2.jpeg)