What are the resolution limits of medical imaging?

To all my physi­cists in the house, will it ever be pos­si­ble for a de­vice to scan the con­tents of a hu­man head at the molec­u­lar level (say, 5 x 5 x 5nm) while the sub­ject is still al­ive? I don’t have a physics back­ground, so if you could also just point me to the ma­te­ri­als I need to read to be able to an­swer the ques­tion, that would be won­der­ful as well.

The back­ground: I want to live to see the far fu­ture and so I’m re­search­ing the fea­si­bil­ity of al­ter­na­tives to cry­on­ics that’ll let peo­ple “back up” them­selves at reg­u­lar in­ter­vals rather than at the point of death. If this is even the­o­ret­i­cally pos­si­ble then I can di­rect my time and dona­tions to­wards med­i­cal imag­ing re­searchers. If not then I’ll con­tinue to sup­port cry­on­ics and plas­ti­na­tion re­search.

I’m look­ing for­ward to your re­sponses!