What prevents x-rays from escaping the tubehead?

The correct answer is leaded-glass housing, which plays a crucial role in the design of x-ray tubeheads. This housing encases the x-ray tube and is specifically designed to absorb and contain the x-ray radiation generated within the tube. As x-rays are produced when high-speed electrons collide with the anode, the leaded-glass housing acts as a barrier that prevents the radiation from escaping into the environment, thereby protecting both the operator and the surrounding area from unnecessary exposure.

In contrast, the anode, tungsten filament, and cathode serve different functions within the x-ray tube. The anode is the target for the electrons and is where x-rays are generated, while the tungsten filament is a component of the cathode, serving as the electron source. The cathode, in its entirety, works to create a cloud of electrons that move toward the anode, facilitating x-ray production but does not have a protective function to prevent radiation leakage like the leaded-glass housing does.