US6246742B1
Expired / Lapsed
US
⏱️ 0.0 years remaining
Local CT image reconstruction with limited x-ray exposure
Assignee: General Electric Co
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Filing: 1999-06-22
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Granted: 2001-06-12
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Expires: 2019-06-22
Abstract
Abstract Methods and apparatus for reconstructing an image of an object utilizing an imaging system, in which a limited width beam of radiation is emitted towards the object, the limited width beam of radiation having a fan beam angle extent selected to encompass a perimeter of a region of interest (ROI) within the object and to encompass less than a perimeter of the object itself; a set of truncated projection data of the object, including projection data of the ROI, is obtained by detecting the radiation from the limited width beam of radiation passing through the object; low frequency components of the set of truncated projection data are estimated; and an image of the ROI within the object is reconstructed utilizing the set of truncated projection data and the estimated low frequency components. Information from a limited set of complete projection data can be used to estimate the low frequency components of the set of truncated projection data, but such information is not required.
Inventors
- 👤 Guy M. Besson
- 👤 Tin-Su Pan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 04:40
CPC Classifications
G; G06; G06T; G06T12/00; G06T12/10; G06T2211/00; G06T2211/40; G06T2211/432; Y; Y10; Y10S; Y10S378/00; Y10S378/901
Claims Analysis
Total Claims: 40
Claim 1
Independent Claim
128 words
A method for reconstructing an image of an object utilizing an imaging system, said method comprising: emitting a limited width beam of radiation towards the object, the limited width beam of radiation having a fan beam angle extent selected to encompass a perimeter of a region of interest (ROI) within the object and to encompass less than a perimeter of the object itself; obtaining a set of truncated projection data of the object, including projection data of the ROI, by detecting the radiation from the limited width beam of radiation passing through the object; estimating low frequency components of the set of truncated projection data; and reconstructing an image of the ROI within the object utilizing the set of truncated projection data and the estimated low frequency components.
Claim 2
Independent Claim
128 words
A method for reconstructing an image of an object utilizing an imaging system, said method comprising: emitting a limited width beam of radiation towards the object, the limited width beam of radiation having a fan beam angle extent selected to encompass a perimeter of a region of interest (ROI) within the object and to encompass less than a perimeter of the object itself; obtaining a set of truncated projection data of the object, including projection data of the ROI, by detecting the radiation from the limited width beam of radiation passing through the object; estimating low frequency components of the set of truncated projection data; and reconstructing an image of the ROI within the object utilizing the set of truncated projection data and the estimated low frequency components.
Claim 3
Dependent Claim
42 words
A method in accordance with claim 1 wherein the limited width beam of radiation is a limited width x-ray beam, and emitting a limited width beam of radiation towards the object comprises the step of emitting an x-ray beam towards the object.
Claim 4
Dependent Claim
91 words
A method in accordance with claim 2 further comprising the steps of emitting a broad x-ray beam having a fan beam angle extent greater than that of the limited width x-ray beam towards the object and obtaining at least one complete projection of the object by detecting radiation from the broad x-ray beam; and wherein estimating low frequency components of the set of truncated projection data comprises the step of estimating low frequency components of the set of truncated projection data utilizing the at least one complete projection of the object.
Claim 5
Dependent Claim
66 words
A method in accordance with claim 3 wherein the imaging system is a scanning imaging system, the limited width x-ray beam and the broad x-ray beam are emitted by an x-ray source mounted on a rotating gantry of the scanning imaging system, and wherein no more than 10% of a total of truncated projections and complete projections sufficient for reconstruction of the image are complete projections.
Claim 6
Dependent Claim
30 words
A method in accordance with claim 4 wherein no more than 1% of the total of truncated projections and complete projections sufficient for reconstruction of the image are complete projections.
Claim 7
Dependent Claim
16 words
A method in accordance with claim 4 wherein no more than four projections are complete projections.
Claim 8
Dependent Claim
67 words
A method in accordance with claim 3 wherein the imaging system is a scanning imaging system, the broad and the limited width x-ray beam are emitted by an x-ray source mounted on a rotating gantry of the scanning imaging system, and further comprising the step of rotating a masking sleeve around the x-ray source to selectively generate the broad x-ray beam and the limited width x-ray beam.
Claim 9
Dependent Claim
34 words
A method in accordance with claim 7 further comprising the step of adjusting the masking sleeve to select an emission direction of the limited width x-ray beam to encompass the perimeter of the ROI.
Claim 10
Dependent Claim
64 words
A method in accordance with claim 8 wherein the rotating gantry has an axis of rotation, said method further comprising the steps of supporting the object on a table repositionable along at least two different axes defining a plane intersecting the axis of rotation of the gantry at a point, and moving the table to position the ROI within the limited width x-ray beam.
Claim 11
Dependent Claim
59 words
A method in accordance with claim 8 wherein the rotating gantry has an axis of rotation, said method further comprising the steps of supporting the object on a table and moving the table in a horizontal direction perpendicular to the axis of rotation of the gantry to position the perimeter of the ROI within the limited width x-ray beam.
Claim 12
Dependent Claim
18 words
A method in accordance with claim 3 wherein estimating a low frequency component includes estimating a DC component.
Claim 13
Dependent Claim
93 words
A method in accordance with claim 2 wherein the imaging system is a scanning imaging system, the limited width x-ray beam is emitted by an x-ray source mounted on a rotating gantry of the scanning imaging system, the rotating gantry has an axis of rotation, said method further comprising the steps of supporting the object on a table repositionable along at least two different axes defining a plane intersecting the axis of rotation of the gantry at a point, and moving the table to position the ROI within the limited width x-ray beam.
Claim 14
Dependent Claim
85 words
A method in accordance with claim 2 wherein the imaging system is a scanning imaging system, the limited width x-ray beam is emitted by an x-ray source mounted on a rotating gantry of the scanning imaging system, the rotating gantry has an axis of rotation, said method further comprising the steps of supporting the object on a table and moving the table in a horizontal direction perpendicular to the axis of rotation of the gantry to position the ROI within the limited width x-ray beam.
Claim 15
Dependent Claim
82 words
A method in accordance with claim 1 wherein estimating low frequency components of the set of truncated projection data comprises the step of fitting values of R and μ i to a uniform circular object defined for each projection of the set of truncated projection data, where R is a radius of the uniform circular object and μ i is an attenuation of the uniform circular object for each truncated projection i, and R is greater than a radius of the ROI.
Claim 16
Dependent Claim
78 words
A method in accordance with claim 14 wherein reconstructing an image of the ROI comprises the steps of subtracting a profile of the fitted circular uniform object from the set of truncated projection data to generate pixel data and adding to the pixel data thereby generated the value ( 1 N ) × ∑ i = 1 N μ i to generate pixels of the image of the ROI, where N is the number of truncated projections.
Claim 17
Dependent Claim
47 words
A method in accordance with claim 15 wherein the ROI has a center and a perimeter, and fitting values of R and μ i comprises the step of estimating R and μ i from projection data obtained at the center and at the perimeter of the ROI.
Claim 18
Dependent Claim
42 words
A method in accordance with claim 16 wherein the limited beam width radiation is a limited width x-ray beam, and obtaining a set of truncated projection data comprises the step of masking an x-ray source to obtain the limited width x-ray beam.
Claim 19
Dependent Claim
84 words
A method in accordance with claim 17 wherein the limited width x-ray beam has a central portion, the set of truncated projection data comprises projection components from the central portion of the limited fan beam angle extent x-ray beam, and estimating a low frequency component of the set of truncated projection data comprises the step of analyzing a summation of projection components from the central portion of the limited width x-ray beam over a plurality of truncated projections from the set of truncated projections.
Claim 20
Dependent Claim
122 words
A method in accordance with claim 14 wherein the limited width beam of radiation is a limited width x-ray beam, and emitting a limited width beam of radiation towards the object comprises the step of emitting an x-ray beam towards the object; said method further comprising the steps of emitting a broad x-ray beam having a fan beam angle extent greater than that of the limited width x-ray beam towards the object; and obtaining at least one complete projection of the object by detecting radiation from the broad x-ray beam; and wherein said step of estimating low frequency components of the set of truncated projection data utilizes the at least one complete projection of the object to estimate the low frequency components.
Claim 21
Dependent Claim
126 words
A imaging system for reconstructing an image of an object, said system configured to: emit a limited width beam of radiation towards the object, the limited width beam of radiation having a fan beam angle extent selected to encompass a perimeter of a region of interest (ROI) within the object and to encompass less than a perimeter of the object itself; obtain a set of truncated projection data of the object, including projection data of the ROI, by detecting the radiation from the limited width beam of radiation passing through the object; estimate low frequency components of the set of truncated projection data; and reconstruct an image of the ROI within the object utilizing the set of truncated projection data and the estimated low frequency components.
Claim 22
Dependent Claim
126 words
A imaging system for reconstructing an image of an object, said system configured to: emit a limited width beam of radiation towards the object, the limited width beam of radiation having a fan beam angle extent selected to encompass a perimeter of a region of interest (ROI) within the object and to encompass less than a perimeter of the object itself; obtain a set of truncated projection data of the object, including projection data of the ROI, by detecting the radiation from the limited width beam of radiation passing through the object; estimate low frequency components of the set of truncated projection data; and reconstruct an image of the ROI within the object utilizing the set of truncated projection data and the estimated low frequency components.
Claim 23
Dependent Claim
37 words
A system in accordance with claim 20 wherein said limited width beam of radiation is a limited width x-ray beam, and said limited width beam of radiation emitted towards the object is said limited width x-ray beam.
Claim 24
Dependent Claim
79 words
A system in accordance with claim 21 further configured to emit a broad x-ray beam having a fan beam angle extent greater than that of said limited width x-ray beam towards the object and to obtain at least one complete projection of the object by detecting radiation from said broad x-ray beam; and said system is configured to estimate low frequency components of said set of truncated projection data utilizing said at least one complete projection of the object.
Claim 25
Dependent Claim
90 words
A system in accordance with claim 22 further comprising: a rotating gantry; and an x-ray source mounted on said rotating gantry; said system configured to scan the object with said x-ray source to obtain said truncated projection data and said at least one complete projection, said x-ray source selectively emitting said limited width x-ray beam and said broad x-ray beam, and said system configured so that no more than 10% of a total of said truncated projections and said complete projections sufficient for reconstruction of the image are complete projections.
Claim 26
Dependent Claim
34 words
A system in accordance with claim 23 configured so that no more than 1% of the total of said truncated projections and said complete projections sufficient for reconstruction of the image are complete projections.
Claim 27
Dependent Claim
22 words
A system in accordance with claim 23 configured to reconstruct the image of the object utilizing no more than four complete projections.
Claim 28
Dependent Claim
79 words
A system in accordance with claim 22 further comprising: a rotating gantry; an x-ray source mounted on said rotating gantry, said system configured to scan the object with said x-ray source to obtain said truncated projection data and said at least one complete projection; and a masking sleeve around said x-ray source, said masking sleeve configured to selectively mask said x-ray source so that said x-ray source selectively emits said limited width x-ray beam and said broad x-ray beam.
Claim 29
Dependent Claim
24 words
A system in accordance with claim 26 wherein said masking sleeve is adjustable to select an emission direction of the limited width x-ray beam.
Claim 30
Dependent Claim
63 words
A system in accordance with claim 27 wherein said rotating gantry has an axis of rotation, said system further comprises a table configured to support the object, and wherein said table is repositionable along at least two different axes defining a plane intersecting the axis of rotation of the gantry at a point to position the ROI within said limited width x-ray beam.
Claim 31
Dependent Claim
59 words
A system in accordance with claim 27 wherein said rotating gantry has an axis of rotation, said system further comprises a table configured to support the object, and wherein said table is repositionable in a horizontal direction perpendicular to said axis of rotation of the gantry to position the perimeter of the ROI within said limited width x-ray beam.
Claim 32
Dependent Claim
21 words
A system in accordance with claim 22 further configured to estimate a DC component of said set of truncated projection data.
Claim 33
Dependent Claim
85 words
A system in accordance with claim 21 further comprising: a rotating gantry having an axis of rotation; an x-ray source mounted on said rotating gantry, said system configured to scan the object with said x-ray source to obtain said truncated projection data; and a table configured to support the object, wherein said table is repositionable along at least two different axes defining a plane intersecting said axis of rotation of the gantry at a point to position the ROI within said limited width x-ray beam.
Claim 34
Dependent Claim
78 words
A system in accordance with claim 21 further comprising: a rotating gantry having an axis of rotation; an x-ray source mounted on said rotating gantry, said system configured to scan the object with said x-ray source to obtain said truncated projection data; and a table configured to support the object, wherein said table is repositionable along a horizontal direction perpendicular to said axis of rotation of the gantry to position the ROI within said limited width x-ray beam.
Claim 35
Dependent Claim
86 words
A system in accordance with claim 20 wherein said system is further configured to fit values of R and μ i to a uniform circular object defined for each projection of the set of truncated projection data for estimating said low frequency components of the set of truncated projection data, where R is a radius of the uniform circular object and μ i is an attenuation of the uniform circular object for each truncated projection i, and R is greater than a radius of the ROI.
Claim 36
Dependent Claim
74 words
A system in accordance with claim 33 wherein said system is configured to subtract a profile of the fitted circular uniform object from the set of truncated projection data to generate pixel data and to add to the pixel data thereby generated the value ( 1 N ) × ∑ i = 1 N μ i to generate pixels of the image of the ROI for reconstruction of an image of the ROI.
Claim 37
Dependent Claim
50 words
A system in accordance with claim 34 wherein the ROI has a center and a perimeter, and said system is configured to estimate R and μ i from projection data obtained at the center and at the perimeter of the ROI for fitting values of R and μ i .
Claim 38
Dependent Claim
44 words
A system in accordance with claim 35 wherein said limited beam width radiation is a limited width x-ray beam, and said system is configured to mask an x-ray source to obtain said limited width x-ray beam for obtaining a set of truncated projection data.
Claim 39
Dependent Claim
86 words
A system in accordance with claim 36 wherein said limited width x-ray beam has a central portion, the set of truncated projection data comprises projection components from the central portion of said limited fan beam angle extent x-ray beam, and said system is configured to analyze a summation of projection components from the central portion of the limited width x-ray beam over a plurality of truncated projections from the set of truncated projections for estimating a low frequency component of the set of truncated projection data.
Claim 40
Dependent Claim
101 words
A system in accordance with claim 33 wherein the limited width beam of radiation is a limited width x-ray beam, and said limited width beam of radiation emitted towards the object is said limited width x-ray beam; said system further configured to emit a broad x-ray beam having a fan beam angle extent greater than that of said limited width x-ray beam towards the object; to obtain at least one complete projection of the object by detecting radiation from said broad x-ray beam; and to utilizes said at least one complete projection of the object to estimate said low frequency components.
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) | 2004-06-11 | 2004-12-11 | 2005-06-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-06-11 | 2008-12-11 | 2009-06-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-06-11 | 2012-12-11 | 2013-06-12 | $7700.00 | Window Closed / Lapsed |