Electrical coupling of rotating members of medical imaging devices

An anode (16), (16') and a cathode (14), (14') are mounted in an evacuated envelope (12), (12') of an x-ray tube (10). One of the anode and cathode is rotatably mounted on bearings (20), (20') relative to the evacuated envelope. In the embodiment in which the anode is rotatably mounted relative to the evacuated housing, a rolling ring assembly (40) provides a current path from the anode through the evacuated housing to ground without the current path passing through the bearing (20). In this manner, pitting and other damage to the bearing due to arcing is eliminated. In the embodiment in which the cathode is rotatably mounted relative to the evacuated envelope, the anode and envelope rotate as the cathode is held stationary (58, 60). A plurality of rolling ring assemblies (40'1, 40'2, . . . ) provide electrical communication between electrical control circuitry disposed outside the rotating housing and the cathode assembly (14'). The electrical communication includes providing current to filaments of cathodes (30'1, 30'2) of the cathode assembly.