US 4,903,204 A · Matrix inversion tomosynthesis improvements in longitudinal X-ray slice imaging · patentgrep

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Abstract

The present invention describes improvements to digital tomosynethesis, whereby a plurality of x-ray projection images are shifted and summed to form a matrix of tomographs at variable plane heights. Prior to tomosynthesis, the projection images are weighted by a weighting function which falls off towards shallower angles of the x-ray tube during acquisition, in order to improve the reconstructability of between-plane structures. A matrix of blurring functions is then determined, describing the blurring of structures in all planes for every tomosynthesis reconstruction. Actual patient structures are then reconstructed by solving a matrix equation containing the matrix of tomosynthesized images and the matrix of blurring functions. The patient structure images are then improved by a hybrid correction routine which combines low spatial frequencies from a wide swing of the x-ray source with high and mid spatial frequencies from a narrow swing of the x-ray source. The data, once hybrid corrected, is further corrected using an interative technique to improve the reconstruction of low spatial frequencies. This iterative technique corrects each column of each image by sequentially determining if errant frequency components are present at the edge of the images where the patient is not present. If errant frequency components are found, they are subtracted from the entire image column. Lastly, a DC level correction is performed which corrects for errant zero frequency components by adding a constant value to each image column to force the edge of each image to zero. The data is finally displayed on a display monitor. An interleaving technique is used to vary reconstructed plane heights in order to permit improved interplane resolution.

Claims94

Dependent claims

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.

6 more elements

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.

6 more elements

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.

7 more elements

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.sub.N and T.sub.W representing said narrow and wide swings of said x-ray tube respectively;
(c) acquiring blurring matrices F.sub.N and F.sub.W having components which represent out-of-focus and in-focus components of said matrices T.sub.N and T.sub.W respectively;
(d) multiplying said matrices T.sub.N and T.sub.W by inverses of said matrices F.sub.N and F.sub.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.sub.N with low spatial frequencies from said matrix P.sub.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.

8 more elements

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 .omega.;
(f) determining if said areas outside said subject at said image of said image counter have a non-zero value at said spatial frequency .omega.;
(g) determining a value of said spatial frequency .omega. to cancel said non-zero value, and adding said value to said image of said subject;
(h) determining if said frequency value .omega. is below a limit;
(i) incrementing said frequency value .omega. 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).

13 more elements

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.sub.N and T.sub.W representing narrow and wide swings of said x-ray tube respectively;
(c) acquiring blurring matrices F.sub.N and F.sub.W having components which represent out-of-focus and in-focus components of said matrices T.sub.N and T.sub.W ;
(d) multiplying said matrices T.sub.N and T.sub.W by inverses of said matrices F.sub.N and F.sub.W respectively to obtain matrices P.sub.N and P.sub.W respectively, each representing only in-focus components of said x-ray imaged subject;
(e) replacing low spatial frequencies in said matrix P.sub.N with low spatial frequencies from said matrix P.sub.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 .omega.;
(i) determining if said areas outside said subject at said image of said image counter have a non-zero value at said frequency .omega.;
(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 .omega. is below said limit and repeating said functions (f), (g), (h) and (i) until above said limit;
(l) incrementing said frequency value .omega. 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.

21 more elements

A method of matrix-inversion tomosynthesis correction, comprising the steps of:

producing a plurality of x-ray projection images of a subject;
weighting each said projection image according to a position of each said image, such that images obtained toward a ninety degree orientation of an 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;
shifting and reconstructing said projection images to obtain a tomosynthesis matrix of images T;
acquiring a blurring matrix F representing out-of-focus and in-focus components of said matrix T;
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
displaying images indicative of the contents of said matrix P.

4 more elements

A method of matrix-inversion tomosynthesis correction, comprising the steps of:

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;
Fourier transforming said plurality of x-ray images;
shifting and reconstructing said x-ray images to obtain tomosynthesis matrices of images T.sub.N and T.sub.W representing said narrow and wide scans of said x-ray tube respectively;
acquiring blurring matrices F.sub.N and F.sub.W having components which represent out-of focus and in-focus components of said matrices T.sub.N and T.sub.W respectively;
multiplying said matrices T.sub.N and T.sub.W by inverses of said matrices F.sub.N and F.sub.W respectively, to obtain matrices P.sub.N and P.sub.W respectively, each representing only in-focus components of said x-ray imaged subject;
replacing low spatial frequencies in said matrix P.sub.N with low spatial frequencies from said matrix P.sub.W to obtain a matrix P;
inverse Fourier transforming said matrix P to obtain a matrix P;
and
displaying images indicative of contents of said matrix P.

6 more elements

A method of matrix-inversion tomosynthesis correction, comprising the steps of:

(a) producing a plurality of x-ray images of a subject and of areas outside said subject;
(b) Fourier transforming said plurality of x-ray images;
(c) shifting and reconstructing said x-ray images to obtain tomosynthesis matrices of images T.sub.N and T.sub.W representing narrow and wide swings of said x-ray tube respectively;
(d) acquiring blurring matrices F.sub.N and F.sub.W having components which represent out-of-focus and in-focus components of said matrices T.sub.N and T.sub.W ;
(e) multiplying said matrices T.sub.N and T.sub.W by inverses of said matrices F.sub.N and F.sub.W respectively to obtain matrices P.sub.N and P.sub.W respectively, each representing only in-focus components of said x-ray imaged subject;
(f) replacing low spatial frequencies in said matrix P.sub.N with low spatial frequencies from said matrix P.sub.W to obtain a matrix P;
(g) 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 .omega.;
(i) determining if said areas outside said subject at said image of said image counter have a non-zero value at said frequency .omega.;
(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 .omega. is below a limit;
(l) incrementing said frequency value .omega. if below said limit and repeating said steps (i)-l) 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 steps (h)-n) 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.

17 more elements

Dependencies are inferred from the claim text.