In one embodiment, a system for thermal management in a CT device comprises first and second thermal management zones, each comprising an x-ray detector, at least one variable speed fan proximate to the x-ray detector, an air temperature sensor positioned to measure an air temperature of the intake air to the variable speed fan, a rail heater in thermal contact with the x-ray detector, a rail temperature sensor in thermal contact with the rail heater to measure a rail temperature, and a controller that controls the variable speed fan as a function of at least the air temperature and the rail heater as a function of the rail temperature to maintain a temperature of the x-ray detector within a predetermined range.