# High intensities in chiasmatic region seems to affect fixel analysis

**URL:** https://community.mrtrix.org/t/high-intensities-in-chiasmatic-region-seems-to-affect-fixel-analysis/2125
**Category:** Uncategorized
**Created:** [December 13, 2018, 10:12am UTC](https://community.mrtrix.org/t/high-intensities-in-chiasmatic-region-seems-to-affect-fixel-analysis/2125 "2018-12-13T10:12:22Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![1111](https://community.mrtrix.org/user_avatar/community.mrtrix.org/1111/32/1578_2.png) [@1111](https://community.mrtrix.org/u/1111)
#### Post date: [December 13, 2018, 10:12am UTC](https://community.mrtrix.org/t/high-intensities-in-chiasmatic-region-seems-to-affect-fixel-analysis/2125/1 "2018-12-13T10:12:22Z")

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Dear experts,

1. We have high intensities in the chiasmatic region in our dMRI data. A similar problem was already described [here](https://community.mrtrix.org/t/dwibiascorrect-with-ants-high-intensity-in-cerebellum-brainstem/1338). How can we solve that problem?

2. This seems to also affect the fixel analysis. As shown in the attached images.

We attached raw dMRI data(1), preprocessed data(2), fod template(3) and fod with fixels(4).

image 1:

 ![screenshot0006](https://community.mrtrix.org/uploads/default/original/2X/a/a892c5ff6e416a7c0e7a318d930d24c408e9d682.png)

image 2:

 ![screenshot0007](https://community.mrtrix.org/uploads/default/original/2X/2/2549585b3073bb0fa2be117b2c1efe1df1c2aa3c.png)

image 3:

 ![screenshot0001](https://community.mrtrix.org/uploads/default/original/2X/a/a367a09a5ffc197f970f67e7e7b1817320f8a2b0.png)

image 4:

 ![screenshot0000](https://community.mrtrix.org/uploads/default/original/2X/c/c303d013395ae9c9d8ebf7b5df2c77e0c1f21232.png)

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<div class="post-metadata">

### Author: ![rsmith](https://community.mrtrix.org/user_avatar/community.mrtrix.org/rsmith/32/2672_2.png) [@rsmith](https://community.mrtrix.org/u/rsmith)
#### Post date: [December 16, 2018, 11:15am UTC](https://community.mrtrix.org/t/high-intensities-in-chiasmatic-region-seems-to-affect-fixel-analysis/2125/2 "2018-12-16T11:15:35Z")

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Hi Ziqian,

The hyper-intensity in the DWIs is caused by a compression of signal due to EPI susceptibility distortions. Without having the requisite image data to correct said distortions, there’s likely nothing you can do about the hyper-intensity itself on a per-subject basis; at least not without grossly altering the quantitative behaviour of AFD…

The relevant fixels could be masked from the FBA analysis using a combination of a manually-defined ROI and the `voxel2fixel` command to produce a fixel analysis mask, and then providing this to `fixelcfestats via the`-mask` option.

Rob