We really need a new trailer or a demonstration or both, we've all clearly gone completely mad.
I think the most likely scenario is that Either:
A. He based the Doctor character off the portrait of Doctor Madnar from MG1, and in doing research on Phantom Pain and neurological disorders, discovered that guy. The 3D modelers needed a reference, although this goes against the idea that Code Talker was the only one they had to create a face for.
B. Paid that guy to use his likeness, or they found someone extremely similar to him. Which isn't uncommon in the world, some people look very similar despite being in completely different parts of the world.
EDIT: I remember Kojima talking about having Doctors around to make sure every procedure or medical issue in the game that happened was accurate, it's entirely possible they had this guy on set and also scanned his likeness.