X-ray image processing
First Claim
1. In a method of x-ray imaging using an intensifying screen to receive x-rays and emit light to be recorded on an x-ray film, a method of calculating from a film image density an energy which was imparted to the intensifying screen, comprising steps of:
- calibrating the film and intensifying screen by measuring a response of the film and intensifying screen to a plurality of different intensities of received x-rays;
fitting a theoretical model of an expected response to the measured response, and using the fitted theoretical model to calculate the imparted energy from image density,wherein the theoretical model is a serpentine curve of the form;
x2y+a2y−
b2x=0,where a and b are constants, x is a logarithm of the energy imparted to the intensifying screen and y is the image density.
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Accused Products
Abstract
A method of enhancing and normalizing x-ray images, particularly mammograms, by correcting the image for digitizer blur, glare from the intensifying screen and the anode-heel effect. The method also allows the calculation of the compressed thickness of the imaged breast and calculation of the contribution to the mammograms of the extra focal radiation. The correction of the image for glare from the intensifying screen allows the detection of noise, such as film shot noise, in the image, and in particular the differentiation between such noise and microcalcifications.
58 Citations
24 Claims
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1. In a method of x-ray imaging using an intensifying screen to receive x-rays and emit light to be recorded on an x-ray film, a method of calculating from a film image density an energy which was imparted to the intensifying screen, comprising steps of:
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calibrating the film and intensifying screen by measuring a response of the film and intensifying screen to a plurality of different intensities of received x-rays; fitting a theoretical model of an expected response to the measured response, and using the fitted theoretical model to calculate the imparted energy from image density, wherein the theoretical model is a serpentine curve of the form;
x2y+a2y−
b2x=0,where a and b are constants, x is a logarithm of the energy imparted to the intensifying screen and y is the image density.
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2. In a method of x-ray imaging using an intensifying screen to receive x-rays and emit light to be recorded on an x-ray film, a method of calculating from a film image density an energy which was imparted to the intensifying screen, comprising steps of:
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calibrating the film and intensifying screen by measuring a response of the film and intensifying screen to a plurality of different intensities of received x-rays; fitting a theoretical model of an expected response to the measured response, and using the fitted theoretical model to calculate the imparted energy from image density, wherein the response of the film and intensifying screen to a plurality of different intensities of received x-rays is measured by exposing the film-screen combination to x-rays through a lucite step wedge and measuring image density produced by the exposing through different steps of the wedge.
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3. Apparatus for calculating from image densities of an x-ray film image the energy which was imparted to an intensifying screen used to receive x-rays and emit light to be recorded on the x-ray film, the apparatus comprising:
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fitting means for fitting a theoretical model of the expected response to the x-ray film and intensifying screen to a plurality of different intensities of received x-rays to a measured response, and calculation means for using the fitted theoretical model to calculate the imparted energy from image density, wherein the theoretical model is a serpentine curve of the form;
x2y+a2y−
b2x=0,where a and b are constants, x is a logarithm of the energy imparted to the intensifying screen and y is the image density.
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4. A computer program storage medium readable by a computer system and encoded with a computer program for controlling a computer to calculate from image densities of an x-ray film the energy which was imparted to an intensifying screen used to receive x-rays and emit light recorded on the x-ray film, by a method comprising steps of:
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fitting a theoretical model of an expected response of the x-ray film and intensifying screen to a plurality of different intensities of received x-rays to a measured response, and using the fitted theoretical model to calculate the imparted energy from image density, wherein the theoretical model is a serpentine curve of the form;
x2y+a2y−
b2x=0,where a and b are constants, x is a logarithm of the energy imparted to the intensifying screen and y is the image density.
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- 5. A method of calculating from a mammogram a compressed thickness of an imaged breast, comprising a step of delimiting in the mammogram a region corresponding to a part of the breast which is compressed from a region corresponding to an uncompressed breast edge by detecting smoothness of curves of equal intensity in the mammogram.
- 12. Apparatus for calculating from a mammogram a compressed thickness of an imaged breast, comprising a display for displaying a mammogram and means for delimiting in the mammogram a region corresponding to a part of the breast which is compressed from a region corresponding to an uncompressed breast edge by detecting smoothness of curves of equal intensity in the mammogram.
- 18. A computer program storage medium readable by a computer system and encoded with a computer program for controlling a computer to calculate from a mammogram a compressed thickness of an imaged breast by a method comprising a step of delimiting in the mammogram a region corresponding to a part of the breast which is compressed from a region corresponding to an uncompressed breast edge by detecting smoothness of curves of equal intensity in the mammogram.
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23. Apparatus for calculating from image densities of an x-ray film image the energy which was imparted to an intensifying screen used to receive x-rays and emit light to be recorded on the x-ray film, the apparatus comprising a processor controlled in accordance with a control program to fit a theoretical model of the expected response of the x-ray film and intensifying screen to a plurality of different intensities of received x-rays to a measured response, and to use the fitted theoretical model to calculate the imparted energy from image density,
wherein the theoretical model is a serpentine curve of the form: -
x2y+a2y−
b2x=0,where a and b are constants, x is a logarithm of the energy imparted to the intensifying screen and y is the image density.
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24. Apparatus for calculating from a mammogram a compressed thickness of an imaged breast, the apparatus comprising a processor controlled in accordance with a control program to delimit in the mammogram a region corresponding to a part of the breast which is compressed from a region corresponding to an uncompressed breast edge by detecting smoothness of curves of equal intensity in the mammogram.
Specification