Patent ID: 7430282

Claim:
A heel effect compensation filter which is configured to have a thickness distribution that uniforms an X-ray intensity angular distribution that is nonuniform in a body axis direction of a subject in an X-ray flux irradiated space, the space being formed by an X-ray flux diverging from an anode in a body width direction of the subject and diverging in a shape of an approximate sector in the body axis direction orthogonal to the body width direction due to the X-ray intensity angular distribution affected by a heel effect, when the X-ray flux generated on the anode by irradiating a thermoelectron beam flux from a cathode to the anode is irradiated on the subject through a wedge filter configured to have a cylindrical concave surface with a curve being formed in the body width direction of the subject, wherein the thickness distribution is defined by Formula 1: ( y ′ z ′ ) = ( L ⁡ ( θ ) ⁢ cos ⁢ ⁢ θ FFD FCD ⁢ ( FCD ⁢ ⁢ tan ⁢ ⁢ θ - L ⁡ ( θ ) ⁢ sin ⁢ ⁢ θ ) ) ⁢ ⁢ ( θ ≤  cone ⁢ ⁢ angle  ) ( Formula ⁢ ⁢ 1 ) where, on a plane containing an irradiation axis of the X-ray flux and a beam irradiation axis of the thermoelectron beam flux, the irradiation axis of the X-ray flux is defined as a Y-axis, and an axis orthogonal to the Y-axis at a distance FCD along the Y-axis in a direction of X-ray flux irradiation is defined as a Z-axis; z′ and y′ represent positions in corresponding axial directions with the proviso that an intersection point of the Z-axis and the Y-axis is defined as an origin point; FFD is defined as a predetermined distance along the Y-axis from a position of the anode; θ is defined as a predetermined angle within a range of a cone angle symmetrically diverging from the position of the anode relative to the irradiation axis of the X-ray flux; and La(θ) is defined as a length in a y′ direction at the angle θ.