Patent ID: 7224771

Claim:
An x-ray tube comprising: an envelope which defines an evacuated chamber; a source of electrons; an anode mounted within the chamber for rotation about an axis of rotation, the anode defining a sloped peripheral region on which a target area is defined, which target area is struck by electrons emitted by the electron source and emits x-rays, the sloped peripheral region including a first annular portion, sloped at first angle relative to a plane perpendicular to the axis of rotation, and a second annular portion, adjacent the first portion, sloped at a second angle, relative to the plane, the second angle being different from the first angle, the target area being defined partially on the first annular portion and partially on the second annular portion, wherein the source of electrons includes a filament having a greater width in a region of the filament which emits electrons that strike the portion of the target area on the first annular portion and a smaller width in a region which emits electrons which strike the portion of the target area on the second annular portion.