I would like to see such a scan done. But I forsee a few problems. One is actually finding
someone who embodies the very high standards of purity that the Buddha extols as present in those who have 'laid down the burden' ("passionless...pride destroyed...pure...sorrowless...(etc). Another is that, (if there are such beings present on the earth today) it is perhaps more likely that arahants would be found in the Monastic orders (but as stated previously, they would not disclose this to lay people (scientists) anyway). Thirdly
Buddha wrote: "And how is the monk a Noble One who has taken down the flag, put down the burden, become unfettered? He has abandoned the conceit of self, has cut it off at the root, removed it from is soil like a palmyra tree, brought it to utter extinction, incapable of arising again. Thus is the monk a Noble One who has taken down the flag, put down the burden, become unfettered.
"When a monk's mind is thus freed, O monks, neither the gods with Indra, nor the gods with Brahma, nor the gods with the Lord of Creatures (Pajaapati), when searching will find on what the consciousness of one thus gone (tathaagata) is based. Why is that? One who has thus gone is no longer traceable here and now, so I say.
-(from the Alagaddupama Sutta (MN 22)
If neither the gods nor Brahma can find 'on what the consciousness of one thus gone (in this case, an arahant) is based' due to the arahant being 'no longer traceable here and now', how are mundane scientists going to do it?
So IMHO, considering all of the above, we won't get any conclusive evidence of what an arahant's brain looks like as compared with a non-arahants brain very easily. On a positive note, I'm sure that practitioners such as Ingram and Folk would be happy enough to submit to such a scan, and it would indeed be interesting to see how the results compare with other (advanced) practitioners who have had them done. I just don't see how any claims to arahantship can be either proved, or disproved, upon that basis.