Methods and apparatus for helical image artifact reduction
First Claim
Patent Images
1. A method for reconstructing a computed tomography image of an object comprising the steps of:
- scanning an object utilizing step-and-shoot mode to acquire a plurality of projection views of the object;
reconstructing an image based on projection data from a particular detector row;
determining a smoothing function based on a cone angle of the detector row and an image pixel distance from an iso-center; and
applying the smoothing function to the reconstructed image.
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Abstract
Methods and apparatus are provided for reducing image artifacts from a computed tomography (CT) image generated using a CT system. A plurality of projection views of an object are obtained and a plane of reconstruction including reconstructed images is defined. A smoothing function is applied to the reconstructed images to reduce image artifacts wherein a greater amount of z-smoothing is applied to images located a greater distance from an iso-center.
83 Citations
42 Claims
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1. A method for reconstructing a computed tomography image of an object comprising the steps of:
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scanning an object utilizing step-and-shoot mode to acquire a plurality of projection views of the object;
reconstructing an image based on projection data from a particular detector row;
determining a smoothing function based on a cone angle of the detector row and an image pixel distance from an iso-center; and
applying the smoothing function to the reconstructed image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 10)
where r ={square root over ((i−
i0+L )2+L +(j−
j0+L )2+L )}, and i0 and j0 are iso-center locations in an image.
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7. A method in accordance with claim 3 wherein said step of applying a smoothing function to the reconstructed image further comprises the step of applying a z-smoothing function to a plurality of pixels in the reconstructed image.
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8. A method in accordance with claim 7 wherein said step of applying a z-smoothing function to a plurality of pixels further comprises the step of applying an increased amount of smoothing to image pixels located farther away from an iso-center.
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10. A method in accordance with claim 7 wherein the reconstructed image comprises a 512×
- 512 pixel array.
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9. A method for reconstructing a computed tomography image of an object comprising the steps of:
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scanning an object utilizing helical mode to acquire a plurality of projection views of the object;
reconstructing an image based on projection data from a plurality of detector rows;
determining a z-smoothing function based on at least one of a helical pitch, an image pixel distance from an iso-center, a number of detector rows, a reconstruction algorithm, and a slice thickness for the particular detector row; and
applying the z-smoothing function to the pixels within the reconstructed image, the amount of smoothing applied to an individual image pixel in the reconstructed image based on a location of the pixel from the iso-center. - View Dependent Claims (11, 12, 13, 14)
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15. An imaging system comprising a computer, a gantry having a detector array, an x-ray source for radiating an x-ray beam along an imaging plane toward a detector array including a plurality of detector cells, the computer coupled to the x-ray source and the gantry, said imaging system configured to:
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scan an object utilizing step-and-shoot mode to acquire a plurality of projection views of the object;
reconstruct an image based on projection data from a particular detector row;
determine a smoothing function based on a cone angle of each detector row and an image pixel distance from an iso-center; and
apply the smoothing function to the reconstructed image. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
where r={square root over ((i−
i0+L )2+L +(j−
j0+L )2+L )}, and i0 and j0 are iso-center locations in an image.
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21. An imaging system in accordance with claim 15 wherein said imaging system is configured to apply a z-smoothing function to a plurality of pixels in the reconstructed image.
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22. An imaging system in accordance with claim 21 wherein said imaging system is configured to apply an increased amount of smoothing to image pixels located farther away from an iso-center.
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23. An imaging system in accordance with claim 15 wherein said imaging system is configured to apply an amount of z-smoothing proportional to a distance the detector row is from a center plane and a cone angle for the detector row.
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24. An imaging system in accordance with claim 23 wherein said imaging system is configured to apply more z-smoothing to a detector row based on the distance the detector row is from the iso-center.
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25. An imaging system in accordance with claim 15 wherein said imaging system is configured to apply no z-smoothing at the iso-center.
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26. An imaging system in accordance with claim 15 wherein said imaging system is configured to apply z-smoothing in a z-axis direction.
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27. An imaging system comprising a computer, a gantry having a detector array, an x-ray source for radiating an x-ray beam along an imaging plane toward a detector array including a plurality of detector cells arranged in rows, the computer coupled to the x-ray source and the gantry, said imaging system configured to:
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scan an object utilizing helical mode to acquire a plurality of projection views of the object;
reconstruct an image based on acquired projection data;
determine a z-smoothing function based on at least one of a helical pitch, an image pixel distance from an iso-center, a number of detector rows, a reconstruction algorithm, and a slice thickness for each particular detector row; and
apply said z-smoothing function to pixels within the reconstructed image, the amount of smoothing applied to an individual image pixel in the reconstructed image based on a location of the pixel from the iso-center. - View Dependent Claims (28, 29, 30, 31, 32, 33)
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34. A processor programmed to reduce image artifacts in a computed tomography system, said processor configured to:
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scan an object to acquire a plurality of projection views of an object;
define a measurement plane;
define a plane of reconstruction perpendicular to a patient axis that intersects the measurement plane at an iso-center;
reconstruct an image from the plurality of projection views;
determine an image pixel distance to the iso-center and a cone angle of detector rows; and
apply a z-smoothing weights, based upon the image pixel distance from the iso-center, to at least one detector channel in a z-axis direction to reduce image artifact. - View Dependent Claims (35, 36, 37)
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38. A computer-readable medium in an imaging system, said computer-readable medium comprising:
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a function to acquire projection data for a plurality of detector rows;
a function to reconstruct images from the projection data;
a function to determine a cone angle for each detector row and an image pixel distance to an iso-center; and
a function for applying a z-smoothing function, based upon the image pixel distance from the iso-center, to the reconstructed images to reduce image artifact. - View Dependent Claims (39, 40, 41, 42)
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Specification