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Hi all,

I have 35 lesion masks which I am analysing in terms of behavioural performance using NiiStat. I would like to use the 'Regress Lesion Volume' setting to, well, regress the lesion volume out of the analysis. However I get an error saying 'Problem regressing for lesion volume! Subject [ppt code].nii does not have the field ".lesion.dat"' for every participant. 

My question then is: how do I create this .lesion.dat file for my data? I can find the volume of the lesion masks using FSL - but how do I then associate it with the files used for NiiStat? Even just seeing the structure of a .lesion.dat file would be useful. I cannot find anything about it online!

TIA,
Lucy

Hi Lucy,

The lesion field of the .mat file contains two fields, 'hdr', and 'dat'.

'hdr' is a [1x1 struct] that contains multiple subfields and looks like this:
fname: '/media/research/POLAREXP/POLAR_Master_In/M10021/wsrLesion_M10021_POLAR.nii'
dim: [157 189 156]
dt: [2 0]
pinfo: [3×1 double]
mat: [4×4 double]
n: [1 1]
descrip: 'Warped'
private: [1×1 struct]

'dat' contains an array with voxel values, for example it may be

dat: [157×189×156 double] 

Within the three dimensional volume represented by this matrix, lesions are coded as 1, healthy tissue as 0.

Roger