Patent US5832055A successfully refreshed from Google Patents.
US5832055A
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Method of correcting a radiation image for defects in the recording member
Assignee: Agfa HealthCare NV
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Filing: 1997-08-06
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Granted: 1998-11-03
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Expires: 2017-08-06
Abstract
Abstract Method of correcting a radiation image for defects in the recording member. Defects in a member for recording a radiation image are corrected by generating a calibration matrix comprising for each pixel a correction value and by applying corresponding elements of the calibration matrix to the pixels of a recorded image. The values of the calibration matrix represent in each pixel the deviation of the value that is effectively obtained in a pixel when the recording member is subjected to a flat field exposure and the value that would be expected in the pixel. Different methods are described for determining the expected value in a pixel. Further, an overlay image is generated wherein local defects are visualised.
Inventors
- 👤 Piet Dewaele
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 12:18
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/77; G06T5/20; G06T5/30; H; H04; H04N; H04N23/00; H04N23/30; A; A61; A61B; A61B6/00; A61B6/44; A61B6/4494; G06T2207/00; G06T2207/10; G06T2207/10116; G06T2207/30; G06T2207/30004
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
121 words
Method of correcting a radiation image stored in a recording member for recording member defects, comprising: generating a calibration matrix for said recording member, said calibration matrix comprising for each pixel on said recording member a correction value that represents a deviation of a first value that is effectively obtained in a pixel and a second value that would be expected when said recording member is subjected to a flat field exposure and subsequently read-out by means of a calibrated read-out system, generating a digital signal representation of said radiation image by reading the image by means of a calibrated read-out system, correcting each pixel of said radiation image by applying to a pixel a corresponding value of said calibration matrix.
Claim 2
Dependent Claim
121 words
Method of correcting a radiation image stored in a recording member for recording member defects, comprising: generating a calibration matrix for said recording member, said calibration matrix comprising for each pixel on said recording member a correction value that represents a deviation of a first value that is effectively obtained in a pixel and a second value that would be expected when said recording member is subjected to a flat field exposure and subsequently read-out by means of a calibrated read-out system, generating a digital signal representation of said radiation image by reading the image by means of a calibrated read-out system, correcting each pixel of said radiation image by applying to a pixel a corresponding value of said calibration matrix.
Claim 3
Dependent Claim
25 words
A method according to claim 1 wherein said calibration matrix is generated in advance, stored in memory and retrieved upon identification of a recording member.
Claim 4
Dependent Claim
49 words
A method according to claim 1 wherein (i) said recording member is a photostimulable phosphor screen and wherein (ii) a radiation image is read-out by scanning said screen by means of stimulating radiation, detecting light emitted upon stimulation, converting detected light into an electric signal and digitizing said signal.
Claim 5
Dependent Claim
93 words
A method according to claim 1 wherein (i) said calibration matrix is obtained by exposing said recording member to a flat field exposure of radiation, reading a flat field image stored in the recording member exposed to said flat field exposure, calculating a global mean value μ R by averaging pixel values of said flat field image, generating a smooth background image g R (i,j) as μ R -g R (i,j), and (ii) each pixel of said radiation image is corrected by adding to a pixel a corresponding value of the calibration matrix.
Claim 6
Dependent Claim
29 words
A method according to claim 4 wherein said smooth background image g R (i,j) is obtained by applying a regression technique to pixel values of said flat field image.
Claim 7
Dependent Claim
25 words
A method according to claim 4 wherein said smooth background image g R (i,j) is obtained by smoothing pixel values of said flat field image.
Claim 8
Dependent Claim
94 words
A method according to claim 4 wherein said digital signal representation of original image `z` is decomposed into a sequence of detail images r 1 , r 2 . . . r L-1 and a rest image g L at a still lower resolution level and wherein said residual image `r` is formed by summing up detail images at M finest resolution levels starting from M-1 up to level 0, each of the detail images being interpolated to the size of a detail image at a next finer resolution level before being summed up.
Claim 9
Dependent Claim
30 words
A method according to claim 4 wherein said smooth background image g R (i,j) is obtained by applying a spline fitting technique to pixel values of said flat field image.
Claim 10
Dependent Claim
146 words
A method according to claim 4 wherein said digital signal representation of original image `z` is decomposed into a sequence of detail images r 1 , r 2 . . . r L-1 and a rest image g L at a still lower resolution level and wherein said residual image `r` is formed by (i) summing the rest image g L and the detail images r i at L-M coarsest resolution levels, starting from resolution level L up to resolution level M, each being interpolated to the size of a detail image at a next finer resolution being summed, to form a downzoomed background image g M , (ii) upzooming background image g M to form a full-size background image `g` by performing M successive interpolations on g M , (iii) subtracting the upzoomed background image `g` from the digital signal representation of original image `z`.
Claim 11
Dependent Claim
92 words
A method according to claim 1 wherein (i) said calibration matrix is obtained by exposing said recording member to a flat field exposure of radiation, reading a flat field image stored in the recording member upon said flat field exposure, calculating a global mean value μ R by averaging pixel values of said flat field exposure, generating a multiplicative calibration matrix C m (i,j) as μ R /g R (i,j), and (ii) each pixel of said radiation image is corrected by multiplying a pixel with a corresponding value of the calibration matrix.
Claim 12
Dependent Claim
29 words
A method according to claim 10 wherein said smooth background image g R (i,j) is obtained by applying a regression technique to pixel values of said flat field image.
Claim 13
Dependent Claim
25 words
A method according to claim 10 wherein said smooth background image g R (i,j) is obtained by smoothing pixel values of said flat field image.
Claim 14
Dependent Claim
30 words
A method according to claim 10 wherein said smooth background image g R (i,j) is obtained by applying a spline fitting technique to pixel values of said flat field image.
Claim 15
Dependent Claim
134 words
Method of localising local defects in a recording member for recording a radiation image comprising the steps of exposing said recording member to a flat field exposure of radiation, reading a flat field image stored in the recording member upon said flat field exposure, generating a smooth background image g R (i,j), generating a residual image r(i,j) by subtracting from a pixel value of the flat field image a corresponding value of the smooth background image g R (i,j), thresholding the absolute value |r(i,j)| of said residual image r(i,j) with a noise dependent threshold T to generate an error image e(i,j) wherein e(i,j)=1 if |r(i,j)|>T, e(i,j)=o elsewhere, and wherein T=ασ R , α being comprised between 3 and 5 and σ R being the variance of the noise distribution in said flat field image.
Claim 16
Dependent Claim
134 words
Method of localising local defects in a recording member for recording a radiation image comprising the steps of exposing said recording member to a flat field exposure of radiation, reading a flat field image stored in the recording member upon said flat field exposure, generating a smooth background image g R (i,j), generating a residual image r(i,j) by subtracting from a pixel value of the flat field image a corresponding value of the smooth background image g R (i,j), thresholding the absolute value |r(i,j)| of said residual image r(i,j) with a noise dependent threshold T to generate an error image e(i,j) wherein e(i,j)=1 if |r(i,j)|>T, e(i,j)=o elsewhere, and wherein T=ασ R , α being comprised between 3 and 5 and σ R being the variance of the noise distribution in said flat field image.
Claim 17
Dependent Claim
94 words
A method according to claim 14 wherein said digital signal representation of original image `z` is decomposed into a sequence of detail images r 1 , r 2 . . . r L-1 and a rest image g L at a still lower resolution level and wherein said residual image `r` is formed by summing up detail images at M finest resolution levels starting from M-1 up to level 0, each of the detail images being interpolated to the size of a detail image at a next finer resolution level before being summed up.
Claim 18
Dependent Claim
25 words
A method according to claim 14 wherein said smooth background image g R (i,j) is obtained by smoothing pixel values of said flat field image.
Claim 19
Dependent Claim
146 words
A method according to claim 14 wherein said digital signal representation of original image `z` is decomposed into a sequence of detail images r 1 , r 2 . . . r L-1 and a rest image g L at a still lower resolution level and wherein said residual image `r` is formed by (i) summing the rest image g L and the detail images r i at L-M coarsest resolution levels, starting from resolution level L up to resolution level M, each being interpolated to the size of a detail image at a next finer resolution being summed, to form a downzoomed background image g M , (ii) upzooming background image g M to form a full-size background image `g` by performing M successive interpolations on g M , (iii) subtracting the upzoomed background image `g` from the digital signal representation of original image `z`.
Claim 20
Dependent Claim
30 words
A method according to claim 14 wherein said smooth background image g R (i,j) is obtained by applying a spline fitting technique to pixel values of said flat field image.
Claim 21
Dependent Claim
23 words
A method according to claim 14 wherein said error image e(i,j) is applied to a hard copy recorder to generate an overlay image.
Claim 22
Dependent Claim
27 words
A method according to claim 14 wherein said error image e(i,j) is subjected to characterisation and classification to generate a report on shape and amplitude of defects.
Claim 23
Dependent Claim
29 words
A method according to claim 14 wherein said smooth background image g R (i,j) is obtained by applying a regression technique to pixel values of said flat field image.
References Cited (Backward Citations)
US4611283A
Cited
EP0238962A2
Cited
US5231574A
Cited
US5151596A
Cited
EP0574969A2
Cited
US5565678A
Cited
US5633510A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 2001-11-02 | 2002-05-04 | 2002-11-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-11-02 | 2006-05-04 | 2006-11-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-11-02 | 2010-05-04 | 2010-11-03 | $7700.00 | Window Closed / Lapsed |