fMRI is an extremely coarse-grained scan and is unlikely to substantially assist in reconstruction. fMRI works by detecting change in blood flow indicating that specific areas of the brain are using more energy to do the task in question. In practice fMRI is so noisy that in order to get good data one generally needs to average a large number of scans of different people together. Otherwise the noise almost completely overrides any data. The smallest region which an fMRI can scan (a voxel) generally has at least millions of distinct neurons. The smallest temporal resolution levels for an fMRI are around a half a second which is a massive length of time for purposes of thought behavior. Overall, the data that this gives for reconstruction is extremely marginal when it is limited to only a handful of scans.
Paul Christiano recently suggested that we can use neuroimaging to form a complete mathematical characterization of a human brain, which a sufficiently powerful superintelligence would be able to reconstruct into a working mind, and the neuroimaging part is already possible today, or close to being possible.
Paul was using this idea as part of an FAI design proposal, but I'm highlighting it here since it seems to have independent value as an alternative or supplement to cryonics. That is, instead of (or in addition to) trying to get your body to be frozen and then preserved in liquid nitrogen after you die, you periodically take neuroimaging scans of your brain and save them to multiple backup locations (1010 bits is only about 1 gigabyte), in the hope that a friendly AI or posthuman will eventually use the scans to reconstruct your mind.
Are there any neuroimaging experts around who can tell us how feasible this really is, and how much such a scan might cost, now or in the near future?
ETA: Given the presence of thermal noise and the fact that a set of neuroimaging data may contain redundant or irrelevant information, 1010 bits ought to be regarded as just a rough lower bound on how much data needs to be collected and stored. Thanks to commenters who pointed this out.