US6108575A
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Helical weighting algorithms for fast reconstruction
Assignee: General Electric Co
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Filing: 1998-02-20
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Granted: 2000-08-22
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Expires: 2018-02-20
Abstract
Abstract CT helical weighting algorithms wherein one source rotation, or 2π, worth of projection data is utilized for fast image reconstruction are described. Particularly, by using a distance function, and by selecting particular classes of such distance function, the discontinuity across the sinogram can be eliminated. Further, by imposing specific necessary conditions on such distance functions, single analytical expressions across the entire 2π sinogram are obtained. Decomposition of these particular single distance functions provides exact, or approximated, fast two-filtering reconstruction algorithms, for which a given projection needs to be filtered only two times for an arbitrary number P of reconstruction planes. In addition, single weighting functions that depend only on the sum of the projection and fan angles can be utilized. Accordingly, after rebinning the fan-beam projections to parallel projections, the corresponding 2π helical weighting algorithms do not include a dependency over the ray parameter (within one parallel projection). For these algorithms, weighting commutes with filtering, and reconstruction of an arbitrary number P of image planes requires only one filtering per projection.
Inventors
- 👤 Guy M. Besson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 02:36
CPC Classifications
G; G06; G06T; G06T12/00; G06T12/20
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
65 words
A system for producing a tomographic image of an object from projection data acquired in a helical scan, said system comprising an image reconstructor system configured to generate helical weighting factors based on a distance function, said distance function based upon a given point in Radon space contributing to the tomographic image as a function of distance from a projection ray to a reconstruction plane.
Claim 2
Independent Claim
65 words
A system for producing a tomographic image of an object from projection data acquired in a helical scan, said system comprising an image reconstructor system configured to generate helical weighting factors based on a distance function, said distance function based upon a given point in Radon space contributing to the tomographic image as a function of distance from a projection ray to a reconstruction plane.
Claim 3
Dependent Claim
19 words
A system in accordance with claim 1 wherein said helical weighting factors are generated using a single weighting function.
Claim 4
Dependent Claim
21 words
A system in accordance with claim 1 wherein said image reconstructor system is configured to execute a generalized helical extrapolative algorithm.
Claim 5
Dependent Claim
21 words
A system in accordance with claim 1 wherein said image reconstructor system is configured to execute a generalized helical interpolative algorithm.
Claim 6
Dependent Claim
21 words
A system in accordance with claim 1 wherein said image reconstructor system is configured to execute a generalized single-filtering helical algorithm.
Claim 7
Dependent Claim
18 words
A system in accordance with claim 1 wherein said helical weighting factors are generated in accordance with: ##EQU21##
Claim 8
Dependent Claim
19 words
A system in accordance with claim 1 wherein said helical weighting factors are generated in accordance with: where d(x,y)=y-x.
Claim 9
Dependent Claim
18 words
A system in accordance with claim 1 wherein said helical weighting factors are generated in accordance with: ##EQU22##
Claim 10
Dependent Claim
23 words
A system in accordance with claim 1 wherein said helical weighting factors are generated in accordance with: where β denotes the source angle.
Claim 11
Dependent Claim
16 words
A system in accordance with claim 9 wherein d(x,y) is selected to equal y-x and: ##EQU23##
Claim 12
Dependent Claim
17 words
A system in accordance with claim 9 wherein d(x,y) is selected to equal sin 2 ((y-x)/2) and
Claim 13
Dependent Claim
8 words
A system in accordance with claim 9 wherein:
Claim 14
Dependent Claim
16 words
A system in accordance with claim 9 wherein d(x,y) is selected to equal |sin (y-x)/2)|.sup.δ and:
Claim 15
Dependent Claim
28 words
A system in accordance with claim 1 wherein said image reconstructuor system enables reconstructor of an arbitrary number of image planes from two filterings of the projection data.
Claim 16
Dependent Claim
28 words
A system in accordance with claim 1 wherein said image reconstructor system enables reconstruction of an arbitrary number of image planes from one filtering of the projection data.
Claim 17
Independent Claim
49 words
A system for producing a tomographic image of an object from projection data acquired in a helical scan, said system comprising an image reconstructor system configured to generate helical weighting factor based on a distance function, said helical weighting factor generated in accordance with: w.sub.1 +w.sub.2 =w(θ). where θ=β+γ.
Claim 18
Independent Claim
49 words
A system for producing a tomographic image of an object from projection data acquired in a helical scan, said system comprising an image reconstructor system configured to generate helical weighting factor based on a distance function, said helical weighting factor generated in accordance with: w.sub.1 +w.sub.2 =w(θ). where θ=β+γ.
Claim 19
Dependent Claim
24 words
A system in accordance with claim 16 wherein said helical weighting factors are generated in accordance with: ##EQU24## where β denotes the source angle.
Claim 20
Dependent Claim
16 words
A system in accordance with claim 17 wherein d(x,y) is selected to equal y-x and: ##EQU25##
Claim 21
Dependent Claim
8 words
A system in accordance with claim 16 wherein:
Claim 22
Dependent Claim
16 words
A system in accordance with claim 16 wherein d(x,y) is selected to equal |sin (y-x)/2).sup.δ and:
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) | 2003-08-22 | 2004-02-21 | 2004-08-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-08-22 | 2008-02-21 | 2008-08-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-08-22 | 2012-02-21 | 2012-08-22 | $7700.00 | Window Closed / Lapsed |