Method and apparatus for measuring and analyzing radiation transmitted at plural angles

Claim 1

An apparatus for examining a body by means of penetrating radiation such as X- or γ-radiation including source means arranged to irradiate a cross-sectional slice of the body, detector means responsive to said radiation and disposed to receive said radiation after passage through the body along a plurality of substantially linear paths and to provide corresponding output signals for processing to construct a representation of the distribution of the absorption of the radiation over said slice, means for rotating the source and detector means around the body causing said source means to irradiate the slice from a plurality of directions and said detector means to provide further output signals, relating to further substantially linear paths, and processing means arranged to multiply some of the output signals derived from said detector means and relating to substantially the same path through the body, but obtained at different times during said rotation, by complementary factors which vary with the extent of said rotation and thereafter to combine said signals.

Claim 2

An apparatus for examining a body by means of penetrating radiation such as X- or γ-radiation including source means arranged to irradiate a cross-sectional slice of the body, detector means responsive to said radiation and disposed to receive said radiation after passage through the body along a plurality of substantially linear paths and to provide corresponding output signals for processing to construct a representation of the distribution of the absorption of the radiation over said slice, means for rotating the source and detector means around the body causing said source means to irradiate the slice from a plurality of directions and said detector means to provide further output signals, relating to further substantially linear paths, and processing means arranged to multiply some of the output signals derived from said detector means and relating to substantially the same path through the body, but obtained at different times during said rotation, by complementary factors which vary with the extent of said rotation and thereafter to combine said signals.

Claim 3

An apparatus for examining a body by means of penetrating radiation such as X- or γ-radiation including source means arranged to irradiate a cross-sectional slice of the body, detector means responsive to said radiation and disposed to receive said radiation after passage through the body along a plurality of substantially linear paths and to provide corresponding output signals for processing to construct a representation of the distribution of the absorption of the radiation over said slice, means for rotating the source and detector means around the body causing said source means to irradiate the slice from a plurality of directions and said detector means to provide further output signals, relating to further substantially linear paths, and processing means arranged to combine some of the output signals provided by the detector means relating to substantially the same path through the body, but obtained at different times in said rotation, in accordance with a predetermined amplitude ratio which varies throughout a predetermined angular range of said rotation.

Claim 4

An apparatus for examining a body by means of penetrating radiation such as X- or γ-radiation including source means arranged to irradiate a cross-sectional slice of the body, detector means responsive to said radiation and disposed to receive said radiation after passage through the body along a plurality of substantially linear paths and to provide corresponding output signals for processing to construct a representation of the distribution of the absorption of the radiation over said slice, means for rotating the source and detector means around the body causing said source means to irradiate the slice from a plurality of directions and said detector means to provide further output signals, relating to further substantially linear paths, and processing means arranged to combine some of the output signals provided by the detector means relating to substantially the same path through the body, but obtained at different times in said rotation, in accordance with a predetermined amplitude ratio which varies throughout a predetermined angular range of said rotation.

Claim 9

An apparatus for examining a body by means of penetrating radiation such as X- or γ-radiation including source means arranged to irradiate a cross-sectional slice of the body, detector means responsive to said radiation and disposed to receive said radiation after passage through the body along each of a plurality of substantially linear beam paths, and to provide output signals indicative of the amount of said radiation transmitted through said body along each of said beam paths, means for rotating the source and detector means around the body causing said source means to irradiate the body from a plurality of directions and said detector means to provide further output signals indicative of the amounts of said radiation transmitted through said body along further substantially linear beam paths, said rotating means causing paths in respect of which output signals were provided at an initial stage of said rotation to be irradiated again at a later stage of said rotation and means being provided for weighting output signals relating to the radiation transmitted through the body along a given beam path at said different stages of said rotation by respective complementary weighting factors and for combining the singals so weighted to produce composite signals; said weighting factors applied to signals obtained during said initial stage of said rotation gradually increasing in amplitude with increasing angle of said rotation and said weighting factors applied to signals obtained during said further stage of said rotation gradually decreasing in amplitude with increasing angle of said rotation, said increase and decrease in amplitude of said weighting factors being such as to produce said complementary relationship between the weighting factors applied to the output signals relating to a given path.

Claim 10

An apparatus for examining a body by means of penetrating radiation such as X- or γ-radiation including source means arranged to irradiate a cross-sectional slice of the body, detector means responsive to said radiation and disposed to receive said radiation after passage through the body along each of a plurality of substantially linear beam paths, and to provide output signals indicative of the amount of said radiation transmitted through said body along each of said beam paths, means for rotating the source and detector means around the body causing said source means to irradiate the body from a plurality of directions and said detector means to provide further output signals indicative of the amounts of said radiation transmitted through said body along further substantially linear beam paths, said rotating means causing paths in respect of which output signals were provided at an initial stage of said rotation to be irradiated again at a later stage of said rotation and means being provided for weighting output signals relating to the radiation transmitted through the body along a given beam path at said different stages of said rotation by respective complementary weighting factors and for combining the singals so weighted to produce composite signals; said weighting factors applied to signals obtained during said initial stage of said rotation gradually increasing in amplitude with increasing angle of said rotation and said weighting factors applied to signals obtained during said further stage of said rotation gradually decreasing in amplitude with increasing angle of said rotation, said increase and decrease in amplitude of said weighting factors being such as to produce said complementary relationship between the weighting factors applied to the output signals relating to a given path.