Abstract: A CT scanner includes a stationary gantry (C) having an examination region (12) centrally therein. A rotating frame or gantry (C) which is mounted for rotation about the examination region carries an x-ray tube assembly (B), a liquid-to-liquid heat exchanger (34), and a liquid-to-air heat exchanger (48) around a peripheral edge thereof. A first closed loop (30) carries a first cooling fluid, particularly oil, between a housing (22) which surrounds an x-ray tube (68) and the liquid-to-liquid heat exchanger to remove heat from the x-ray tube. A second closed loop (40) conveys a second cooling fluid, particularly water, between the liquid-to-liquid heat exchanger and the peripheral liquid-to-air heat exchanger. The second closed loop includes a reservoir (44) for storing a substantial volume of water such that a significant portion of the heat generated during an x-ray examination can be stored by the water in the reservoir.