Patent US5646752A successfully refreshed from Google Patents.
Patent US5774521A successfully refreshed from Google Patents.
US5774521A
Expired / Lapsed
US
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Regularization technique for densitometric correction
Assignee: Cedars-Sinai Medical Center
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Filing: 1996-07-08
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Granted: 1998-06-30
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Expires: 2016-07-08
Abstract
Abstract Method and apparatus for scatter-glare correction in x-ray diagnostic images from a patient. A reference object placed between the x-ray source and the subject is imaged in superposition with the subject without completely blocking any area of the subject image. The density distribution of the reference object is designed to have very small spatial correlation with the density distribution of the subject. The scatter-glare component is modeled by convoluting the primary component with a parameterized response function. During post-processing of the digital image, the unknown parameters of the response function are adjusted to minimize a cost function based on the expectation that the correlation between the reference object and the subject should be small and that the values of the parameters not deviate significantly from the estimated values for a typical patient. The scatter-glare component of the subject and the reference object, as well as the image of the reference object, are subsequently subtracted from the raw image to yield the image of the subject free of scatter-glare effects.
Inventors
- 👤 Robert Alan Close
- 👤 James Stuart Whiting
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 12:57
CPC Classifications
G; G01; G01N; G01N23/00; G01N23/02; G01N23/04; A; A61; A61B; A61B6/00; A61B6/52; A61B6/5258; A61B6/5282; G01N23/046; G01N2223/00; G01N2223/40; G01N2223/419; G01N2223/60; G01N2223/612
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
152 words
A method for recording an x-ray image of a subject having an unknown x-ray density distribution and correcting for image degradation effects, the method comprising: placing the subject between an x-ray source and an x-ray detector; placing a reference object between the x-ray source and the x-ray detector, said reference object having a known x-ray density distribution that is substantially spatially uncorrelated to the x-ray density distribution of the subject; producing digital information representing at least one x-ray image using the x-ray detector, said image comprising images of the subject and the reference object as well as image degradation effects; and processing the digital information until a measurement of the correlation between the density distributions of the reference object and the subject is substantially within a predefined range, whereby the processed digital information represents corrected density distribution of the subject free from the image degradation effects; and displaying the processed digital information.
Claim 2
Independent Claim
152 words
A method for recording an x-ray image of a subject having an unknown x-ray density distribution and correcting for image degradation effects, the method comprising: placing the subject between an x-ray source and an x-ray detector; placing a reference object between the x-ray source and the x-ray detector, said reference object having a known x-ray density distribution that is substantially spatially uncorrelated to the x-ray density distribution of the subject; producing digital information representing at least one x-ray image using the x-ray detector, said image comprising images of the subject and the reference object as well as image degradation effects; and processing the digital information until a measurement of the correlation between the density distributions of the reference object and the subject is substantially within a predefined range, whereby the processed digital information represents corrected density distribution of the subject free from the image degradation effects; and displaying the processed digital information.
Claim 3
Dependent Claim
87 words
The method of claim 1, wherein the processing of the digital information comprises: providing a cost function based upon a model for the image degradation effects, said model comprising at least one parameter, said cost function comprising at least one term representing the value of the spatial correlation between the density distribution of the reference object and the corrected subject density distribution; providing an initial value for each said parameter of the model; and obtaining an acceptable value for each said parameter by minimizing the cost function.
Claim 4
Dependent Claim
16 words
The method of claim 2, wherein the image degradation effects are scatter and veiling glare effects.
Claim 5
Dependent Claim
32 words
The method of claim 3, wherein the model for the image degradation effects comprises a spatial convolution of a response function with the density distributions of the subject and the reference object.
Claim 6
Dependent Claim
28 words
The method of claim 3, wherein the cost function further comprises at least one weighted term representing a deviation of at least one parameter from the initial value.
Claim 7
Dependent Claim
20 words
The method of claim 5, wherein the initial value for the parameter reflects the expected physical properties of the subject.
Claim 8
Dependent Claim
38 words
The method of claim 5, further comprising adjusting the relative weights of the terms of the cost function so that the term representing the spatial correlation falls within a predetermined acceptable range when the cost function is minimized.
Claim 9
Dependent Claim
35 words
The method of claim 7, wherein the predetermined acceptable range is determined based upon knowledge of the range of spatial correlations between the reference object and actual objects having similar physical properties as the subject.
Claim 10
Dependent Claim
34 words
The method of claim 2, wherein the produced digital information represents a plurality of x-ray images of the same subject, and wherein one acceptable value for each said parameter is obtained for all images.
Claim 11
Dependent Claim
38 words
The method of claim 9, wherein the producing of digital information representing a plurality of x-ray images further comprises changing the relative position or orientation of the reference object with respect to the subject between successive x-ray images.
Claim 12
Dependent Claim
24 words
The method of claim 1, wherein the x-ray density distributions of the subject and the reference object are defined in the x-ray detector plane.
Claim 13
Dependent Claim
23 words
The method of claim 1, wherein the x-ray density distribution of the reference object is defined at the position of the reference object.
Claim 14
Dependent Claim
18 words
The method of claim 1, wherein the x-ray density distribution of the reference object is a random distribution.
Claim 15
Dependent Claim
19 words
The method of claim 1, wherein the x-ray density distribution of the reference object is a highly structured distribution.
Claim 16
Independent Claim
158 words
An apparatus for recording an x-ray image of a subject having an unknown x-ray density distribution and correcting for image degradation effects comprising: an x-ray source for producing a beam of x-rays to be passed through the subject that produces artifacts in addition to image information; an x-ray detector for producing a digital representation of the x-ray beams passed through the subject including artifact information; a reference object having a known x-ray density distribution that is spatially substantially uncorrelated to the x-ray density distribution of the subject, said reference object being placed between the x-ray source and the x-ray detector; a processor responsive to a stored cost function comprising at least one parameter and stored information regarding the reference object, for processing the digital representation produced by the x-ray detector to remove information representing the artifacts from the digital representation to produce a corrected image representation; and display means for displaying the corrected image representation on a medium.
Claim 17
Independent Claim
158 words
An apparatus for recording an x-ray image of a subject having an unknown x-ray density distribution and correcting for image degradation effects comprising: an x-ray source for producing a beam of x-rays to be passed through the subject that produces artifacts in addition to image information; an x-ray detector for producing a digital representation of the x-ray beams passed through the subject including artifact information; a reference object having a known x-ray density distribution that is spatially substantially uncorrelated to the x-ray density distribution of the subject, said reference object being placed between the x-ray source and the x-ray detector; a processor responsive to a stored cost function comprising at least one parameter and stored information regarding the reference object, for processing the digital representation produced by the x-ray detector to remove information representing the artifacts from the digital representation to produce a corrected image representation; and display means for displaying the corrected image representation on a medium.
Claim 18
Dependent Claim
29 words
The apparatus of claim 15, wherein the known x-ray density distribution of the reference object comprises a density for each pixel of a constant term plus a random term.
Claim 19
Dependent Claim
15 words
The apparatus of claim 16, wherein the random term is a sample of Gaussian noise.
Claim 20
Dependent Claim
29 words
The apparatus of claim 17, wherein the Gaussian noise has a spectrum, the spectrum having a flat frequency response up to the inverse of the size of the pixel.
Claim 21
Dependent Claim
25 words
The apparatus of claim 15 wherein the processor performs: initializing the parameters of the cost function; altering the initialized parameters to minimize the cost function.
Claim 22
Dependent Claim
19 words
The apparatus of claim 15, wherein the x-ray density distribution of the reference object is a highly structured distribution.
Claim 23
Independent Claim
162 words
An apparatus for recording an x-ray image of a subject having an unknown x-ray density distribution and correcting for artifacts comprising: an x-ray source for producing a beam of x-rays to be passed through the subject that produces artifacts in addition to subject image information; an x-ray detector for producing a digital representation of the x-ray beams passed through the subject including artifact information; a reference object having a known x-ray density distribution that is spatially substantially uncorrelated to the x-ray density distribution of the subject, said reference object being placed between the x-ray source and the x-ray detector; and a processor for processing the digital representation produced by the x-ray detector, the processor being operable to calculate a measurement of the correlation between the density distributions of the reference object and the subject and to produce a corrected subject image representation based on the measurement of the correlation, whereby the corrected subject image representation is substantially free of the artifact information.
Claim 24
Independent Claim
162 words
An apparatus for recording an x-ray image of a subject having an unknown x-ray density distribution and correcting for artifacts comprising: an x-ray source for producing a beam of x-rays to be passed through the subject that produces artifacts in addition to subject image information; an x-ray detector for producing a digital representation of the x-ray beams passed through the subject including artifact information; a reference object having a known x-ray density distribution that is spatially substantially uncorrelated to the x-ray density distribution of the subject, said reference object being placed between the x-ray source and the x-ray detector; and a processor for processing the digital representation produced by the x-ray detector, the processor being operable to calculate a measurement of the correlation between the density distributions of the reference object and the subject and to produce a corrected subject image representation based on the measurement of the correlation, whereby the corrected subject image representation is substantially free of the artifact information.
Claim 25
Dependent Claim
35 words
The apparatus of claim 21, wherein the processor produces the corrected subject image representation by minimizing a cost function having at least one parameter and at least one term representing the measurement of the correlation.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-06-29 | 2001-12-29 | 2002-06-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-06-29 | 2005-12-29 | 2006-06-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-06-29 | 2009-12-29 | 2010-06-30 | $7700.00 | Window Closed / Lapsed |