I am seeing some sort of artefact on an acquisition that I can’t seem to resolve. It clearly appears when a multiband factor of 3 is used (although it is there but not very noticeable when a factor of 2 is used, and no artefact when a lower parallel imaging factor is used). I have tried different head coils but the result is always the same.
It is very clear on the noise map and also appears when averaging the shell (b=1000).
I have tried different dwidenoise options and different mtnormalise options but the result is always the same. Does anyone have any insight as to what could be causing this artefact?