assigning arbitrary values to surface parcels: method 2

The previous post describes a method for assigning arbitrary values to surface MMP parcels via GIfTI files. Tim Coalson kindly pointed me to another method, which I'll demonstrate here. Both methods work, but one or the other might be easier in particular situations.

In the previous post I used matlab and ran wb_command from the command prompt (on Windows, by opening a command window in the directory with wb_command.exe, then using full paths to the input and output files). Here, I use R, and call wb_command from within R using its system() function. You may need to adjust system for other operating systems, or simply replace it with print and copy-paste the full line to the command prompt.

 rm(list=ls());  # clear R's memory  
   
 setwd("d:/Workbench/workbench-v1.2.3/bin_windows64/"); # location of wb_command.exe, to call wb_command functions via system() within R  
   
 local.path <- "d:/temp/";  # local directory for reading and writing files  
 s1200.path <- "d:/Workbench/HCP_S1200_GroupAvg_v1/"; # HCP S1200 Group Average Data Release  
 template.fname <- "MMPtemplate.pscalar.nii";  # filename for the template we'll make  
   
 # make a template pscalar.nii from the MMP atlas  
 system(paste0("wb_command -cifti-parcellate ", s1200.path, "S1200.thickness_MSMAll.32k_fs_LR.dscalar.nii ",   
        s1200.path, "Q1-Q6_RelatedValidation210.CorticalAreas_dil_Final_Final_Areas_Group_Colors.32k_fs_LR.dlabel.nii COLUMN ",  
        local.path, template.fname));  
 if (!file.exists(paste0(local.path, template.fname))) { stop(paste0("missing: ", local.path, template.fname)); }  
   
 # you can make a text version of the template, which has 360 rows, but the values in each row aren't the parcel numbers.  
 # system(paste0("wb_command -cifti-convert -to-text ", local.path, template.fname, " ", local.path, "temp.txt"));  
   
 # the text file needs to be arranged with the 180 right hemisphere parcels in the first 180 rows (in order),   
 # then the 180 parcels for the left hemisphere.  
 # build a text file with the values to plot.   
 out.vec <- rep(0,360);  
 out.vec[c(1,10,15)] <- 1;  # right hemisphere parcels given value 1  
 out.vec[c(180+1,180+10,180+15)] <- 2;  # corresponding left hemisphere parcels given value 2  
 write.table(out.vec, paste0(local.path, "plotDemo.txt"), col.names=FALSE, row.names=FALSE);  
   
 # create a CIFTI from the text file for viewing in Workbench  
 system(paste0("wb_command -cifti-convert -from-text ", local.path, "plotDemo.txt ", local.path, template.fname, " ", local.path, "plotDemo.pscalar.nii"));  
 if (!file.exists(paste0(local.path, "plotDemo.pscalar.nii"))) { stop(paste("missing:", local.path, "plotDemo.pscalar.nii")); }  

And here is the resulting image, with parcels 1, 10, and 15 plotted in pink on the right hemisphere (1), and yellow on the left (2). Instructions for generating this view are below the jump.

assigning arbitrary values to surface parcels: method 1

This tutorial describes a method for plotting arbitrary per-parcel values (such as from an analysis) on the surface. For example, let's say I want to display MMP parcels 1, 10, and 15 (only) in red, or (more usefully) to assign continuous numbers to each parcel, and then display parcels with larger numbers in hotter colors.

This post describes a method using matlab and creating GIfTI files; see the next post for a method using R, wb_command functions, and creating a CIFTI file. Both methods work, but one or the other might be more convenient in particular situations.

I assume that you have a surface version of the parcellation to use as a template. For example, the MMP parcellation was released in CIFTI format as part of the HCP 1200 release, and the Gordon (2014) parcellation can be downloaded here.

I'll be using the MMP in this example; if you want to follow along, download a copy of the S1200 Group Average Data Release; I put mine at d:/Workbench/HCP_S1200_GroupAvg_v1/. The MMP template is named Q1-Q6_RelatedValidation210.CorticalAreas_dil_Final_Final_Areas_Group_Colors.32k_fs_LR.dlabel.nii. (If you're not sure how to use the files in the S1200 release, try this tutorial to get started.)

I have the values to assign to the parcels in a text file with 180 lines (one line for each MMP parcel). For this tutorial, let's do the simple example of assigning a color to parcels 1, 10, and 15 only. An easy way to do this is to make a text file with 1s on these rows and 0s on all the other rows. I prefer R, but since the GIfTI library is in matlab, here's matlab code for making the little text file:

 out = repelem(0, 180);  
 out(1) = 1;  
 out(10) = 1;  
 out(15) = 1;  
 csvwrite('D:\temp\parcelNums.csv', out')  

The MMP template is in CIFTI format, but we can extract GIfTI files for each hemisphere using wb_command cifti-separate:

 wb_command -cifti-separate D:\Workbench\HCP_S1200_GroupAvg_v1\Q1-Q6_RelatedValidation210.CorticalAreas_dil_Final_Final_Areas_Group_Colors.32k_fs_LR.dlabel.nii COLUMN -metric CORTEX_LEFT D:\temp\mmpL.func.gii  
 wb_command -cifti-separate D:\Workbench\HCP_S1200_GroupAvg_v1\Q1-Q6_RelatedValidation210.CorticalAreas_dil_Final_Final_Areas_Group_Colors.32k_fs_LR.dlabel.nii COLUMN -metric CORTEX_RIGHT D:\temp\mmpR.func.gii  

This matlab code reads in the text file with the new parcel values and the GIfTI templates, then writes GIfTI files with the new parcel values substituted for the parcel label numbers:

 addpath 'C:/Program Files/MATLAB/gifti-1.6';  % so matlab can find the library  
 mmpL = gifti('D:\temp\mmpL.func.gii');  % load the left side gifti MMP atlas  
 mmpR = gifti('D:\temp\mmpR.func.gii');  % and the right side MMP atlas  
 newvals = csvread('D:\temp\parcelNums.csv');  % 180 integers; new value for each parcel  
 Lout = mmpL;  % output gifti  
 Lout.cdata(:,1) = repelem(0, size(mmpL.cdata,1));  % replace the values with zeros  
 Rout = mmpR;  
 Rout.cdata(:,1) = repelem(0, size(mmpR.cdata,1));   
 for i=1:180  % i = 1;  
   inds = find(mmpR.cdata == i);  % find vertices for parcel i  
   Rout.cdata(inds,1) = newvals(i);  % put the new value in for this parcel's vertices  
   inds = find(mmpL.cdata == (i+180)); % in MMP, left hemisphere vertices are 181:360  
   Lout.cdata(inds,1) = newvals(i);    
 end  
 save(Lout,'D:\temp\plotL.func.gii','Base64Binary');  % save the gifti  
 save(Rout,'D:\temp\plotR.func.gii','Base64Binary');  

You can now to plot these GIfTIs in Workbench (see this post if you're not sure how); I plotted them on the S1200 Group Average (MNI) anatomy:

I clicked to put a marker in the left visual parcel. The value at this vertex is 1, as assigned (green lines). I loaded in the MMP atlas as well (blue lines), so it tells me (correctly!) that the marker is in the L_V1_ROI.

UPDATE 9 November 2018: I added making this same gifti on the fly and plotting in a knitr to my gifti plotting demo.

not all MB4 fMRI scans are free of gradients and banding

I was encouraged by the images in the previous post: it looked like the gradient and banding ("washing out") artifacts were not visible in the MB4 people. I need to revise that a bit: I do have bands and gradients in at least some MB4 people, though to a much lesser degree than in our MB8 datasets. How much this affects our task analyses is still to be determined.

On the left is the same MB4 person and run from the previous post (27 September 2017), voxelwise standard deviation over time of a task fMRI run, after going through the HCP minimal preprocessing pipelines. I was glad to see that the vessels were brightest (as they should be), though concerned about the frontal dropout. The person on the right is another person scanned at MB4 (doing the same task; same encoding, scanner, etc.); same preprocessing and color scaling for both.

The vessels clearly don't stand out as much in the person on the right. It's hard to tell in the above image, but there's a gradient in the standard deviation and tSNR images, with better signal on the edges than in the center of the brain. Below is another run from the person on the right, tSNR calculated on the images ready to go into afni for GLM calculation (so through the HCP minimal preprocessing pipelines, plus smoothing and voxelwise normalizing). This tSNR image is shown at six different color scalings; it's easier to see interactively (download the NIfTI here), but hopefully it's clear that the darker colors (lower tSNR) spreads from the center of the brain to the edges, rather than uniformly.

Here is the same person and run again, with the standard deviation (first two) and tSNR (right pane) of the raw (no preprocessing, first and lower) and minimally preprocessed (right two) images. I marked a banding distortion with green lines, as well as the frontal dropout. The banding is perfectly horizontal in the raw image, at 1/4 of the way up the image (see larger image), which makes sense, since this is an MB4 acquisition. I included the larger view of this raw image since all three banding artifacts are somewhat visible; in our dataset the inferior band is generally the most prominent.

The banding and gradient artifacts are certainly less visually prominent in our MB4 than our MB8 images, but they are present in some MB4 people. I haven't systematically evaluated (and probably won't be able to soon) all of our participants, so don't have a sense of how often this occurs, or how much it impacts detection of task BOLD (which is of course the key question).

Below the jump: movement regressors for the two runs in the top image; the person with the banding and gradients had very low motion; less than the person from the September post.