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