Image processor for enhancing contrast between subregions of a region of interest
First Claim
1. A method for processing an image, said image comprising a plurality of pixels representing a region of interest partitioned into a plurality of voxels, said method comprising the steps of:
- providing a plurality of multidimensional signals, each of said signals being associated with each of said voxels, said plurality of voxels being mapped into said plurality of signals in a signal space by a mapping M;
computing a density function representative of the frequency of occurrence of each of said multidimensional signals in said signal space; and
assigning a tone value to each of said plurality of voxels in accordance with said density function
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Abstract
An imaging technique is disclosed for enhancing the contrast of an image, in particular for enhancing the contrast between subregions of a region of interest which may have similar signal characteristics and significantly distinct physical properties. A distribution density function describing the density of the signal in a signal space assigned to a voxel of the region to be imaged is first computed. This distribution function is then convolved with a resolution function, preferably a Gaussian function. Advantageously, the variance of the Gaussian is greater and a multiple of the variance of the noise statistics of the input image. The result of the convolution of the distribution function with the resolution function defines a scale, preferably a grey scale which assigns a particular tone to a pixel of the image corresponding to the voxel of the region to be imaged. The standard deviation is preferably chosen by the user and defines the resolution of the final image in the signal space. The noise in the output image can be decreased by increasing the standard deviation of the convolving Gaussian. For large values of the variance of the Gaussian, the contrast-to-noise ratio is comparable to standard images. The resulting gray scale creates a greater contrast between areas of different volumes having similar signal characteristics. Other resolution functions can be used.
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Citations
32 Claims
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1. A method for processing an image, said image comprising a plurality of pixels representing a region of interest partitioned into a plurality of voxels, said method comprising the steps of:
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providing a plurality of multidimensional signals, each of said signals being associated with each of said voxels, said plurality of voxels being mapped into said plurality of signals in a signal space by a mapping M; computing a density function representative of the frequency of occurrence of each of said multidimensional signals in said signal space; and assigning a tone value to each of said plurality of voxels in accordance with said density function
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2. A method for processing an image, said image comprising a plurality of pixels representing a region of interest partitioned into a plurality of voxels, comprising the steps of:
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providing a plurality of multidimensional signals, each of said multidimensional signals comprising a plurality of parameters containing information about said region of interest, each of said signals being further associated with each of said voxels, said plurality of voxels being mapped into said plurality of signals in a signal space by a mapping M, said mapping M being a multidimensional random variable having a density function; computing said density function representative of the frequency of occurrence of each of said multidimensional signals in said signal space; convolving said density function with a resolution function so as to provide a real valued probability density function defined for each of said plurality of voxels; assigning a tone value to each of said plurality of voxels corresponding to the value of said probability density function for each of said voxels; and displaying a tone level image wherein each voxel is represented by a pixel with said assigned tone value. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A method for processing an image, said method comprising a plurality of pixels representing a region of interest partitioned into a plurality of voxels, comprising the steps of:
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providing a plurality of multidimensional signals, each of said signals being associated with each of said voxels, said plurality of voxels being mapped into said plurality of signals in a signal space by a mapping M, said mapping M being a multidimensional random variable and defining a probability measure in said signal space; computing the Radon-Nikodym derivative of said probability measure of said mapping M, said Radon-Nikodym derivative defining a probability density function; assigning a tone value to each of said plurality of voxels corresponding to the value of said probability density function for each of said voxels; and displaying a tone level image wherein each voxel is represented by a pixel with said assigned tone value.
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27. An apparatus for processing an image comprising a plurality of pixels representing a region of interest partitioned into a plurality of voxels, said apparatus comprising:
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an input imaging device for providing a plurality of multidimensional signals, each of said signals being associated with each of said voxels, said plurality of voxels being mapped into said plurality of signals in a signal space by a mapping M, said mapping M being a multidimensional random variable and defining a probability measure in said signal space; means for computing a density function representative of the frequency of occurrence of each of said multidimensional signals in said signal space; means for convolving said density function with a resolution function so as to provide a real valued probability density function defined for each of said plurality of voxels; means for assigning a tone value to each of said plurality of voxels corresponding to the value of said probability density function for each of said voxels; and means for displaying a tone level image wherein each voxel is represented by a pixel with said assigned tone value.
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28. An apparatus for processing an image comprising a plurality of pixels representing a region of interest partitioned into a plurality of voxels, said apparatus comprising:
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an input imaging device for providing a plurality of multidimensional signals, each of said signals being associated with each of said voxels, said plurality of voxels being mapped into said plurality of signals in a signal space by a mapping M, said mapping M being a multidimensional random variable and defining a probability measure in said signal space; means for computing the Radon-Nikodym derivative of said probability measure of said mapping M, said Radon-Nikodym derivative defining a probability density function; means for assigning a tone value to each of said plurality of voxels corresponding to the value of said probability density function for each of said voxels; and means for displaying a tone level image wherein each voxel is represented by a pixel with said assigned tone value.
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29. An apparatus for processing an image comprising a plurality of pixels representing a region of interest partitioned into a plurality of voxels, said apparatus comprising:
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an input imaging device for providing a plurality of multidimensional signals, each of said signals being associated with each of said voxels, said plurality of voxels being mapped into said plurality of signals in a signal space by a mapping M, said mapping M being a multidimensional random variable and defining a probability measure in said signal space; means for computing a density function representative of the frequency of occurrence of each of said multidimensional signals in said signal space; means for assigning a tone value to each of said plurality of voxels corresponding to the value of said probability density function for each of said voxels; and means for displaying a tone level image wherein each voxel is represented by a pixel with said assigned tone value. - View Dependent Claims (30, 31, 32)
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Specification