Method for reducing noise in energy subtraction images
First Claim
1. A method for processing an energy substraction image in energy subtraction processing, comprising the steps of:
- reading image data representing at least two radiation images of an object from at least two recording media, respectively, on which different images of at least a part of the object have been recorded, to obtain at least two analog original image signals, each of which is made up of a series of image signal components;
converting said at least two analog original image signals into original digital image signals, respectively;
subtracting image signal components of one of said original image signals from image signal components of the other one of said original digital image signals to obtain a difference signal representing an image of a specific structure of the object;
carrying out a smoothing process on one of said original digital image signals to obtain a smoothed image signal;
weighting and averaging image signal components of said difference signal and said image signal components of said one of said original digital image signals such that the weight given to said one of said original digital image signals is made larger as an image density represented by said smoothed image signal with respect to a picture element becomes lower; and
reproducing a visible radiation image of the object utilizing a composite image signal obtained from said weighting and averaging step.
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Abstract
Radiation images of an object, which have been recorded on recording media and in which different images of at least part of the object are embedded, are read out from the recording media, and a plurality of original image signals, each of which is made up of a series of image signal components, are thereby obtained. The image signal components of the original image signals, which represent corresponding picture elements in the radiation images, are then subtracted from each other, and a difference signal representing an image of a specific structure of the object is thereby obtained. A smoothing process is carried out on an original image signal, and a smoothed image signal is thereby obtained. The image signal components of the original image signal and the difference signal, which represent corresponding picture elements in the images, are weighted such that the weight given to the original image signal may be made larger as the image density represented by the smoothed image signal with respect to a picture element becomes lower. The weighted image signal components are then averaged. A composite image signal obtained from the weighted averaging process is utilized for reproduction of a visible radiation image of the object.
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Citations
11 Claims
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1. A method for processing an energy substraction image in energy subtraction processing, comprising the steps of:
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reading image data representing at least two radiation images of an object from at least two recording media, respectively, on which different images of at least a part of the object have been recorded, to obtain at least two analog original image signals, each of which is made up of a series of image signal components; converting said at least two analog original image signals into original digital image signals, respectively; subtracting image signal components of one of said original image signals from image signal components of the other one of said original digital image signals to obtain a difference signal representing an image of a specific structure of the object; carrying out a smoothing process on one of said original digital image signals to obtain a smoothed image signal; weighting and averaging image signal components of said difference signal and said image signal components of said one of said original digital image signals such that the weight given to said one of said original digital image signals is made larger as an image density represented by said smoothed image signal with respect to a picture element becomes lower; and reproducing a visible radiation image of the object utilizing a composite image signal obtained from said weighting and averaging step. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for processing an energy substraction image in energy subtraction processing, comprising the steps of:
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reading image data of at least two radiation images representing an object from at least two recording media, respectively, on which different images of at least a part of the object have been recorded, to obtain at least two analog original image signals, each of which is made up of a series of image signal components; converting said at least two analog original image signals into original digital image signals, respectively; subtracting image signal components of one of said original image signals from image signal components of the other one of said original digital image signals to obtain a difference signal representing an image of a specific structure of the object; adding said image signal components of said original digital image signals to generate a superposition signal; carrying out a smoothing process on said superposition signal to obtain a smoothed image signal; weighting and averaging image signal components of said difference signal and said image signal components of said smoothed image signal such that the weight given to said difference signal is made larger as an image density, represented by said smoothed image signal with respect to a picture element, becomes lower; and reproducing a visible radiation image of the object utilizing a composite image signal obtained from said weighting and averaging step.
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9. A method for processing an energy substraction image in energy subtraction processing, comprising the steps of:
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reading image data of at least two radiation images representing an object from at least two recording media, respectively, on which different images of at least a part of the object have been recorded, to obtain at least two analog original image signals, each of which is made up of a series of image signal components; converting said at least two analog original image signals into original digital image signals, respectively; subtracting image signal components of one of said original image signals from image signal components of the other one of said original digital image signals to obtain a difference signal representing an image of a specific structure of the object; adding said image signal components of said original digital image signals to generate a superposition signal; carrying out a smoothing process on said difference signal to obtain a smoothed image signal; weighting and averaging image signal components of said smoothed image signal and image signal components of said superposition signal; subtracting weighted image signal components of said smoothed image signal and weighted image signal components of said superposition signal from each other to obtain a composite image signal; and reproducing a visible radiation image of the object utilizing said composite image signal. - View Dependent Claims (10)
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11. A method for processing an energy substraction image in energy subtraction processing, comprising the steps of:
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reading image data of at least two radiation images representing an object from at least two recording media, respectively, on which different images of at least a part of the object have been recorded, to obtain at least two analog original image signals, each of which is made up of a series of image signal components; converting said at least two analog original image signals into original digital image signals, respectively; weighting and subtracting image signal components of one of said original image signals from image signal components of the other one of said original digital image signals in accordance with the following equations to obtain a first difference signal S1 and a second difference signal S2, ##EQU5## where SO1 and SO2 respectively correspond to first and second ones of said original digital image signals;
μ
Lt and μ
Ht respectively represent absorption coefficients of soft tissues with respect to low energy components of radiation images and high energy components of radiation images;
μ
Lb and μ
Hb respectively represent absorption coefficients of bones with respect to low energy components of radiation images and high energy components of radiation images; and
C and C'"'"' each denote a bias component;carrying out a smoothing process on said first difference signal to obtain a smoothed image signal; subtracting image signal components of said smoothed image signal from image signal components of said first difference signal to obtain a noise signal; weighting said image signal components of said second one difference signal and image signal components of said noise signal; adding weighted image signal components of said second difference signal and weighted image signal components of said noise signal to each other to generate a superposition signal; and reproducing a visible radiation image of the object utilizing said superposition signal.
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Specification