Tube shielding refers to the use of a material within the X-ray tube housing to limit leakage of scattered radiation, to protect both patients and staff from unnecessary exposure.
Lead (Pb) is an ideal material for this purpose due to its high atomic density (Z = 82). Due to these properties, it is also preferred for its use in personal protective equipment.
Typically, a thin sheet of lead (2-3 mm thickness) is lined within the tube housing.
Tube shielding is regulated so that the legal limit of radiation leakage from an X-ray tube running at its maximum voltage does not exceed 1 mGy in 1 hour at 1 meter from the anode.