Computationally efficient noise reduction filter for enhancement of ultrasound images
First Claim
1. An ultrasound imaging system comprising a data acquisition system for acquiring acoustic data, an image processor for converting acoustic data into a set of pixel intensity values for each image, a display monitor for displaying images, and a computer programmed to perform the following steps:
- (a) shrinking an initial image by a predetermined factor to produce a shrunken image;
(b) creating a first binary mask as a function of whether pixels of said shrunken image have gradients greater than a gradient threshold and locations more than a predetermined distance from a near field in said shrunken image;
(c) filtering pixels corresponding to structural components in said shrunken image in accordance with a first filtering algorithm, said structural components being identified by said first binary mask;
(d) filtering pixels corresponding to non-structural components in said shrunken image in accordance with a second filtering algorithm different than said first filtering algorithm, said non-structural components being identified by said first binary mask (e) expanding said filtered image and said first binary mask by said predetermined factor to produce an expanded image and a first expanded binary mask;
(f) blending one or more selected regions of the expanded image with a corresponding region or regions of the initial image, said blending being a function of said first binary mask;
(g) adding uniform random noise to one or more selected echogenic nonstructural regions of the expanded image; and
(h) outputting a final image to said display monitor, said final image being derived by performing at least steps (a) through (h).
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Abstract
In ultrasound imaging, acquired images are corrupted by slowly varying multiplicative non-uniformity. When the image is corrected for non-uniformity alone, noise in the dark regions of the original image becomes multiplicatively enhanced, thereby providing an unnatural look to the image. A pre-filtering technique is used to reduce noise in ultrasound pixel images by shrinking initial image data and processing the shrunken image with known segmentation-based filtering techniques that identify and differentially process structures within the image. The segmentation is based on both gradient threshold and the distance from the near field of the ultrasound image. This modification selectively suppresses near-field artifacts. After processing, the shrunken image is enlarged to the dimensions of the initial data and then blended with the initial image to form the final image. During blending, a small predetermined fraction of intensity-dependent, uniform random noise is added to the non-structure region pixels whose intensities are above a pre-specified intensity threshold, to mitigate ultrasound speckles while leaving non-echogenic regions undisturbed.
38 Citations
28 Claims
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1. An ultrasound imaging system comprising a data acquisition system for acquiring acoustic data, an image processor for converting acoustic data into a set of pixel intensity values for each image, a display monitor for displaying images, and a computer programmed to perform the following steps:
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(a) shrinking an initial image by a predetermined factor to produce a shrunken image;
(b) creating a first binary mask as a function of whether pixels of said shrunken image have gradients greater than a gradient threshold and locations more than a predetermined distance from a near field in said shrunken image;
(c) filtering pixels corresponding to structural components in said shrunken image in accordance with a first filtering algorithm, said structural components being identified by said first binary mask;
(d) filtering pixels corresponding to non-structural components in said shrunken image in accordance with a second filtering algorithm different than said first filtering algorithm, said non-structural components being identified by said first binary mask (e) expanding said filtered image and said first binary mask by said predetermined factor to produce an expanded image and a first expanded binary mask;
(f) blending one or more selected regions of the expanded image with a corresponding region or regions of the initial image, said blending being a function of said first binary mask;
(g) adding uniform random noise to one or more selected echogenic nonstructural regions of the expanded image; and
(h) outputting a final image to said display monitor, said final image being derived by performing at least steps (a) through (h). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for filtering an ultrasound image, comprising the following steps:
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(a) shrinking an initial image by a, predetermined factor to produce a shrunken image;
(b) creating a first binary mask as a function of whether pixels of said shrunken image have gradients greater than a gradient threshold and locations more than a predetermined distance from a near field in said shrunken image;
(c) filtering pixels corresponding to structural components in said shrunken image in accordance with a first filtering algorithm, said structural components being identified by said first binary mask;
(d) filtering pixels corresponding to non-structural components in said shrunken image in accordance with a second filtering algorithm different than said first filtering algorithm, said non-structural components being identified by said first binary mask (e) expanding said filtered image and said first binary mask by said predetermined factor to produce an expanded image and a first expanded binary mask;
(f) blending one or more selected regions of the expanded image with a corresponding region or regions of the initial image, said blending being a function of said first binary mask; and
(g) adding uniform random noise to one or more selected echogenic nonstructural regions of the expanded image to form a final image suitable for display or further image enhancement. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
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23. An ultrasound image filter comprising:
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means for shrinking an initial image by a predetermined factor to produce a shrunken image;
means for orientation smoothing pixels corresponding to structural components in said shrunken image;
means for iteratively low-pass filtering pixels corresponding to non-structural components in said shrunken image;
means for expanding said filtered image by said predetermined factor to produce an expanded image;
means for blending one or more selected regions of the expanded image with a corresponding region or regions of the initial image, said blending being a function of whether the corresponding pixel of said shrunken image has a gradient greater than a gradient threshold and a location more than a predetermined distance from a near field in said shrunken image; and
means for adding uniform random noise to one or more selected echogenic non-structural regions of the expanded image to form a final image suitable for display or further image enhancement. - View Dependent Claims (24, 25)
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26. A method for filtering an ultrasound image, comprising the following steps:
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shrinking an initial image by a predetermined factor to produce a shrunken image;
orientation smoothing pixels corresponding to structural components in said shrunken image;
iteratively low-pass filtering pixels corresponding to non-structural components in said shrunken image;
expanding said filtered image by said predetermined factor to produce an expanded image;
blending one or more selected regions of the expanded image with a corresponding region or regions of the initial image, said blending being a function of whether the corresponding pixel of said shrunken image has a gradient greater than a gradient threshold and a location more than a predetermined distance from a near field in said shrunken image; and
adding uniform random noise to one or more selected echogenic non-structural regions of the expanded image to form a final image suitable for display or further image enhancement.
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27. A method for mitigating speckle in an ultrasound image, comprising the following steps:
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creating a binary mask having a first value binary value for each pixel of an image that satisfies a first condition of having a gradient greater than a gradient threshold and a second condition of having an intensity greater than a predetermined intensity level, and a second binary value for each pixel that does not meet both said first and second conditions; and
adding uniform random noise to each pixel of said image that corresponds to a pixel in said binary mask having said first binary value and not adding noise to other pixels of said image.
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28. An ultrasound imaging system comprising a data acquisition system for acquiring acoustic data, an image processor for converting acoustic data into a set of pixel intensity values for each image, a display monitor for displaying images, and a computer programmed to perform the following steps:
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(a) creating a binary mask having a first value binary value for each pixel of an image that satisfies a first condition of having a gradient greater than a gradient threshold and a second condition of having an intensity greater than a predetermined intensity level, and a second binary value for each pixel that does not meet both said first and second conditions;
(b) adding uniform random noise to each pixel of said image that corresponds to a pixel in said binary mask having said first binary value and not adding noise to other pixels of said image; and
(c) outputting a final image to said display monitor, said final image being derived by performing at least steps (a) and (b).
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Specification