Hello all,

I have a set of ROIs, in MNI-space and nifti format - basically binary boxes 
where '1' indicates the ROI. I'd like to use these masks to process some of the 
group-averaged rfMRI data, extracting activation time series and computing 
cross-correlations and so on. But I'm having trouble projecting either 
data-type onto the other.

HCP Data:
When I read the file:  
<HCP_Q1-Q6_R468_rfMRI_groupPCA_d4500_Eigenmaps.dtseries.nii> into Matlab (using 
cifitopen), I get a 2D matrix which is ~92,000x4500 cells. As I understand (but 
please correct me I'm wrong), this matrix has 'grayordinates' as rows and time 
as columns.

ROIs:
My regions are in boxes, in MNI space of size [91,109,91]. These regions have 
been used as seeds for other analyses that don't involve HCP data, so even 
though they may be 'worse' than the HCP data, in the sense that they don't 
represent surface features explicitly, I'm not keen to dump them in favour of a 
more natively surface-including parcellation.

What I need to do, is work out what grayordinates go with what ROI (or vice 
versa). I either need to convert the HCP data into 4D (brain-box + time), or 
convert my brain-box ROIs into grayordinate vectors. I've searched the forum 
for answers here, and tried to convert the HCP files to nifti, but even 
allowing for the rather odd 'wrapping' of the voxels into 3 dimensions, I'm 
finding I can't quite work the conversion out.

Can anyone help?

Many thanks,

Tom

Thomas Hope

Wellcome Trust Centre for Neuroimaging
Institute of Neurology
University College London
12 Queen Square
LONDON, WC1N 3BG
E-mail: [email protected]<mailto:[email protected]>
Website: www.ucl.ac.uk/ploras<http://www.ucl.ac.uk/ploras>

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