X-Ray detector with compensation for height-dependent sensitivity and method of using same

Claim 1

An x-ray imaging apparatus, comprising: (a) an x-ray source providing a substantially planar beam of x-ray energy; (b) an x-ray detector positioned in a spaced-apart relationship from said x-ray source such that an object to be studied may be accomodated therebetween, said x-ray detector having: (1) a first plurality of detector cells substantially coplanar with said x-ray beam, each of said detector cells including a radiation-receiving aperture having a dimension in a direction orthogonal to the plane of said beam exceeding the thickness of said beam measured in the same direction, said plurality of detector cells containing an x-ray-detecting medium and being disposed for detecting x-ray radiation transmitted through said object; (2) a second plurality of x-ray detector cells, substantially identical to said first plurality of cells, for detecting a portion of said x-ray radiation beam transmitted past said object without substantial attenuation; and (c) an x-ray attenuative member fixedly disposed between said x-ray source and at least one, but not all, of said second plurality of detector cells, said x-ray member having a variable x-ray transmissive capability in a direction substantially perpendicular to the plane of said x-ray beam for controllably admitting into said one detector cell a predetermined fraction of the total radiation incident thereon in accordance with the position of said x-ray beam on the radiation-receiving aperture of said one cell, as a consequence of which the output thereof exhibits a corresponding dependence on the position of said x-ray beam.

Claim 17

A method for compensating for height-dependent sensitivity of an x-ray detector useful in apparatus of the type including an x-ray source having an anode and producing a planar beam of x-ray radiation, and wherein said x-ray detector includes a first plurality of detector cells for detecting radiation transmitted through an object disposed between said source and said detector, and a second plurality of detector cells for detecting x-ray radiation transmitted past said object without substantial attenuation, said detector cells having a radiation-receiving aperture with a dimension in a direction orthogonal to the plane of said beam exceeding the thickness of said beam measured in the same direction, said method comprising the steps of: (a) determining the sensitivity profile of each of said first plurality of detector cells; (b) calculating a plurality of sensitivity correction factors for each of said first plurality of detector cells, said correction factors being dependent on the position of said x-ray beam on the radiation-receiving aperture of said detector cells; (c) measuring the position of said x-ray beam on the x-ray detector cell radiation-receiving aperture while scanning said object with said x-ray beam; (d) selecting a sensitivity-correction factor for each of said first plurality of detector cells in accordance with the measured position of said x-ray beam; and (e) adjusting the output level of each of said first plurality of detector cells based on the selected sensitivity-correction factor.

Claim 18

A method for compensating for height-dependent sensitivity of an x-ray detector useful in apparatus of the type including an x-ray source having an anode and producing a planar beam of x-ray radiation, and wherein said x-ray detector includes a first plurality of detector cells for detecting radiation transmitted through an object disposed between said source and said detector, and a second plurality of detector cells for detecting x-ray radiation transmitted past said object without substantial attenuation, said detector cells having a radiation-receiving aperture with a dimension in a direction orthogonal to the plane of said beam exceeding the thickness of said beam measured in the same direction, said method comprising the steps of: (a) determining the sensitivity profile of each of said first plurality of detector cells; (b) calculating a plurality of sensitivity correction factors for each of said first plurality of detector cells, said correction factors being dependent on the position of said x-ray beam on the radiation-receiving aperture of said detector cells; (c) measuring the position of said x-ray beam on the x-ray detector cell radiation-receiving aperture while scanning said object with said x-ray beam; (d) selecting a sensitivity-correction factor for each of said first plurality of detector cells in accordance with the measured position of said x-ray beam; and (e) adjusting the output level of each of said first plurality of detector cells based on the selected sensitivity-correction factor.