Motion correction method in dual energy radiography
AssigneeAgfa NV
InventorTom Bertens
Life of this patent
Estimating the term…
Abstract
A motion correction method includes two steps. The first step includes a global motion correction using the bilinear warping technique and a rough delineation of the lung fields. One of the native images (low energy image, high energy image) is deformed to match the other image. In a second step, local motion corrections are applied to the globally motion corrected image by computing a proximity value in small overlapping tiles. Only tiles with a sufficient high proximity value are taken into account. The maximum shift applied in this second step is limited to a few pixels to avoid strong deformations of the native images.
Claims12
A method for correcting motion artifacts in a dual energy radiography image, the method comprising the steps of:
- correcting a global position to globally correct positions of pixels in at least one of a high energy radiographic native image and a low energy radiographic native image of a same subject to obtain a globally corrected image;
- and
- after the step of correcting the global position, correcting a local position to locally correct pixel positions in the globally corrected image;
- wherein
- the step of correcting the global position includes:
- determining, for pre-defined control points in one of the high energy radiographic native image and the low energy radiographic native image, a local proximity value for multiple translation offsets using local image patches centered at the pre-defined control points;
- deriving a displacement vector for each of the pre-defined control points from the determined local proximity values;
- deducing warping coefficients for a warping transformation from the displacement vectors;
- and
- applying the warping transformation to one of the high energy radiographic native image and the low energy radiographic native image to obtain the globally corrected image;
- and
- the step of correcting the local position of the globally corrected image includes:
- defining overlapping tiles in the globally corrected image and a non-globally corrected high energy radiographic native image or a non-globally corrected low energy radiographic native image;
- computing local displacement vectors for each of the overlapping tiles;
- using the local displacement vectors to build a displacement map;
- and
- applying the displacement map to the globally corrected image.
A non-transitory computer readable medium comprising computer executable program code adapted to carry out, when the computer executable program code is executed on a computer, the steps of:
- correcting a global position to globally correct positions of pixels in at least one of a high energy radiographic native image and a low energy radiographic native image of a same subject to obtain a globally corrected image;
- and
- after the step of correcting the global position, correcting a local position to locally correct pixel positions in the globally corrected image;
- wherein
- the step of correcting the global position includes:
- determining, for pre-defined control points in one of the high energy radiographic native image and the low energy radiographic native image, a local proximity value for multiple translation offsets using local image patches centered at the pre-defined control points;
- deriving a displacement vector for each of the pre-defined control points from the determined local proximity values;
- deducing warping coefficients for a warping transformation from the displacement vectors;
- and
- applying the warping transformation to one of the high energy radiographic native image and the low energy radiographic native image to obtain the globally corrected image;
- and
- the step of correcting the local position of the globally corrected image includes:
- defining overlapping tiles in the globally corrected image and a non-globally corrected high energy radiographic native image or a non-globally corrected low energy radiographic native image;
- computing local displacement vectors for each of the overlapping tiles;
- using the local displacement vectors to build a displacement map;
- and
- applying the displacement map to the globally corrected image.
Dependencies are inferred from the claim text.