Patent US3885182A successfully refreshed from Google Patents.
US5828718A
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Method and apparatus for helical computed tomography scanning with asymmetric detector system
Assignee: Analogic Corp
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Filing: 1997-03-31
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Granted: 1998-10-27
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Expires: 2017-03-31
Abstract
Abstract A system for and method of generating a reconstructed tomographic image is described using an asymmetric detector array during a helical scan. An improved helical weighting system applies a helical halfscan technique to data collected by a symmetric portion of an asymmetric detector system and applies a helical fullscan technique to data collected by an asymmetric portion of the asymmetric detector system. The preferred system comprises an equi-angle interpolator, a streak artifact suppression filter, and an isocenter interpolator that preserve the distinction between even and odd data points in parallel beam projection data.
Inventors
- 👤 Christopher C. Ruth
- 👤 John M. Dobbs
- 👤 Carl R. Crawford
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:32
CPC Classifications
A; A61; A61B; A61B6/00; A61B6/02; A61B6/03; A61B6/032; A61B6/027; Y; Y10; Y10S; Y10S378/00; Y10S378/901
Claims Analysis
Total Claims: 53
Claim 1
Independent Claim
181 words
A method of acquiring projection data on a tomographic imaging system of the type comprising (a) means for acquiring data from a series of fan beam projections of an imaged object at a plurality of angles as a source of x-rays revolves about a z-axis about a mechanical center of rotation within an imaging plane, (b) means for translating the imaged object and imaging plane relative to one another along the z-axis, wherein the each of the fan beam projections subtends maximum angles φ 1 and φ 2 respectively with respect to a line connecting the apex of the fan beam with the mechanical center of rotation, wherein φ 1 and φ 2 are different, said method comprising the steps of: identifying a slice plane at a position along the z-axis relative to the imaged object; translating the object and imaging plane relative to one another along the z-axis to move the slice plane through the imaging plane; acquiring a tomographic set of data comprised of data from a plurality of projections; and reconstructing a tomographic image at the slice plane.
Claim 2
Independent Claim
181 words
A method of acquiring projection data on a tomographic imaging system of the type comprising (a) means for acquiring data from a series of fan beam projections of an imaged object at a plurality of angles as a source of x-rays revolves about a z-axis about a mechanical center of rotation within an imaging plane, (b) means for translating the imaged object and imaging plane relative to one another along the z-axis, wherein the each of the fan beam projections subtends maximum angles φ 1 and φ 2 respectively with respect to a line connecting the apex of the fan beam with the mechanical center of rotation, wherein φ 1 and φ 2 are different, said method comprising the steps of: identifying a slice plane at a position along the z-axis relative to the imaged object; translating the object and imaging plane relative to one another along the z-axis to move the slice plane through the imaging plane; acquiring a tomographic set of data comprised of data from a plurality of projections; and reconstructing a tomographic image at the slice plane.
Claim 3
Dependent Claim
22 words
The method of claim 1, further including the step of weighting said projections prior to the step of reconstructing said tomographic image.
Claim 4
Dependent Claim
26 words
The method of claim 2, wherein the step of reconstructing the tomographic image includes the step of using filtered back projection to reconstruct said tomographic image.
Claim 5
Dependent Claim
54 words
The method of claim 2, wherein the step of acquiring a tomographic set of data includes the step of acquiring at least 720 degrees of fan beam projections, and wherein the step of reconstructing a tomographic image includes the step of using the 720 degrees of fan beam projections to reconstruct the tomographic image.
Claim 6
Dependent Claim
25 words
The method of claim 4, wherein the step of reconstructing the tomographic image includes the step of back projecting 720 degrees of fan beam projections.
Claim 7
Dependent Claim
35 words
The method of claim 4, wherein the step of reconstructing the tomographic image includes the steps of combining fan beam projections displaced by 360 degrees and back projecting 360 degrees of combined fan beam projections.
Claim 8
Dependent Claim
106 words
The method of claim 4, wherein the system includes a plurality of detectors, and φ describes the angle subtended by a detector and the line connecting the apex of the fan with the mechanical center-of-rotation, φ max is the greater of the two values of φ 1 and φ 2 and where φ min is the lesser of the two values of φ 1 and φ 2 , the method further comprising the steps of using a first weighting scheme for weighting data acquired by detectors with |φ|<φ min and using a second weighting scheme for data acquired by detectors with φ min <φ<φ max .
Claim 9
Dependent Claim
33 words
The method of claim 7, wherein the step of using the first weighting scheme includes the step of setting projections to zero over a range of 360 degrees minus 4 φ max .
Claim 10
Dependent Claim
28 words
The method of claim 7, wherein the step of using the first weighting scheme includes the step of setting projections to zero over a range of 360 degrees.
Claim 11
Dependent Claim
26 words
The method of claim 7, wherein the step of using the first weighting scheme includes the step of using weights corresponding to linear interpolation of data.
Claim 12
Dependent Claim
29 words
The method of claim 7, wherein the step of using the first weighting scheme includes the step of using weights corresponding to linear interpolation and linear extrapolation of data.
Claim 13
Dependent Claim
26 words
The method of claim 7, wherein the step of using the second weighting scheme includes the step of using weights corresponding to linear interpolation of data.
Claim 14
Dependent Claim
29 words
The method of claim 7, wherein the step of using the second weighting scheme includes the step of using weights corresponding to linear interpolation and linear extrapolation of data.
Claim 15
Dependent Claim
31 words
The method of claim 7, wherein the steps of using the first and second weighting schemes includes the step of blending said first and second weighting schemes for |φ|<φ min .
Claim 16
Dependent Claim
18 words
The method of claim 14, wherein the step of blending includes the step of using linear blending functions.
Claim 17
Dependent Claim
18 words
The method of claim 14, wherein the step of blending includes the step of using quadratic blending functions.
Claim 18
Dependent Claim
19 words
The method of claim 14, wherein the step of blending is used over the angle subtended by ten detectors.
Claim 19
Dependent Claim
27 words
The method of claim 1, further including the step of converting said fan beam projections to parallel projections prior to the step of reconstructing the tomographic image.
Claim 20
Dependent Claim
29 words
The method of claim 18, wherein the step of converting includes the steps of interpolating data so as to form parallel projections with equal spacing in the detector direction.
Claim 21
Dependent Claim
22 words
The method of claim 19, wherein the step of interpolating data includes the step of using data acquired by every other detector.
Claim 22
Dependent Claim
26 words
The method of claim 18, further including the step of interleaving parallel projections displaced by 180 degrees prior to the step of reconstructing the tomographic image.
Claim 23
Dependent Claim
23 words
The method of claim 21, wherein the step of interleaving parallel projections includes the step of nonlinearly filtering data of the parallel projections.
Claim 24
Dependent Claim
22 words
The method of claim 22, wherein the step of nonlinearly filtering includes the step of using data acquired from every other detector.
Claim 25
Dependent Claim
28 words
The method of claim 18, further including the step of weighting the fan beam projections prior to the step of converting said fan beam projections to parallel projections.
Claim 26
Dependent Claim
23 words
The method of claim 18, further including the step of weighting the parallel projections prior to the step of reconstructing the tomographic image.
Claim 27
Dependent Claim
168 words
A tomographic imaging system for creating a tomographic image of an object, said system comprising: (a) means for defining a plurality of fan beam projections as a source of x-rays revolves around a z-axis about a mechanical center of rotation within an imaging plane, wherein each of the fan beam projections subtends maximum angles φ 1 and φ 2 respectively with respect to a line connecting the apex of the fan beam with the mechanical center of rotation, wherein φ 1 and φ 2 are different; (b) means for translating the object and imaging plane relative to one another along the z-axis; (c) means for acquiring a tomographic projection set of data from a series of fan beam projections of the imaged object at a plurality of angles about the z-axis as the source revolves around the z-axis about a mechanical center of rotation, and the object and imaging plane are translated relative to one another; and (d) means for reconstructing the tomographic image from the acquired data.
Claim 28
Dependent Claim
168 words
A tomographic imaging system for creating a tomographic image of an object, said system comprising: (a) means for defining a plurality of fan beam projections as a source of x-rays revolves around a z-axis about a mechanical center of rotation within an imaging plane, wherein each of the fan beam projections subtends maximum angles φ 1 and φ 2 respectively with respect to a line connecting the apex of the fan beam with the mechanical center of rotation, wherein φ 1 and φ 2 are different; (b) means for translating the object and imaging plane relative to one another along the z-axis; (c) means for acquiring a tomographic projection set of data from a series of fan beam projections of the imaged object at a plurality of angles about the z-axis as the source revolves around the z-axis about a mechanical center of rotation, and the object and imaging plane are translated relative to one another; and (d) means for reconstructing the tomographic image from the acquired data.
Claim 29
Dependent Claim
86 words
The system of claim 26, wherein said means for translating the object and the imaging plane relative to one another includes means for identifying a slice plane at a position along the z-axis relative to the imaged object; and means for translating the object and imaging plane relative to one another along the z-axis to move the slice plane through the imaging plane; and said means for reconstructing a tomographic image from the acquired data includes means for reconstructing the tomographic image at the slice plane.
Claim 30
Dependent Claim
18 words
The system of claim 27, further including means for weighting said projections prior to reconstructing said tomographic image.
Claim 31
Dependent Claim
25 words
The system of claim 27, wherein the means for reconstructing the tomographic image includes means for filtered back projecting data to reconstruct said tomographic image.
Claim 32
Dependent Claim
52 words
The system of claim 27, wherein the means for acquiring a tomographic projection set of data includes means for acquiring at least 720 degrees of fan beam projections, and wherein means for reconstructing a tomographic image includes means for using the 720 degrees of fan beam projections to reconstruct the tomographic image.
Claim 33
Dependent Claim
24 words
The system of claim 30, wherein the means for reconstructing the tomographic image includes means for back projecting 720 degrees of fan beam projections.
Claim 34
Dependent Claim
36 words
The system of claim 30, wherein the means for reconstructing the tomographic image includes means for combining fan beam projections displaced by 360 degrees and means for back projecting 360 degrees of combined fan beam projections.
Claim 35
Dependent Claim
105 words
The system of claim 30, further including a plurality of detectors, and φ describes the angle subtended by a detector and the line connecting the apex of the fan with the mechanical center-of-rotation, φ max is the greater of the two values of φ 1 and φ 2 and where φ min is the lesser of the two values of φ 1 and φ 2 , the system further comprising means for using a first weighting scheme for weighting data acquired by detectors with |φ|<φ min and means for using a second weighting scheme for data acquired by detectors with φ min <φ<φ max .
Claim 36
Dependent Claim
32 words
The system of claim 33, wherein the means for using the first weighting scheme includes means for setting projections to zero over a range of 360 degrees minus 4 φ max .
Claim 37
Dependent Claim
27 words
The system of claim 33, wherein the means for using the first weighting scheme includes means for setting projections to zero over a range of 360 degrees.
Claim 38
Dependent Claim
25 words
The system of claim 33, wherein the means for using the first weighting scheme includes means for using weights corresponding to linear interpolation of data.
Claim 39
Dependent Claim
28 words
The system of claim 33, wherein the means for using the first weighting scheme includes means for using weights corresponding to linear interpolation and linear extrapolation of data.
Claim 40
Dependent Claim
25 words
The system of claim 33, wherein the means for using the second weighting scheme includes means for using weights corresponding to linear interpolation of data.
Claim 41
Dependent Claim
28 words
The system of claim 33, wherein the means for using the second weighting scheme includes means for using weights corresponding to linear interpolation and linear extrapolation of data.
Claim 42
Dependent Claim
30 words
The system of claim 33, wherein the means for using the first and second weighting schemes includes means for blending the first and second weighting schemes for |φ|<φ min .
Claim 43
Dependent Claim
17 words
The system of claim 40, wherein the means for blending includes means for using linear blending functions.
Claim 44
Dependent Claim
17 words
The system of claim 40, wherein the means for blending includes means for using quadratic blending functions.
Claim 45
Dependent Claim
19 words
The system of claim 40, wherein the means for blending is used over the angle subtended by ten detectors.
Claim 46
Dependent Claim
23 words
The system of claim 27, further including means for converting said fan beam projections to parallel projections prior to reconstructing the tomographic image.
Claim 47
Dependent Claim
28 words
The system of claim 44, wherein the means for converting includes means for interpolating data so as to form parallel projections with equal spacing in the detector direction.
Claim 48
Dependent Claim
21 words
The system of claim 45, wherein the means for interpolating data includes means for using data acquired by every other detector.
Claim 49
Dependent Claim
25 words
The system of claim 44, further including means for interleaving parallel projections displaced by 180 degrees prior to the step of reconstructing the tomographic image.
Claim 50
Dependent Claim
22 words
The system of claim 47, wherein the means for interleaving parallel projections includes means for nonlinearly filtering data of the parallel projections.
Claim 51
Dependent Claim
21 words
The system of claim 48, wherein the means for nonlinearly filtering includes means for using data acquired from every other detector.
Claim 52
Dependent Claim
23 words
The system of claim 44, further including means for weighting the fan beam projections prior converting said fan beam projections to parallel projections.
Claim 53
Dependent Claim
19 words
The system of claim 44, further including means for weighting the parallel projections prior to reconstructing the tomographic image.
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) | 2001-10-26 | 2002-04-27 | 2002-10-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-10-26 | 2006-04-27 | 2006-10-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-10-26 | 2010-04-27 | 2010-10-27 | $7700.00 | Window Closed / Lapsed |