Imax Corp., the maker of giant- screen movie-projection systems, rose to a six-month high today after saying box-office revenue increased 45 percent this year through Feb. 12 from the same period in 2011. the Mississauga, Ontario-based company said worldwide receipts at Imax cinemas totaled $55 million. About half of the sales came from the Tom Cruise movie “Mission: Impossible - Ghost Protocol,’’ which has grossed $70 million at Imax theaters since its release in December. Revenue “is well ahead of our expectations, given that we are forecasting $90 million in box office for the quarter,’’ Aravinda Galappatthige, an analyst at Canaccord Financial Corp., wrote in a note to clients.