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Instructions FreeSurfer subcortical segmentation Preparations


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Written by Derrek Hibar, Neda Jahanshad, Roberto Toro, Katharina Wittfeld, Ian Bowman (last updated March 26, 2012), adapted by Anita van Loenhoud


Instructions FreeSurfer subcortical segmentation
1. Preparations

In your Linux environment, create a folder called “enigma” that contains the folders “input” and “output”:




mkdir
/enigma


mkdir
/enigma/input enigma/output

Your input-folder should contain the scans of all your participants in a nii.gz-format. Make sure that each nii.gz-file is called “subj[number].nii.gz” (e.g. subj01.nii.gz, subj02.nii.gz, subj03.nii.gz).


If you have both 1.5T and 3T-scans, you should keep them in separate folders. So for example, you may have an enigma/15T/input and enigma/3T/input and

enigma/15T/output and enigma/3T/output. For simplicity, in these instructions we assume that you only have scans of one type.
It is recommended to use the c-shell or enhanced c-shell for FreeSurfer, you can do this by simply typing:



csh

or:

tcsh










You can set this shell permanently as your default:


chsh -s /bin/csh

or:

chsh -s /bin/tcsh


2. Setup FreeSurfer

All information on how to set up and install FreeSurfer can be found on this webpage: https://surfer.nmr.mgh.harvard.edu/fswiki/QuickInstall


Make sure that you also register to obtain a license to use FreeSurfer:

https://surfer.nmr.mgh.harvard.edu/registration.html
Before you want to work with FreeSurfer, you must make sure three things have happened:

  1. The variable FREESURFER_HOME is set (so your computer knows where FreeSurfer is installed):




setenv FREESURFER_HOME <freesurfer_installation_directory>/freesurfer




  1. The FreeSurfer set up script must be sourced (so FreeSurfer knows the location of everything it needs):




source $FREESURFER_HOME/SetUpFreeSurfer.csh




  1. FreeSurfer has been pointed to a directory of subjects to work on:




setenv SUBJECTS_DIR 
/enigma/input



3. Run preprocessing pipeline

The next step is to run “recon–all” on the subjects in your input-folder (http://surfer.nmr.mgh.harvard.edu/fswiki/recon-all). In your input-folder, make a text-file (e.g. nano list_subjects.txt) containing a list of all your subjects:




subj01

subj02

subj03


You can create the following script (e.g. nano loop_recon-all) to run “recon-all” on multiple subjects:


#!/bin/bash

exec

while read x; do

recon-all –i $x.nii.gz –s $x –all

mv $x/
/enigma/output


done

To run this script, make it executable with the following command:




chmod u+x loop_recon_all

Then, run the script:




./loop_recon_all

Depending on the number of your scans and the processing speed of your computer, this script will take several days to finish (24 to 36 hours/subject). When “recon-all” is done and you have unpacked all files, you will see a folder for each subject in your output-folder, in which you will find 10 new folders (such as ‘mri’, ‘stats’, ‘surf’ etc).



4. Extract subcortical volumes

To extract subcortical volumes, run the following commands:




cd
/enigma/output


bash

echo "SubjID,LLatVent,RLatVent,Lthal,Rthal,Lcaud,Rcaud,Lput,Rput,Lpal,Rpal,Lhippo,Rhippo,Lamyg,Ramyg,Laccumb,Raccumb,ICV" > LandRvolumes.csv

for subj_id in `ls -d subj*`; do

printf "%s," "${subj_id}" >> LandRvolumes.csv

for x in Left-Lateral-Ventricle Right-Lateral-Ventricle Left-Thalamus-Proper Right-Thalamus-Proper Left-Caudate Right-Caudate Left-Putamen Right-Putamen Left-Pallidum Right-Pallidum Left-Hippocampus Right-Hippocampus Left-Amygdala Right-Amygdala Left-Accumbens-area Right-Accumbens-area; do

printf "%g," `grep ${x} ${subj_id}/stats/aseg.stats | awk '{print $4}'` >> LandRvolumes.csv

done

printf "%g" `cat ${subj_id}/stats/aseg.stats | grep IntraCranialVol | awk -F, '{print $4}'` >> LandRvolumes.csv

echo "" >> LandRvolumes.csv

done

This will create a new file, called “LandRvolumes.csv”. It should contain a table with volumes (in mm3) of the ventricles, thalamus, caudate, putamen, pallidum, hippocampus, amygdala and accumbens and intracranial volume (ICV) for each subject. Open the file (e.g. nano LandRvolumes.csv) to check if this information is actually there.


5. Generate histogram plots

In the next step, we generate histogram plots of our data. To do this, you need to have R installed on your Linux-system (http://cran.r-project.org/). Furthermore, you need to download the following script: http://users.loni.ucla.edu/~dhibar/enigma_plots.R.


Create a new folder in your enigma-folder, called “figures”:


mkdir
/enigma/figures/

Then, copy the LandRvolumes.csv-file (which we created earlier) to this folder:




cp
/enigma/output/LandRvolumes.csv
/enigma/figures/

LandRvolumes.csv should look like this:




SubjID,LLatVent,RLatVent,Lthal,Rthal,Lcaud,Rcaud,Lput,Rput,Lpal,Rpal,Lhippo,Rhippo,Lamyg,Ramyg,Laccumb,Raccumb,ICV

subj01,6523.3,9343.5,7598.5,4488.2,4752.4,5665.3,5864.59,2052.69,1842.28,3398.2,4052.37,787.061,702.422,591.68,576.65,0.908024

subj02,5362.22,7786.76,7885.63,4106.95,3923.44,4746.09,5222.29,1819.34,1961.72,3454.37,3675.85,933.398,880.4,x,x,0.737983

subj03,4476.45,5984.82,5984.82,4583.94,4466.07,4263.57,3899.71,x,x,3172.76,3083.38,599.59,435.85,146.338,253.916,0.677593

subj04,3375.55,7115.98,6468.93,x,4078.48,5056.96,5150.3,567.949,617.783,3628.39,3214.69,1091.6,1033.86,435.85,208.037,0.637183

Make sure that the columns are in the same order as in the file above. Also, note that the “x” is the marker that should be used to mark files as poorly segmented or excluded (see step 9). Also, you need to make sure that there are no missing values in the file. In the LandRvolumes.csv file missing values will appear as two commas in a row “,,”. Missing values are probably easier to see in a spreadsheet program like Microsoft Excel, there it will just be a blank cell. You need to put an “x” value for any missing value so that it will be excluded from the analysis.


Move the ENIGMA_plots.R script to the figures-folder:



mv
/downloads/ENIGMA_plots.R
/enigma/figures/

Make sure you are in your new folder:




cd
/enigma/figures

Run the R script to generate the plots:




R --no-save --slave < ENIGMA_plots.R

It should only take a few minutes to generate all of the plots. If you get errors, they should tell you what things need to be changed in the file in order to work properly. Just make sure that your input file is in *.csv format similar to the file above.


The output will be SummaryStats.txt and a series of PNG image files that you can open in any standard picture viewer. You need to go through each of the PNG files to make sure that your histograms look approximately normal.

6. Perform outlier detection

Now we will run a semi-automated script to detect outliers, which is based on the SummaryStats.txt-file you created with R, and LandRvolumes.csv. This is done by defining the Interquartile Interval (IQI), defined as Quartile 1 (Q1) – 1.5 times the Interquartile Range (IQR) to Quartile 3 (Q3) + 1.5 times the IQR. For a normal distribution this is equivalent to the mean+/-2.698 standard deviations. This script assumes a normal distribution.




#!/bin/bash

echo "Region,MNminus1.5IQI,MNplus1.5IQI" > IQI_range.csv

sed '1d' SummaryStats.txt | grep -v "Assym" | grep -v "Avg_" | awk ' { print $1","$4-2.698*$5","$4+2.698*$5 } ' >> IQI_range.csv

N_regions=`more LandRvolumes.csv | head -n 1 | awk -F "," ' { print NF } '`

for (( c=2; c<=$N_regions; c++))

do roi=`more LandRvolumes.csv | head -n 1 | awk -F "," ' { print $'$c' } '`

IQI_low=`more IQI_range.csv | grep $roi | awk -F "," ' { print $2 }'`

IQI_high=`more IQI_range.csv | grep $roi | awk -F "," ' { print $3 }'`

IQI_low_int=`printf "%10.0f\n" $IQI_low`

IQI_high_int=`printf "%10.0f\n" $IQI_high`

echo "Looking for subjects with "$roi" volumes outside of "$IQI_low":"$IQI_high

cnt=1

for textline in `sed '1d' LandRvolumes.csv | awk -F "," ' { print $'$c' } '`

do cnt=`echo $cnt+1 | bc `

textline_int=`printf "%10.0f\n" $textline`

if [ $textline_int -gt $IQI_high_int ];

then sid=`more LandRvolumes.csv | head -n $cnt | tail -n 1 | awk -F "," ' { print $1 } '`

echo $sid" has a "$roi" of "$textline", this volume is high"

fi

if [ $textline_int -lt $IQI_low_int ];

then sid=`more LandRvolumes.csv | head -n $cnt | tail -n 1 | awk -F "," ' { print $1 } '`

echo $sid" has a "$roi" of "$textline", this volume is low"

fi

done

done

Save the above script as mkIQIrange.sh , as it will be used in the following script to visualize the outlying subjects. This script requires a working FSLview. First, make mkIQIrange.sh executable:




chmod u+x mkIQIrange.sh

Then run the following commands:




#!/bin/bash

./mkIQIrange.sh > jnk.txt
more jnk.txt | grep "has" | awk -F/ ' { print $NF } ' | awk ' { print $1 } '| sort | uniq > jnk2.txt

more jnk2.txt | wc -l

hd=`pwd`
for img in `more jnk2.txt`

do echo $img

cd /enigma/output/$img/mri/

mri_convert --out_orientation RAS --in_type mgz --out_type nii T1.mgz T1.nii ;

mri_convert --out_orientation RAS --in_type mgz --out_type nii aseg.mgz aseg.nii ;

more $hd/jnk.txt | grep $img

fslview T1.nii aseg.nii -t 0.2 -l "MGH-Subcortical";

rm *.nii

done

FSLView will open automatically to visualize the subjects that were identified as outliers, so that you can verify that the structure is delineated properly.


Note: If a subject is identified as an outlier, but after inspection you decide the subject is properly segmented, you should NOT exclude its structures from your LandRvolumes.csv (see step 9).
7. Create PNGs for the quality check

Download the ENIGMA Matlab scripts into your enigma-folder (http://enigma.ini.usc.edu/wp-content/uploads/CORTEX/QC_ENIGMA_Cortex.zip) (called QC_ENIGMA_Cortex.zip) and unzip them. Also download the scripts attached to the instructions-email (‘func_make_subcorticalFS_ENIGMA_QC.m’ and ‘make_subcortical_ENIGMA_QC_webpage.sh’) and move them to the same folder containing all other matlab scripts.


Start Matlab:



/matlab

Add the ENIGMA_QC folder containing all of the required scripts to Matlab’s path: File -> Set Path -> Add Folder -> {OK} -> {Save} -> {Close}


When you work in Matlab without a GUI, you can instead type:


addpath
/enigma/QC_ENIGMA

In the Matlab console window, change directories to the folder with all of your FreeSurfer subject folders.




cd
/enigma/output/

Make a directory to store all of the QC output.




mkdir
/enigma/output/QC/

In the Matlab command window we can do:




QC_output_directory='
/enigma/output/QC/';


FS_directory='
/enigma/output/';


a=dir(char(strcat(FS_directory,'/subj*')));%Choose this so that it selects only %your subject folders that contain FS output

for x = 1:size(a,1)

[c,b,d]=fileparts(a(x,1).name); %b becomes the subject_name

try

func_make_subcorticalFS_ENIGMA_QC(QC_output_directory, b, [FS_directory,'/', b, '/mri/orig.mgz'], [FS_directory,'/',b, '/mri/aparc+aseg.mgz']);

end

display(['Done with subject: ', b,': ',num2str(x-2), ' of ', num2str(size(a,1)-2)]);

end

The func_make_subcorticalFS_ENIGMA_QC-script should take approximately 7 seconds/subject and will output a series of *.png image files separated by individual subject folders.


NB: if you run into problems with this Matlab loop try removing the last “/” in the QC_output_directory variable. So, QC_output_directory='/enigma/output/QC/'; would become QC_output_directory='
/enigma/output/QC’;

8. Perform quality check on the webpage

To create a webpage for easy viewing of the QC output you just generated in Matlab, go to the directory where you stored the script make_subcortical_ENIGMA_QC_webpage.sh and make sure it is executable:




chmod 777 make_subcortical_ENIGMA_QC_webpage.sh

Now to run the script, just give the script the full path to the directory where you stored the Matlab QC output files:



./make_subcortical_ENIGMA_QC_webpage.sh
/enigma/output/QC/

NB: If you have trouble running this script, it’s possible that you need to fix the line endings in the script before running. You can do this by running this command:




sed -i -e 's/\r$//' make_subcortical_ENIGMA_QC_webpage.sh

The script will create multiple webpages (e.g. ‘ENIGMA_Amyg_volume_QC.html’, ENIGMA_Subcortical_QC.html’) in the same folder as your QC output. To open one of these webpages in a browser of your choice in a Linux environment. For example:




firefox
/enigma/output/QC/ENIGMA_Subcortical_QC.html

If you want to check the segmentation on another computer, you can just copy over the whole QC-folder to your computer and open the webpage from there.


9. Exclude poor segmentations

Based on the histogram plots, outlier detection and the quality check on the webpage, you may have identified some poor segmentations. You can try to re-run “recon-all” on the subjects showing poor segmentations and go through step 4 to 6 again.


If this does not help, then you have to exclude these volumes from LandRvolumes.csv by marking them with an “x” and re-run the ENIGMA_plots.R on your updated LandRvolumes.csv (see step 5). Send us the new histograms and SummaryStats.txt once you are finished.


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