Matching geometry generation and display of mammograms and tomosynthesis images
View Patent ↗A method and a system for using tomosynthesis projection images of a patient's breast to reconstruct slice tomosynthesis images such that anatomical structures that appear superimposed in a mammogram are at conforming locations in the reconstructed images.
1. A method comprising:
obtaining digital information describing a plurality of 2D x-ray tomosynthesis projection images of a patient's breast taken at different angles and at least one 2D x-ray projection mammogram image of the breast;
using at least some of the information describing the tomosynthesis projection images to derive information describing 2D reconstructed tomosynthesis images representative of respective breast slices;
wherein said reconstructed tomosynthesis images conform to a geometric coordinate system that matches a geometric coordinate system of the projection mammogram image such that anatomical structures that appear in the mammogram image appear at geometrically matching places in respective ones of the reconstructed tomosynthesis images; and
displaying at least some of the mammogram image and the reconstructed tomosynthesis images.
2. A method as in claim 1 wherein said using step comprise using a computer-implemented cone beam reconstruction algorithm that directly generates the information describing said reconstructed tomosynthesis images from information describing said projection tomosynthesis images.
3. A method as in claim 1 wherein said using step comprises generating information describing preliminary tomosynthesis images that represent breast slices but in which anatomical structures that are at different heights in the breast but overlap in the mammogram image appear at geometrically mismatched positions, and using at least some of the information describing the preliminary tomosynthesis images to generate said reconstructed tomosynthesis images.
4. A method as in claim 3 wherein the generating of information describing the preliminary tomosynthesis images comprises conforming the preliminary tomosynthesis images to a preliminary coordinate system different from a coordinate system to which the mammogram image conforms, and processing at least some of the information describing the preliminary tomosynthesis images into information describing said reconstructed tomosynthesis images.
5. A method as in claim 4 wherein the preliminary tomosynthesis images differ from each other in pixel spacing while said reconstructed tomosynthesis images are the same in pixel spacing.
6. A method as in claim 5 wherein the pixel spacing in the reconstructed tomosynthesis images conforms to that of the mammogram image.
7. A method as in claim 1 wherein the reconstructed tomosynthesis images are characterized by pixel spacing that conforms to that of the mammogram image.
8. A method as in claim 1 comprising filtering at least some of the information defining the projection tomosynthesis images to generate filtered information, and backprojecting at least some of the filtered information to generate said information defining the reconstructed tomosynthesis images, for one of said slices at a time, using a geometry matrix as follows,
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u
v
s
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=
(
M
i
)
(
x
y
z
1
)
d
x
=
u
/
s
d
y
=
v
/
s
where M i is a 3×4 geometry matrix for a backprojection i, (x,y,z) is a location of an image pixel in one of said reconstructed tomosynthesis images, and (d x , d y ) is a location on an x-ray detector element or area for a line that connects a focal spot from which the x-ray emanate and the image pixel.
9. A method as in claim 8 further comprising applying a 4×4 matrix multiplication operation to said 3×4 geometry matrix M i according to
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(
M
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)
(
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3
x
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(
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where
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=
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T
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(
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to thereby orient said reconstructed tomosynthesis images at selected directions defined by a choice of said 4×4 matrix.
10. An x-ray system comprising:
an data acquisition unit that uses x-rays emanating from an origin and an x-ray receptor to obtain information describing at least one projection x-ray mammogram of a patient's breast and a plurality of projection tomosynthesis images of the breast taken at respective angles;
a pre-processor that receives said information from the x-ray receptor and subjects it to pre-processing computer operations;
a tomo/mammo image reconstruction unit that receives the pre-processed information and subjects it to further computer processing to form a mammogram image for display and to form reconstructed tomosynthesis images that represent respective slices of the breast for display;
wherein anatomical structures that are at different heights in the breast and are superimposed in the mammogram image appear at locations in the reconstructed tomosynthesis images that conform to their location in the mammogram image; and
a display unit that selectively displays one or more of the reconstructed tomosynthesis images and the mammogram image, said display unit comprising a user interface controlling the display of said images.
11. A system as in claim 10 wherein said image reconstruction unit comprises a computer-implemented cone beam reconstruction algorithm directly generating the reconstructed tomosynthesis images.
12. A system as in claim 10 wherein said image reconstruction unit comprises an algorithm generating information describing preliminary tomosynthesis images that represent breast slices but in which anatomical structures that are at different heights in the breast but overlap in the mammogram image appear at geometrically mismatched positions, and using at least some of the information describing the preliminary tomosynthesis images to generate said reconstructed tomosynthesis images.
13. A system as in claim 12 wherein said reconstruction unit comprises an algorithm conforming the preliminary tomosynthesis images to a preliminary coordinate system different from a coordinate system to which the mammogram image conforms, and processing at least some of the information describing the preliminary tomosynthesis images into information describing said reconstructed tomosynthesis images.
14. A system as in claim 13 wherein said reconstruction unit forms the preliminary tomosynthesis images at pixel spacing that differ from each other and forms said reconstructed tomosynthesis images in pixel spacing that are the same for a plurality of the reconstructed tomosynthesis images.
15. A system as in claim 14 wherein said reconstruction unit forms the reconstructed tomosynthesis images at a pixel spacing that conforms to that of the mammogram image.
16. A system as in claim 10 wherein said reconstruction unit forms the reconstructed tomosynthesis images at a pixel spacing that conforms to that of the mammogram image.
17. A system as in claim 10 in which said reconstruction unit comprises and algorithm filtering at least some of the information defining the projection tomosynthesis images to generate filtered information, and backprojecting at least some of the filtered information to generate said information defining the reconstructed tomosynthesis images, for one of said slices at a time, using a geometry matrix as follows,
(
u
v
s
)
=
(
M
i
)
(
x
y
z
1
)
d
x
=
u
/
s
d
y
=
v
/
s
where M i is a 3×4 geometry matrix for a backprojection i, (x,y,z) is a location of an image pixel in one of said reconstructed tomosynthesis images, and (d x , d y ) is a location on an x-ray detector element or area for a line that connects a focal spot from which the x-ray emanate and the image pixel.
18. A system as in claim 17 wherein said algorithm further comprises applying a 4×4 matrix multiplication operation to said 3×4 geometry matrix M i according to
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u
v
s
)
=
(
M
i
)
(
R
3
x
3
T
3
O
3
T
I
1
)
(
x
′
y
′
z
′
1
)
where
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x
y
z
1
)
=
(
R
3
x
3
T
3
O
3
T
I
1
)
(
x
′
y
′
z
′
1
)
to thereby orient said reconstructed tomosynthesis images at selected directions defined by a choice of said 4×4 matrix.