Calculating a Laterality Index using FSL?

Software Support
1

Hi all,

I am very new to fMRI analysis and want to ensure I am calculating a laterality index properly. I am also new to Neurostars and so apologies in advance if this is posted in the wrong section. Here are the steps I have been following:

  1. I have two (left and right) binarized images of 5mm spheres built around ROIs in the patient’s native space from which I want to extract the LI.

  2. I have been using the following script to get two new images that contain the overlap of the ROIs and the patients activation map.

fslmaths /Volumes/maxone1/Masters/GLM/sub-y0007/mask-con123_thr-4lvl_var-5_art.nii -mul /Volumes/maxone1/Masters/GLM/sub-y0007/LEFT_ROI_NATIVE_SPACE_5mm.nii.gz /Volumes/maxone1/Masters/GLM/sub-y0007/LEFT_ACTIVE_5mm_lvl4.nii

fslmaths /Volumes/maxone1/Masters/GLM/sub-y0007/mask-con123_thr-4lvl_var-5_art.nii -mul /Volumes/maxone1/Masters/GLM/sub-y0007/RIGHT_ROI_NATIVE_SPACE_5mm.nii.gz /Volumes/maxone1/Masters/GLM/sub-y0007/RIGHT_ACTIVE_5mm_lvl4.nii.gz
  1. I have then been calculating an LI by getting a count of all the voxels in the left and right and then dividing the difference by their sum.
LEFT=$(fslstats /Volumes/maxone1/Masters/GLM/sub-y0007/LEFT_ACTIVE_5mm_lvl4.nii -V | awk '{print $1}'); RIGHT=$(fslstats /Volumes/maxone1/Masters/GLM/sub-y0007/RIGHT_ACTIVE_5mm_lvl4.nii.gz -V | awk '{print $1}'); echo "scale=3; ($LEFT - $RIGHT) / ($LEFT + $RIGHT)" | bc

So far, my results appear logical but I thought it would be a good idea to post this and see if any major flaws were apparent.