Apparatus and method for removing scatter from an x-ray image
First Claim
1. A two-dimensional x-ray imaging system for taking images of a subject, said system comprising:
- (a) in physical sequence from front to back, an x-ray source, a front two-dimensional x-ray detector assembly, a collimator, and a rear two-dimensional x-ray detector assembly, said subject being located between said x-ray source and said front detector assembly;
(b) said x-ray source adapted to emit x-rays for passage through said subject;
(c) said x-rays including primary x-rays having their direction of travel unaltered by interaction with said subject;
(d) said x-rays including scatter x-rays having their direction of travel altered by interaction with said subject;
(e) said front detector assembly receiving said primary x-rays and said scatter x-rays;
(f) said collimator being adjacent to said front detector assembly, said collimator permitting the passage of a portion of said primary x-rays and blocking the passage of the remainder of said primary x-rays and said scatter x-rays; and
(g) said rear detector assembly being adjacent to said collimator, said rear detector receiving only said portion of said primary x-rays passing through said collimator.
1 Assignment
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Accused Products
Abstract
An apparatus, for producing scatter-free two-dimensional X-ray images and eliminating scattering effects on integrated detector arrays, includes, in physical sequence from front to back, an X-ray source, a front two-dimensional detector positioned behind a subject for detecting both primary and scatter X-rays produced from striking the subject with the source'"'"'s radiation, a collimator with holes for passing a portion of the primary X-rays, and a rear two-dimensional detector for receiving this portion. A method for producing scatter-free images which includes the steps of; X-raying the subject with high and low energy, retrieving an image pair IrHl and IrLl from the rear detector, normalizing and subtracting dark signals from IrHl and IrLl to yield an image pair DrHl and DrLl, solving DrHl and DrLl to determine b and s, retrieving an image Ifh from the front detector, normalizing and subtracting dark signals from Ifh to yield Dfh representing the primary and scatter X-rays sum, determining DfSl of image Dfh at the detector cells using b and s, interpolating DfSl for the front detector cells to yield DfSh, subtracting DfSh from Dfh to yield DfPh representing the two-dimensional scatter-free image of the subject.
50 Citations
37 Claims
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1. A two-dimensional x-ray imaging system for taking images of a subject, said system comprising:
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(a) in physical sequence from front to back, an x-ray source, a front two-dimensional x-ray detector assembly, a collimator, and a rear two-dimensional x-ray detector assembly, said subject being located between said x-ray source and said front detector assembly; (b) said x-ray source adapted to emit x-rays for passage through said subject; (c) said x-rays including primary x-rays having their direction of travel unaltered by interaction with said subject; (d) said x-rays including scatter x-rays having their direction of travel altered by interaction with said subject; (e) said front detector assembly receiving said primary x-rays and said scatter x-rays; (f) said collimator being adjacent to said front detector assembly, said collimator permitting the passage of a portion of said primary x-rays and blocking the passage of the remainder of said primary x-rays and said scatter x-rays; and (g) said rear detector assembly being adjacent to said collimator, said rear detector receiving only said portion of said primary x-rays passing through said collimator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A two-dimensional x-ray imaging system for taking images of a subject, said system comprising:
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(a) in physical sequence from front to back, an x-ray source, a front two-dimensional x-ray detector assembly, a collimator, and a rear two-dimensional x-ray detector assembly, said subject being located between said x-ray source and said front detector assembly; (b) said x-ray source adapted to emit x-rays with an energy in the range of from approximately 20 keV to approximately 100 key for passage through said subject; (c) said x-rays including primary x-rays having their direction of travel unaltered by interaction with said subject; (d) said x-rays including scatter x-rays having their direction of travel altered by interaction with said subject; (e) said front detector assembly receiving said primary x-rays and said scatter x-rays; (f) said collimator being adjacent to said front detector assembly, said collimator permitting the passage of a portion of said primary x-rays and blocking the passage of the remainder of said primary x-rays and said scatter x-rays, collimator being composed substantially of an x-ray-absorbent material having a large number of through holes, the axes of said holes being parallel to said direction of travel of said primary x-rays, said collimator holes having a pitch of between approximately 5 mm and 50 mm; (g) said rear detector assembly being adjacent to said collimator, said rear detector receiving only said portion of said primary x-rays passing through said collimator. - View Dependent Claims (14, 15, 16, 17, 18, 23)
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19. A method for taking a two-dimensional x-ray image of a subject using a two-dimensional x-ray imaging system, said system including, in physical sequence from front to back, an x-ray source emitting x-rays, a front two-dimensional x-ray detector having a plurality of front detector cells on a coordinate system represented by the notation (x,y), a collimator having a plurality of through holes axially aligned with said x-rays and permitting the passage of a portion of primary x-rays and blocking substantially all scatter x-rays, a rear low-energy two-dimensional x-ray detector having a plurality of rear low-energy detector cells on a coordinate system represented by the notation (i,j), a rear x-ray energy spectral filter, and a rear high-energy two-dimensional x-ray detector having a plurality of rear high-energy detector cells on the same coordinate system as said rear low-energy detector cells, a plurality of projection lines extending radially from said x-ray source through said collimator holes, said subject being substantially composed of two different materials having area densities of A and B in terms of interaction with said x-rays and being located between said x-ray source and said front detector, said method comprising:
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(a) illuminating said subject with said x-rays; (b) retrieving a high-resolution image Ifh from substantially all of said front detector cells and processing said image Ifh to normalize it and to subtract dark signals, yielding an image Dfh, which is composed of primary x-ray signals and scatter x-ray signals; (c) constructing a low-resolution image Dfl from the portion of said image Dfh retrieved from said front detector cells that are intersected by said projection lines; (d) retrieving a low-resolution image IrHl from said rear high-energy detector cells that are intersected by said projection lines and processing said image IrHl to normalize it and to subtract dark signals, yielding an image DrHl, said image DrHl being composed of substantially only primary x-ray signals; (e) retrieving a low-resolution image IrLl from said rear low-energy detector cells that are intersected by said projection lines and processing said image IrLl to normalize it and to subtract dark signals, yielding an image DrLl, said image DrLl being composed of substantially only primary x-ray signals; (f) calculating a low-resolution primary x-ray image DfPl of said front detector from a low-resolution dual-energy primary x-ray imaging pair composed of said image DrHl and said image DrLl ; (g) calculating a low-resolution scatter x-ray image DfSl of said front detector by subtracting said image DfPl from said image Dfl ; (h) calculating a high-resolution scatter image DfSh by extending said low-resolution scatter image DfSl to the entire image area of said front detector through interpolation; and (i) calculating a high-resolution primary image DfPh by subtracting said high-resolution scatter image DfSh from said high-resolution image Dfh ; (j) whereby said high-resolution primary image DfPh is a two-dimensional image of said subject at said front detector after scatter x-rays have been substantially eliminated, said image DfPh having a spatial resolution as high as said front detector can provide. - View Dependent Claims (20, 21, 22)
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24. A method for taking a two-dimensional x-ray image of a subject using a two-dimensional x-ray imaging system, said system including, in physical sequence from front to back, an x-ray source emitting x-rays, a front two-dimensional x-ray detector having a plurality of front detector cells on a coordinate system represented by the notation (x,y), a collimator having a plurality of through holes axially aligned with said x-rays and permitting the passage of a portion of primary x-rays and blocking substantially all scatter x-rays, a rear two-dimensional x-ray detector having a plurality of rear detector cells on a coordinate system represented by the notation (i,j), a plurality of projection lines extending radially from said x-ray source through said collimator holes, said subject being substantially composed of two different materials having area densities of A and B in terms of interaction with said x-rays and being located between said x-ray source and said front detector, said method comprising:
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(a) illuminating said subject with x-rays of energy level H; (b) retrieving a high-resolution image IfHh from substantially all of said front detector cells and processing said image IfHh to normalize it and to subtract dark signals, yielding an image DfHh, which is composed of primary x-ray signals and scatter x-ray signals; (c) constructing a low-resolution image DfHl from the portion of said image DfHh retrieved from said front detector cells that are intersected by said projection lines; (d) retrieving a low-resolution image IrHl from said rear detector cells that are intersected by said projection lines and processing said image IrHl to normalize it and to subtract dark signals, yielding an image DrHl, said image DrHl being composed of substantially only primary x-ray signals; (e) illuminating said subject with x-rays of energy level L; (f) retrieving a high-resolution image IfLh from substantially all of said front detector cells and processing said image IfLh to normalize it and to subtract dark signals, yielding an image DfLh, which is composed of primary x-ray signals and scatter x-ray signals; (g) constructing a low-resolution image DfLl from the portion of said image DfLh retrieved from said front detector cells that are intersected by said projection lines; (h) retrieving a low-resolution image IrLl from said rear detector cells that are intersected by said projection lines and processing said image IrLl to normalize it and to subtract dark signals, yielding an image DrLl, said image DrLl being composed of substantially only primary x-ray signals; (i) calculating a pair of low-resolution primary x-ray images DfLPl and DfHPl of said front detector from a low-resolution dual-energy primary x-ray imaging pair composed of said image DrHl and said image DrLl ; (j) calculating a pair of low-resolution scatter x-ray images DfLSl and DfHSl of said front detector by subtracting said image DfLPl from said image DfLl and subtracting said image DfHPl from said image DfHl ; (k) calculating a pair of high-resolution scatter images DfLSh and DfHSh by extending said pair of low-resolution scatter images DfLSl and DfHSl to the entire image area of said front detector through interpolation; and (l) calculating a pair of high-resolution primary images DfLPh and DfHPh by subtracting said high-resolution scatter image DfLSh from said high-resolution image DfLh and subtracting said high-resolution scatter image DfHSh from said high-resolution image DfHh ; (m) whereby said pair of high-resolution primary images DfLPh and DfHPh is a pair of high-resolution two-dimensional dual-energy x-ray images of said subject at said front detector after scatter x-rays have been substantially eliminated, said primary image pair DfLPh and DfHPh having a spatial resolution as high as said front detector can provide. - View Dependent Claims (25, 26, 27, 28, 29)
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30. A method for taking a two-dimensional x-ray image of a subject using a two-dimensional x-ray imaging system, said system including, in physical sequence from front to back, an x-ray source emitting x-rays, a front low-energy two-dimensional x-ray detector having a plurality of front low-energy detector cells on a coordinate system represented by the notation (x,y), a front x-ray energy spectral filter, a front high-energy two-dimensional x-ray detector having a plurality of front high-energy detector cells on the same coordinate system as said front low-energy detector cells, a collimator having a plurality of through holes axially aligned with said x-rays and permitting the passage of a portion of primary x-rays and blocking substantially all scatter x-rays, a rear low-energy two-dimensional x-ray detector having a plurality of rear low-energy detector cells on a coordinate system represented by the notation (i,j), a rear x-ray energy spectral filter, and a rear high-energy two-dimensional x-ray detector having a plurality of rear high-energy detector cells on the same coordinate system as said rear low-energy detector cells, a plurality of projection lines extending radially from said x-ray source through said collimator holes, said subject being substantially composed of two different materials having area densities of A and B in terms of interaction with said x-rays and being located between said x-ray source and said front detector, said method comprising:
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(a) illuminating said subject with x-rays; (b) retrieving a high-resolution image IfLh from substantially all of said front low-energy detector cells and processing said image IfLh to normalize it and to subtract dark signals, yielding an image DfLh, which is composed of primary x-ray signals and scatter x-ray signals; (c) constructing a low-resolution image DfLl from the portion of said image DfLh retrieved from said front low-energy detector cells that are intersected by said projection lines; (d) retrieving a high-resolution image IfHh from substantially all of said front high-energy detector cells and processing said image IfHh to normalize it and to subtract dark signals, yielding an image DfHh, which is composed of primary x-ray signals and scatter x-ray signals; (e) constructing a low-resolution image DfHl from the portion of said image DfHh retrieved from said front high-energy detector cells that are intersected by said projection lines; (f) retrieving a low-resolution image IrLl from said rear low-energy detector cells that are intersected by said projection lines and processing said image IrLl to normalize it and to subtract dark signals, yielding an image DrLl, said image DrLl being composed of substantially only primary x-ray signals; (g) retrieving a low-resolution image IrHl from said rear high-energy detector cells that are intersected by said projection lines and processing said image IrHl to normalize it and to subtract dark signals, yielding an image DrHl, said image DrHl being composed of substantially only primary x-ray signals; (h) calculating a pair of low-resolution primary x-ray images DfLPl of said front low-energy detector and DfHPl of said front high-energy detector from a low-resolution dual-energy primary x-ray imaging pair composed of said image DrHl and said image DrLl ; (j) calculating a pair of low-resolution scatter x-ray images DfLSl of said front low-energy detector and DfHSl of said front high-energy detector by subtracting said image DfLPl from said image DfLl and subtracting said image DfHPl from said image DfHl ; (k) calculating a pair of high-resolution scatter images DfLSh and DfHSh by extending said pair of low-resolution scatter images DfLSl and DfHSl to the entire image area of said front low-energy detector and said front high-energy detector through interpolation; and (l) calculating a pair of high-resolution primary images DfLPh and DfHPh by subtracting said high-resolution scatter image DfLSh from said high-resolution image DfLh and subtracting said high-resolution scatter image DfHSh from said high-resolution image DfHh ; (m) whereby said pair of high-resolution primary images DfLPh and DfHPh is a pair of high-resolution two-dimensional dual-energy x-ray images of said subject at said front low-energy detector and said front high-energy detector after scatter x-rays have been substantially eliminated, said primary image pair DfLPh and DfHPh having a spatial resolution as high as said front detector can provide. - View Dependent Claims (31, 32, 33, 34, 35)
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36. A method for taking a two-dimensional x-ray image of a subject using a two-dimensional x-ray imaging system, said system including, in physical sequence from front to back, an x-ray source emitting x-rays that can be approximated as having a single energy E0, a front two-dimensional x-ray detector having a plurality of front detector cells on a coordinate system represented by the notation (x,y), a collimator having a plurality of through holes axially aligned with said x-rays and permitting the passage of a portion of primary x-rays and blocking substantially all scatter x-rays, a rear two-dimensional x-ray detector having a plurality of rear detector cells on a coordinate system represented by the notation (i,j), a plurality of projection lines extending radially from said x-ray source through said collimator holes, said subject being substantially composed of two different materials having area densities of A and B in terms of interaction with said x-rays and being located between said x-ray source and said front detector, said method comprising:
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(a) illuminating said subject with said x-rays; (b) retrieving a high-resolution image Ifh from substantially all of said front detector cells and processing said image Ifh to normalize it and to subtract dark signals, yielding an image Dfh, which is composed of primary x-ray signals and scatter x-ray signals; (c) constructing a low-resolution image Dfl from the portion of said image Dfh retrieved from said front detector cells that are intersected by said projection lines; (d) retrieving a low-resolution image Irl from said rear detector cells that are intersected by said projection lines and processing said image Irl to normalize it and to subtract dark signals, yielding an image Drl, said image Drl being composed of substantially only primary x-ray signals; (e) calculating a low-resolution primary x-ray image DfPl of said front detector from said image Drl by multiplying said image Drl by a predetermined value C, the energy reduction constant of said collimator at said energy E0 ; (f) calculating a low-resolution scatter x-ray image DfSl of said front detector by subtracting said image DfPl from said image Dfl ; (g) calculating a high-resolution scatter image DfSh by extending said low-resolution scatter image DfSl to the entire image area of said front detector through interpolation; and (h) calculating a high-resolution primary image DfPh by subtracting said high-resolution scatter image DfSh from said high-resolution image Dfh ; (i) whereby said high-resolution primary image DfPh is a two-dimensional image of said subject at said front detector after scatter x-rays have been substantially eliminated, said image DfPh having a spatial resolution as high as said front detector can provide.
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37. A method for taking a two-dimensional x-ray image of a subject using a two-dimensional x-ray imaging system, said system including, in physical sequence from front to back, an x-ray source emitting x-rays that can be approximated as having an average energy E0, a front two-dimensional x-ray detector having a plurality of front detector cells on a coordinate system represented by the notation (x,y), a collimator having a plurality of through holes axially aligned with said x-rays and permitting the passage of a portion of primary x-rays and blocking substantially all scatter x-rays, a rear two-dimensional x-ray detector having a plurality of rear detector cells on a coordinate system represented by the notation (i,j), a plurality of projection lines extending radially from said x-ray source through said collimator holes, said subject being substantially composed of two different materials having area densities of A and B in terms of interaction with said x-rays and being located between said x-ray source and said front detector, said method comprising:
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(a) illuminating said subject with said x-rays; (b) retrieving a high-resolution image Ifh from substantially all of said front detector cells and processing said image Ifh to normalize it and to subtract dark signals, yielding an image Dfh, which is composed of primary x-ray signals and scatter x-ray signals; (c) constructing a low-resolution image Dfl from the portion of said image Dfh retrieved from said front detector cells that are intersected by said projection lines; (d) retrieving a low-resolution image Irl from said rear detector cells that are intersected by said projection lines and processing said image Irl to normalize it and to subtract dark signals, yielding an image Drl, said image Drl being composed of substantially only primary x-ray signals; (e) calculating a low-resolution primary x-ray image DfPl of said front detector from said image Drl by multiplying said image Drl by a predetermined value C, the energy reduction constant of said collimator at said energy E0 ; (f) calculating a low-resolution scatter x-ray image DfSl of said front detector by subtracting said image DfPl from said image Dfl ; (g) calculating a high-resolution scatter image DfSh by extending said low-resolution scatter image DfSl to the entire image area of said front detector through interpolation; and (h) calculating a high-resolution primary image DfPh by subtracting said high-resolution scatter image DfSh from said high-resolution image Dfh ; (i) whereby said high-resolution primary image DfPh is a two-dimensional image of said subject at said front detector after scatter x-rays have been substantially eliminated, said image DfPh having a spatial resolution as high as said front detector can provide.
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Specification