Scanning mammography system with reduced scatter radiation

Apparatus for generating a point source, fan-shaped X-ray beam having minimum off-focus radiation comprising:

• an X-ray tube having a cathode for generating X-ray radiation generally directed in a predetermined direction, said radiation originating from a predetermined focal spot in said tube;
• an X-ray transmissive window positioned in said tube and aligned in said predetermined direction for passing said X-ray radiation outwardly of said tube;
• a grid assembly extending in a transverse direction across a target area and having a relatively narrow width in a beam scanning direction;
• drive means coupled to said grid for moving said grid in a predetermined scanning direction in synchronism with the X-ray beam;
• an X-ray impervious belt coupled to said grid, said belt extending in the transverse direction across said target area and being movable with said grid for covering the target area outside said grid;
• and
• an X-ray impervious member positioned adjacent to and overlaying said window, said member having a rectangularly shaped central aperture for passing X-ray radiation.

A method for generating a point source fan-shaped X-ray beam having minimum off-focus radiation from an X-ray tube emitting radiation through and X-ray window, said method comprising the steps of:

• positioning a substantially X-ray impervious member, having a rectangular shaped central aperture, adjacent to and overlaying the X-ray window;
• passing radiation through the central aperture whereby off-focus radiation is attenuated by the member;
• positioning a collimator having a rectangular shaped central slit in a line to receive the radiation, the collimator being spaced from the member and being formed of an X-ray attenuating material;
• reciprocally pivoting the X-ray tube and the X-ray impervious member about a preselected axis for effecting scanning motion of the radiation;
• and
• driving the collimator along a linear path in synchronism with motion of the X-ray tube for maintaining the collimator window in alignment with the radiation and wherein a grid assembly is positioned above a target area in alignment with the X-ray radiation and a radiation blocking medium is operatively associated with the grid assembly for blocking radiation outside the grid assembly from impinging on the target ares, the method further comprising the step of reciprocally moving the grid assembly in synchronism with motion of the X-ray tube to maintain a primary radiation path through the grid assembly.