US5802133A
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US
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Method and apparatus of X-ray computerized tomography
Assignee: Hitachi Healthcare Manufacturing Ltd
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Filing: 1996-11-27
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Granted: 1998-09-01
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Expires: 2016-11-27
Abstract
Abstract A method of X-ray computerized tomography whereby a scanner in which an X-ray source for irradiating an X-ray in a cone-beam shape to an object and a two-dimensional detector for detecting the X-ray transmitted through the object are installed is rotated around the object and a projection angle is changed and a distribution of X-ray attenuation coefficients of the object is reconstructed from the transmitted X-ray images obtained at a plurality of projection angles. This method has the steps of: (1) measuring a first transmitted X-ray image measured in a state in which a contrast medium is injected into the object, a second transmitted X-ray image measured in a state in which no contrast medium is injected into the object, and a third transmitted X-ray image measured in a state in which no object is positioned in the apparatus; (2) calculating a first projection image from a difference between logarithms of the first and second transmitted X-ray images obtained at the same projection angle, calculating a second projection image from a difference between logarithms of the second and third transmitted X-ray images obtained at the same projection angle, and simultaneously reconstructing a first reconstructed image from the first projection image and a second reconstructed image from the second projection image in parallel; and (3) composing the first and second reconstructed images, thereby forming a composed image.
Inventors
- 👤 Hiroyuki Kawai
- 👤 Kensuke Sekihara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:39
CPC Classifications
A; A61; A61B; A61B6/00; A61B6/48; A61B6/481; A61B6/02; A61B6/03; A61B6/032; A61B6/46; A61B6/461; A61B6/463; A61B6/50; A61B6/504; Y; Y10; Y10S; Y10S378/00; Y10S378/901
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
230 words
A method of X-ray computerized tomography whereby a scanner in which an X-ray source for irradiating an X-ray in a cone-beam shape to an object and a two-dimensional detector for detecting the X-ray transmitted through said object are installed is rotated around said object and a projection angle is changed and a distribution of X-ray attenuation coefficients of said object is reconstructed from transmitted X-ray images obtained at a plurality of said projection angles, comprising the steps of: (1) measuring a first transmitted X-ray image measured in a state in which a contrast medium is injected into said object, a second transmitted X-ray image measured in a state in which no contrast medium is injected into said object, and a third transmitted X-ray image measured in a state in which no object is positioned in the apparatus, all at the same projection angle; (2) calculating a first projection image from a difference between logarithms of said first and second transmitted X-ray images obtained at said same projection angle, calculating a second projection image from a difference between logarithms of said second and third transmitted X-ray images obtained at said same projection angle, and simultaneously reconstructing a first reconstructed image from said first projection image and a second reconstructed image from said second projection image in parallel; and (3) composing said first and second reconstructed images, thereby forming a composed image.
Claim 2
Independent Claim
230 words
A method of X-ray computerized tomography whereby a scanner in which an X-ray source for irradiating an X-ray in a cone-beam shape to an object and a two-dimensional detector for detecting the X-ray transmitted through said object are installed is rotated around said object and a projection angle is changed and a distribution of X-ray attenuation coefficients of said object is reconstructed from transmitted X-ray images obtained at a plurality of said projection angles, comprising the steps of: (1) measuring a first transmitted X-ray image measured in a state in which a contrast medium is injected into said object, a second transmitted X-ray image measured in a state in which no contrast medium is injected into said object, and a third transmitted X-ray image measured in a state in which no object is positioned in the apparatus, all at the same projection angle; (2) calculating a first projection image from a difference between logarithms of said first and second transmitted X-ray images obtained at said same projection angle, calculating a second projection image from a difference between logarithms of said second and third transmitted X-ray images obtained at said same projection angle, and simultaneously reconstructing a first reconstructed image from said first projection image and a second reconstructed image from said second projection image in parallel; and (3) composing said first and second reconstructed images, thereby forming a composed image.
Claim 3
Dependent Claim
118 words
A method according to claim 1, wherein on said transmitted X-ray images, when a u axis is set to a rotation tangential direction of said scanner and a v axis is set to a rotation center axial direction of said scanner, at a projection angle (a), now assuming that said first transmitted X-ray image is set to I1(a,u,v), said second transmitted X-ray image is set to I2(a,u,v), said third transmitted X-ray image is set to I3(a,u,v), said first projection image is set to P1(a,u,v), and said second projection image is set to P2(a,u,v), in said step (2), said first projection image P1(a,u,v) and said second projection image P2(a,u,v) are calculated in accordance with the following equations (a): ##EQU6##
Claim 4
Dependent Claim
89 words
A method according to claim 1, wherein in said step (2), a reconstruction calculation for simultaneously reconstructing in parallel said first and second reconstructed images includes a filtering process, and in said filtering process, said first and second projection images obtained at said same projection angle are packed to thereby form a packed projection image, said packed projection image is filtered to thereby obtain a packed filtered projection image, and a first filtered projection image and a second filtered projection image are unpacked from said packed filtered projection image.
Claim 5
Dependent Claim
98 words
A method according to claim 3, wherein the reconstruction calculation for simultaneously reconstructing in parallel said first and second reconstructed images further includes a backprojection process, and in said backprojection process, backprojection coordinates on the projection image to be backprojected to coordinates on the reconstructed image are calculated, and when said first reconstructed image is backprojected from said first filtered projection image obtained at said same projection angle and said second reconstructed image is backprojected from said second filtered projection image obtained at said same projection angle, a backprojection calculation is executed by using said same backprojection coordinates.
Claim 6
Dependent Claim
115 words
A method according to claim 4, wherein the calculation of said backprojection coordinates is a calculation such that when a rotation center axis of said scanner is set to a z axis and fixed xyz coordinates are determined on said object and the reconstructed image is set to f(x,y,z), a point (u',v') on the projection image at a projection angle (a) to be backprojected to a point (x,y,z) on said xyz coordinates is obtained, and assuming that SID denotes a distance between said X-ray source and said detector and SOD denotes a distance between said X-ray source and the rotation center, said backprojection coordinates (u',v') are calculated in accordance with the following equations (b): ##EQU7##
Claim 7
Dependent Claim
100 words
A method according to claim 3, wherein in the formation of said packed projection image, data constructed by a complex number in which said first projection image obtained at said same projection angle is set to a real part and said second projection image obtained at said same projection angle is set to an imaginary part is set to said packed projection image or data constructed by a complex number in which said first projection image is set to an imaginary part and said second projection image is set to a real part is set to said packed projection image.
Claim 8
Dependent Claim
89 words
A method according to claim 3, wherein in the unpacking of said first and second filtered projection images from said packed filtered projection image, a real part of said packed filtered projection image obtained at said same projection angle is set to said first filtered projection image and an imaginary part is set to said second filtered projection image, or the imaginary part of said packed filtered projection image is set to said first filtered projection image and the real part is set to said second filtered projection image.
Claim 9
Independent Claim
489 words
A method of X-ray computerized tomography whereby a scanner in which an X-ray source for irradiating an X-ray in a cone-beam shape to an object and a two-dimensional detector for detecting the X-ray transmitted through said object are installed is rotated around said object and a projection angle is changed and a distribution of X-ray attenuation coefficients of said object is reconstructed from transmitted X-ray images obtained at a plurality of said projection angles, comprising the steps of: (1) measuring a first transmitted X-ray image measured in a state in which a contrast medium is injected into said object, a second transmitted X-ray image measured in a state in which no contrast medium is injected into said object, and a third transmitted X-ray image measured in a state in which no object is positioned in the apparatus, all at the same projection angle; (2) calculating a first projection image from a difference between logarithms of said first and second transmitted X-ray images obtained at said same projection angle, calculating a second projection image from a difference between logarithms of said second and third transmitted X-ray images obtained at said same projection angle, and simultaneously reconstructing a first reconstructed image from said first projection image and a second reconstructed image from said second projection image in parallel; and (3) composing said first and second reconstructed images, thereby forming a composed image, wherein in said step (2), a reconstruction calculation for simultaneously reconstructing in parallel said first and second reconstructed images includes a filtering process, and in said filtering process, said first and second projection images obtained at said same projection angle are packed to thereby form a packed projection image, said packed projection image is filtered to thereby obtain a packed filtered projection image, and a first filtered projection image and a second filtered projection image are unpacked from said packed filtered projection image, in the formation of said packed projection image, data constructed by a complex number in which said first projection image obtained at said same projection angle is set to a real part and said second projection image obtained at said same projection angle is set to an imaginary part is set to said packed projection image or data constructed by a complex number in which said first projection image is set to an imaginary part and said second projection image is set to a real part is set to said packed projection image, and in the unpacking of said first and second filtered projection images from said packed filtered projection image, a real part of said packed filtered projection image obtained at said same projection angle is set to said first filtered projection image and an imaginary part is set to said second filtered projection image, or the imaginary part of said packed filtered projection image is set to said first filtered projection image and the real part is set to said second filtered projection image.
Claim 10
Independent Claim
489 words
A method of X-ray computerized tomography whereby a scanner in which an X-ray source for irradiating an X-ray in a cone-beam shape to an object and a two-dimensional detector for detecting the X-ray transmitted through said object are installed is rotated around said object and a projection angle is changed and a distribution of X-ray attenuation coefficients of said object is reconstructed from transmitted X-ray images obtained at a plurality of said projection angles, comprising the steps of: (1) measuring a first transmitted X-ray image measured in a state in which a contrast medium is injected into said object, a second transmitted X-ray image measured in a state in which no contrast medium is injected into said object, and a third transmitted X-ray image measured in a state in which no object is positioned in the apparatus, all at the same projection angle; (2) calculating a first projection image from a difference between logarithms of said first and second transmitted X-ray images obtained at said same projection angle, calculating a second projection image from a difference between logarithms of said second and third transmitted X-ray images obtained at said same projection angle, and simultaneously reconstructing a first reconstructed image from said first projection image and a second reconstructed image from said second projection image in parallel; and (3) composing said first and second reconstructed images, thereby forming a composed image, wherein in said step (2), a reconstruction calculation for simultaneously reconstructing in parallel said first and second reconstructed images includes a filtering process, and in said filtering process, said first and second projection images obtained at said same projection angle are packed to thereby form a packed projection image, said packed projection image is filtered to thereby obtain a packed filtered projection image, and a first filtered projection image and a second filtered projection image are unpacked from said packed filtered projection image, in the formation of said packed projection image, data constructed by a complex number in which said first projection image obtained at said same projection angle is set to a real part and said second projection image obtained at said same projection angle is set to an imaginary part is set to said packed projection image or data constructed by a complex number in which said first projection image is set to an imaginary part and said second projection image is set to a real part is set to said packed projection image, and in the unpacking of said first and second filtered projection images from said packed filtered projection image, a real part of said packed filtered projection image obtained at said same projection angle is set to said first filtered projection image and an imaginary part is set to said second filtered projection image, or the imaginary part of said packed filtered projection image is set to said first filtered projection image and the real part is set to said second filtered projection image.
Claim 11
Independent Claim
236 words
An apparatus of X-ray computerized tomography comprising a scanner in which an X-ray source for irradiating an X-ray in a cone-beam shape to an object and a two-dimensional detector for detecting the X-ray transmitted through said object are installed and means for rotating said scanner around said object, changing a projection angle, and reconstructing a distribution of X-ray attenuation coefficients of said object from the transmitted X-ray images obtained at a plurality of said projection angles, comprising: memory means for storing a first transmitted X-ray image measured in a state in which a contrast medium is injected into said object, a second transmitted X-ray image measured in a state in which no contrast medium is injected into said object, and a third transmitted X-ray image measured in a state in which no object is positioned in the apparatus, all at the same projection angle; calculating means for respectively calculating a first projection image from a difference between logarithms of said first and second transmitted X-ray images obtained at said same projection angle, calculating a second projection image from a difference between logarithms of said second and third transmitted X-ray images obtained at said same projection angle, and simultaneously reconstructing a first reconstructed image from said first projection image and a second reconstructed image from said second projection image in parallel; and imaging processing means for forming a composed image from said first and second reconstructed images.
Claim 12
Independent Claim
236 words
An apparatus of X-ray computerized tomography comprising a scanner in which an X-ray source for irradiating an X-ray in a cone-beam shape to an object and a two-dimensional detector for detecting the X-ray transmitted through said object are installed and means for rotating said scanner around said object, changing a projection angle, and reconstructing a distribution of X-ray attenuation coefficients of said object from the transmitted X-ray images obtained at a plurality of said projection angles, comprising: memory means for storing a first transmitted X-ray image measured in a state in which a contrast medium is injected into said object, a second transmitted X-ray image measured in a state in which no contrast medium is injected into said object, and a third transmitted X-ray image measured in a state in which no object is positioned in the apparatus, all at the same projection angle; calculating means for respectively calculating a first projection image from a difference between logarithms of said first and second transmitted X-ray images obtained at said same projection angle, calculating a second projection image from a difference between logarithms of said second and third transmitted X-ray images obtained at said same projection angle, and simultaneously reconstructing a first reconstructed image from said first projection image and a second reconstructed image from said second projection image in parallel; and imaging processing means for forming a composed image from said first and second reconstructed images.
Claim 13
Dependent Claim
116 words
An apparatus according to claim 9, wherein on said transmitted X-ray images, when a u axis is set to a rotation tangential direction of said scanner and a v axis is set to a rotation center axial direction of said scanner, at a projection angle (a), now assuming that said first transmitted X-ray image is set to I1(a,u,v), said second transmitted X-ray image is set to I2(a,u,v), said third transmitted X-ray image is set to I3(a,u,v), said first projection image is set to P1(a,u,v), and said second projection image is set to P2(a,u,v), said calculating means calculates said first projection image P1(a,u,v) and said second projection image P2(a,u,v) in accordance with the following equations (c): ##EQU8##
Claim 14
Dependent Claim
79 words
An apparatus according to claim 9, wherein said calculating means includes a filtering operating part, said filtering operating part has: projection image packing means for forming a packed projection image by packing said first and second projection images obtained at said same projection angle; filtering means for obtaining packed filtered projection image by filtering said packed projection image; and filtered projection image unpacking means for unpacking said first and second filtered projection images from said packed filtered projection image.
Claim 15
Dependent Claim
96 words
An apparatus according to claim 11, wherein said calculating means further includes a backprojection operating part, and said backprojection operating part has: backprojection coordinate calculating means for calculating backprojection coordinates on a projection image to be backprojected to coordinates on the reconstructed image; and backprojection operating means for performing a backprojection calculation by using said same backprojection coordinates when said first reconstructed image is backprojected from said first filtered projection image obtained at said same projection angle and said second reconstructed image is backprojected from said second filtered projection image obtained at said same projection angle.
Claim 16
Dependent Claim
116 words
An apparatus according to claim 12, wherein said backprojection coordinate calculating means executes a calculation such that when a rotation center axis of said scanner is set to a z axis and fixed xyz coordinates are determined on said object and the reconstructed image is set to f(x,y,z), a point (u',v') on the projection image at a projection angle (a) to be backprojected to a point (x,y,z) on said xyz coordinates is obtained, and assuming that SID is set to a distance between said X-ray source and said detector and SOD denotes a distance between said X-ray source and the rotation center, said backprojection coordinates (u',v') are calculated in accordance with the following equations (d): ##EQU9##
Claim 17
Dependent Claim
98 words
An apparatus according to claim 11, wherein in said projection image packing means, data constructed by a complex number in which said first projection image obtained at said same projection angle is set to a real part and said second projection image obtained at said same projection angle is set to an imaginary part is set to said packed projection image or data constructed by a complex number in which said first projection image is set to an imaginary part and said second projection image is set to a real part is set to said packed projection image.
Claim 18
Dependent Claim
79 words
An apparatus according to claim 11, wherein in said filtered projection image unpacking means, a real part of said packed filtered projection image obtained at said same projection angle is set to said first filtered projection image and an imaginary part is set to said second filtered projection image, or the imaginary part of said packed filtered projection image is set to said first filtered projection image and the real part is set to said second filtered projection image.
Claim 19
Independent Claim
472 words
A apparatus of X-ray computerized tomography comprising a scanner in which an X-ray source for irradiating an X-ray in a cone-beam shape to an object and a two-dimensional detector for detecting the X-ray transmitted through said object are installed and means for rotating said scanner around said object, changing a projection angle, and reconstructing a distribution of X-ray attenuation-coefficients of said object from the transmitted X-ray images obtained at a plurality of said projection angles, comprising: memory means for storing a first transmitted X-ray image measured in a state in which a contrast medium is injected into said object, a second transmitted X-ray image measured in a state in which no contrast medium is injected into said object, and a third transmitted X-ray image measured in a state in which no object is positioned in the apparatus, all at the same projection angle; calculating means for respectively calculating a first projection image from a difference between logarithms of said first and second transmitted X-ray images obtained at said same projection angle, calculating a second projection image from a difference between logarithms of said second and third transmitted X-ray images obtained at said same projection angle, and simultaneously reconstructing a first reconstructed image from said first projection image and a second reconstructed image from said second projection image in parallel; and imaging processing means for forming a composed image from said first and second reconstructed images, wherein said calculating means includes a filtering operating part, said filtering operating part has: projection image packing means for forming a packed projection image by packing said first and second projection images obtained at said same projection angle; filtering means for obtaining packed filtered projection image by filtering said packed projection image; and filtered projection image unpacking means for unpacking said first and second filtered projection images from said packed filtered projection image, in said projection image packing means, data constructed by a complex number in which said first projection image obtained at said same projection angle is set to a real part and said second projection image obtained at said same projection angle is set to an imaginary part is set to said packed projection image or data constructed by a complex number in which said first projection image is set to an imaginary part and said second projection image is set to a real part is set to said packed projection image, and in said filtered projection image unpacking means, a real part of said packed filtered projection image obtained at said same projection angle is set to said first filtered projection image and an imaginary part is set to said second filtered projection image, or the imaginary part of said packed filtered projection image is set to said first filtered projection image and the real part is set to said second filtered projection image.
Claim 20
Independent Claim
472 words
A apparatus of X-ray computerized tomography comprising a scanner in which an X-ray source for irradiating an X-ray in a cone-beam shape to an object and a two-dimensional detector for detecting the X-ray transmitted through said object are installed and means for rotating said scanner around said object, changing a projection angle, and reconstructing a distribution of X-ray attenuation-coefficients of said object from the transmitted X-ray images obtained at a plurality of said projection angles, comprising: memory means for storing a first transmitted X-ray image measured in a state in which a contrast medium is injected into said object, a second transmitted X-ray image measured in a state in which no contrast medium is injected into said object, and a third transmitted X-ray image measured in a state in which no object is positioned in the apparatus, all at the same projection angle; calculating means for respectively calculating a first projection image from a difference between logarithms of said first and second transmitted X-ray images obtained at said same projection angle, calculating a second projection image from a difference between logarithms of said second and third transmitted X-ray images obtained at said same projection angle, and simultaneously reconstructing a first reconstructed image from said first projection image and a second reconstructed image from said second projection image in parallel; and imaging processing means for forming a composed image from said first and second reconstructed images, wherein said calculating means includes a filtering operating part, said filtering operating part has: projection image packing means for forming a packed projection image by packing said first and second projection images obtained at said same projection angle; filtering means for obtaining packed filtered projection image by filtering said packed projection image; and filtered projection image unpacking means for unpacking said first and second filtered projection images from said packed filtered projection image, in said projection image packing means, data constructed by a complex number in which said first projection image obtained at said same projection angle is set to a real part and said second projection image obtained at said same projection angle is set to an imaginary part is set to said packed projection image or data constructed by a complex number in which said first projection image is set to an imaginary part and said second projection image is set to a real part is set to said packed projection image, and in said filtered projection image unpacking means, a real part of said packed filtered projection image obtained at said same projection angle is set to said first filtered projection image and an imaginary part is set to said second filtered projection image, or the imaginary part of said packed filtered projection image is set to said first filtered projection image and the real part is set to said second filtered projection image.
Claim 21
Independent Claim
233 words
An apparatus of X-ray computerized tomography comprising a scanner in which an X-ray source for irradiating an X-ray in a cone-beam shape to an object and a two-dimensional detector for detecting the X-ray transmitted through said object are installed and means for rotating said scanner around said object, changing a projection angle, and reconstructing a distribution of X-ray attenuation coefficients of said object from the transmitted X-ray images obtained at a plurality of said projection angles, comprising: a memory medium for storing a first transmitted X-ray image measured in a state in which a contrast medium is injected into said object, a second transmitted X-ray image measured in a state in which no contrast medium is injected into said object, and a third transmitted X-ray image measured in a state in which no object is positioned in the apparatus, all at the same projection angle; and a computer for respectively calculating a first projection image from a difference between logarithms of said first and second transmitted X-ray images obtained at said same projection angle, calculating a second projection image from a difference between logarithms of said second and third transmitted X-ray images obtained at said same projection angle, simultaneously reconstructing a first reconstructed image from said first projection image and a second reconstructed image from said second projection image in parallel, and forming a composed image from said first and second reconstructed images.
Claim 22
Independent Claim
233 words
An apparatus of X-ray computerized tomography comprising a scanner in which an X-ray source for irradiating an X-ray in a cone-beam shape to an object and a two-dimensional detector for detecting the X-ray transmitted through said object are installed and means for rotating said scanner around said object, changing a projection angle, and reconstructing a distribution of X-ray attenuation coefficients of said object from the transmitted X-ray images obtained at a plurality of said projection angles, comprising: a memory medium for storing a first transmitted X-ray image measured in a state in which a contrast medium is injected into said object, a second transmitted X-ray image measured in a state in which no contrast medium is injected into said object, and a third transmitted X-ray image measured in a state in which no object is positioned in the apparatus, all at the same projection angle; and a computer for respectively calculating a first projection image from a difference between logarithms of said first and second transmitted X-ray images obtained at said same projection angle, calculating a second projection image from a difference between logarithms of said second and third transmitted X-ray images obtained at said same projection angle, simultaneously reconstructing a first reconstructed image from said first projection image and a second reconstructed image from said second projection image in parallel, and forming a composed image from said first and second reconstructed images.
References Cited (Backward Citations)
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