During body-scan ('sweeping') meditation, what does brain-imaging (e.g. fMRI) look like?
Disclaimer: I'm not a brain expert or brain-imaging expert or neuroscientist.

In this YouTube video at around 15 minutes, you can find Dr. Zindel Segal presenting fMRI scans on depression patients practising mindfulness-based meditation (most probably Mindfulness Based Cognitive Therapy or MBCT). But I'm not sure if it includes body scanning. MBCT was based on Kabat-Zinn's Mindfulness Based Stress Reduction (MBSR).

There are more fMRI scans shown in this YouTube video by neuroscientists presenting at the 10th Global Conference on Buddhism in Toronto this year. Again, I'm not sure if it includes body scanning.

Probably, you can contact the four neuroscientists in these videos plus Kabat-Zinn, to seek the precise answer to your question. Who knows? Maybe you might give them a new idea for a study, if it has not been done already.

Also see this answer.