Hi @Nayo,
Looks to me like this might be a similar problem to what’s going on in this parallel discussion: One of the mask images derived during the response function estimation algorithm is empty, which is resulting in a call to mrstats not returning any result. In your particular case this subsequently results in a malformed call to mrcalc (See the double space between ‘safe_sdm.mif’ and ‘-subtract’? There’s supposed to be a number in the middle), but it’s the preceding empty mask that’s the fundamental problem. My guess is that there’s something particularly unusual about your data that’s breaking one of the assumptions within the dwi2response dhollander algorithm; so the best bet would be to make an example image available so that the problem can be reproduced at our end.
Cheers
Rob