I can't figure out how they would collect depth information from the resulting photon pattern.
I believe reflected photons are much more useful, by measuring how long in between signal and response you can get flight time which tells you depth. Of course I have no idea if infrared light reflects on anything in the brain.
I suspect they do a radon transform of the paths to determine the infrared transmissibility value. Similar to how CT scans are constructed from 1000's of micro x-rays.
I believe reflected photons are much more useful, by measuring how long in between signal and response you can get flight time which tells you depth. Of course I have no idea if infrared light reflects on anything in the brain.