Method for obtaining tomosynthesis images

Patent metadata

Field	Value
Publication number	US-9861323-B2
Application number	US-201314065864-A
Country	US
Kind code	B2
Filing date	Oct 29, 2013
Priority date	Oct 30, 2012
Publication date	Jan 9, 2018
Grant date	Jan 9, 2018

Abstract

A method for obtaining tomosynthesis images of an object of interest using an imaging system, wherein the imaging system comprises an X-ray source arranged to facing a detector on which the object of interest is positioned. The method comprises acquiring a plurality of projected 2D images of the object of interest in a plurality of orientations identified relative to a perpendicular to the detector, wherein a zero orientation is closest to the perpendicular and applying at least one filter to the acquired projected 2D images to obtain filtered, projection images of the object of interest. The method further comprises determining a reconstruction slice of the object of interest from the backprojection of at least two of the filtered projections, the set of reconstruction slices being the filtered, reconstructed volume of the object of interest, wherein a filter used on the 2D projection images is an adaptive filter.

First claim

What is claimed is:

1. A method for obtaining tomosynthesis images of an object of interest using an imaging system, wherein the imaging system comprises an X-ray source with an X-ray tube facing a detector on which the object of interest is positioned, the method comprising:
acquiring a plurality of projected 2D images of the object of interest in a plurality of orientations at which the X-ray source emits an X-ray beam, where the orientations are identified relative to the X-ray beam axis direction perpendicular to the detector, wherein a zero orientation is closest to the perpendicular;
applying at least one filter to the acquired projected 2D images to obtain filtered, projection images of the object of interest,
wherein at least one of the at least one filter applied to the acquired projected 2D images enhances high frequencies relative to low frequencies of the correspondingly obtained filtered projection images,
wherein at least one of the at least one filter applied comprises an amplification factor which varies according to x, y coordinates of pixels in the plane of the acquired projected 2D images, and
wherein at least one of the at least one filter is applied in the direction corresponding to an X-ray beam scanning direction in the acquired projected 2D images;
wherein at least one of the at least one filter applied to the acquired projected 2D images is a sum of a low-pass filter and an amplification factor of a difference between a value of a pixel at a given point and a value filtered by a low-pass filter for the pixel at the given point, and wherein the low pass filter is applied as a Gaussian distribution over values of pixels within a predetermined window neighboring the pixel at the given point; and

obtaining a set of tomosynthesis images of the object of interest from a backprojection of at least two of the filtered projection images, the set of tomosynthesis images being a filtered, reconstructed volume of the object of interest,
wherein at least one of the at least one filter is an adaptive type filter.

2. The method according to claim 1 , wherein at least one of the at least one filter applied to the acquired projected 2D images is an unsharp masking type filter.

3. The method according to claim 2 , wherein at least one of the at least one filter applied to the acquired projected 2D images is a sum of a bilateral filter and an amplification of the difference between the value of a pixel at a given point and a value filtered by this bilateral filter for this pixel.

4. The method according to claim 1 , wherein at least one of the at least one filter applied to the acquired projected 2D images enhances the high frequencies with an amplification factor which is a function of the local contrast of the processed projected 2D image.

5. The method according to claim 4 , wherein the local contrast in a pixel of the acquired projected 2D images is the difference between the value of this pixel and the value filtered by a low-pass filter for this pixel.

6. The method according to claim 4 , wherein the local contrast in a pixel of the acquired projected 2D images is the difference between the value of this pixel and the value filtered by a bilateral filter for this pixel.

7. The method according to claim 1 , wherein at least one of the at least one filter applied to the acquired projected 2D images enhances the high frequencies with an amplification factor which is a function of a distance to the edge of a breast.

8. The method according to claim 1 , wherein in an application to mammography, at least one of the at least one filter applied to the acquired projected 2D images is a function of a thickness of a breast tissue relative to the perpendicular to the detector and/or of the orientation at which a given projected 2D image is acquired.

9. The method according to claim 1 , wherein in an application to mammography, at least one of the at least one filter applied to the acquired projected 2D images applies enhancement processing to the pixels with an amplification factor which is function of a thickness of a breast tissue relative to the perpendicular to the detector and/or of the orientation at which a given projected 2D image is acquired.

10. The method according to claim 1 , wherein in an application to mammography, the frequency on and after which the amplification is applied is a function of a thickness of a breast tissue relative to the perpendicular to the detector and/or of the orientation at which a given projected 2D image is acquired.

11. The method according to claim 1 , wherein after obtaining the filtered reconstructed volume, obtaining a 2D image resembling a 2D radiological image by combining an image re-projected from the filtered reconstructed volume and the acquired 2D projected image initially acquired in a given orientation of the source.

12. The method according to claim 11 , wherein the combining is a pixel-by-pixel linear combination, and the backprojection and the re-projection is performed in a single computing step.

13. The method according to claim 1 , comprising combining an intermediate 2D image with the acquired 2D projected image initially acquired in an orientation in which the X-ray source emits the X-ray beam in the direction perpendicular to the plane of the detector, in a pixel by pixel linear combination, to obtain a final 2D image of the object of interest.

14. An imaging system comprising:
an X-ray detector on which an object of interest is positioned;
an X-ray emitting source comprising an X-ray tube facing the X-ray detector; and
a processing unit configured to obtain a set of tomosynthesis images of the object of interest, wherein the processing unit is further configured to:
acquire a plurality of projected 2D images of the object of interest in a plurality of orientations at which the X-ray source emits an X-ray beam, where the orientations are identified relative to the X-ray beam axis direction perpendicular to the detector, wherein a zero orientation is closest to the perpendicular;
apply at least one filter to the acquired projected 2D images to obtain filtered, projection images of the object of interest,
wherein at least one of the at least one filter applied to the acquired projected 2D images enhances high frequencies relative to low frequencies in the correspondingly obtained filtered projection images, and
wherein at least one of the at least one filter applied comprises an amplification factor which varies according to x, y coordinates of pixels in the plane of the acquired projected 2D images, and
wherein at least one of the at least one filter is applied in the direction corresponding to an X-ray beam scanning direction in the acquired projected 2D images;
wherein at least one of the at least one filter applied to the acquired projected 2D images is a sum of a low-pass filter and an amplification factor of a difference between a value of a pixel at a given point and a value filtered by a low-pass filter for the pixel at the given point, and wherein the low pass filter is applied as a Gaussian distribution over values of pixels within a predetermined window neighboring the pixel at the given point; and
wherein the set of tomosynthesis images of the object of interest are obtained by performing a backprojection of at least two of the filtered projection images, the set of tomosynthesis images being a filtered reconstructed volume of the object of interest, wherein at least one of the at least one filter is an adaptive type filter.

Assignees

• Gen Electric

Inventors

• Bernard Sylvain
• Souchay Henri

Classifications

• A61B6/5205

  involving processing of raw data to produce diagnostic data · CPC title

• A61B6/502

  for diagnosis of breast, i.e. mammography · CPC title

• A61B6/025 Primary

  Tomosynthesis · CPC title