# Processing BOLD Data¶

Scenario: You’ve collected some BOLD data and you’re interested in functional connectivity.

This example will walk you through the typical functional connectivity pipeline in the 4dfp suite - generic BOLD pre-processing, fcMRI pre-processing, and seed-based correlation.

## Preparing DICOM data¶

Once you have DICOM data downloaded and transferred to your project directory, you will start by sorting your DICOM data. How to run this will depend on the DICOM directory structure. In the following examples we’ll use NEWT002_s1 for an example MR session, and assume that the DICOM data is under the SCANS/ directory:

$cd /path/to/project$ cd NEWT002_s1
$ls SCANS$ ls SCANS


If SCANS/ contains a flat list of DICOMs, you will use dcm_sort:

$dcm_sort SCANS  If SCANS/ contains numbered directories, you will use pseudo_dcm_sort.csh: $ pseudo_dcm_sort.csh SCANS


This will create study folders for each of the scans downloaded from CNDA, as well as a SCANS.studies.txt file that contains the mapping of study number to series description

$ls SCANS study10 study21 study25 study29 SCANS.studies.txt study14 study23 study27$ cat SCANS.studies.txt
10   tfl3d1_16ns    ABCD_T1w_MPR_vNav                                   176
14   spc_314ns      ABCD_T2w_SPC_vNav                                   176
21   epse2d1_90     SpinEchoFieldMap_AP_2p4mm_64sl                        3
23   epse2d1_90     SpinEchoFieldMap_PA_2p4mm_64sl                        3
25   epfid2d1_90    fMRI_AP_2p4mm_MB4_tr1230_te33                       250
27   epfid2d1_90    fMRI_AP_2p4mm_MB4_tr1230_te33                       250
29   epfid2d1_90    fMRI_AP_2p4mm_MB4_tr1230_te33                       250


## Generic BOLD pre-processing¶

Now that we have our DICOM data sorted, we are ready to begin BOLD pre-processing. In the 4dfp suite, this is done via cross_bold_pp_161012.csh.

In order to run cross bold, we first need to set up some input files. If you look at the usage for cross bold, it has one required argument and one optional. As mentioned in Params/Instructions files, the convention is to use both, putting subject-specific parameters in the params file and study-specific parametes in the instructions file. When creating these files, you’ll want to have the list of variables handy. These can be found in the cross_bold_pp_161012.csh docs.

The instructions file contains customizations for the processing pipeline in addition to information about the scan sequence. To obtain the scan parameters, you can use dcm_dump_file. Since we are looking to process BOLD data, be sure to grab a DICOM from one of the BOLD study folders:

$dcm_dump_file -t study25/NEWT002_s1.MR.head_Hershey.25.173.20161130.131330.19u1n9g.dcm  This will print out tags from the DICOM header, including echo time and repetition time. An excerpt is shown here: 0018 0023 2 // ACQ MR Acquisition Type //2D 0018 0024 12 // ACQ Sequence Name//epfid2d1_90 0018 0025 2 // ACQ Angio Flag//N 0018 0050 16 // ACQ Slice Thickness//2.4000000953674 0018 0080 4 // ACQ Repetition Time//1230 0018 0081 2 // ACQ Echo Time//33 0018 0083 2 // ACQ Number of Averages//1 0018 0084 10 // ACQ Imaging Frequency//123.246868 0018 0085 2 // ACQ Imaged Nucleus//1H 0018 0086 2 // ACQ Echo Number//1 0018 0087 2 // ACQ Magnetic Field Strength//3 0018 0088 16 // ACQ Spacing Between Slices//2.4000000349655 0018 0089 2 //ACQ Number of Phase Encoding Steps//90  Attention Be sure to pay attention to units. The DICOM header stores times in milliseconds and some cross_bold variables are in seconds. Some variables don’t match a specific tag in the DICOM header and need to be calculated. • nx and ny You will need to grab the ‘Img Rows’ (0028,0010), ‘Img Columns’ (0028,0011) and ‘NumberOfImagesInMosiac’ (0019,100a) tags. $ dcm_dump_file -t study25/NEWT002_s1.MR.head_Hershey.25.173.20161130.131330.19u1n9g.dcm | grep '0028 0010' | awk '{print $8}' 720 # imgRows$ dcm_dump_file -t study25/NEWT002_s1.MR.head_Hershey.25.173.20161130.131330.19u1n9g.dcm | grep '0028 0011' | awk '{print $8}' 720 # imgColumns$ dcm_dump_file -t study25/NEWT002_s1.MR.head_Hershey.25.173.20161130.131330.19u1n9g.dcm | grep '0019 100a' | awk '{print $7}' 64 # numImgs  With these numbers, you can calculate nx and ny with the following formulas: $nx = imgRows / ceil(sqrt(numImgs))$ $ny = imgColumns / ceil(sqrt(numImgs))$ • dwell You will need to grab the ‘BandwidthPerPixelPhaseEncode’ (0019,1028) tag and nx (or ny) calculated above. $ strings study25/NEWT002_s1.MR.head_Hershey.25.173.20161130.131330.19u1n9g.dcm | grep BandwidthPer -A 1
BandwidthPerPixelPhaseEncode
18.83200000


You can then calculate dwell using the following formula, using nx for ‘MatrixPhase’:

$dwell = imgRows / (BandwidthPerPixelPhaseEncode * MatrixPhase)$

Tip

For Siemens 3T fMRI, dwell times should be in the range 0.4 - 0.6 ms.

• delta

If you are using a gradient-echo field map (which the current example does not), you will need to calculate delta. To do so, you will need to grab the values of the ‘Echo Time’ (0018,0081) field from your maginitude field map image.

% dcm_dump_file -t /path/to/magnitude/fm/image | grep "0018 0081"
0018 0081        4 //                  ACQ Echo Time//7.38
0018 0081        4 //                  ACQ Echo Time//4.92


To get delta, compute the difference of the echo time values.

Tip

For Siemens GRE field map sequences, delta is typically 2.46 ms.

• seqstr

The slice acquisition sequence in multiband fMRI does not follow the old “Siemens_interleave” rule. In this case, the slice sequence depends on the number of slices and the multiband factor to ensure there is no adjacent slice excitation. Siemens now provides an exact listing of slice times in each fMRI DICOM header in the ‘MosaicRefAcqTimes’ (0019,1029) tag.

In order to correct slice timing for multiband sequences, the slice sequence needs to be identified and passed to frame_align_4dfp via the seqstr parameter.

AFNI has a function dicom_hdr that you can use to extract the slice timing from the header:

$dicom_hdr -slice_times SCANS/25/DICOM/NEWT002_s1.MR.head_Hershey.25.1.20161130.131330.adfigp.dcm -- Siemens timing (64 entries): 0.0 530.0 1057.5 377.5 907.5 227.5 755.0 75.0 605.0 1135.0 452.5 982.5 302.5 832.5 150.0 680.0 0.0 530.0 1057.5 377.5 907.5 227.5 755.0 75.0 605.0 1135.0 452.5 982.5 302.5 832.5 150.0 680.0 0.0 530.0 1057.5 377.5 907.5 227.5 755.0 75.0 605.0 1135.0 452.5 982.5 302.5 832.5 150.0 680.0 0.0 530.0 1057.5 377.5 907.5 227.5 755.0 75.0 605.0 1135.0 452.5 982.5 302.5 832.5 150.0 680.0  Based on the timing output, we can see that there are 64 slices and a multiband factor of 4. This gives us 16 slices per band. With this information, we can now calculate the slice order for a single band: # replace <num_slice_per_band> before use$ dicom_hdr -slice_times SCANS/25/DICOM/NEWT002_s1.MR.head_Hershey.25.1.20161130.131330.adfigp.dcm | cut -d ":" -f2 | tr " " "\n" | tail -n <num_slice_per_band> | gawk '{print NR, $1}' | sort -n -k 2,2 | gawk '{printf("%d,",$1);}'
1,8,15,6,13,4,11,2,9,16,7,14,5,12,3,10,


Alternatively, you can run strings on the header:

$strings SCANS/25/DICOM/NEWT002_s1.MR.head_Hershey.25.1.20161130.131330.adfigp.dcm | grep 'MosaicRefAcqTimes' -A 66 MosaicRefAcqTimes sGRADSPEC.asGPAData[0].sEddyCompensationX.aflT 0.00000000 530.00000000 1057.50000000 377.50000000 907.50000000 227.50000001 755.00000000 75.00000001 605.00000001 1135.00000001 452.50000001 982.50000001 302.49999999 832.50000002 149.99999999 679.99999999 ...  You can then copy the slice timing of one band into a file (i.e. temp.dat), and run the following: $ cat temp.dat | gawk '{print NR, $1}' | sort -n -k 2,2 | gawk '{printf("%d,",$1);}'
1,8,15,6,13,4,11,2,9,16,7,14,5,12,3,10,


Now that we know how to source information for the instructions file, we’ll go ahead and put one together. In this example, we will assume nothing besides dcm_sort has already been run on the data and we won’t skip any processing steps.

Since we’ve chosen to set up our instruction file to define study-level params, we’ll store it in the project directory.

$cd /path/to/project$ gedit NEWT_study.params

NEWT_study.params
set inpath = /path/to/project/${patid} set target =$REFDIR/TRIO_KY_NDC
set go = 1
set sorted = 1
set economy = 0
set epi2atl = 1
set normode = 0

set nx = 90
set ny = 90

set skip = 0

set FDthresh = 0.2
set FDtype = 1
set anat_aveb = 10 # use 10mm preblur (voxel size < 3mm)

set TR_vol = 1.23
set TR_slc = 0 # use default (TR_vol/nslices)
set epidir = 0
set MBfac = 4
set seqstr = 1,8,15,6,13,4,11,2,9,16,7,14,5,12,3,10 # non-standard interleaving
set lomotil = 2 # filter FD in phase-encoding direction

set TE_vol = 33
set dwell = .59
set ped = y-
set rsam_cmnd = one_step_resample.csh


Our params file, on the other hand, needs to be specified per subject as it contains a mapping to a subject’s specific scan numbers. The file outputted by dcm_sort, SCANS.studies.txt, is a good reference to have handy when creating a subject’s params file.

$cd NEWT002_s1$ cat SCANS.studies.txt
$gedit NEWT002_s1.params  NEWT002_s1.params set patid = NEWT002_s1 set mprs = ( 10 ) set tse = ( 14 ) set irun = ( 1 2 3 ) set fstd = ( 25 27 29 ) set sefm = ( 21 23 )  Since our subjects have a T2 image and spin-echo field maps, we specified tse and sefm, respectively. However, which parameters are specified here will depend on the data you have available. For EPI to atlas registration, you should specify either tse, pdt2, or neither. For field map correction, you should specify either sefm or gre. Now, we run cross bold: $ cross_bold_pp_161012.csh NEWT002_s1.params ../NEWT_study.params


Afterwards, you’ll have the following subject anf bold directory structures:

$ls atlas NEWT002_s1_fmri_unwarp_170616_se.log SCANS.studies.txt study23 bold1 NEWT002_s1_one_step_resample.log sefm study25 bold2 NEWT002_s1.params study10 study27 bold3 NEWT002_s1_xr3d.lst study14 study29 movement SCANS study21 unwarp$ ls bold1
NEWT002_s1_b1.4dfp.hdr                         NEWT002_s1_b1_faln_dbnd_r3d_avg_norm.4dfp.ifh
NEWT002_s1_b1.4dfp.ifh                         NEWT002_s1_b1_faln_dbnd_r3d_avg_norm.4dfp.img
NEWT002_s1_b1.4dfp.img                         NEWT002_s1_b1_faln_dbnd_r3d_avg_norm.4dfp.img.rec
NEWT002_s1_b1.4dfp.img.rec                     NEWT002_s1_b1_faln_dbnd_xr3d.mat
NEWT002_s1_b1_faln.4dfp.ifh                    NEWT002_s1_b1_faln_dbnd_xr3d_norm.4dfp.hdr
NEWT002_s1_b1_faln.4dfp.img                    NEWT002_s1_b1_faln_dbnd_xr3d_norm.4dfp.ifh
NEWT002_s1_b1_faln.4dfp.img.rec                NEWT002_s1_b1_faln_dbnd_xr3d_norm.4dfp.img
NEWT002_s1_b1_faln_dbnd.4dfp.hdr               NEWT002_s1_b1_faln_dbnd_xr3d_norm.4dfp.img.rec
NEWT002_s1_b1_faln_dbnd.4dfp.ifh               NEWT002_s1_b1_faln_dbnd_xr3d_norm.ddat
NEWT002_s1_b1_faln_dbnd.4dfp.img               NEWT002_s1_b1_faln_dbnd_xr3d_norm_dsd0.4dfp.hdr
NEWT002_s1_b1_faln_dbnd.4dfp.img.rec           NEWT002_s1_b1_faln_dbnd_xr3d_norm_dsd0.4dfp.ifh
NEWT002_s1_b1_faln_dbnd.dat                    NEWT002_s1_b1_faln_dbnd_xr3d_norm_dsd0.4dfp.img
NEWT002_s1_b1_faln_dbnd_r3d_avg.4dfp.ifh       NEWT002_s1_b1_faln_dbnd_xr3d_norm_dsd0.4dfp.img.rec
NEWT002_s1_b1_faln_dbnd_r3d_avg.4dfp.img       NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl.4dfp.hdr
NEWT002_s1_b1_faln_dbnd_r3d_avg.4dfp.img.rec   NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl.4dfp.ifh
NEWT002_s1_b1_faln_dbnd_r3d_avg.hist           NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl.4dfp.img
NEWT002_s1_b1_faln_dbnd_r3d_avg_norm.4dfp.hdr  NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl.4dfp.img.rec


Tip

A lot of files get generated per run and the folders can get cluttered. If you don’t intend to use the intermediate files, you should set the economy flag to 5 to remove some of them.

## fcMRI pre-processing¶

After running bold pre-processing, you’ll want to run functional connectivity specific processing. However, before we can run fcMRI_preproc_161012.csh, there is a prerequiste step of running Freesurfer to generate masks for the subjects which will be used to calculate the nuisance regressors.

If you don’t already have a SUBJECTS_DIR for your project, go ahead and make one:

$mkdir /path/to/project/freesurfer$ setenv SUBJECTS_DIR /path/to/project/freesurfer


Next we’ll need to get a DICOM from our T1w image to use as our input file for Freesurfer:

$cd /path/to/project/NEWT002_s1$ cat SCANS.studies.txt | grep T1w
10   tfl3d1_16ns    ABCD_T1w_MPR_vNav                                   176

$ls SCANS/10/DICOM/*10.1.* ../SCANS/10/DICOM/NEWT002_s1.MR.head_Hershey.10.1.20161130.131330.1ldrvyd.dcm  With this information at hand, we can now launch the Freesurfer job $ at now
at> setenv SUBJECTS_DIR /path/to/project/freesurfer
at> recon-all -all -s NEWT002_s1 -i /path/to/project/NEWT002_s1/SCANS/10/DICOM/NEWT002_s1.MR.head_Hershey.10.1.20161130.131330.1ldrvyd.dcm
at> <ctrl-d>


Same as before, fcMRI_preproc accepts a params and instructions file. If you look at the variable specification for fcMRI_preproc_161012.csh, you’ll see that it shares some variables with cross_bold_pp_161012.csh - we’ll leave those the same and simply add in the fcMRI-specific ones:

$gedit /path/to/project/NEWT_study.params  NEWT_study.params # BOLD variables set inpath = /path/to/project/${patid}
set target = $REFDIR/TRIO_KY_NDC set go = 1 set sorted = 1 set economy = 0 set epi2atl = 1 set normode = 0 set nx = 90 set ny = 90 set skip = 0 set FDthresh = 0.2 set FDtype = 1 set anat_aveb = 10 # use 10mm preblur (voxel size < 3mm) set TR_vol = 1.23 set TR_slc = 0 # use default (TR_vol/nslices) set epidir = 0 set MBfac = 4 set seqstr = 1,8,15,6,13,4,11,2,9,16,7,14,5,12,3,10 # non-standard interleaving set lomotil = 2 # filter FD in phase-encoding direction set TE_vol = 33 set dwell = .59 set ped = y- set rsam_cmnd = one_step_resample.csh # fcMRI pre-processing set srcdir =$cwd
set FSdir = /path/to/project/freesurfer/${patid} set fcbolds = (${irun} )
set CSF_lcube = 3
set CSF_sd1t = 25
set CSF_svdt = .2
set WM_lcube = 5
set WM_svdt = .15
set bpss_params = ( -bh .1 -oh 2 )
set blur = .73542


No changes are needed to the session params file, so now we can run the script:

$fcMRI_preproc_161012.csh NEWT002_s1.params ../NEWT_study.params  Afterwards, we will have the following new files: # per run % ls -tr bold1/*atl_* NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_dsd0.4dfp.img NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_dsd0.4dfp.ifh NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_dsd0.4dfp.hdr NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_dsd0.4dfp.img.rec NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_uout.4dfp.img NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_uout.4dfp.ifh NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_uout.4dfp.hdr NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_uout.4dfp.img.rec NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss.4dfp.img NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss.4dfp.ifh NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss.4dfp.hdr NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss.4dfp.img.rec NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss_resid.4dfp.img NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss_resid.4dfp.ifh NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss_resid.4dfp.hdr NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss_resid.4dfp.img.rec NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss_resid_g7.4dfp.img NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss_resid_g7.4dfp.ifh NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss_resid_g7.4dfp.hdr NEWT002_s1_b1_faln_dbnd_xr3d_uwrp_atl_bpss_resid_g7.4dfp.img.rec  ## Seed-based correlation¶ After preprocessing, we can now generate a seed-to-seed correlation matrix for our subject. If you look at the docs for seed_correl_161012.csh, you’ll see that we only need to add which regions to analyze (ROIs) to our instructions file. Here we’ll use a prescribed list file of ROIs as our input. NEWT_study.params # BOLD variables set inpath = /path/to/project/${patid}
set target = $REFDIR/TRIO_KY_NDC set go = 1 set sorted = 1 set economy = 0 set epi2atl = 1 set normode = 0 set nx = 90 set ny = 90 set skip = 0 set FDthresh = 0.2 set FDtype = 1 set anat_aveb = 10 # use 10mm preblur (voxel size < 3mm) set TR_vol = 1.23 set TR_slc = 0 # use default (TR_vol/nslices) set epidir = 0 set MBfac = 4 set seqstr = 1,8,15,6,13,4,11,2,9,16,7,14,5,12,3,10 # non-standard interleaving set lomotil = 2 # filter FD in phase-encoding direction set TE_vol = 33 set dwell = .59 set ped = y- set rsam_cmnd = one_step_resample.csh # fcMRI pre-processing set srcdir =$cwd
set FSdir = /path/to/project/freesurfer/${patid} set fcbolds = (${irun} )
set CSF_lcube = 3
set CSF_sd1t = 25
set CSF_svdt = .2
set WM_lcube = 5
set WM_svdt = .15
set bpss_params = ( -bh .1 -oh 2 )
set blur = .73542

# seed_corrl ROIs
set ROIdir = ${REFDIR}/CanonicalROIsNP705 set ROIlistfile = CanonicalROIsNP705.lst  Now we can go ahead and run it: $ seed_correl_161012.csh NEWT002_s1.params ../NEWT_study.params


This produces a correlation matrix, ${FCdir}/${patid}_seed_regressors_CCR.dat.

You can display the matrix by importing the data into matlab and using the imagesc function.