I'll answer your question first before questioning the line of thinking you're on...
Yes it is possible, although probably not in the way you are imagining. It would be surprising to me if a mechanism was found for remote scanning a brain at that resolution, not to mention the practical difficulties of recording the image. But as a proof of concept(ual analysis) I'll point you at Freitas' work to show that it would be possible in principle to in-situ destructively scan and then recreate neuron cells, a small number of cells at a time.
However I hope that answer shows a third possibility to consider beyond imaging and cryonics. Perhaps the most promising path through the singularity is intelligence augmentation / neural upgrades. Scan the neuron just as described above, but rather than re-create it with biology, use a machine neuron instead. Once the process is finished and biology left firmly behind, you can overclock the brain and/or add redundancy.
The trick to living forever should be strengthening the body, not regular backups in my not-so-humble opinion. Your backup is not you, just someone who thinks it is you. If you want to live forever, then focus on yourself.
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!