Matrix inversion tomosynthesis improvements in longitudinal X-ray slice imaging

Claim 2

A tomosynthesis apparatus, comprising: an x-ray tomography machine for producing a plurality of x-ray projection images of a subject including an x-ray source, and detection means; and processing means, connected to receive said plurality of projection images, for: (a) shifting and reconstructing said projection x-ray images to obtain a tomosynthesis matrix of images T; (b) acquiring a blurring matrix F having components which represent out-of-focus and in-focus components of said matrix T; (c) obtaining a matrix P representing only in-focus components of said imaged subject by solving a matrix equation including said matrix T and said matrix F; (d) correcting said matrix P for low spatial frequency components; and (e) displaying images indicative of contents of said matrix P.

Claim 3

An apparatus as in claim 1 wherein said processing means is also for correcting said images to improve reconstruction of between-plane structures.

Claim 4

An apparatus as in claim 1 wherein said processing means is also for weighting said projection images before said shifting and reconstructing, each said image being weighted in a way such that images obtained towards a ninety-degree orientation of said x-ray source and detection means are more heavily weighted than images obtained towards shallower angle orientation of said x-ray source and detection means.

Claim 5

An apparatus as in claim 3 wherein said processing means includes means for imaging an area outside said subject and correcting all of said image by an amount to cancel non-zero image components of said area outside said subject, to correct for said low spatial frequencies.

Claim 6

An apparatus as in claim 4 wherein said imaging means includes means for imaging an area outside said subject, means for determining a DC level in a predetermined area of said area outside of the subject, and means for adding a correction factor to said image to reduce said DC level to zero in said predetermined area.

Claim 7

An apparatus as in claim 5 wherein said imaging means includes means for iteratively determining low spatial frequency components of said area outside the subject, means for determining inverses of said low spatial frequency components, and means for adding said inverses to said image to zero out said low spatial frequency components in said area outside the subject.

Claim 8

An apparatus as in claim 6 wherein said tomography machine includes means for producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and wherein said processing means is also for replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 9

An apparatus as in claim 7 wherein said x-ray tomography machine comprises: a patient table for receiving a patient; an x-ray source on one side of said patient; and means for receiving an x-ray image on the other side of said patient.

Claim 10

An apparatus as in claim 8 further comprising an array processor coupled to said processing means, for Fourier transforming said plurality of x-ray images and for solving said matrix equation, thereby accelerating said processing means.

Claim 11

An apparatus as in claim 1 wherein said processing means includes means for imaging an area outside said subject and correcting all of said image by an amount to cancel non-zero image components of said area outside said subject, to correct for said low spatial frequencies.

Claim 12

An apparatus as in claim 10 wherein said imaging means includes means for determining a DC level in a predetermined area of said area outside of the subject, and means for adding a correction factor to said image to reduce said DC level to zero in said predetermined area.

Claim 13

An apparatus as in claim 10 wherein said imaging means includes means for iteratively determining low spatial frequency components of said area outside the subject, means for determining inverses of said low spatial frequency components, and means for adding said inverses to said image to zero out said low spatial frequency components in said area outside the subject.

Claim 14

An apparatus as in claim 1 wherein said tomography machine includes means for producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and wherein said processing means is also for replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 15

A tomosynthesis apparatus, comprising: an x-ray tomography machine for producing a plurality of x-ray projection images of a subject including an x-ray source, and detection means; and processing means, connected to receive said plurality of projection images, for: (a) weighting each said projection image according to a position of each said image, such that images obtained toward a ninety degree orientation of said x-ray source and detection means are more heavily weighted than images obtained towards shallower angle orientations of said x-ray source and detection means; (b) shifting and reconstructing said projection images to obtain a tomosynthesis matrix of images T; (c) acquiring a blurring matrix F representing out-of-focus and in-focus components of said matrix T; (d) obtaining a matrix P representing only in-focus components of said x-ray imaged subject by solving a matrix equation including said matrix T and said matrix F; and (e) displaying images indicative of the contents of said matrix P.

Claim 16

A tomosynthesis apparatus, comprising: an x-ray tomography machine for producing a plurality of x-ray projection images of a subject including an x-ray source, and detection means; and processing means, connected to receive said plurality of projection images, for: (a) weighting each said projection image according to a position of each said image, such that images obtained toward a ninety degree orientation of said x-ray source and detection means are more heavily weighted than images obtained towards shallower angle orientations of said x-ray source and detection means; (b) shifting and reconstructing said projection images to obtain a tomosynthesis matrix of images T; (c) acquiring a blurring matrix F representing out-of-focus and in-focus components of said matrix T; (d) obtaining a matrix P representing only in-focus components of said x-ray imaged subject by solving a matrix equation including said matrix T and said matrix F; and (e) displaying images indicative of the contents of said matrix P.

Claim 17

An apparatus as in claim 14 wherein said processing means includes means for imaging an area outside said subject and correcting for non-zero components thereof.

Claim 18

An apparatus as in claim 15 further comprising: means for analyzing an image area of a particular column of a particular image of said matrix P, said image area being one outside the subject; means for determining a non-zero component of said image area and producing a correction value substantially equal to said non-zero component, but having a negative value compared therewith; means for adding said correction value to said column to zero out said area outside said subject; and means for controlling said analyzing means, said determining means and said adding means to operate for all of said columns in all of said images in said matrix P.

Claim 19

An apparatus as in claim 16 wherein said processing means further comprises: means for imaging an area outside the subject; means for iteratively determining a plurality of low spatial frequencies; means for determining non-zero components of said area outside the subject respectively occurring at said plurality of low spatial frequencies; and means for adding a value of each of said spatial frequencies to said image which cancels said low spatial frequencies in said area.

Claim 20

An apparatus as in claim 17 wherein said tomography machine includes means for producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and wherein said processing means is also for replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 21

An apparatus as in claim 14 further comprising: means for analyzing an image area of a particular column of a particular image of said matrix P, said image area being one outside the subject; means for determining a non-zero component of said image area and producing a correction value substantially equal to said non-zero component, but having a negative value compared therewith; means for adding said correction value to said column to zero out said area outside said subject; and means for controlling said analyzing means, said determining means and said adding means to operate, for all of said columns in all of aid images in said matrix P.

Claim 22

An apparatus as in claim 14 wherein said processing means further comprises: means for imaging an area outside the subject; means for iteratively determining a plurality of low spatial frequencies; means for determining non-zero components of said area outside the subject respectively occurring at said plurality of low spatial frequencies; and means for adding a value of each of said spatial frequencies to said image which cancels said low spatial frequencies in said area.

Claim 23

An apparatus as in claim 20 wherein said processing means further comprises a column counter and a frequency counter for maintaining a count of respective columns and frequencies, respectively.

Claim 24

An apparatus as in claim 14 wherein said tomography machine includes means for producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and wherein said processing means is also for replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 25

An apparatus as in claim 12 wherein said processing means is also for receiving said plurality of images and Fourier transforming said plurality of images.

Claim 26

An apparatus as in claim 14 wherein said processing means is also for: (f) initiating an image counter which points to a specific image contained in said matrix P; (g) initiating a frequency counter which maintains a spatial frequency value ω; (h) determining if areas outside said subject for said image represented by said image counter have a non-zero value at said frequency ω; (i) determining a value to cancel said non-zero value, and adding said value to said image of said subject; (j) determining if said frequency value ω is below a limit; (k) incrementing said frequency value ω if below said limit and repeating said functions (h)-(k) until above said limit; (l) determining if said image counter is above a limit; (m) incrementing said image counter if below said limit and repeating said functions (g)-(m) until said image counter is above said limit; and (n) displaying images indicative of contents of said matrix P as corrected by said functions (f)-(m).

Claim 27

An apparatus as in claim 24 wherein said processing means includes means for imaging an area outside said subject and correcting all of said image by an amount to cancel non-zero image components of said area outside said subject, to correct for low spatial frequencies.

Claim 28

An apparatus as in claim 25 wherein said imaging means includes means for imaging an area outside said subject, means for determining a DC level in a predetermined area of said area outside of the subject, and means for adding a correction factor to said image to cancel out said DC level in said predetermined area.

Claim 29

An apparatus as in claim 26 wherein said imaging means includes means for iteratively determining non-zero components of said area outside the subject and adding a correction for specific spatial frequency components to zero out said non-zero areas.

Claim 30

An apparatus as in claim 27 wherein said tomography machine includes means for producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and wherein said processing means is also for replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 31

An apparatus as in claim 28 wherein said x-ray tomography machine comprises a patient table for receiving a patient; an x-ray source on one side of said patient; and means for receiving an x-ray image on the other side of said patient.

Claim 32

An apparatus as in claim 29 wherein said imaging means further comprises: a frequency counter for maintaining a count of a particular spatial frequency; a column counter for maintaining a count of a particular image column; means for analyzing an image area which is outside the subject for said particular image column to determine a value of said particular frequency; means for adding a value of said frequency to said column in order to cancel out said particular frequency; means for incrementing said frequency counter; and means for incrementing said column counter.

Claim 33

A tomosynthesis apparatus, comprising: an x-ray tomography machine for producing a plurality of x-ray projection images of a subject and of an area outside said subject including an x-ray source, and detection means; and processing means, connected to receive said plurality of images, for: (a) shifting and reconstructing said projection x-ray images to obtain a tomosynthesis matrix of images T; (b) acquiring a blurring matrix F having components which represent out-of-focus and in-focus components of said matrix T; (c) obtaining a matrix P representing only in-focus components of said x-ray imaged subject by solving a matrix equation including said matrix T and said matrix F; (d) determining a DC level in at least a portion of said area outside of the subject; (e) adding a correction factor to said image to substantially zero out said DC level in said predetermined area, to form a corrected matrix P; and (f) displaying images indicative of contents of said corrected matrix P.

Claim 34

A tomosynthesis apparatus, comprising: an x-ray tomography machine for producing a plurality of x-ray projection images of a subject and of an area outside said subject including an x-ray source, and detection means; and processing means, connected to receive said plurality of images, for: (a) shifting and reconstructing said projection x-ray images to obtain a tomosynthesis matrix of images T; (b) acquiring a blurring matrix F having components which represent out-of-focus and in-focus components of said matrix T; (c) obtaining a matrix P representing only in-focus components of said x-ray imaged subject by solving a matrix equation including said matrix T and said matrix F; (d) determining a DC level in at least a portion of said area outside of the subject; (e) adding a correction factor to said image to substantially zero out said DC level in said predetermined area, to form a corrected matrix P; and (f) displaying images indicative of contents of said corrected matrix P.

Claim 35

An apparatus as in claim 31 wherein said processing means is also for weighting said projection images before shifting and correcting, each image being weighted in a way such that images obtained towards a ninety-degree orientation of said x-ray source and detection means are weighted higher than images obtained towards shallower angle orientation on said x-ray source and detection means.

Claim 36

An apparatus as in claim 32 wherein said processing means includes means for iteratively determining non-zero components of said area outside the subject and adding a correction for specific spatial frequency components to zero out said non-zero areas.

Claim 37

An apparatus as in claim 33 wherein said tomography machine includes means for producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and wherein said processing means is also for replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 38

An apparatus as in claim 34 wherein said processing means comprises: means for analyzing an image area outside the subject for a particular column in a particular image; means for determining a non-zero DC component of said column; and means for adding values to each of said columns in said images which zeros out said area outside said subject.

Claim 39

An apparatus as in claim 31 wherein said processing means includes means for iteratively determining non-zero components of said area outside the subject and adding a correction for specific spatial frequency components to zero out said non-zero areas.

Claim 40

An apparatus as in claim 31 wherein said tomography machine includes means for producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and wherein said processing means is also for replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 41

An apparatus as in claim 31 wherein said processing means comprises: means for analyzing an image area outside the subject for a particular column in a particular image; means for determining a non-zero DC component of said column; and means for adding values to each of said columns in said images which zero out said area outside said subject.

Claim 42

An apparatus as in claim 31 wherein said imaging means further comprises: a frequency counter for maintaining a count of a particular spatial frequency: a column counter for maintaining a count of a particular image column; means for analyzing an image area outside the subject for said particular column to determine a value of said particular frequency; means for adding a value of said frequency to said column which zeros out said particular frequency; means for incrementing said frequency counter; and means for incrementing said column counter.

Claim 43

A tomosynthesis apparatus, comprising: an x-ray tomography machine including an x-ray source, and detection means for producing a plurality of x-ray images of a subject including data from a wide scan of said x-ray source and data from a narrow scan of an x-ray source; and processing means, connected to receive said plurality of images, for; (a) Fourier transforming said plurality of x-ray images; (b) shifting and reconstructing said x-ray images to obtain tomosynthesis matrices of images T N and T W representing said narrow and wide swings of said x-ray tube respectively; (c) acquiring blurring matrices F N and F W having components which represent out-of-focus and in-focus components of said matrices T N and T W respectively; (d) multiplying said matrices T N and T W by inverses of said matrices F N and F W respectively, to obtain matrices PN and PW respectively, each representing only in-focus components of said x-ray imaged subject; (e) replacing low spatial frequencies in said matrix P N with low spatial frequencies from said matrix P W to obtain a matrix P; (f) inverse Fourier transforming said matrix P to obtain a matrix P; and (g) displaying images indicative of contents of said matrix P.

Claim 44

A tomosynthesis apparatus, comprising: an x-ray tomography machine including an x-ray source, and detection means for producing a plurality of x-ray images of a subject including data from a wide scan of said x-ray source and data from a narrow scan of an x-ray source; and processing means, connected to receive said plurality of images, for; (a) Fourier transforming said plurality of x-ray images; (b) shifting and reconstructing said x-ray images to obtain tomosynthesis matrices of images T N and T W representing said narrow and wide swings of said x-ray tube respectively; (c) acquiring blurring matrices F N and F W having components which represent out-of-focus and in-focus components of said matrices T N and T W respectively; (d) multiplying said matrices T N and T W by inverses of said matrices F N and F W respectively, to obtain matrices PN and PW respectively, each representing only in-focus components of said x-ray imaged subject; (e) replacing low spatial frequencies in said matrix P N with low spatial frequencies from said matrix P W to obtain a matrix P; (f) inverse Fourier transforming said matrix P to obtain a matrix P; and (g) displaying images indicative of contents of said matrix P.

Claim 45

An apparatus as in claim 40 wherein said processing means is also for weighting said projection images before shifting and correcting, each image being weighted in a way such that images obtained towards a ninety-degree orientation of said x-ray source and detection means are weighted heavier than images obtained towards shallower angle orientation of said x-ray source and detection means.

Claim 46

An apparatus as in claim 41 wherein said correcting means is also for imaging an area outside said subject and correcting for non-zero spatial frequency components of said area outside said subject.

Claim 47

An apparatus as in claim 42 wherein said processing means further includes means for imaging an area outside said subject, means for determining a DC level in a predetermined area outside of said subject, and means for adding a correction factor to said image to zero out said DC level in said predetermined area.

Claim 48

An apparatus as in claim 43 wherein said processing means includes means for iteratively determining non-zero spatial frequency components of said area outside the subject and adding a correction to said image to zero out said non-zero areas.

Claim 49

An apparatus as in claim 44 wherein said processing means includes an array processor for Fourier transforming said images and for performing matrix operations.

Claim 50

An apparatus as in claim 45 wherein said imaging means further comprises: a frequency counter for maintaining a count of a particular image column; a column counter for maintaining a count of a particular image column; means for analyzing an image area which is outside the subject for said particular column to determine a value of said particular frequency; means for adding a value of said spatial frequency to said column in said image which cancels out said particular frequency in said area outside the subject; means for incrementing said frequency counter; and means for incrementing said column counter.

Claim 51

An apparatus as in claim 40 wherein said processing means is also for imaging an area outside said subject and correcting for non-zero spatial frequency components of said area outside said subject.

Claim 52

An apparatus as in claim 47 wherein said processing means further includes means for determining a DC level in a predetermined area outside of said subject, and means for adding a correction factor to said image to zero out said DC level in said predetermined area.

Claim 53

An apparatus as in claim 47 wherein said processing means includes means for iteratively determining non-zero spatial frequency components of said area outside the subject and adding a correction to said image to zero out said non-zero areas.

Claim 54

An apparatus as in claim 40 wherein said processing means includes an array processor for Fourier transforming said images and for performing said matrix operations.

Claim 55

An apparatus as in claim 40 wherein said imaging means further comprises: a frequency counter for maintaining a count of a particular frequency; a column counter for maintaining a count of a particular image column; means for analyzing an image area which is outside the subject for said particular column to determine a value of said particular frequency; means for adding a value of said spatial frequency to said column in said image which conceals out said particular frequency in said area outside the subject; means for incrementing said frequency counter; and means for incrementing said column counter.

Claim 56

A tomosynthesis apparatus, comprising: an x-ray tomography machine for producing a plurality of x-ray projection images of a subject and of areas outside said subject including an x-ray source, and detection means; and processing means, connected to receive said plurality of images, for: (a) shifting and reconstructing said x-ray images to obtain a tomosynthesis matrix of images T; (b) acquiring a blurring matrix F having components which represent out-of-focus and in-focus components of said matrix T; (c) obtaining a matrix P representing only in-focus components of said x-ray imaged subject by solving a matrix equation including said matrix T and said matrix F; (d) initiating an image counter which points to a specific image in said matrix P; (e) initiating a frequency counter which maintains a spatial frequency value ω; (f) determining if said areas outside said subject at said image of said image counter have a non-zero value at said spatial frequency ω; (g) determining a value of said spatial frequency ω to cancel said non-zero value, and adding said value to said image of said subject; (h) determining if said frequency value ω is below a limit; (i) incrementing said frequency value ω if below said limit and repeating said functions (f), (g), (h) and (i) until above said limit; (j) determining if said image counter is above a limit; (k) incrementing said image counter if below said limit and repeating said functions (e)-(k) until said image counter is above said limit; and (l) displaying images indicative of contents of said matrix P as corrected by said functions (d)-(k).

Claim 57

A tomosynthesis apparatus, comprising: an x-ray tomography machine for producing a plurality of x-ray projection images of a subject and of areas outside said subject including an x-ray source, and detection means; and processing means, connected to receive said plurality of images, for: (a) shifting and reconstructing said x-ray images to obtain a tomosynthesis matrix of images T; (b) acquiring a blurring matrix F having components which represent out-of-focus and in-focus components of said matrix T; (c) obtaining a matrix P representing only in-focus components of said x-ray imaged subject by solving a matrix equation including said matrix T and said matrix F; (d) initiating an image counter which points to a specific image in said matrix P; (e) initiating a frequency counter which maintains a spatial frequency value ω; (f) determining if said areas outside said subject at said image of said image counter have a non-zero value at said spatial frequency ω; (g) determining a value of said spatial frequency ω to cancel said non-zero value, and adding said value to said image of said subject; (h) determining if said frequency value ω is below a limit; (i) incrementing said frequency value ω if below said limit and repeating said functions (f), (g), (h) and (i) until above said limit; (j) determining if said image counter is above a limit; (k) incrementing said image counter if below said limit and repeating said functions (e)-(k) until said image counter is above said limit; and (l) displaying images indicative of contents of said matrix P as corrected by said functions (d)-(k).

Claim 58

An apparatus as in claim 52 wherein said processing means is also for weighting said projection images before shifting and correcting, each image being weighted in a way such that images obtained towards a ninety-degree orientation of said x-ray source and detection means are weighted higher than images obtained towards shallower angle orientation of said x-ray source and detection means.

Claim 59

An apparatus as in claim 53 wherein said processing means is also for imaging an area outside said subject, determining a DC level in a predetermined area outside of the subject, and for adding a correction factor to said image to zero out said DC level of said predetermined area.

Claim 60

An apparatus as in claim 54 wherein said tomography machine includes means for producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and wherein said processing means is also for replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 61

An apparatus as in claim 55 wherein said x-ray tomography machine comprises a patient table for receiving a patient; an x-ray source on one side of said patient; and means for receiving an x-ray image on the other side of said patient.

Claim 62

An apparatus as in claim 52 wherein said processing means is also for determining a DC level in a predetermined area outside of the subject, and for adding a correction factor to said image to zero out said DC level of said predetermined area.

Claim 63

An apparatus as in claim 52 wherein said tomography machine includes means for producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and wherein said processing means is also for replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 64

A tomosynthesis apparatus, comprising: an x-ray tomography machine for producing a plurality of x-ray images of a subject and of areas outside said subject; and processing means, connected to receive said plurality of x-ray images of a subject and of areas outside said subject; and processing means, connected to receive said plurality of images, for: (a) Fourier transforming said plurality of x-ray images; (b) shifting and reconstructing said x-ray images to obtain tomosynthesis matrices of images T N and T W representing narrow and wide swings of said x-ray tube respectively; (c) acquiring blurring matrices F N and F W having components which represent out-of-focus and in-focus components of said matrices T N and T W ; (d) multiplying said matrices T N and T W by inverses of said matrices F N and F W respectively to obtain matrices P N and P W respectively, each representing only in-focus components of said x-ray imaged subject; (e) replacing low spatial frequencies in said matrix P N with low spatial frequencies from said matrix P W to obtain a matrix P; (f) inverse Fourier transforming said matrix P to obtain a matrix P; (g) initiating an image counter which points to a specific image of said matrix P; (h) initiating a frequency counter which maintains a spatial frequency value ω; (i) determining if said areas outside said subject at said image of said image counter have a non-zero value at said frequency ω; (j) determining a value of said spatial frequency to cancel said non-zero value, and adding said value to said image of said subject; (k) determining if said frequency value ω is below said limit and repeating said functions (f), (g), (h) and (i) until above said limit; (l) incrementing said frequency value ω if below said limit and repeating said functions (f), (g), (h) and (i) until above said limit; (m) determining if said image counter is above a limit; (n) incrementing said image counter if below said limit and repeating said functions (e)-(k) until said image counter is above said limit; and (o) determining a DC level in at least a portion of said area outside of the subject; (p) adding a correction factor to said image to substantially zero out said DC level in said portion; and (q) displaying images indicative of contents of a corrected matrix P.

Claim 65

A tomosynthesis apparatus, comprising: an x-ray tomography machine for producing a plurality of x-ray images of a subject and of areas outside said subject; and processing means, connected to receive said plurality of x-ray images of a subject and of areas outside said subject; and processing means, connected to receive said plurality of images, for: (a) Fourier transforming said plurality of x-ray images; (b) shifting and reconstructing said x-ray images to obtain tomosynthesis matrices of images T N and T W representing narrow and wide swings of said x-ray tube respectively; (c) acquiring blurring matrices F N and F W having components which represent out-of-focus and in-focus components of said matrices T N and T W ; (d) multiplying said matrices T N and T W by inverses of said matrices F N and F W respectively to obtain matrices P N and P W respectively, each representing only in-focus components of said x-ray imaged subject; (e) replacing low spatial frequencies in said matrix P N with low spatial frequencies from said matrix P W to obtain a matrix P; (f) inverse Fourier transforming said matrix P to obtain a matrix P; (g) initiating an image counter which points to a specific image of said matrix P; (h) initiating a frequency counter which maintains a spatial frequency value ω; (i) determining if said areas outside said subject at said image of said image counter have a non-zero value at said frequency ω; (j) determining a value of said spatial frequency to cancel said non-zero value, and adding said value to said image of said subject; (k) determining if said frequency value ω is below said limit and repeating said functions (f), (g), (h) and (i) until above said limit; (l) incrementing said frequency value ω if below said limit and repeating said functions (f), (g), (h) and (i) until above said limit; (m) determining if said image counter is above a limit; (n) incrementing said image counter if below said limit and repeating said functions (e)-(k) until said image counter is above said limit; and (o) determining a DC level in at least a portion of said area outside of the subject; (p) adding a correction factor to said image to substantially zero out said DC level in said portion; and (q) displaying images indicative of contents of a corrected matrix P.

Claim 68

A method as in claim 60 comprising the further step of weighting said images before shifting and correcting, each plane being weighted in a way such that images obtained toward a ninety degree orientation of said x-ray source and detection means are more heavily weighted than images obtained towards shallower angle orientations of said x-ray source and detection means.

Claim 69

A method as in claim 61 comprising the further steps of iteratively determining non-zero components of said area outside the subject and adding a correction for specified spatial frequency components to zero out said non-zero areas.

Claim 70

A method as in claim 60 comprising the further steps of iteratively determining non-zero components of said area outside the subject and adding a correction for specific spatial frequency components to zero out said non-zero areas.

Claim 71

A method as in claim 60 comprising the further steps of producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and wherein said processing means is also for replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 74

A method as in claim 65 comprising the further step of imaging an area outside said subject and correcting for non-zero components thereof.

Claim 75

A method as in claim 66 comprising the further steps of: analyzing an image area of a particular column of a particular image of said matrix P, said image area being one outside the subject; determining a non-zero component of said image area and producing a correction value substantially equal to said non-zero component, but having a negative value compared therewith; adding said correction value to said column to zero out said area outside said subject; and controlling said analyzing step, said determining step and said adding step to operate for all of said columns in all of said images in said matrix P.

Claim 76

A method as in claim 67 comprising the further steps of: imaging an area outside the subject; iteratively determining a plurality of low spatial frequencies; determining non-zero components of said area outside the subject respectively occurring at said plurality of low spatial frequencies; and adding a value of each of said spatial frequencies to said image which cancels said low spatial frequencies in said area.

Claim 77

A method as in claim 68 comprising the further steps of: producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 78

A method as in claim 65 comprising the further steps of: analyzing an image area of a particular column of a particular image of said matrix P, said image area being one outside the subject; determining a non-zero component of said image area and producing a correction value substantially equal to said non-zero component, but having a negative value compared therewith; adding said correction value to said column to zero out said area outside said subject; and controlling said analyzing step, said determining step and said adding step to operate for all of said columns in all of said images in said matrix P.

Claim 79

A method as in claim 65 comprising the further steps of: imaging an area outside the subject; iteratively determining a plurality of low spatial frequencies; determining non-zero components of said area outside the subject respectively occurring at said plurality of low spatial frequencies; and adding a value of each of said spatial frequencies to said image which cancels said low spatial frequencies in said area.

Claim 80

A method as in claim 71 comprising the further step of: maintaining a count of respective columns and frequencies, respectively.

Claim 81

A method as in claim 65 comprising the steps of: producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 82

A method as in claim 65 comprising the further steps of: (a) initiating an image counter which points to a specific image contained in said matrix P; (b) initiating a frequency counter which maintains a spatial frequency value ω; (c) determining if areas outside said subject for said image represented by said image counter have a non-zero value at said frequency ω; (d) determining a value to cancel said non-zero value, and adding said value to said image of said subject; (e) determining if said frequency value ω is below a limit; (f) incrementing said frequency value ω if below said limit and repeating said steps (c)-(f) until above said limit; (g) determining if said image counter is above a limit; (h) incrementing said image counter if below said limit and repeating said steps (b)-(h) until said image counter is above said limit; and (i) displaying images indicative of contents of said matrix P as corrected.

Claim 83

A method as in claim 65 comprising the further steps of: maintaining a count of a particular spatial frequency; maintaining a count of a particular image column; analyzing an image area which is outside the subject for said particular image column to determine a value of said particular frequency; adding a value of said frequency to said column in order to cancel out said particular frequency; incrementing said frequency counter; and incrementing said column counter.

Claim 86

A method as in claim 76 comprising the further step of: weighting said projection images before shifting and correcting, each image being weighted in a way such that images obtained towards a ninety-degree orientation of an x-ray source and detection means are weighted higher than images obtained towards shallower angle orientations of said x-ray source and detection means.

Claim 87

A method as in claim 77 comprising the further step of: iteratively determining non-zero components of said area outside the subject and adding a correction for specific spatial frequency components to zero out said non-zero areas.

Claim 88

A method as in claim 78 comprising the further steps of: producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 89

A method as in claim 79 comprising the further steps of: analyzing an image area outside the subject for a particular column in a particular image; determining a non-zero DC component of said column; and adding values to each of said columns in said images which zero out said area outside said subject.

Claim 90

A method as in claim 76 comprising the further step of: iteratively determining non-zero components of said area outside the subject and adding a correction for specific spatial frequency components to zero out said non-zero areas.

Claim 91

A method as in claim 76 comprising the further step of: producing data from a wide scan of an x-ray source and data from a narrow scan of an x-ray source, and replacing low spatial frequencies from said narrow scan of said x-ray source with low spatial frequencies from said wide scan of said x-ray source.

Claim 92

A method as in claim 76 comprising the further steps of: analyzing an image area outside the subject for a particular column in a particular image; determining a non-zero DC component of said column; and adding values to each of said columns in said images which zero out said area outside said subject.

Claim 93

A method as in claim 76 comprising the further steps of: maintaining a count of a particular spatial frequency; maintaining a count of a particular image column; analyzing an image area outside the subject for said particular column to determine a value of said particular frequency; adding a value of said frequency to said column which zeros out said particular frequency; incrementing said frequency counter; and incrementing said column counter.

Claim 96

A method as in claim 85 comprising the further steps of weighting said projection images before shifting and correcting, each image being weighted in a way such that images obtained towards a ninety-degree orientation of said x-ray source and detection means are weighted heavier than images obtained towards shallower angle orientations of said x-ray source and detection means.

Claim 97

A method as in claim 86 comprising the further steps of imaging an area outside said subject and correcting for non-zero spatial frequency components of said area outside said subject.

Claim 98

A method as in claim 87 comprising the further steps of imaging an area outside said subject, determining a DC level in a predetermined area outside of said subject, adding a correction factor to said image to zero out said DC level in said image to zero out said DC level in said predetermined area.

Claim 99

A method as in claim 88 comprising the further steps of iteratively determining non-zero spatial frequency components of said area outside the subject and adding a correction to said image to zero out said non-zero areas.

Claim 100

A method as in claim 85 comprising the further steps of imaging an area outside said subject and correcting for non-zero spatial frequency components of said area outside said subject.

Claim 101

A method as in claim 90 comprising the further steps of determining a DC level in a predetermined area outside of said subject, and adding a correction factor to said image to zero said DC level in said predetermined area.

Claim 102

A method as in claim 90 comprising the further steps of iteratively determining non-zero spatial frequency component of said area outside the subject and adding a correction to said image to zero out said non-zero areas.