The idea is for Watson to digest huge quantities of medical information and deliver useful real-time information to physicians, perhaps eventually in response to voice questions. If successful, the system could help medical experts diagnose conditions or create a treatment plan. But it could prove a far more challenging trick than winning a game show. “The medical domain doubles in knowledge every few years,” said Janet Dillione, executive vice president and general manager of the health-care division of Nuance. “No human brain can possibly retain all the information that’s out there.”