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Method and system for automatic computed radiography (CR) image composition by white band detection and consistency rechecking
Assignee: Siemens Healthcare GmbH
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Filing: 2001-05-15
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Granted: 2004-06-29
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Expires: 2021-05-15
Abstract
Abstract A method for automatic CR image composition includes the following steps for each image in a CR image pair. A vertical gradient image is projected onto a y-axis to obtain a y-axis projection. Edge positions (candidates) are identified from white band edge positions based on an absolute maximum value of the y-axis projection. An intensity change constancy identifies candidates having orientation angles less than a threshold angle with respect to a horizontal. An intensity change value verifies intensity value differences on two candidate sides. A cross-correlation score is computed for the candidates having an error value below a threshold for the intensity change constancy and the intensity change value, by comparing a consistency of the candidates against image data of the CR image pair. A final overlap is identified for the CR image pair, based upon the cross-correlation score.
Inventors
- 👤 Guo-Qing Wei
- 👤 Zhenyu Wu
- 👤 Jianzhong Qian
- 👤 Helmut Schramm
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 11:14
CPC Classifications
A; A61; A61B; A61B6/00; A61B6/52; A61B6/5211; A61B6/5229; A61B6/5235; A61B6/5241; G; G06; G06T; G06T3/00; G06T3/40; G06T3/4038; G06T7/00; G06T7/10; G06T7/13; G06T7/30; G06T7/32; G06T7/33; G06T2207/00; G06T2207/10; G06T2207/10116
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
267 words
A method for automatic Computed Radiography (CR) image composition by white band detection and consistency rechecking, comprising the steps of: receiving an original CR image pair for composition; for each image in the original CR image pair, generating a horizontal gradient image and a vertical gradient image; projecting the vertical gradient image onto a y-axis of the each image to obtain a y-axis projection; identifying candidate edge positions from among at least two white band edge positions according to a relative value of each of the at least two white band edge positions with respect to a percentage value of an absolute maximum value of the y-axis projection; determining an intensity change constancy of the candidate edge positions to identify the candidate edge positions having orientation angles less than a pre-defined threshold angle with respect to a horizontal, the orientation angles being orthogonal with respect to angles of maximum intensity change for pixels on the candidate edge positions; determining an intensity change value to verify intensity value differences on two sides of the candidate edge positions with respect to predefined criteria; defining an error function to respectively obtain an error value for each of the candidate edge positions with respect to the intensity change constancy and the intensity change value; selecting the candidate edge positions having the error value below a pre-specified threshold; computing a cross-correlation score for the selected candidate edge positions, by comparing a consistency of the selected candidate edge positions against image data corresponding to the original image pair; and identifying a final overlap for the original image pair, based upon the cross-correlation score.
Claim 2
Independent Claim
267 words
A method for automatic Computed Radiography (CR) image composition by white band detection and consistency rechecking, comprising the steps of: receiving an original CR image pair for composition; for each image in the original CR image pair, generating a horizontal gradient image and a vertical gradient image; projecting the vertical gradient image onto a y-axis of the each image to obtain a y-axis projection; identifying candidate edge positions from among at least two white band edge positions according to a relative value of each of the at least two white band edge positions with respect to a percentage value of an absolute maximum value of the y-axis projection; determining an intensity change constancy of the candidate edge positions to identify the candidate edge positions having orientation angles less than a pre-defined threshold angle with respect to a horizontal, the orientation angles being orthogonal with respect to angles of maximum intensity change for pixels on the candidate edge positions; determining an intensity change value to verify intensity value differences on two sides of the candidate edge positions with respect to predefined criteria; defining an error function to respectively obtain an error value for each of the candidate edge positions with respect to the intensity change constancy and the intensity change value; selecting the candidate edge positions having the error value below a pre-specified threshold; computing a cross-correlation score for the selected candidate edge positions, by comparing a consistency of the selected candidate edge positions against image data corresponding to the original image pair; and identifying a final overlap for the original image pair, based upon the cross-correlation score.
Claim 3
Dependent Claim
64 words
The method according to claim 1 , wherein I (x,y) represents the each image in the original CR image pair, I x (x,y) and I y (x,y) respectively represent the horizontal gradient image and the vertical gradient image, and the y-axis projection is equal to P ( y ) = ∑ x I y ( x , y ) .
Claim 4
Dependent Claim
32 words
The method according to claim 1 , wherein the absolute maximum value of the y-axis projection is equal to Max_Py = max y P ( y ) .
Claim 5
Dependent Claim
94 words
The method according to claim 1 , wherein Ω={c|c=1,2, . . . , N c } represents a set of indices for the candidate edge positions having y-coordinates at {Y c |c=1,2, . . . , N c } in the each image, the angles of maximum intensity change for the pixels on a candidate edge position c from among the candidate edge positions are R c (x)=arctan(I y (x,y c ),I x (x,y c ); x∈D c ,c∈Ω, where D c is a set of points having a vertical gradient that is non-zero.
Claim 6
Independent Claim
22 words
The method according to clam 4 , wherein the set of points D c is used to exclude over-saturated and under-exposed pixels.
Claim 7
Independent Claim
22 words
The method according to clam 4 , wherein the set of points D c is used to exclude over-saturated and under-exposed pixels.
Claim 8
Dependent Claim
84 words
The method according to claim 4 , wherein an orthogonal angle to R c (x) is R ⊥ c (x), an average angle of R ⊥ c (x) represents an orientation angle of the candidate edge position c, and is equal to A c , A c = ∑ x ∈ D c R c ⊥ ( x ) / D c , and |D c | is a number of elements in the set of points D c .
Claim 9
Dependent Claim
30 words
The method according to claim 1 , further comprising the step of excluding any of the candidate edge positions having an average angle below a pre-determined threshold from further consideration.
Claim 10
Dependent Claim
92 words
The method according to claim 1 , wherein said step of determining the intensity change constancy comprises the steps of: for each of the candidate edge positions, determining a direction of maximum intensity change for each of pixels on the each of the candidate edge positions; determining an orthogonal angle with respect to the direction of maximum intensity change; calculating a deviation of an orientation angle, measured as an average angle of the orthogonal angle, from the horizontal; and identifying the candidate edge positions having the deviation less than the pre-defined threshold.
Claim 11
Dependent Claim
48 words
The method according to claim 1 , wherein said step of determining the intensity change value comprises the steps of: measuring a relative intensity change across a candidate edge position c at two different, pre-defined offset values; and verifying that the relative intensity change satisfies the pre-defined criteria.
Claim 12
Dependent Claim
225 words
The method according to claim 9 , wherein said measuring step comprises the step of determining Δ I 1 , c = ∑ x ∈ D c I ( x , y c + δ 1 ) - I ( x , y c - δ 1 ) ; min { ∑ x ∈ D c I ( x , y c + δ 1 ) , ∑ x ∈ D c I ( x , y c - δ 1 ) } c ∈ Ω Δ I 2 , c = ∑ x ∈ D c I ( x , y c + δ 2 ) - I ( x , y c - δ 2 ) ; min { ∑ x ∈ D c I ( x , y c + δ 2 ) , ∑ x ∈ D c I ( x , y c - δ 2 ) } c ∈ Ω , where δ 1 and δ 2 are the two different, pre-defined offset values, and ΔI 1,c and ΔI 2,c indicate the relative intensity change across the candidate edge position c at the two different, pre-defined offset values.
Claim 13
Dependent Claim
133 words
The method according to claim 10 , wherein said verifying step comprises the step of verifying Δ I min , c = def min ( Δ I 1 , c , Δ I 2 , c ) > Δ min ; Δ I max , c = def max ( Δ I 1 , c , Δ I 2 , c ) < Δ max ; and γ = def min ( Δ I 1 , c , Δ I 2 , c ) / max ( Δ I 1 , c , Δ I 2 , c ) > γ min .
Claim 14
Dependent Claim
25 words
The method according to claim 1 , wherein said selecting step comprises the step of selecting a candidate edge position having a smallest error value.
Claim 15
Dependent Claim
38 words
The method according to claim 12 , wherein said selecting step further comprises the step of selecting any remaining candidate edge positions having the error value that is less than a pre-specified percentage of the smallest error value.
Claim 16
Independent Claim
330 words
A system for automatic Computed Radiography (CR) image composition by white band detection and consistency rechecking, comprising: means for receiving an original CR image pair for composition; a gradient determinator for generating a horizontal gradient image and a vertical gradient image, for each image in the original CR image pair; a gradient projector for projecting, for the each image, the vertical gradient image onto a y-axis of the each image to obtain a y-axis projection; a candidate generator for identifying, for the each image, candidate edge positions from among at least two white band edge positions according to a relative value of each of the at least two white band edge positions with respect to a percentage value of an absolute maximum value of the y-axis projection; an intensity change constancy determinator for determining an intensity change constancy of the candidate edge positions for the each image, to identify the candidate edge positions having orientation angles less than a pre-defined threshold angle with respect to a horizontal, the orientation angles being orthogonal with respect to angles of maximum intensity change for pixels on the candidate edge positions; an intensity change value determinator for determining an intensity change value to verify intensity value differences on two sides of the candidate edge positions, for the each image with respect to predefined criteria; an error determinator for defining an error function to respectively obtain an error value for each of the candidate edge positions for the each image with respect to the intensity change constancy and the intensity change value, and for selecting the candidate edge positions, for the each image, having the error value below a pre-specified threshold; and an overlap determinator for computing a cross-correlation score for the selected candidate edge positions for the each image by comparing a consistency of the selected candidate edge positions against image data corresponding to the original image pair, and for identifying a final overlap for the original image pair, based upon the cross-correlation score.
Claim 17
Independent Claim
330 words
A system for automatic Computed Radiography (CR) image composition by white band detection and consistency rechecking, comprising: means for receiving an original CR image pair for composition; a gradient determinator for generating a horizontal gradient image and a vertical gradient image, for each image in the original CR image pair; a gradient projector for projecting, for the each image, the vertical gradient image onto a y-axis of the each image to obtain a y-axis projection; a candidate generator for identifying, for the each image, candidate edge positions from among at least two white band edge positions according to a relative value of each of the at least two white band edge positions with respect to a percentage value of an absolute maximum value of the y-axis projection; an intensity change constancy determinator for determining an intensity change constancy of the candidate edge positions for the each image, to identify the candidate edge positions having orientation angles less than a pre-defined threshold angle with respect to a horizontal, the orientation angles being orthogonal with respect to angles of maximum intensity change for pixels on the candidate edge positions; an intensity change value determinator for determining an intensity change value to verify intensity value differences on two sides of the candidate edge positions, for the each image with respect to predefined criteria; an error determinator for defining an error function to respectively obtain an error value for each of the candidate edge positions for the each image with respect to the intensity change constancy and the intensity change value, and for selecting the candidate edge positions, for the each image, having the error value below a pre-specified threshold; and an overlap determinator for computing a cross-correlation score for the selected candidate edge positions for the each image by comparing a consistency of the selected candidate edge positions against image data corresponding to the original image pair, and for identifying a final overlap for the original image pair, based upon the cross-correlation score.
Claim 18
Dependent Claim
63 words
The system according to claim 14 , wherein I (x,y) represents the each image in the original CR image pair, I x (x,y) and I y (x,y) respectively represent the horizontal gradient image and the vertical gradient image, and the y-axis projection is equal to P ( y ) = ∑ x I y ( x , y ) .
Claim 19
Dependent Claim
32 words
The system according to claim 14 , wherein the absolute maximum value of the y-axis projection is equal to Max_Py = max y P ( y ) .
Claim 20
Dependent Claim
95 words
The system according to claim 14 , wherein Ω={c| c=1,2, . . . , N c } represents a set of indices for the candidate edge positions having y-coordinates at {Y c |c=1,2, . . . , N c } in the each image, the angles of maximum intensity change for the pixels on a candidate edge position c from among the candidate edge positions are R c (x)=arctan(I y (x,y c ),I x (x,y c ); x∈D c ,c∈Ω, where D c is a set of points having a vertical gradient that is non-zero.
Claim 21
Independent Claim
22 words
The system according to clam 17 , wherein the set of points D c is used to exclude over-saturated and under-exposed pixels.
Claim 22
Independent Claim
22 words
The system according to clam 17 , wherein the set of points D c is used to exclude over-saturated and under-exposed pixels.
Claim 23
Dependent Claim
84 words
The system according to claim 17 , wherein an orthogonal angle to R c (x) is R ⊥ c (x), an average angle of R ⊥ c (x) represents an orientation angle of the candidate edge position c, and is equal to A c , A c = ∑ x ∈ D c R c ⊥ ( x ) / D c , and |D c | is a number of elements in the set of points D c .
Claim 24
Dependent Claim
31 words
The system according to claim 14 , wherein said intensity change constancy determinator excludes any of the candidate edge positions having an average angle below a pre-determined threshold from further consideration.
Claim 25
Dependent Claim
85 words
The system according to claim 14 , wherein said intensity change constancy determinator, for each of the candidate edge positions, determines a direction of maximum intensity change for each of pixels on the each of the candidate edge positions, determines an orthogonal angle with respect to the direction of maximum intensity change, calculates a deviation of an orientation angle, measured as an average angle of the orthogonal angle, from the horizontal, and identifies the candidate edge positions having the deviation less than the pre-defined threshold.
Claim 26
Dependent Claim
41 words
The system according to claim 14 , wherein said intensity change value determinator measures a relative intensity change across a candidate edge position c at two different, pre-defined offset values, and verifies that the relative intensity change satisfies the pre-defined criteria.
Claim 27
Dependent Claim
242 words
The system according to claim 22 , wherein said intensity change value determinator measures the relative intensity change across the candidate edge position c at the two different, pre-defined offset values by determining Δ I 1 , c = ∑ x ∈ D c I ( x , y c + δ 1 ) - I ( x , y c - δ 1 ) ; min { ∑ x ∈ D c I ( x , y c + δ 1 ) , ∑ x ∈ D c I ( x , y c - δ 1 ) } c ∈ Ω Δ I 2 , c = ∑ x ∈ D c I ( x , y c + δ 2 ) - I ( x , y c - δ 2 ) ; min { ∑ x ∈ D c I ( x , y c + δ 2 ) , ∑ x ∈ D c I ( x , y c - δ 2 ) } c ∈ Ω , where δ 1 and δ 2 are the two different, pre-defined offset values, and ΔI 1,c and ΔI 2,c indicate the relative intensity change across the candidate edge position c at the two different, pre-defined offset values.
Claim 28
Dependent Claim
142 words
The system according to claim 23 , wherein said intensity change value determinator verifies that the relative intensity change satisfies the pre-defined criteria by verifying Δ I min , c = def min ( Δ I 1 , c , Δ I 2 , c ) > Δ min ; Δ I max , c = def max ( Δ I 1 , c , Δ I 2 , c ) < Δ max ; and γ = def min ( Δ I 1 , c , Δ I 2 , c ) / max ( Δ I 1 , c , Δ I 2 , c ) > γ min .
Claim 29
Dependent Claim
21 words
The system according to claim 14 , wherein said error determinator selects a candidate edge position having a smallest error value.
Claim 30
Dependent Claim
34 words
The system according to claim 25 , wherein said error determinator further selects any remaining candidate edge positions having the error value that is less than a pre-specified percentage of the smallest error value.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2007-06-29 | 2007-12-29 | 2008-06-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2011-06-29 | 2011-12-29 | 2012-06-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2015-06-29 | 2015-12-29 | 2016-06-29 | $7700.00 | Window Closed / Lapsed |