Best way to combine independant components in one .nii file


I have successfully performed an independent component analysis (ICA) on fMRI data using the NeuroMark toolbox for MATLAB. However, I now have 53 independent components (IC) each in their own .nii file that I wish to combine into 7 brain network files (e.g., default mode network). I know which components I need to combine together but I am not sure what the best method is.

At the moment, I have used SPM12 and the ImCalc command to combine ICs into brain networks (I just added them all together i1+i2+i3…iK). However, this feels crass and I’m not sure if I’m doing the right thing.

I was hoping that someone might be able to point me in the right direction or give me the validation I require.

Thanks in advance!