Spheres masker in nilearn


It may seem to be a trivial question, but I was wondering what kind of region exactly the sphere masker in Nilearn extracts. Is it really a sphere or an approximate cube, say with a 5mm-radius sphere in a 2-2-2mm resolution image? I would like to clarify this because I’m looking at lesioned data and I’d like to know how much a “sphere” is lesioned. (Or is there a way to find out about this?)

Thank you in advance!

It’s approximately a sphere: it include all the voxels that are at a distance smaller or equal than the radius.